WO2021240898A1 - Electronic control device - Google Patents

Abstract

To suppress electrode wear of a spark plug in an internal combustion engine while suppressing poor ignition of fuel by the spark plug. This control device of an internal combustion engine takes a timing of occurrence of an n'th (where n is a natural number) inflection point in a secondary voltage generated at a secondary coil 320 from a point in time at which an ignition signal SA is transmitted to a main primary coil 310, as a start point, as an n'th inflection time point, and with a timing at which an n+1'th inflection point occurs as the n+1'th inflection time point, and transmits an ignition signal SB to a sub-primary coil 360 in a case in which a secondary voltage exceeds a first predetermined value between the n'th inflection time point and the n+1'th inflection time point.

Description

Electronic control device

The present invention relates to an electronic control device.

In recent years, in order to improve the fuel efficiency of vehicles, an internal combustion engine that has introduced a technology to operate an internal combustion engine by burning an air-fuel mixture thinner than the stoichiometric air-fuel ratio and a technology to take in a part of the exhaust gas after combustion and re-intake it. Control device has been developed.

In the control device of this type of internal combustion engine, the amount of fuel and air in the combustion chamber deviates from the theoretical value, so that ignition failure of the fuel by the spark plug is likely to occur. Therefore, by increasing the gas flow velocity in the combustion chamber, the flow velocity between the electrodes of the spark plug is increased so that the discharge path is formed longer, so that the contact length between the discharge path and the gas is lengthened. There is a way to suppress ignition failure.
However, when the flow velocity between the electrodes of the spark plug is increased, the frequency of blowout of the discharge path and the accompanying re-discharge increases. During re-discharging, dielectric breakdown occurs due to capacitive discharge. Since the current density of the capacitive discharge is high, the electrode melts due to the high current, and the wear of the electrode is promoted.

In order to reduce the frequency of capacitive discharge and suppress spark plug electrode wear, it is necessary to maintain the discharge path for as long as possible by continuing to supply current with a sufficient amount of current after the discharge path is formed. be. However, in general, since the internal energy of the ignition coil continues to decrease with the lapse of time from the start of discharge, the ignition coil gradually becomes unable to supply the current required to maintain the discharge path.
As a result, the discharge path cannot be maintained during the combustion of the gas, which causes a problem that re-discharge is required.

In Patent Document 1, an ignition coil having a main primary coil and a secondary primary coil is used, and after the spark plug is generated with a discharge spark by the main primary coil, it is determined in consideration of the time necessary and sufficient for the spark plug to be discharged. A control device for an internal combustion engine is disclosed in which a current is superposed by a secondary primary coil until the superimposition current energization time elapses.

Japanese Unexamined Patent Publication No. 2019-31911

In the technique disclosed in Patent Document 1, since the superimposed current energization time is constant regardless of the combustion state, the superimposition current energization time cannot be appropriately adjusted according to the cycle fluctuation of the internal combustion engine. In order to be able to cope with cycle fluctuations, it is necessary to set the superimposed current energization time including an excessive margin. However, if the superimposed current energization time is set in this way, the superimposed current will flow in excess of the amount required to maintain the discharge path, causing problems such as heat generation of the ignition coil, wear of the spark plug electrode, and deterioration of energy efficiency. Become. On the contrary, if the margin of the superimposed current energization time is reduced, the energy inside the ignition coil is reduced, and there is a possibility that the discharge path cannot be maintained.

Therefore, the present invention has been made by paying attention to the above-mentioned problems, and an object thereof is to suppress the electrode wear of the spark plug in the internal combustion engine while suppressing the ignition failure of the gas by the spark plug.

The electronic control device according to the present invention controls the energization of an ignition coil including a main primary coil and a sub primary coil arranged on the primary side and a secondary coil arranged on the secondary side, respectively. Therefore, in the secondary voltage generated in the secondary coil, the timing at which the nth (where n is a natural number) variation point occurs from the time when the ignition signal to the main primary coil is transmitted is the nth. When the time of the change is set and the timing at which the n + 1st change point occurs is the time of the n + 1th change, the secondary voltage is the second voltage between the nth change point and the n + 1th change point. When the predetermined value of 1 is exceeded, an ignition signal to the sub-primary coil is transmitted.

According to the present invention, it is possible to suppress the electrode wear of the spark plug in the internal combustion engine while suppressing the ignition failure of the gas by the spark plug.

It is a figure explaining the main part structure of the internal combustion engine and the control device of the internal combustion engine which concerns on embodiment. It is a partially enlarged view explaining the spark plug. It is a functional block diagram explaining the functional configuration of the control device which concerns on embodiment. It is a figure explaining the relationship between the operating state of an internal combustion engine, and the gas flow velocity around a spark plug. It is a figure explaining the relationship between the discharge path and the flow velocity between the electrodes of a spark plug. It is a figure explaining the electric circuit including the conventional ignition coil. It is a figure which shows an example of the timing chart explaining the relationship between the control signal input to the ignition coil and the output in the conventional discharge control. It is a figure explaining the electric circuit including the ignition coil which concerns on 1st Embodiment. It is a figure which shows an example of the timing chart explaining the relationship between the control signal input to the ignition coil and the output in the discharge control which concerns on 1st Embodiment. It is an example of the flowchart explaining the control method of the ignition coil which concerns on 1st Embodiment. It is a figure explaining the method of finding the next inflection period based on the approximate line by the least squares method.

Hereinafter, the electronic control device according to the embodiment of the present invention will be described.

Hereinafter, the control device 1 which is one aspect of the electronic control device according to the embodiment of the present invention will be described. In this embodiment, a case where the control device 1 controls the discharge (ignition) of the spark plug 200 provided in each cylinder 150 of the four-cylinder internal combustion engine 100 will be illustrated and described.
Hereinafter, in the embodiment, a combination of a partial configuration or all configurations of the internal combustion engine 100 and a partial configuration or all configurations of the control device 1 is referred to as a control device 1 of the internal combustion engine 100.

[Internal combustion engine]
FIG. 1 is a diagram illustrating a main configuration of an internal combustion engine 100 and an ignition device for an internal combustion engine.
FIG. 2 is a partially enlarged view illustrating electrodes 210 and 220 of the spark plug 200.

In the internal combustion engine 100, the air sucked from the outside passes through the air cleaner 110, the intake pipe 111, and the intake manifold 112, and when the intake valve 151 is opened, it flows into each cylinder 150. The amount of air flowing into each cylinder 150 is adjusted by the throttle valve 113, and the amount of air adjusted by the throttle valve 113 is measured by the flow rate sensor 114.

The throttle valve 113 is provided with a throttle opening sensor 113a that detects the opening of the throttle. The opening degree information of the throttle valve 113 detected by the throttle opening degree sensor 113a is output to the control device (Electronic Control Unit: ECU) 1.

The throttle valve 113 uses an electronic throttle valve driven by an electric motor, but may be another method as long as the air flow rate can be appropriately adjusted.

The temperature of the gas flowing into each cylinder 150 is detected by the intake air temperature sensor 115.

A crank angle sensor 121 is provided on the radial outer side of the ring gear 120 attached to the crankshaft 123. The crank angle sensor 121 detects the rotation angle of the crankshaft 123. In the embodiment, the crank angle sensor 121 detects the rotation angle of the crankshaft 123, for example, every 10 ° and every combustion cycle.

A water temperature sensor 122 is provided on the water jacket (not shown) of the cylinder head. The water temperature sensor 122 detects the temperature of the cooling water of the internal combustion engine 100.

Further, the vehicle is provided with an accelerator position sensor (Accelerator Position Sensor: APS) 126 that detects the displacement amount (depression amount) of the accelerator pedal 125. The accelerator position sensor 126 detects the torque required by the driver. The required torque of the driver detected by the accelerator position sensor 126 is output to the control device 1 described later. The control device 1 controls the throttle valve 113 based on this required torque.

