JP7318125B2 - electronic controller - Google Patents

Description

The present invention relates to electronic control units.

In recent years, in order to improve the fuel efficiency of vehicles, internal combustion engines that have introduced technology that burns a mixture that is leaner than the stoichiometric air-fuel ratio to operate the internal combustion engine, and technology that takes in part of the exhaust gas after combustion and re-breathes it. has been developed.

In this type of control device for an internal combustion engine, the amount of fuel and air in the combustion chamber deviates from the theoretical values, so that the spark plug is more likely to fail to ignite the fuel. Therefore, by increasing the gas flow velocity in the combustion chamber, the flow velocity between the electrodes of the spark plug is increased to form a long discharge path, thereby increasing the length of contact between the discharge path and the gas. There is a method for suppressing ignition failure.
However, if the flow velocity between the electrodes of the spark plug is increased, the blowout of the discharge path and the accompanying redischarge occur more frequently. During re-discharge, 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 wear of the electrode is accelerated.

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

In Patent Document 1, an ignition coil having a main primary coil and a sub-primary coil is used, and after the main primary coil generates a discharge spark in the spark plug, it is determined in consideration of the necessary and sufficient time for the spark plug to discharge. A control device for an internal combustion engine is disclosed in which current is superimposed by an auxiliary primary coil until the superimposed current application time elapses.

JP 2019-31911 A

In the technique disclosed in Patent Document 1, the superimposed current application time is constant regardless of the combustion state, so the superimposed current application time cannot be appropriately adjusted according to cycle fluctuations of the internal combustion engine. In order to cope with cycle fluctuations, it is necessary to set the superimposed current conduction time including an excessive margin. However, when the superimposed current energization time is set in this way, the superimposed current that exceeds the amount necessary to maintain the discharge path flows, causing problems such as heat generation of the ignition coil, wear of the spark plug electrode, and deterioration of energy efficiency. Become. Conversely, if the margin of the superimposed current supply time is reduced, the energy inside the ignition coil will decrease, which may make it impossible to maintain the discharge path.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problem, and an object of the present invention is to suppress electrode wear of a spark plug in an internal combustion engine while suppressing poor ignition of gas by the spark plug.

An electronic control unit according to the present invention controls energization of an ignition coil having a main primary coil and a sub primary coil arranged on the primary side, respectively, and a secondary coil arranged on the secondary side. In the secondary voltage generated in the secondary coil, the timing at which the n-th (where n is a natural number) inflection point occurs from the point of time when the ignition signal is transmitted to the main primary coil is the n-th When the timing at which the (n+1)th inflection point occurs is the (n+1)th inflection point, the secondary voltage changes between the nth inflection point and the (n+1)th inflection point. If it exceeds a predetermined value of 1, it sends an ignition signal to the secondary primary coil.

ADVANTAGE OF THE INVENTION According to this invention, the electrode abrasion of the spark plug in an internal combustion engine can be suppressed, suppressing the ignition failure to gas by a spark plug.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining the main configuration of an internal combustion engine and a control device for the internal combustion engine according to an embodiment; FIG. 3 is a partially enlarged view for explaining a spark plug; It is a functional block diagram explaining the functional composition of the control device concerning an embodiment. FIG. 4 is a diagram for explaining the relationship between the operating state of the internal combustion engine and the gas flow velocity around the spark plug; FIG. 4 is a diagram for explaining the relationship between the discharge path between the electrodes of the ignition plug and the flow velocity; It is a figure explaining the electric circuit containing the conventional ignition coil. FIG. 5 is a diagram showing an example of a timing chart for explaining the relationship between a control signal input to an ignition coil and an output in conventional discharge control. It is a figure explaining an electric circuit containing an ignition coil concerning a 1st embodiment. FIG. 5 is a diagram showing an example of a timing chart for explaining the relationship between a control signal input to an ignition coil and an output in discharge control according to the first embodiment; It is an example of the flowchart explaining the control method of the ignition coil concerning 1st Embodiment. It is a figure explaining the method of calculating|requiring the next inflection period based on the approximation line by the least-squares method.

An electronic control device according to an embodiment of the present invention will be described below.

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

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

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

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

An electronic throttle valve driven by an electric motor is used as the throttle valve 113, but other methods may be used as long as the flow rate of air can be appropriately adjusted.

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

A crank angle sensor 121 is provided radially outside 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 every 10 degrees and every combustion cycle, for example.

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

The vehicle is also provided with an accelerator position sensor (APS) 126 that detects the amount of displacement (depression amount) of an accelerator pedal 125 . This accelerator position sensor 126 detects the torque requested by the driver. The driver's requested torque detected by the accelerator position sensor 126 is output to the control device 1, which will be described later. The control device 1 controls the throttle valve 113 based on this required torque.