The fuel stored in the fuel tank 130 is sucked and pressurized by the fuel pump 131, then flows through the fuel pipe 133 provided with the pressure regulator 132, and is guided to the fuel injection valve (injector) 134. The fuel output from the fuel pump 131 is adjusted to a predetermined pressure by the pressure regulator 132, and is injected into each cylinder 150 from the fuel injection valve (injector) 134. As a result of pressure adjustment by the pressure regulator 132, excess fuel is returned to the fuel tank 130 via a return pipe (not shown).

The cylinder head (not shown) of the internal combustion engine 100 is provided with a combustion pressure sensor (CylinderPressure Sensor: CPS, also referred to as an in-cylinder pressure sensor) 140. The combustion pressure sensor 140 is provided in each cylinder 150 and detects the pressure (combustion pressure) in the cylinder 150.

As the combustion pressure sensor 140, a piezoelectric or gauge type pressure sensor is used, and it is possible to detect the combustion pressure (in-cylinder pressure) in the cylinder 150 over a wide temperature range.

Each cylinder 150 is equipped with an exhaust valve 152 and an exhaust manifold 160 that exhausts the gas (exhaust gas) after combustion to the outside of the cylinder 150. A three-way catalyst 161 is provided on the exhaust side of the exhaust manifold 160. When the exhaust valve 152 is opened, exhaust gas is discharged from the cylinder 150 to the exhaust manifold 160. This exhaust gas is purified by the three-way catalyst 161 through the exhaust manifold 160 and then discharged to the atmosphere.

An upstream air-fuel ratio sensor 162 is provided on the upstream side of the three-way catalyst 161. The upstream air-fuel ratio sensor 162 continuously detects the air-fuel ratio of the exhaust gas discharged from each cylinder 150.

Further, a downstream air-fuel ratio sensor 163 is provided on the downstream side of the three-way catalyst 161. The downstream air-fuel ratio sensor 163 outputs a switch-like detection signal in the vicinity of the theoretical air-fuel ratio. In the embodiment, the downstream air-fuel ratio sensor 163 is, for example, an O2 sensor.

Further, a spark plug 200 is provided on the upper part of each cylinder 150. Due to the discharge (ignition) of the spark plug 200, sparks are ignited in the air-fuel mixture in the cylinder 150, an explosion occurs in the cylinder 150, and the piston 170 is pushed down. When the piston 170 is pushed down, the crankshaft 123 rotates.

The spark plug 200 is connected to an ignition coil 300 that generates electrical energy (voltage) supplied to the spark plug 200. The voltage generated by the ignition coil 300 causes a discharge between the center electrode 210 and the outer electrode 220 of the spark plug 200 (see FIG. 2).

As shown in FIG. 2, in the spark plug 200, the center electrode 210 is supported by the insulator 230 in an insulated state. A predetermined voltage (for example, 20,000V to 40,000V in the embodiment) is applied to the center electrode 210.

The outer electrode 220 is grounded. When a predetermined voltage is applied to the center electrode 210, a discharge (ignition) occurs between the center electrode 210 and the outer electrode 220.

In the spark plug 200, the voltage at which discharge (ignition) occurs due to dielectric breakdown of the gas component fluctuates depending on the state of the gas (gas) existing between the center electrode 210 and the outer electrode 220 and the in-cylinder pressure. .. The voltage at which this discharge occurs is called the breakdown voltage.

The discharge control (ignition control) of the spark plug 200 is performed by the ignition control unit 83 of the control device 1 described later.

Returning to FIG. 1, the output signals from various sensors such as the throttle opening sensor 113a, the flow rate sensor 114, the crank angle sensor 121, the accelerator position sensor 126, the water temperature sensor 122, and the combustion pressure sensor 140 described above are sent to the control device 1. It is output. The control device 1 detects the operating state of the internal combustion engine 100 based on the output signals from these various sensors, and controls the amount of air sent into the cylinder 150, the fuel injection amount, the ignition timing of the spark plug 200, and the like. ..

[Hardware configuration of controller]
Next, the overall configuration of the hardware of the control device 1 will be described.

As shown in FIG. 1, the control device 1 includes an analog input unit 10, a digital input unit 20, an A / D (Analog / Digital) conversion unit 30, a RAM (Random Access Memory) 40, and an MPU (Micro-). It has a Processing Unit) 50, a ROM (Read Only Memory) 60, an I / O (Input / Output) port 70, and an output circuit 80.

The analog input unit 10 is provided with various sensors such as a throttle opening sensor 113a, a flow rate sensor 114, an accelerator position sensor 126, an upstream air fuel ratio sensor 162, a downstream air fuel ratio sensor 163, a combustion pressure sensor 140, and a water temperature sensor 122. An analog output signal is input.

The A / D conversion unit 30 is connected to the analog input unit 10. The analog output signals from various sensors input to the analog input unit 10 are converted into digital signals by the A / D conversion unit 30 after signal processing such as noise removal, and stored in the RAM 40.

A digital output signal from the crank angle sensor 121 is input to the digital input unit 20.

An I / O port 70 is connected to the digital input unit 20, and the digital output signal input to the digital input unit 20 is stored in the RAM 40 via the I / O port 70.

Each output signal stored in the RAM 40 is arithmetically processed by the MPU 50.

The MPU 50 executes a control program (not shown) stored in the ROM 60 to perform arithmetic processing on the output signal stored in the RAM 40 according to the control program. The MPU 50 calculates a control value that defines the operating amount of each actuator (for example, throttle valve 113, pressure regulator 132, spark plug 200, etc.) that drives the internal combustion engine 100 according to a control program, and temporarily stores it in the RAM 40. ..

The control value that defines the operating amount of the actuator stored in the RAM 40 is output to the output circuit 80 via the I / O port 70.

The output circuit 80 is provided with a function of an ignition control unit 83 (see FIG. 3) that controls a voltage applied to the spark plug 200.

[Control device functional block]
Next, the functional configuration of the control device 1 according to the embodiment of the present invention will be described.

FIG. 3 is a functional block diagram illustrating the functional configuration of the control device 1 according to the embodiment of the present invention. Each function of the control device 1 is realized in the output circuit 80, for example, by the MPU 50 executing a control program stored in the ROM 60.

As shown in FIG. 3, the output circuit 80 of the control device 1 according to the first embodiment includes an overall control unit 81, a fuel injection control unit 82, and an ignition control unit 83.

The overall control unit 81 is connected to the accelerator position sensor 126 and the combustion pressure sensor 140 (CPS), and has the required torque (acceleration signal S1) from the accelerator position sensor 126 and the output signal S2 from the combustion pressure sensor 140. Accept.

The overall control unit 81 controls the fuel injection control unit 82 and the ignition control unit 83 as a whole based on the required torque (acceleration signal S1) from the accelerator position sensor 126 and the output signal S2 from the combustion pressure sensor 140. I do.

The fuel injection control unit 82 includes a cylinder discrimination unit 84 that discriminates each cylinder 150 of the internal combustion engine 100, an angle information generation unit 85 that measures the crank angle of the crankshaft 123, and a rotation speed information generation unit that measures the engine rotation speed. The cylinder discrimination information S3 from the cylinder discrimination unit 84, the crank angle information S4 from the angle information generation unit 85, and the engine rotation speed information S5 from the rotation speed information generation unit 86 are connected to the 86. accept.

Further, the fuel injection control unit 82 measures the temperature of the engine cooling water, the intake amount measuring unit 87 that measures the intake amount of the air taken into the cylinder 150, the load information generation unit 88 that measures the engine load, and the engine cooling water. Connected to the water temperature measuring unit 89, the intake air amount information S6 from the intake air amount measuring unit 87, the engine load information S7 from the load information generation unit 88, and the cooling water temperature information S8 from the water temperature measuring unit 89. , Is accepted.

The fuel injection control unit 82 calculates the injection amount and injection time of the fuel injected from the fuel injection valve 134 (fuel injection valve control information S9) based on each received information, and the calculated fuel injection amount and injection. The fuel injection valve 134 is controlled based on the time.

The ignition control unit 83 is connected to the cylinder discrimination unit 84, the angle information generation unit 85, the rotation speed information generation unit 86, the load information generation unit 88, and the water temperature measurement unit 89, in addition to the overall control unit 81. We accept each information from these.

Based on each received information, the ignition control unit 83 energizes the primary side coil (not shown) of the ignition coil 300 with the current amount (energization angle), the energization start time, and the primary side coil. Calculate the time to cut off the current (ignition time).

The ignition control unit 83 outputs an ignition signal SA to the primary coil of the ignition coil 300 based on the calculated energization angle, the energization start time, and the ignition time, thereby controlling the discharge (ignition) by the spark plug 200. Control).

At least, the function of the ignition control unit 83 to control the ignition of the spark plug 200 by using the ignition signal SA corresponds to the electronic control device of the present invention.

FIG. 4 is a diagram illustrating the relationship between the operating state of the internal combustion engine 100 and the gas flow velocity around the spark plug 200. As shown in FIG. 4, generally, the higher the engine speed and the load, the higher the gas flow rate in the cylinder 150, and the higher the gas flow rate around the spark plug 200. Therefore, the gas flows at high speed between the center electrode 210 and the outer electrode 220 of the spark plug 200. Further, in the internal combustion engine 100 in which exhaust gas recirculation (EGR: Exhaust Gas Recirculation) is performed, the EGR rate is set, for example, as shown in FIG. 4, according to the relationship between the engine rotation speed and the load. It should be noted that the larger the high EGR region in which the EGR rate is set higher, the lower the fuel consumption and the lower the exhaust gas, but the ignition failure is likely to occur in the spark plug 200.

FIG. 5 is a diagram illustrating the relationship between the discharge path and the flow velocity between the electrodes of the spark plug 200.
When a high voltage is generated in the secondary side coil of the ignition coil 300 and dielectric breakdown occurs between the center electrode 210 and the outer electrode 220 of the spark plug 200, the current flowing between these electrodes becomes a constant value or less. Meanwhile, a discharge path is formed between the electrodes of the spark plug 200. When combustible gas comes into contact with this discharge path, flame nuclei grow and lead to combustion. Since the discharge path moves under the influence of the gas flow between the electrodes, the higher the gas flow velocity, the longer the discharge path is formed, and the lower the gas flow velocity, the shorter the discharge path. FIG. 5A shows an example of the discharge path 211 when the gas flow velocity is high, and FIG. 5B shows an example of the discharge path 212 when the gas flow velocity is low.

When the internal combustion engine 100 is operated at a high EGR rate, the probability that the flame nucleus grows even if the combustible gas comes into contact with the discharge path decreases, so it is necessary to increase the chances that the combustible gas comes into contact with the discharge path. As described above, since the discharge path is generated by breaking the insulation of the gas, if the current required to maintain the discharge path is constant, it is necessary to output electric power according to the length of the discharge path. Therefore, when the gas flow velocity is high, the energization control of the ignition coil 300 is performed so that a large amount of electric power is output from the ignition coil 300 to the spark plug 200 in a short time, whereby the long discharge path as shown in FIG. 5A is performed. It is preferable to form 211 to obtain contact opportunities with gas in a wider space. On the other hand, when the gas flow velocity is low, the energization control of the ignition coil 300 is performed so that a small amount of power is continuously output from the ignition coil 300 to the spark plug 200 for a long period of time, whereby the short power as shown in FIG. 5 (b) is controlled. By maintaining the formation of the discharge path 212, it is preferable to obtain a contact opportunity with the gas passing near the electrode of the spark plug 200 for a longer period of time.

[Electric circuit of conventional ignition coil]
Next, before explaining the embodiment of the present invention, the conventional ignition coil will be described.

FIG. 6 is a diagram illustrating an electric circuit 400C including a conventional ignition coil 300C as a comparative example of the present invention. In the electric circuit 400C, the ignition coil 300C includes a primary coil 310 wound with a predetermined number of turns and a secondary coil 320 wound with a larger number of turns than the primary coil 310. Will be done.

One end of the primary side coil 310 is connected to the DC power supply 330. As a result, a predetermined voltage (for example, 12V) is applied to the primary coil 310.

The other end of the primary coil 310 is connected to the igniter 340 and is grounded via the igniter 340. A transistor, a field effect transistor (FET), or the like is used for the igniter 340.

The base (B) terminal of the igniter 340 is connected to the ignition control unit 83. The ignition signal SA output from the ignition control unit 83 is input to the base (B) terminal of the igniter 340. When the ignition signal SA is input to the base (B) terminal of the igniter 340, the collector (C) terminal and the emitter (E) terminal of the igniter 340 are energized, and the collector (C) terminal and the emitter (E) terminal are connected to each other. Current flows through. As a result, the ignition signal SA is output from the ignition control unit 83 to the primary coil 310 of the ignition coil 300 via the igniter 340, a current flows through the primary coil 310, and electric power (electrical energy) is accumulated.

When the output of the ignition signal SA from the ignition control unit 83 is stopped and the current flowing through the primary coil 310 is cut off, a high voltage corresponding to the coil turns ratio with respect to the primary coil 310 is applied to the secondary side. It occurs in the coil 320.

When a high voltage generated in the secondary coil 320 by the ignition signal SA is applied to the spark plug 200 (center electrode 210), a potential difference is generated between the center electrode 210 of the spark plug 200 and the outer electrode 220. do. When the potential difference generated between the center electrode 210 and the outer electrode 220 becomes equal to or higher than the dielectric breakdown voltage Vm of the gas (air-fuel mixture in the cylinder 150), the gas component is dielectrically broken down to the center electrode 210 and the outer electrode 220. A discharge occurs between the two, and the fuel (air-fuel mixture) is ignited (ignited).

In the comparative example, the ignition control unit 83 controls the energization of the ignition coil 300A by using the ignition signal SA by the operation of the electric circuit 400C as described above. As a result, ignition control for controlling the spark plug 200 is performed.

[Conventional ignition coil discharge control]
Next, the discharge control of the conventional ignition coil will be described. FIG. 7 is a diagram showing an example of a timing chart for explaining the relationship between the control signal input to the ignition coil and the output in the conventional discharge control. The timing chart of FIG. 7 is an example when the spark plug 200 is discharged when the gas has a high flow velocity by using the conventional ignition coil 300C. In FIG. 7, the ignition signal SA output from the ignition control unit 83, the primary current I1 flowing through the primary coil 310 in response to the ignition signal SA, the electrical energy E stored in the ignition coil 300C, and the secondary side The relationship between the secondary current I2 flowing through the coil 320 and the secondary voltage V2 generated in the secondary coil 320 is shown. As shown in FIG. 6, the measurement points of the secondary current I2 and the secondary voltage V2 are between the spark plug 200 and the ignition coil 300C. The measurement point of the primary current I1 is between the DC power supply 330 and the ignition coil 300C.

When the ignition signal SA becomes HIGH, the igniter 340 energizes the primary coil 310 and the primary current I1 rises. While the primary coil 310 is energized, the electric energy E in the ignition coil 300C rises with time.