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

A cylinder head (not shown) of the internal combustion engine 100 is provided with a combustion pressure sensor (Cylinder Pressure Sensor: CPS, also called an in-cylinder pressure sensor) 140 . Combustion pressure sensor 140 is provided in each cylinder 150 and detects the pressure in cylinder 150 (combustion pressure).

A piezoelectric or gauge pressure sensor is used as the combustion pressure sensor 140 so that the combustion pressure (in-cylinder pressure) in the cylinder 150 can be detected over a wide temperature range.

Each cylinder 150 is provided with an exhaust valve 152 and an exhaust manifold 160 for discharging 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 exhaust valve 152 is opened, exhaust gas is discharged from cylinder 150 to exhaust manifold 160 . This exhaust gas passes through an exhaust manifold 160 and is purified by a three-way catalyst 161 before being discharged into the atmosphere.

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

A downstream side air-fuel ratio sensor 163 is provided downstream of the three-way catalyst 161 . This downstream air-fuel ratio sensor 163 outputs a switch-like detection signal near the theoretical air-fuel ratio. In an embodiment, downstream air-fuel ratio sensor 163 is, for example, an O2 sensor.

A spark plug 200 is provided at the top of each cylinder 150 . Due to the discharge (ignition) of the spark plug 200, a spark is ignited in the mixture of air and fuel in the cylinder 150, causing an explosion in the cylinder 150 and pushing down the piston 170. As the piston 170 is pushed down, the crankshaft 123 rotates.

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

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

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

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

Discharge control (ignition control) of the spark plug 200 is performed by an ignition control section 83 of the control device 1, which will be described later.

Returning to FIG. 1, 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, the combustion pressure sensor 140, etc. are sent to the control device 1. 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 amount of fuel injection, the ignition timing of the spark plug 200, and the like. .

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

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

The analog input unit 10 receives signals from 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.

An A/D conversion section 30 is connected to the analog input section 10 . Analog output signals from various sensors input to the analog input unit 10 are subjected to signal processing such as noise removal, then converted to digital signals by the A/D converter 30 and stored in the RAM 40 .

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

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

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

By executing a control program (not shown) stored in the ROM 60, the MPU 50 arithmetically processes the output signal stored in the RAM 40 according to the control program. According to the control program, the MPU 50 calculates a control value that defines the operation amount of each actuator (for example, the throttle valve 113, the pressure regulator 132, the spark plug 200, etc.) that drives the internal combustion engine 100, and temporarily stores it in the RAM 40. .

A control value that defines the actuation 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 functions such as an ignition control section 83 (see FIG. 3) that controls the voltage applied to the spark plug 200 .

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

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

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

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

The overall control unit 81 controls the overall fuel injection control unit 82 and the ignition control unit 83 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 speed. 86, and transmits cylinder identification information S3 from the cylinder identification unit 84, crank angle information S4 from the angle information generation unit 85, and engine speed information S5 from the rotation speed information generation unit 86. accept.

The fuel injection control unit 82 also includes an intake air amount measurement unit 87 that measures the amount of air taken into the cylinder 150, a load information generation unit 88 that measures the engine load, and a temperature of the engine cooling water. The intake air amount information S6 from the intake air amount measuring unit 87, the engine load information S7 from the load information generating unit 88, and the cooling water temperature information S8 from the water temperature measuring unit 89 are connected to the water temperature measuring unit 89. , accept.

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

The ignition control unit 83 is connected to the overall control unit 81 as well as 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. and accept each information from them.

Based on the received information, the ignition control unit 83 controls the amount of current (energization angle) to be energized to the primary coil (not shown) of the ignition coil 300, the energization start time, and the amount of current to be energized to the primary coil. The time (ignition time) for interrupting the current is calculated.

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, energization start time, and ignition time, thereby performing discharge control (ignition control) by the spark plug 200. control).

Note that at least the function of the ignition control unit 83 performing ignition control of the spark plug 200 using the ignition signal SA corresponds to the electronic control device of the present invention.

FIG. 4 is a diagram for explaining the relationship between the operating state of internal combustion engine 100 and the flow velocity of gas around spark plug 200. As shown in FIG. As shown in FIG. 4, generally, the higher the engine speed and load, the higher the gas flow velocity in the cylinder 150 and the higher the flow velocity of the gas around the spark plug 200 . Therefore, gas flows at high speed between the center electrode 210 and the outer electrode 220 of the spark plug 200 . Also, in the internal combustion engine 100 in which exhaust gas recirculation (EGR) is performed, the EGR rate is set, for example, as shown in FIG. 4 according to the relationship between the engine speed and the load. As the high EGR region in which the EGR rate is set higher is expanded, lower fuel consumption and lower exhaust emissions can be achieved, but ignition failure in the spark plug 200 is more likely to occur.