After that, when the ignition signal SA becomes LOW, the igniter 340 cuts off the energization of the primary coil 310. As a result, an electromotive force is generated in the secondary coil 320, and the supply of electric energy E from the ignition coil 300C to the spark plug 200 is started. When the insulation between the electrodes of the spark plug 200 is broken, the spark plug 200 starts to be discharged. The discharge of the spark plug 200 accompanied by such dielectric breakdown is called capacitive discharge. After the discharge of the spark plug 200 is started, the electric energy E in the ignition coil 300C decreases with time, and the discharge of the spark plug 200 is maintained. The discharge of the spark plug 200 without such dielectric breakdown is called an induced discharge.

The secondary current I2 greatly increases when the capacity is discharged. The secondary current I2 due to this capacity discharge ends in a short time. When the discharge of the spark plug 200 is started and a discharge path is formed between the electrodes, the secondary current I2 drops sharply and then drops with time during the subsequent induced discharge. Since the discharge path extends with the flow of gas, the secondary voltage V2 rises with the passage of time, and the electric energy (discharge required energy) required to maintain the discharge path rises accordingly. On the other hand, the electric energy E supplied from the ignition coil 300C to the spark plug 200 decreases with time as described above. As a result, when the required discharge energy exceeds the energy supplied from the ignition coil 300C, the discharge path cannot be maintained and the discharge path is blown out.

Here, since the discharge period of the spark plug 200 is as short as about 1 to 2 msec, the gas flow between the electrodes during the discharge period can be regarded as almost constant. However, since the electrode itself becomes an obstacle to the gas flow, a Karman vortex is generated downstream of the electrode. As a result, on the downstream side of the electrode, a change in gas pressure due to vortex shedding occurs at regular intervals. Then, this change in gas pressure destabilizes the discharge path, which triggers the discharge path to blow out. Therefore, as shown in FIG. 7, after the discharge start point A at the secondary voltage V2, the inflection points B, C, and D indicating the gas pressure change during the continuous discharge and the inflection points indicating the blowout of the discharge path are shown. E occurs at regular intervals. That is, the timing of the next and subsequent inflection points is estimated from the period of the inflection point of the secondary voltage V2, and the estimation result of the timing of the next inflection point when the secondary voltage V2 becomes a certain value or more is used. If additional electric energy E is supplied to the spark plug 200 at that timing, the probability that the discharge path will be blown out can be reduced.

If sufficient electrical energy E still remains in the ignition coil 300C when the discharge path is blown out, the spark plug 200 uses this electrical energy E to discharge at the shortest distance between the electrodes. It will be resumed. As a result, as shown in FIG. 7, the spark plug 200 repeatedly blows out and re-discharges the discharge path. When the discharge is restarted, the dielectric breakdown between the electrodes occurs, so that the secondary current I2 flowing between the electrodes momentarily becomes a high current, causing evaporation of the electrode material. In particular, when the gas flow in the cylinder 150 is large, the discharge path expands quickly, so that the discharge is likely to occur, the re-discharge cycle is shortened, and the number of re-discharges increases. This causes an increase in the amount of evaporation of the electrode material and causes a decrease in the life of the electrode. Therefore, it is desired to reduce the blowout during the discharge period as much as possible.

In the present invention, instead of the ignition coil 300C described with reference to FIG. 6, an ignition coil 300 having two primary side coils is adopted, and discharge control is performed on the ignition coil 300 to suppress the number of capacitance discharges. The discharge of the spark plug 200 is realized.

[First Embodiment: Electric circuit of ignition coil]
Next, the electric circuit 400 including the ignition coil 300 according to the first embodiment of the present invention will be described.

FIG. 8 is a diagram illustrating an electric circuit 400 including an ignition coil 300 according to the first embodiment of the present invention. In the electric circuit 400, the ignition coil 300 has two types of primary coil 310 and 360 wound with a predetermined number of turns and a secondary side wound with a number of turns larger than the primary coil 310 and 360. It is configured to include and include a coil 320. Here, at the time of ignition of the spark plug 200, the electric power from the primary coil 310 is first supplied to the secondary coil 320, and the electric power from the primary coil 360 is superimposed on the electric power to the secondary coil 320. Is supplied to. Therefore, in the following, the primary coil 310 will be referred to as a "main primary coil" and the primary coil 360 will be referred to as a "secondary primary coil". Further, the current flowing through the main primary coil 310 is referred to as "main primary current", and the current flowing through the primary sub coil 360 is referred to as "secondary primary current".

One end of the main primary coil 310 is connected to the DC power supply 330. As a result, a predetermined voltage (for example, 12V in the embodiment) is applied to the main primary coil 310.

The other end of the main primary coil 310 is connected to an igniter 340, which is a switch element for switching the conduction state of the main primary coil 310, and is grounded via the igniter 340. A transistor, a field effect transistor (FET), or the like is used for the igniter 340.

The base (B) terminal of the igniter 340 is connected to the ignition signal output unit 384 provided in the ignition control unit 83. The ignition signal output unit 384 outputs an ignition signal SA as a signal for controlling the on / off of the igniter 340. The ignition signal SA output from the ignition signal output unit 384 is input to the base (B) terminal of the igniter 340. When the ignition signal SA is input to the base (B) terminal of the igniter 340, the igniter 340 is turned on and the collector (C) terminal and the emitter (E) terminal are energized, and the collector (C) terminal and the emitter (E) are energized. ) Current flows between the terminals. As a result, the ignition signal SA is output from the ignition control unit 83 to the main primary coil 310 of the ignition coil 300 via the igniter 340, and the main primary current flows through the main primary coil 310 to accumulate electric power (electrical energy). Will be done.

When the output of the ignition signal SA from the ignition signal output unit 384 is stopped and the igniter 340 is turned off and the main primary current flowing through the main primary coil 310 is cut off, the coil of the coil with respect to the main primary coil 310 is cut off. A high voltage corresponding to the turns ratio is generated in the secondary coil 320.

One end of the secondary primary coil 360 is connected to the DC power supply 330 in common with the main primary coil 310. As a result, a predetermined voltage (for example, 12V in the embodiment) is also applied to the secondary primary coil 360.

The other end of the sub-primary coil 360 is connected to the igniter 350, which is a switch element for switching the conduction state of the sub-primary coil 360, and is grounded via the igniter 350. For the igniter 350, a transistor, a field effect transistor (FET), or the like is used.

The base (B) terminal of the igniter 350 is connected to the ignition signal output unit 384 provided in the ignition control unit 83. The ignition signal output unit 384 outputs an ignition signal SB as a signal for controlling the on / off of the igniter 350. The ignition signal SB output from the ignition signal output unit 384 is input to the base (B) terminal of the igniter 350. When the ignition signal SB is input to the base (B) terminal of the igniter 350, the igniter 350 is turned on and the collector (C) terminal and the emitter (E) terminal are energized according to the voltage change of the ignition signal SB. A current corresponding to the voltage change of the ignition signal SB flows between the collector (C) terminal and the emitter (E) terminal. As a result, the ignition signal SB is output from the ignition control unit 83 to the sub-primary coil 360 of the ignition coil 300 via the igniter 350, and the sub-primary current flows through the sub-primary coil 360 to generate electric power (electrical energy). do.

When the output of the ignition signal SB from the ignition signal output unit 384 changes and the sub-primary current flowing through the sub-primary coil 360 changes, the high voltage corresponding to the coil turns ratio with respect to the sub-primary coil 360 becomes 2. It occurs in the next coil 320.

The high voltage generated in the secondary coil 320 by the ignition signal SA is applied to the high voltage generated in the secondary coil 320 by the ignition signal SB and applied to the spark plug 200 (center electrode 210) to ignite. A potential difference is generated between the center electrode 210 of the plug 200 and the outer electrode 220. When the potential difference generated between the center electrode 210 and the outer electrode 220 becomes equal to or higher than the dielectric breakdown voltage Vm of the gas (air-fuel mixture in the cylinder 150), the gas component is dielectrically broken down to the center electrode 210 and the outer electrode 220. A discharge occurs between the two, and the fuel (air-fuel mixture) is ignited (ignited).