FIG. 5 is a diagram for explaining the relationship between the discharge path between the electrodes of the spark plug 200 and the flow velocity.
When a high voltage is generated in the secondary side coil of the ignition coil 300 and a dielectric breakdown occurs between the center electrode 210 and the outer electrode 220 of the spark plug 200, the current flowing between these electrodes decreases to a certain value or less. During this time, a discharge path is formed between the electrodes of spark plug 200 . When combustible gas comes into contact with this discharge path, a flame kernel grows and burns. Since the discharge path moves under the influence of the gas flow between the electrodes, the higher the gas flow rate, the shorter the discharge path is formed, and the lower the gas flow rate, the shorter the discharge path. FIG. 5(a) shows an example of the discharge path 211 when the gas flow velocity is high, and FIG. 5(b) 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 flame kernel is less likely to grow even if the combustible gas comes into contact with the discharge path, so it is necessary to increase the chances of the combustible gas coming into contact with the discharge path. As described above, the discharge path is generated by breaking the gas insulation, so if the current required to maintain the discharge path is constant, it is necessary to output power corresponding 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. By forming 211, it is preferable to obtain a wider space of gas and contact opportunities. 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 electric power is continuously output from the ignition coil 300 to the ignition plug 200 for a long period of time. By maintaining the formation of the discharge path 212, it is preferable to obtain contact opportunities with the gas passing near the electrodes of the spark plug 200 for a longer period of time.

[Electric circuit of conventional ignition coil]
Next, prior to describing embodiments of the present invention, a 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. be done.

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

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

A base (B) terminal of the igniter 340 is connected to the ignition control section 83 . The ignition signal SA output from the ignition control section 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 electrically connected. 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, 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 interrupted, a high voltage corresponding to the turns ratio of the coil to the primary coil 310 is applied to the secondary coil. It occurs in coil 320 .

A high voltage generated in the secondary coil 320 by the ignition signal SA is applied to the spark plug 200 (center electrode 210), thereby generating a potential difference 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 mixture in the cylinder 150), the gas component breaks down and the center electrode 210 and the outer electrode 220 are separated. Discharge is generated between and ignition of the fuel (air-fuel mixture) is performed.

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

[Conventional discharge control of ignition coil]
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 conventional discharge control. The timing chart of FIG. 7 is an example when the spark plug 200 is discharged when the conventional ignition coil 300C is used and the gas flows at a high velocity. In FIG. 7, the ignition signal SA output from the ignition control unit 83, the primary current I1 flowing through the primary side coil 310 in response to the ignition signal SA, the electric energy E accumulated in the ignition coil 300C, the secondary side The relationship between secondary current I2 flowing in coil 320 and secondary voltage V2 generated in secondary coil 320 is shown. The secondary current I2 and the secondary voltage V2 are measured at points between the ignition plug 200 and the ignition coil 300C, as shown in FIG. 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 increases. While the primary coil 310 is energized, the electric energy E in the ignition coil 300C increases 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 secondary coil 320, and supply of electric energy E from ignition coil 300C to spark plug 200 is started. When the insulation between the electrodes of spark plug 200 is broken, discharge of spark plug 200 is started. Discharge of spark plug 200 accompanied by such dielectric breakdown is called capacitive discharge. After the ignition plug 200 starts discharging, the electric energy E in the ignition coil 300C decreases with time, and the discharge of the ignition plug 200 is maintained. A discharge of the spark plug 200 without such dielectric breakdown is called an inductive discharge.

The secondary current I2 rises significantly during capacity discharge. The secondary current I2 due to this capacitive discharge ends in a short period of 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 decreases with time during subsequent induction discharge. Since the discharge path expands along with the flow of gas, the secondary voltage V2 rises with the lapse of time, and along with this, the electrical energy required to maintain the discharge path (discharge required energy) rises. On the other hand, the electric energy E supplied from the ignition coil 300C to the ignition 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 blows 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 substantially 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, gas pressure changes associated with vortex separation occur at regular intervals. Since this gas pressure change destabilizes the discharge path, it causes the discharge path to blow out. Therefore, as shown in FIG. 7, after the discharge start point A at the secondary voltage V2, there are inflection points B, C, and D representing changes in the gas pressure during the continuation of the discharge, and inflection points representing blow-out of the discharge path. E occurs at regular intervals. That is, from the period of the inflection point of the secondary voltage V2, the timing of the inflection point after the next time is estimated, and from the estimation result of the timing of the next inflection point when the secondary voltage V2 reaches or exceeds a certain value, If the additional electrical energy E is supplied to the spark plug 200 in time with the timing, the probability of blowout of the discharge path can be reduced.

Further, if sufficient electrical energy E still remains in the ignition coil 300C when the discharge path blows out, the spark plug 200 uses this electrical energy E to discharge at the shortest distance between the electrodes. resumed. As a result, as shown in FIG. 7, the spark plug 200 repeatedly blows out the discharge path and re-discharges. Since dielectric breakdown occurs between the electrodes when discharge is restarted, 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 blowing out tends to occur, and the cycle of re-discharge becomes shorter, resulting in an increase in the number of re-discharges. Since this causes an increase in the amount of evaporation of the electrode material and causes a decrease in the life of the electrode, it is desirable to reduce blowout during the discharge period as much as possible.

In the present invention, instead of the ignition coil 300C described in FIG. 6, an ignition coil 300 having two primary coils is adopted, and discharge control is performed on this ignition coil 300, thereby suppressing the number of capacitive discharges. discharge of the ignition plug 200 is realized.

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

FIG. 8 is a diagram illustrating an electric circuit 400 including the ignition coil 300 according to the first embodiment of the invention. In the electric circuit 400, the ignition coil 300 includes two types of primary coils 310 and 360 each wound with a predetermined number of turns, and a secondary coil 310 and 360 wound with a larger number of turns than the primary coils 310 and 360. and a coil 320 . Here, when the ignition plug 200 is ignited, the power from the primary coil 310 is first supplied to the secondary coil 320, and then the power from the primary coil 360 is supplied to the secondary coil 320 on top of that power. supplied to Therefore, hereinafter, primary coil 310 is referred to as "main primary coil", and primary coil 360 is referred to as "sub primary coil". Also, the current flowing through the main primary coil 310 is referred to as "main primary current", and the current flowing through the primary secondary coil 360 is referred to as "sub primary current".

One end of the main primary coil 310 is connected to the DC power supply 330 . Thereby, a predetermined voltage (for example, 12 V 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 that is a switch element for switching the conductive 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 .

A base (B) terminal of the igniter 340 is connected to an ignition signal output section 384 provided in the ignition control section 83 . The ignition signal output unit 384 outputs an ignition signal SA as a signal for controlling on/off of the igniter 340 . The ignition signal SA output from the ignition signal output section 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. ) 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, the main primary current flows through the main primary coil 310, and electric power (electrical energy) is accumulated. 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, the main primary current flowing through the main primary coil 310 is interrupted. A high voltage corresponding to the turns ratio is generated in the secondary coil 320 .

One end of the sub 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 (eg, 12 V in the embodiment) is applied to the sub primary coil 360 as well.

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

A base (B) terminal of the igniter 350 is connected to an ignition signal output section 384 provided in the ignition control section 83 . The ignition signal output unit 384 outputs an ignition signal SB as a signal for controlling on/off of the igniter 350 . The ignition signal SB output from the ignition signal output section 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 secondary primary coil 360 of the ignition coil 300 via the igniter 350, and the secondary primary current flows through the secondary 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 turns ratio of the coil with respect to the sub primary coil 360 changes to 2. It occurs in the secondary coil 320 .

The high voltage generated in the secondary coil 320 by the ignition signal SA is added to the high voltage generated in the secondary coil 320 by the ignition signal SB. 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 mixture in the cylinder 150), the gas component breaks down and the center electrode 210 and the outer electrode 220 are separated. Discharge is generated between and ignition of the fuel (air-fuel mixture) is performed.

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

The ignition control section 83 is provided with an inflection point detection section 381 , a calculation section 382 , a prediction section 383 and an ignition signal output section 384 . These are implemented as functions of the ignition control unit 83, and as described with reference to FIGS. be done.

The inflection point detection unit 381 calculates a differential value of the secondary voltage V2 detected by the voltage detection unit 370, and changes the value of the secondary voltage V2 at that time when the differential value exceeds a predetermined threshold. Detect as an inflection point. 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 is set when the inflection point detection unit 381 detects an inflection point.

The calculator 382 calculates the period of the inflection points detected by the inflection point detector 381 . Here, as described above, in the secondary voltage V2, the cycle of the inflection point is calculated assuming that the inflection point corresponding to the gas pressure change caused by the separation of the Karman vortices occurs at regular intervals. 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 (where k is a natural number) inflection point and the next k+1-th inflection point The time interval is measured and the period of inflection points is calculated from this time interval.

Based on the cycle of the inflection points calculated by the calculation unit 382, the prediction unit 383 predicts the next and subsequent inflection points in the secondary voltage V2. Specifically, the timing of the next inflection point is predicted to be the time when the cycle of the inflection point has passed since the time when the last inflection point was detected.