A voltage detection unit 370 for detecting the secondary voltage V2 flowing through the secondary coil 320 is provided between the secondary coil 320 and the spark plug 200. The voltage detection unit 370 transmits the detected secondary voltage value to the inflection point detection unit 381 and the ignition signal output unit 384 provided in the ignition control unit 83.

The ignition control unit 83 is provided with an inflection point detection unit 381, a calculation unit 382, a prediction unit 383, and an ignition signal output unit 384. These are realized as the functions of the ignition control unit 83, respectively, and are realized in the output circuit 80 by, for example, the MPU 50 executing the control program stored in the ROM 60 as described with reference to FIGS. 1 and 3. Will be done.

The inflection point detection unit 381 calculates the differential value of the secondary voltage V2 detected by the voltage detection unit 370, and when this differential value exceeds a predetermined threshold value, the value of the secondary voltage V2 at that time is changed. Detect as an inflection. The threshold information stored in advance in the ignition control unit 83 is input to the inflection point detection unit 381. Based on this threshold information, a threshold value when the inflection point detecting unit 381 detects an inflection point is set.

The calculation unit 382 calculates the cycle of the inflection point detected by the inflection point detection unit 381. Here, as described above, the period of the inflection point is calculated assuming that the inflection point corresponding to the gas pressure change due to the separation of the Karman vortex occurs at a fixed period in the secondary voltage V2. For example, starting from the time when the ignition signal SA is transmitted from the ignition signal output unit 384 to the main primary coil 310, the k-th (however, k is a natural number) inflection point and the next k + 1-th inflection point. The time interval is measured, and the cycle of the inflection point is calculated from this time interval.

The prediction unit 383 predicts the time point at which the next and subsequent inflection points will occur in the secondary voltage V2 based on the period of the inflection points calculated by the calculation unit 382. Specifically, the time when the cycle of the inflection has elapsed from the time when the last inflection is detected is predicted as the timing of the next inflection.

The ignition signal output unit 384 controls the output of the ignition signals SA and SB. In the case of the ignition signal SA, the ignition signal output unit 384 controls the output according to the state of the internal combustion engine 100. That is, as described above, the energization angle, energization start time, ignition time, etc. of the ignition coil 300 are calculated based on the crank angle, engine rotation speed, engine load, cooling water temperature, etc., and these calculation results are used. The output timing of the ignition signal SA is determined. On the other hand, in the case of the ignition signal SB, the ignition signal output unit 384 performs output control using the prediction result of the next inflection point by the prediction unit 383 and the secondary voltage V2 detected by the voltage detection unit 370. The specific output control method of the ignition signal SB will be described later.

The ignition control unit 83 controls the energization of the ignition coil 300 by using the ignition signals SA and SB by the operation of the electric circuit 400 as described above. As a result, ignition control for controlling the spark plug 200 is performed.

In the ignition signal output unit 384, the portion that controls the output of the ignition signal SA and the portion that controls the output of the ignition signal SB may be configured separately. In this case, the portion that controls the output of the ignition signal SB may not be provided inside the ignition control unit 83. In any case, since the portion operates according to the control of the ignition control unit 83, it can be said that the ignition control unit 83 controls the energization of the ignition coil 300.

[First Embodiment: Discharge control of ignition coil]
Next, the discharge control of the ignition coil according to the first embodiment of the present invention will be described. FIG. 9 is a diagram showing an example of a timing chart for explaining the relationship between the control signal input to the ignition coil and the output in the discharge control according to the first embodiment of the present invention. The timing chart of FIG. 9 is an example when the spark plug 200 is discharged when the gas has a high flow velocity by using the ignition coil 300 of the present embodiment. In FIG. 9, an ignition signal SA output from the ignition signal output unit 384, a main primary current I1 flowing through the main primary coil 310 according to the ignition signal SA, and an ignition signal output from the ignition signal output unit 384. The SB, the sub-primary current I3 flowing in the sub-primary coil 360 according to the ignition signal SB, the electric energy E stored in the ignition coil 300, the secondary current I2 flowing in the secondary coil 320, and the secondary side. The relationship between the secondary voltage V2 generated in the coil 320 and the differential value dV2 / dt of the secondary voltage V2 is shown. As shown in FIG. 8, the secondary voltage V2 is detected by the voltage detection unit 370 provided between the spark plug 200 and the ignition coil 300. Further, the differential value dV2 / dt of the secondary voltage V2 is calculated by the inflection point detecting unit 381 as described above.

When the ignition signal SA becomes HIGH, the igniter 340 energizes the main primary coil 310, and the main primary current I1 rises. While the main primary coil 310 is energized, the electric energy E in the ignition coil 300 rises with time.

After that, when the ignition signal SA becomes LOW, the igniter 340 cuts off the energization of the main primary coil 310. As a result, an electromotive force is generated in the secondary coil 320, and the supply of electric energy E from the ignition coil 300 to the spark plug 200 is started. When the insulation between the electrodes of the spark plug 200 is broken, discharge (capacitive discharge) of the spark plug 200 is started. After the discharge of the spark plug 200 is started, the electric energy E in the ignition coil 300 decreases with time, and the discharge (induced discharge) of the spark plug 200 is maintained.

The secondary current I2 and the secondary voltage V2 greatly increase when the capacity is discharged. The increase in the secondary current I2 and the secondary voltage V2 due to this capacitance discharge ends in a short time. When the discharge of the spark plug 200 is started and a discharge path is formed between the electrodes, the secondary current I2 and the secondary voltage V2 each drop sharply. During the subsequent induced discharge, the secondary current I2 decreases with time. On the other hand, since the discharge path extends with the flow of gas, the secondary voltage V2 rises with the passage of time.

After the ignition signal SA changes from HIGH to LOW and capacitance discharge is started, when the differential value dV2 / dt of the secondary voltage V2 becomes equal to or higher than a predetermined threshold value dV2 / dt_th set in advance, the inflection point detection unit 381 , The value of the secondary voltage V2 at that time is detected as an inflection point. As a result, the inflection points B, C, D, E, and F are sequentially detected each time the value of the secondary voltage V2 becomes equal to or higher than the threshold value dV2 / dt_th after the discharge start point A has elapsed.

When the change point detection unit 381 detects the change points B and C of the secondary voltage V2, the calculation unit 382 calculates the time interval T1 from the change point B to the change point C, and this time interval Let T1 be the variation period T of the secondary voltage V2. The prediction unit 383 predicts the timing of the next inflection point of the secondary voltage V2 by using the inflection period T = T1 obtained by the calculation unit 382. That is, it is presumed that the next inflection point D occurs at the secondary voltage V2 when the inflection period T1 elapses from the inflection point C.

Similarly, when the inflection point D is detected by the inflection point detection unit 381, the calculation unit 382 calculates the time interval T2 from the inflection point C to the inflection point D, and uses this time interval T2. The inflection period T of the secondary voltage V2 is updated. The prediction unit 383 predicts the timing of the next inflection point of the secondary voltage V2 by using the inflection period T = T2 obtained by the calculation unit 382. That is, it is presumed that the next inflection point E occurs at the secondary voltage V2 when the inflection period T2 elapses from the inflection point D.

When the value of the secondary voltage V2 between the inflection point D and the inflection point E exceeds a predetermined threshold value V2_th, the ignition signal output unit 384 determines the time when the latest inflection point (here, the inflection point D) occurs. The transmission timing of the ignition signal SB is determined so that the ignition signal SB is output within a period including at least the next inflection point E. That is, the timing at which the ignition signal SB is changed to HIGH and LOW so that the igniter 350 is turned on between the inflection point D and the next inflection point E and the igniter 350 is turned off after the inflection point E, respectively. To decide.