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

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

In the ignition signal output section 384, the part that controls the output of the ignition signal SA and the part 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 section 83 . In either case, since the relevant portion operates according to the control of the ignition control section 83, it can be said that the ignition control section 83 controls the energization of the ignition coil 300. FIG.

[First Embodiment: Ignition Coil Discharge Control]
Next, 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 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 ignition coil 300 of the present embodiment is used and the gas flows at a high velocity. FIG. 9 shows an ignition signal SA output from the ignition signal output section 384, a main primary current I1 flowing through the main primary coil 310 in response to the ignition signal SA, and an ignition signal output from the ignition signal output section 384. SB, the sub primary current I3 flowing through the sub primary coil 360 in response to the ignition signal SB, the electrical energy E accumulated in the ignition coil 300, the secondary current I2 flowing through the secondary coil 320, and the secondary side It shows the relationship between the secondary voltage V2 generated in the coil 320 and the differential value dV2/dt of the secondary voltage V2. The secondary voltage V2 is detected by a voltage detector 370 provided between the ignition plug 200 and the ignition coil 300, as shown in FIG. Also, the differential value dV2/dt of the secondary voltage V2 is calculated by the inflection point detector 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 increases. While the main primary coil 310 is energized, the electric energy E in the ignition coil 300 increases 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 secondary coil 320, and supply of electrical energy E from ignition coil 300 to spark plug 200 is started. When the insulation between the electrodes of spark plug 200 is broken, discharge (capacitive discharge) of spark plug 200 is started. After the ignition plug 200 starts discharging, the electric energy E in the ignition coil 300 decreases with time, and the discharge (induction discharge) of the ignition plug 200 is maintained.

Secondary current I2 and secondary voltage V2 rise significantly during capacity discharge. The increase in secondary current I2 and secondary voltage V2 due to this capacity discharge ends in a short period of time. When spark plug 200 starts to discharge and a discharge path is formed between the electrodes, secondary current I2 and secondary voltage V2 drop sharply. During the subsequent inductive discharge, the secondary current I2 decreases with time. On the other hand, since the discharge path expands with the gas flow, the secondary voltage V2 increases with time.

After the ignition signal SA changes from HIGH to LOW and capacity discharge is started, when the differential value dV2/dt of the secondary voltage V2 becomes equal to or greater than a predetermined threshold 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, each time the value of the secondary voltage V2 becomes equal to or greater than the threshold dV2/dt_th after the discharge start point A has passed, the inflection points B, C, D, E, and F are sequentially detected.

When the inflection points B and C of the secondary voltage V2 are detected by the inflection point detection unit 381, the calculation unit 382 calculates the time interval T1 from the inflection point B to the inflection point C, and determines the time interval T1 from the inflection point B to the inflection point C. Let T1 be the inflection period T of the secondary voltage V2. The prediction unit 383 uses the inflection period T=T1 obtained by the calculation unit 382 to predict the timing of the next inflection point of the secondary voltage V2. That is, it is estimated that the next inflection point D occurs in the secondary voltage V2 when the inflection period T1 has passed from the inflection point C. FIG.

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 uses the inflection period T=T2 obtained by the calculation unit 382 to predict the timing of the next inflection point of the secondary voltage V2. That is, it is estimated that the next inflection point E occurs in the secondary voltage V2 when the inflection period T2 has passed from the inflection point D.

When the value of the secondary voltage V2 exceeds a predetermined threshold value V2_th between the inflection point D and the inflection point E, the ignition signal output unit 384 detects the occurrence time of the most recent inflection point (here, the inflection point D). , 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 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. to decide.

Specifically, if the time point at which the most recent inflection point is detected is tn, the timing for changing the ignition signal SB to HIGH (overlapping discharge start time th) and the timing for returning the ignition signal SB to LOW after that (overlapping discharge start time th) are determined. The end time tl) is represented by, for example, the following equations (1) and (2), respectively.
th=tn+TP (1)
tl=tn+T+p (2)

In Equation (1), P represents the energization time of the sub primary coil 360 . This energization time P is set in advance according to the amount of electric energy to be supplied from the sub primary coil 360 to the ignition plug 200 in order to suppress blowout of the discharge path and the amount of electric energy that can be stored in the sub primary coil 360. is set. Also, in the expression (2), p represents the margin of the energization time for the sub primary coil 360 . This margin p is included in the energization period of the sub 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 H.383.