Specifically, assuming that the time point at which the latest inflection point is detected is tun, the timing at which the ignition signal SB is changed to HIGH (the overlap discharge start time th) and the timing at which the ignition signal SB is returned to LOW after that (overlap discharge). The end time point tl) is expressed by, for example, the following equations (1) and (2), respectively.
th = tun + T-P ... (1)
tl = tun + T + p ... (2)

In equation (1), P represents the energization time of the secondary primary coil 360. This energization time P is set in advance according to the amount of electric energy to be supplied from the secondary primary coil 360 to the spark plug 200 in order to suppress the blowout of the discharge path and the amount of electric energy that can be stored in the secondary primary coil 360. It is set. Further, in the equation (2), p represents the margin of energization time for the secondary primary coil 360. This margin p is included in the energization period of the secondary primary coil 360 even if there is a deviation between the prediction result of the timing of the next inflection point and the actual inflection point. It is preset according to the prediction accuracy of the next inflection point in 383.

When the value of the secondary voltage V2 exceeds a predetermined threshold value V2_th, the ignition signal output unit 384 repeats the above control until the secondary current I2 drops and the discharge between the electrodes stops. As a result, the ignition signals SB are output to the inflection points E and F according to the transmission timing determined as described above. In the ignition signal SB of FIG. 9, the points G and I represent the overlapping discharge start time points th for the inflection points E and F, respectively, and these are determined based on the equation (1). Further, the points H and J represent the time points th at the end of the overlapping discharge with respect to the inflection points E and F, respectively, and these are determined based on the equation (2).

While the ignition signal output unit 384 outputs the ignition signal SB to the igniter 350, the high voltage generated in the secondary side coil 320 by the ignition signal SA and the high voltage generated in the secondary side coil 320 by the ignition signal SB are generated. Join. This high voltage is applied to the spark plug 200 (center electrode 210). As a result, the secondary current I2 is increased and the maintenance of the discharge path is continued. Therefore, in the spark plug 200, the occurrence of re-discharge (re-discharge) accompanied by capacitance discharge is suppressed. The secondary current I2 at this time includes the current flowing through the secondary side coil 320 by the main primary coil 310 (hereinafter referred to as “first induced current”) and the secondary side coil by the secondary primary coil 360. The current flowing through the 320 (hereinafter referred to as “second induced current”) is included.

As shown in FIG. 9, since the change in voltage value is small at the inflection point of the secondary voltage V2, even if an attempt is made to directly detect the inflection point from the change in the secondary voltage V2, the required detection sensitivity cannot be obtained. In some cases. Therefore, in the present embodiment, the inflection point of the secondary voltage V2 is detected by calculating the differential value dV2 / dt obtained by time-differentiating the secondary voltage V2 and comparing this differential value with the predetermined threshold value dV2 / dt_th. I try to do it. However, the time derivative is not limited to the first derivative, and the second derivative or the third derivative may be used as needed. If the inflection point required for calculating the cycle cannot be detected by the time the threshold value dV2 / dt_th is reached, the ignition timing for the secondary coil is determined based on the predetermined value defined in advance. May be.

[First Embodiment: Discharge control flow of ignition coil]
Next, a method of controlling the ignition coil 300 by the ignition control unit 83 when carrying out the above discharge control will be described. FIG. 10 is an example of a flowchart illustrating a method of controlling the ignition coil 300 by the ignition control unit 83 according to the first embodiment of the present invention. In the present embodiment, when the ignition switch of the vehicle is turned on and the power of the internal combustion engine 100 is turned on, the ignition control unit 83 starts controlling the ignition coil 300 according to the flowchart of FIG. The process shown in the flowchart of FIG. 10 represents the process for one cycle of the internal combustion engine 100, and the ignition control unit 83 carries out the process shown in the flowchart of FIG. 10 for each cycle.

In step S201, when the ignition signal SA changes from HIGH to LOW and the spark plug 200 starts to be discharged, the ignition control unit 83 starts an operation to control the ignition signal SB.

In step S202, the ignition control unit 83 sets the internal memory variable i and the initial value of the inflection cycle. Here, i = 1 and T = 0 are set as initial values, respectively.

In step S203, the inflection point detection unit 381 in the ignition control unit 83 calculates the time derivative dV2 / dt of the secondary voltage V2 detected by the voltage detection unit 370 and compares it with the predetermined threshold value dV2 / dt_th. As a result, when the differential value dV2 / dt exceeds the threshold value dV2 / dt_th, the current value of the secondary voltage V2 is detected as an inflection point, and the process proceeds to step S204. On the other hand, if the differential value dV2 / dt is equal to or less than the threshold value dV2 / dt_th, the process proceeds to step S209 without detecting the inflection point.

In step S204, the ignition control unit 83 records the current time in the internal memory as the inflection time ti representing the timing at which the i-th inflection point occurs from the start of discharge of the spark plug 200.

In step S205, the ignition control unit 83 determines whether or not the current value of the variable i is 2 or more. If i is 2 or more, the process proceeds to step S206, and if it is less than 2, that is, if the initial value of 1 remains, the process proceeds to step S208.

In step S206, the calculation unit 382 in the ignition control unit 83 calculates the time interval from the previous inflection point to the current inflection point. Here, the inflection time t (i-1) recorded for the i-1st inflection in the previous step S204 and the i-th inflection recorded in the current step S204. The difference from the inflection time ti is obtained, and this difference value is set as the i-1st time interval T (i-1).

In step S207, the prediction unit 383 in the ignition control unit 83 uses the value of the i-1st time interval T (i-1) calculated in step S206 as the variation period T of the secondary voltage V2 as an internal memory. Record in. As a result, the timing at which the i + 1th and subsequent inflection points occur in the secondary voltage V2 is predicted.

In step S208, the ignition control unit 83 adds 1 to the variable i.

In step S209, the ignition control unit 83 compares the value of the current secondary voltage V2 detected by the voltage detection unit 370 with the predetermined threshold value V2_th. Further, by applying the above equations (1) and (2) to the latest inflection point ti recorded in step S204 with tun = ti, the time point at which the overlapping discharge is started with respect to the i-th inflection point ti, respectively. The th and the overlap discharge end time tl are determined, and it is determined whether or not the current time is between them. As a result, if the value of the secondary voltage V2 is equal to or higher than the threshold value V2_th and the current time is between the overlap discharge start time th and the overlap discharge end point tl, that is, within the overlap discharge period, the process proceeds to step S210. .. On the other hand, if the value of the secondary voltage V2 is less than the threshold value V2_th, or if the current time is outside the overlapping discharge period, the process proceeds to step S211.

In step S210, the ignition signal output unit 384 in the ignition control unit 83 sets the ignition signal SB output to the igniter 350 to HIGH. As a result, when the value of the secondary voltage V2 exceeds the threshold value V2_th, the igniter 350 is turned on at the overlap discharge start time th between the latest change point ti and the next change time t (i + 1). The ignition signal SB to the sub-primary coil 360 is transmitted to. After that, the process returns to step S203.

In step S21, the ignition signal output unit 384 in the ignition control unit 83 sets the ignition signal SB output to the igniter 350 to LOW. As a result, the ignition signal SB to the sub-primary coil 360 is transmitted so as to turn off the igniter 350 at the end point tl of the overlapping discharge after the next change point t (i + 1). After that, the process returns to step S203.