When the value of the secondary voltage V2 exceeds the predetermined threshold value V2_th, the ignition signal output unit 384 repeats the above control until the secondary current I2 decreases and the discharge between the electrodes stops. As a result, the ignition signal SB is 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, points G and I represent superimposed discharge start times th with respect to inflection points E and F, respectively, which are determined based on equation (1). Also, points H and J represent overlapped discharge end times th with respect to inflection points E and F, respectively, which are determined based on equation (2).

While the ignition signal output unit 384 is outputting the ignition signal SB to the igniter 350, the high voltage generated in the secondary coil 320 by the ignition signal SB is added to the high voltage generated in the secondary coil 320 by the ignition signal SA. Join. This high voltage is applied to spark plug 200 (center electrode 210). As a result, the secondary current I2 increases to continue maintaining the discharge path. Therefore, occurrence of re-discharge (restrike) accompanied by capacitive discharge in spark plug 200 is suppressed. The secondary current I2 at this time includes the current flowing through the secondary coil 320 from the main primary coil 310 (hereinafter referred to as "first induced current") and the current flowing through the secondary coil from the sub primary coil 360. 320 (hereinafter referred to as "second induced current").

As shown in FIG. 9, since the change in the 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 necessary detection sensitivity cannot be obtained. Sometimes. Therefore, in the present embodiment, the differential value dV2/dt is calculated by time-differentiating the secondary voltage V2, and the inflection point of the secondary voltage V2 is detected by comparing this differential value with a predetermined threshold value dV2/dt_th. I am trying to However, the time differentiation is not limited to the first-order differentiation, and second-order differentiation and third-order differentiation may be used as necessary. If the inflection point necessary for calculating the period cannot be detected before the threshold value dV2/dt_th is reached, the ignition timing for the secondary coil is determined based on a predefined specified value. can be

[First Embodiment: Ignition Coil Discharge Control Flow]
Next, a method of controlling the ignition coil 300 by the ignition control unit 83 when performing the above discharge control will be described. FIG. 10 is an example of a flowchart illustrating a control method for the ignition coil 300 by the ignition control section 83 according to the first embodiment of the present invention. In this embodiment, when the ignition switch of the vehicle is turned on and the internal combustion engine 100 is powered on, the ignition control unit 83 starts controlling the ignition coil 300 according to the flowchart of FIG. The processing shown in the flowchart of FIG. 10 represents the processing for one cycle of the internal combustion engine 100, and the ignition control unit 83 performs the processing 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 discharge, the ignition control unit 83 starts operating to control the ignition signal SB.

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

In step S203, the inflection point detector 381 in the ignition controller 83 calculates the time differential dV2/dt of the secondary voltage V2 detected by the voltage detector 370, and compares it with a predetermined threshold value dV2/dt_th. As a result, when the differentiated 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 an inflection point.

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

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 less than 2, i.e., if i remains at the initial value of 1, the process proceeds to step S208.

In step S206, the calculator 382 in the ignition controller 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-1th inflection point in the previous step S204 and the i-th inflection point recorded for the i-th inflection point in this step S204 A difference from the inflection point ti is obtained, and this difference value is defined as the i-1 time interval T(i-1).

In step S207, the prediction unit 383 in the ignition control unit 83 stores the value of the i−1-th time interval T(i−1) calculated in step S206 as the inflection period T of the secondary voltage V2 in the internal memory. to record. Thus, the timing at which the (i+1)th 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 current value of the secondary voltage V2 detected by the voltage detection unit 370 with a predetermined threshold value V2_th. Also, by applying the above-described formulas (1) and (2) with tn=ti to the most recent inflection point ti recorded in step S204, the overlapping discharge start time for the i-th inflection point ti 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 greater than the threshold value V2_th and the current time is between the superimposed discharge start time th and the superimposed discharge end time tl, that is, within the superimposed 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 section 384 in the ignition control section 83 makes the ignition signal SB output to the igniter 350 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 overlapping discharge start time th between the latest inflection time ti and the next inflection time t(i+1). , the ignition signal SB to the secondary primary coil 360 is transmitted. After that, the process returns to step S203.

In step S211, the ignition signal output section 384 in the ignition control section 83 sets the ignition signal SB to be output to the igniter 350 to LOW. As a result, the ignition signal SB to the sub primary coil 360 is transmitted so that the igniter 350 is turned off at the overlapping discharge end time tl after the next inflection time t(i+1). After that, the process returns to step S203.

Here, in steps S209 and S210, the ignition signal SB is output when both the condition that the value of the secondary voltage V2 is equal to or greater than the threshold V2_th and the condition that the current time is within the overlapping discharge period are satisfied. HIGH. Therefore, when the value of the secondary voltage V2 exceeds the threshold value V2_th before the superimposed discharge start time th, the ignition signal SB becomes HIGH at the superimposed discharge start time th, and the igniter 350 is turned on accordingly. As a result, the supply of electric energy from the secondary coil 360 to the secondary coil 320 is started. On the other hand, when the value of the secondary voltage V2 exceeds the threshold V2_th after the overlapping discharge start time th, the ignition signal SB is made HIGH at the time when the value of the secondary voltage V2 exceeds the threshold V2_th. When the igniter 350 is turned on in response, electric energy supply from the auxiliary primary coil 360 to the secondary coil 320 is started. Therefore, in either case, electric energy can be supplied from the secondary 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 after the next time is estimated on the assumption 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 air dilution increases, it is necessary to advance the ignition timing in accordance with the decrease in combustion speed. In this case, the volume inside the cylinder during the discharge period is relatively large, and the gas flow state is maintained at a high flow rate. Therefore, the period of the inflection point of the secondary voltage V2 cannot be kept constant. In this way, when the change in gas flow velocity and turbulence in 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 flow velocity change 1]
The calculation unit 382 in the ignition control unit 83 calculates an approximation line using the least squares method from the inflection period for each inflection point obtained in the past, and determines the next inflection period based on the approximation line. . Specifically, for example, in step S206 of FIG. 10, time intervals Ti(i = 1 to n-1) are calculated. In such a case, an approximate straight line 500 that approximates the relationship between points 501 to 507 is calculated by the method of least squares, and the value of point 508 on the approximate straight line 500 when i=n is the n-th inflection point. to the next (n+1)-th inflection point. That is, the time interval between the k-th (where k is a natural number satisfying k<n) and the k+1-th inflection point in the secondary voltage V2 is measured for a plurality of k values, and the measured k The relationship between the value and each time interval is obtained by the method of least squares, and the next inflection period T can be calculated from the relationship. Since this method requires complicated calculations in a short calculation cycle, it is appropriate to use a linear correlation for the least squares method.

[Response to flow velocity change 2]
If the flow velocity changes irregularly, the above method increases the number of orders and increases the computational load, making it impractical. In such a case, the next inflection period can be obtained by weighted averaging the inflection period for each inflection point obtained in the past. In this method, when the number of samples of the inflection period to be weighted and averaged is small, the weighting factor of each inflection period may be changed according to the number of samples. For example, if the number of samples is 2, that is, if up to three inflection points have already been detected, and the calculation unit 382 has already calculated these time intervals as inflection periods T1 and T2, each inflection period is set to 0.5. Further, when the number of samples is 3, that is, when up to four inflection points have already been detected and the calculation unit 382 has already calculated these time intervals as inflection periods T1, T2, and T3, each inflection point The weighting factor of the music cycle is set to 0.33.
Furthermore, a difference may be added to the weighting factor for each inflection period. For example, the inflection period of an older (earliest order) inflection point can be given a smaller weighting factor, and conversely, the weighting factor of a newer (slower order) inflection point can be given a larger weighting factor.

[Response to flow turbulence 1]
When the in-cylinder flow tumble collapses, 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 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 point whose time interval from the calculated immediately preceding inflection point is less than a predetermined minimum pulse width (period) may be excluded from subsequent processing. Note that, for example, a digital filter can be applied in this method.

[Response to flow turbulence 2]
Further, as a simple method when it is difficult to apply a digital filter, within a predetermined time from the start of discharge, or predetermined secondary voltage V2, secondary current I2, tertiary current I3, 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 inflection period. By doing so, it becomes possible to suppress wasteful energy consumption in a state in which the possibility of blowing out of the discharge path is low.

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

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

(2) The ignition signal SB to the sub primary coil 360 is a signal for controlling on/off of the igniter 350 which is a switching element connected to one end of the sub primary coil 360 . The control device 1 turns on the igniter 350 between the n-th inflection point and the n+1-th inflection point, and turns off the igniter 350 after the n+1-th inflection point. to send an ignition signal to Specifically, T is the inflection period obtained from the k-th (where k is a natural number satisfying k<n) inflection point and the k+1-th inflection point in the secondary voltage V2, and the sub primary coil 360 On the other hand, when the predetermined energization time is P, the time after TP has passed from the n-th inflection time tn represented by Equation (1) is set as the superimposed discharge start time th, and this superimposed discharge start time th to turn on the igniter 350 at step S209, S210. Since this is done, additional electrical energy E is supplied from the ignition coil 300 to the spark plug 200 in time with the timing of the next inflection point when the secondary voltage V2 exceeds a certain level. An ignition signal SB to the primary coil 360 can be sent. Therefore, it is possible to effectively reduce the probability that the discharge path will blow out due to periodic changes in gas pressure associated with separation of Karman vortices generated downstream of the electrode.