Here, in steps S209 and S210, the ignition signal SB is set when both the condition that the value of the secondary voltage V2 is equal to or greater than the threshold value V2_th and the condition that the current time is within the overlapping discharge period are satisfied. It is set to HIGH. Therefore, when the value of the secondary voltage V2 exceeds the threshold value V2_th before the stacking discharge start time th, the ignition signal SB is set to HIGH at the stacking discharge start time th, and the igniter 350 is turned on accordingly. As a result, the supply of electric energy from the secondary primary coil 360 to the secondary coil 320 is started. On the other hand, when the value of the secondary voltage V2 exceeds the threshold value V2_th after the start time th of the overlapping discharge, the ignition signal SB is set to HIGH when the value of the secondary voltage V2 exceeds the threshold value V2_th. When the igniter 350 is turned on accordingly, the electric energy supply from the secondary primary coil 360 to the secondary coil 320 is started. Therefore, in either case, the electric energy can be supplied from the secondary primary coil 360 to the secondary coil 320 at an appropriate timing according to the next inflection point.

In the above embodiment, the timing of the inflection point from the next time onward is estimated by assuming that the gas flow velocity between the electrodes during the discharge period is constant, and the transmission timing of the ignition signal SB is determined. Depending on the state of, this assumption may not hold. For example, when the EGR rate or the air dilution becomes large, it is necessary to advance the ignition timing according to the decrease in the combustion rate. In this case, since the in-cylinder volume during the discharge period is relatively large and the gas flow state is maintained at a high flow rate, changes in the gas flow velocity and turbulence of the gas flow are likely to occur in a short time. Therefore, the period of the inflection point of the secondary voltage V2 cannot be kept constant. As described above, when the change in the flow velocity of the gas or the turbulence of the flow cannot be ignored, it is necessary to determine the transmission timing of the ignition signal SB by, for example, the following method in consideration of this.

[Response to changes in flow velocity 1]
In the calculation unit 382 in the ignition control unit 83, an approximate line is calculated from the inflection period for each inflection obtained in the past by using the least squares method, and the next inflection period is obtained based on the approximate line. .. Specifically, for example, in step S206 of FIG. 10, for each of the first to nth inflections detected so far, the time interval Ti (i) as shown in points 501 to 507 of FIG. It is assumed that the values of = 1 to n-1) have been calculated. In such a case, an approximate straight line 500 that approximates the relationship between points 501 to 507 is calculated by the least squares method, and the value of the point 508 on the approximate straight line 500 when i = n is used as the nth inflection point. It is obtained as the inflection period Tn from to the next n + 1th inflection point. That is, the time interval between the k-th inflection (where k is a natural number satisfying k <n) and the k + 1-th inflection in the secondary voltage V2 is measured for each of a plurality of k values, and the measured k is. The relationship between the value and each time interval can be obtained by the minimum square method, and the next inflection period T can be calculated from the relationship. Since this method requires complicated operations in a short operation period, it is appropriate to use a first-order correlation for the least squares method.

[Response to changes in flow velocity 2]
If the change in the flow velocity is irregular, the above method becomes impractical because the order increases and the calculation load increases. In such a case, the next inflection cycle can be obtained by weighted averaging the inflection cycles obtained in the past for each inflection point. When the number of samples of the variation period to be weighted averaged in this method is small, the weighting coefficient of each variation cycle may be changed according to the number of samples. For example, when the number of samples is 2, that is, when the inflection points up to the third have been detected and the calculation unit 382 has calculated these time intervals as the inflection cycles T1 and T2, each inflection cycle. Let the weighting factor of be 0.5. Further, when the number of samples is 3, that is, when the inflection points up to the 4th have been detected and the calculation unit 382 has already calculated these time intervals as the inflection cycles T1, T2, T3, each variation. Set the weighting coefficient of the song cycle to 0.33.
Further, the weighting coefficient of each inflection cycle may be different. For example, the weighting coefficient can be made smaller as the inflection period of the old (earlier) inflection point is smaller, and conversely, the weighting coefficient can be made larger as the inflection period of the newer (later order) inflection point is made.

[Response to flow turbulence 1]
At the time of tumble collapse of the in-cylinder flow, the turbulence of the flow between the electrodes becomes strong, and an inflection point of the secondary voltage V2 may occur due to a cause other than the electrode. In this case, in order to exclude the inflection point from the calculation target of the inflection cycle, in step S206 among the inflection points detected by the inflection point detection unit 381 in the calculation unit 382 in the ignition control unit 83. An inflection whose time interval from the calculated inflection immediately before is less than a predetermined minimum pulse width (cycle) may be excluded from the subsequent processing targets. In this method, for example, a digital filter can be applied.

[Correspondence to turbulence of flow 2]
Further, as a simple method when it is difficult to apply the digital filter, a predetermined time from the start of discharge or a predetermined secondary voltage V2, secondary current I2, tertiary current I3, and tertiary voltage V3 ( Within the range of Vce) of the IGBT, the ignition signal SB may be forcibly set to Low regardless of the calculation result of the variation period. By doing so, it becomes possible to suppress wasteful energy consumption in a state where the possibility that the discharge path is blown out is low.

According to the embodiment of the present invention described above, the following effects are exhibited.

(1) The control device 1 which is an electronic control device is an ignition provided with a main primary coil 310 and a secondary primary coil 360 arranged on the primary side, respectively, and a secondary coil 320 arranged on the secondary side. It controls the energization of the coil 300. In the secondary voltage V2 generated in the secondary coil 320, the timing at which the nth (where n is a natural number) inflection occurs from the time when the ignition signal SA to the main primary coil 310 is transmitted (the inflection point D). (Timing) is the nth inflection time, and the timing at which the n + 1th inflection occurs (the timing of the inflection point E) is the n + 1st inflection time, the nth inflection time and the n + 1st inflection time. When the secondary voltage V2 exceeds the first predetermined value (threshold V2_th) between the time of the inflection and the time of the inflection, the ignition signal SB to the sub-primary coil 360 is transmitted. Since this is done, it is possible to suppress the electrode wear of the spark plug 200 in the internal combustion engine 100 while suppressing the ignition failure of the gas by the spark plug 200. Further, since the cycle of the inflection point fluctuates depending on the operating state, there is an advantage that it is possible to cope with various states as compared with the case of ignition control at a predetermined timing.

(2) The ignition signal SB to the sub-primary coil 360 is a signal for controlling the on / off of the igniter 350, which is a switch element connected to one end of the sub-primary coil 360. The control device 1 turns on the igniter 350 between the nth turn point and the n + 1th change point, and turns off the igniter 350 after the n + 1th change point. Send an ignition signal to. Specifically, the inflection period obtained from the k-th inflection (where k is a natural number satisfying k <n) and the k + 1-th inflection in the secondary voltage V2 is T, and the sub-primary coil 360 is used. On the other hand, when the predetermined energization time is P, the time point after the lapse of TP from the nth inflection time point tn represented by the equation (1) is set as the overlapped discharge start time point th. The ignition signal SB to the sub-primary coil 360 is transmitted so as to turn on the igniter 350 (steps S209 and S210). Since this is done, the auxiliary electric energy E is supplied from the ignition coil 300 to the spark plug 200 at the timing of the next inflection when the secondary voltage V2 exceeds a certain level. The ignition signal SB for the primary coil 360 can be transmitted. Therefore, it is possible to effectively reduce the probability that the discharge path is blown out due to the periodic change of the gas pressure due to the separation of the Karman vortex generated on the downstream side of the electrode.

(3) The control device 1 includes an inflection point detection unit 381, a calculation unit 382, and a prediction unit 383. When the differential value dV2 / dt of the secondary voltage V2 exceeds the second predetermined value (threshold value dV2 / dt_th), the inflection point detection unit 381 detects it as an inflection point of the secondary voltage V2 (step S203). ). The calculation unit 382 calculates the inflection cycle T based on the time interval between the k-th inflection point and the k + 1-th inflection point detected by the inflection point detection unit 381 (step S206). The prediction unit 383 predicts the time point at which the k + second and subsequent inflection points occur in the secondary voltage V2 based on the inflection period T calculated by the calculation unit 382 (step S207). Since this is done, the timing of the next inflection can be reliably predicted by reflecting the periodic change of the gas pressure due to the separation of the Karman vortex.

(4) The calculation unit 382 can measure the time interval for each of the plurality of k values, and calculate the variation period T based on each measured time interval. For example, the variation period T can be calculated based on the relationship between the value of k obtained by the least squares method and each time interval or the weighted average of each time interval. By doing so, even when the change in the flow velocity of the gas or the turbulence of the flow cannot be ignored, the transmission timing of the ignition signal SB to the secondary primary coil 360 can be appropriately determined.

(5) Further, the calculation unit 382 excludes inflection points whose time interval from the immediately preceding inflection point is less than a predetermined value among the plurality of inflection points detected by the inflection point detection unit 381. The period T can also be calculated. By doing so, even if the turbulence of the flow between the electrodes becomes strong and an inflection point of the secondary voltage V2 occurs due to a cause other than the electrode, the ignition signal SB for the secondary primary coil 360 is generated. The transmission timing can be appropriately determined.

(6) When calculating the inflection cycle T in the calculation unit 382, the inflection cycle T is calculated from the time interval between the latest inflection point and the previous inflection point with k = n-1. Can be done. By doing so, it is possible to easily and accurately calculate the inflection period T according to the timing of the next inflection, reflecting the latest gas state in the cylinder.

(7) When the secondary voltage V2 exceeds the first predetermined value before the stacking discharge start time th, the control device 1 is set to turn on the igniter 350 at the stacking discharge start time th. The ignition signal SB to the primary coil 360 is transmitted (steps S209 and S210). Further, when the secondary voltage V2 exceeds the first predetermined value after the overlap discharge start time th, the igniter 350 is turned on when the secondary voltage V2 exceeds the first predetermined value. , The ignition signal SB to the sub-primary coil 360 is transmitted (steps S209, S210). Since this is done, in any case, the electric energy can be supplied from the secondary primary coil 360 to the secondary coil 320 at an appropriate timing according to the next inflection point.

(8) The control device 1 detects an inflection point in the secondary voltage V2 generated on the secondary side of the ignition coil 300 (step S203), and based on the timing when the inflection point is detected in the past, the next inflection Predict the timing of the inflection (step S207). Since this is done, the timing of the next inflection can be reliably predicted by reflecting the periodic change of the gas pressure due to the separation of the Karman vortex.

The embodiments and various modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. Further, although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects considered within the scope of the technical idea of the present invention are also included within the scope of the present invention.

1: Control device, 10: Analog input unit, 20: Digital input unit, 30: A / D conversion unit, 40: RAM, 50: MPU, 60: ROM, 70: I / O port, 80: Output circuit, 81 : Overall control unit, 82: Fuel injection control unit, 83: Ignition control unit, 84: Cylinder discrimination unit, 85: Angle information generation unit, 86: Rotation speed information generation unit, 87: Intake amount measurement unit, 88: Load information Generation unit, 89: Water temperature measurement unit, 100: Internal engine, 110: Air cleaner, 111: Intake pipe, 112: Intake manifold, 113: Throttle valve, 113a: Throttle opening sensor, 114: Flow sensor, 115: Intake temperature sensor , 120: Ring gear, 121: Crank angle sensor, 122: Water temperature sensor, 123: Crank shaft, 125: Accelerator pedal, 126: Accelerator position sensor, 130: Fuel tank, 131: Fuel pump, 132: Pressure regulator, 133: Fuel piping, 134: Fuel injection valve, 140: Combustion pressure sensor, 150: Cylinder, 151: Intake valve, 152: Exhaust valve, 160: Exhaust manifold, 161: Three-way catalyst, 162: Upstream air fuel ratio sensor, 163: Downstream air fuel ratio sensor, 170: piston, 200: ignition plug, 210: center electrode, 220: outer electrode, 230: insulator, 300, 300C: ignition coil, 310: main primary coil, 320: secondary side coil , 330: DC power supply, 340, 350: Igniter, 360: Secondary primary coil, 370: Voltage detection unit, 381: Curved point detection unit, 382: Calculation unit, 383: Prediction unit, 384: Ignition signal output unit, 400,400C: Electric circuit

Claims (10)

1. An electronic control device that controls the energization of an ignition coil including a main primary coil and a sub primary coil arranged on the primary side and a secondary coil arranged on the secondary side, respectively.
   In the secondary voltage generated in the secondary coil, the timing at which the nth (where n is a natural number) inflection occurs from the time when the ignition signal to the main primary coil is transmitted is the nth inflection time. Then, when the timing at which the n + 1st inflection occurs is set to the n + 1th inflection time, the secondary voltage is the first predetermined value between the nth inflection time point and the n + 1st inflection time point. An electronic control device that transmits an ignition signal to the sub-primary coil when the value is exceeded.
2. In the electronic control device according to claim 1,
   The ignition signal to the sub-primary coil is a signal for controlling the on / off of the switch element connected to one end of the sub-primary coil.
   The sub-primary coil is such that the switch element is turned on between the nth turn point and the n + 1th turn point, and the switch element is turned off after the n + 1th turn point. An electronic control device that sends an ignition signal to.
3. In the electronic control device according to claim 2.
   The inflection period obtained from the k-th inflection (where k is a natural number satisfying k <n) and the k + 1-th inflection in the secondary voltage is T, and is predetermined for the sub-primary coil. When the energization time is P, the time point after the lapse of TP from the nth inflection time point is set as the overlapped discharge start time point, and the sub-primary so as to turn on the switch element at the overlapped discharge start time point. An electronic control device that sends an ignition signal to the coil.
4. In the electronic control device according to claim 3,
   An inflection point detecting unit that detects an inflection point of the secondary voltage when the differential value of the secondary voltage exceeds a second predetermined value.
   A calculation unit that calculates the inflection cycle T based on the time interval between the k-th inflection point detected by the inflection point detection unit and the k + 1th inflection point.
   An electronic control device including a prediction unit that predicts a time point at which a k + second or subsequent inflection occurs in the secondary voltage based on the inflection period T calculated by the calculation unit.
5. In the electronic control device according to claim 4,
   The calculation unit is an electronic control device that measures the time interval for each of a plurality of k values and calculates the variation period T based on each measured time interval.
6. In the electronic control device according to claim 5,
   The calculation unit is an electronic control device that calculates the variation period T based on the relationship between the value of k obtained by the least squares method and each time interval or the weighted average of each time interval.
7. In the electronic control device according to claim 4,
   The calculation unit excludes inflection points whose time interval from the immediately preceding inflection point is less than a predetermined value from among the plurality of inflection points detected by the inflection point detection unit, and sets the inflection cycle T. Electronic control device to calculate.
8. In the electronic control device according to claim 3,
   An electronic control device in which k = n-1.
9. In the electronic control device according to claim 3,
   When the secondary voltage exceeds the first predetermined value before the start of the stacking discharge, the switch element is turned on at the start of the stacking discharge to the sub-primary coil. Send an ignition signal,
   When the secondary voltage exceeds the first predetermined value after the start of the stacking discharge, the switch element is turned on when the secondary voltage exceeds the first predetermined value. An electronic control device that transmits an ignition signal to the sub-primary coil.
10. Detects the inflection point in the secondary voltage generated on the secondary side of the ignition coil,
    An electronic control device that predicts the timing of the next inflection based on the timing at which the inflection was detected in the past.

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