(3) The control device 1 includes an inflection point detector 381 , a calculator 382 , and a predictor 383 . The inflection point detection unit 381 detects an inflection point of the secondary voltage V2 when the differential value dV2/dt of the secondary voltage V2 exceeds a second predetermined value (threshold dV2/dt_th) (step S203). ). The calculation unit 382 calculates the inflection period T based on the time interval between the kth inflection point and the k+1th inflection point detected by the inflection point detection unit 381 (step S206). Based on the inflection period T calculated by the calculation unit 382, the prediction unit 383 predicts the time points at which the k+2th and subsequent inflection points occur in the secondary voltage V2 (step S207). Since this is done, the timing of the next inflection point can be reliably predicted by reflecting the periodic change in the gas pressure that accompanies separation of the Karman vortices.

(4) The calculator 382 can measure the time intervals for a plurality of k values and calculate the inflection period T based on each measured time interval. For example, the inflection period T can be calculated based on the relationship between the value of k obtained by the method of least squares and each time interval or the weighted average of each time interval. In this way, even if changes in gas flow velocity or turbulence in the flow cannot be ignored, the transmission timing of the ignition signal SB to the sub primary coil 360 can be appropriately determined.

(5) The calculation unit 382 also excludes an inflection point 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 381, The period T can also be calculated. In this way, 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 electrodes, the ignition signal SB to the sub primary coil 360 is generated. The transmission timing can be appropriately determined.

(6) When calculating the inflection period T in the calculation unit 382, k=n−1 and calculating the inflection period T from the time interval between the most recent inflection point and the previous inflection point. 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 point, reflecting the most recent gas state in the cylinder.

(7) If the secondary voltage V2 exceeds the first predetermined value before the superimposed discharge start time th, the control device 1 turns on the igniter 350 at the superimposed discharge start time th. An ignition signal SB is transmitted to the primary coil 360 (steps S209, S210). Further, when the secondary voltage V2 exceeds the first predetermined value after the superimposed discharge start time th, the igniter 350 is turned on when the secondary voltage V2 exceeds the first predetermined value. , an ignition signal SB to the auxiliary primary coil 360 (steps S209, S210). Since it did in this way, even if it is any case, electric energy supply to the secondary side coil 320 from the sub primary coil 360 to the appropriate timing according to the next inflection point can be performed.

(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 determines the next inflection point based on the timing at which the inflection point was detected in the past. The timing of the curve point is predicted (step S207). Since this is done, the timing of the next inflection point can be reliably predicted by reflecting the periodic change in the gas pressure that accompanies separation of the Karman vortices.

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. Moreover, although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

1: control device, 10: analog input section, 20: digital input section, 30: A/D conversion section, 40: RAM, 50: MPU, 60: ROM, 70: I/O port, 80: output circuit, 81 82: Fuel injection control unit 83: Ignition control unit 84: Cylinder determination unit 85: Angle information generation unit 86: Rotational speed information generation unit 87: Intake amount measurement unit 88: Load information Generation unit 89: Water temperature measurement unit 100: Internal combustion engine 110: Air cleaner 111: Intake pipe 112: Intake manifold 113: Throttle valve 113a: Throttle opening sensor 114: Flow rate sensor 115: Intake air temperature sensor , 120: ring gear, 121: crank angle sensor, 122: water temperature sensor, 123: crankshaft, 125: accelerator pedal, 126: accelerator position sensor, 130: fuel tank, 131: fuel pump, 132: pressure regulator, 133: Fuel pipe 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: Spark plug 210: Center electrode 220: Outer electrode 230: Insulator 300, 300C: Ignition coil 310: Main primary coil 320: Secondary coil , 330: DC power supply, 340, 350: igniter, 360: secondary primary coil, 370: voltage detection unit, 381: inflection point detection unit, 382: calculation unit, 383: prediction unit, 384: ignition signal output unit, 400, 400C: electric circuit

Claims (10)

An electronic control device for controlling energization of an ignition coil having a main primary coil and a sub primary coil arranged on the primary side and a secondary coil arranged on the secondary side,
In the secondary voltage generated in the secondary coil, the n-th inflection point is the timing at which the n-th (where n is a natural number) inflection point occurs from the point of time when the ignition signal to the main primary coil is transmitted. Assuming that the timing at which the (n+1)th inflection point occurs is the (n+1)th inflection point, the secondary voltage between the nth inflection point and the (n+1)th inflection point is the first predetermined An electronic controller that sends an ignition signal to the sub-primary coil when a value is exceeded. In the electronic control device according to claim 1,
The ignition signal to the sub primary coil is a signal for controlling on/off of a switch element connected to one end of the sub primary coil,
The auxiliary primary coil is turned on between the n-th inflection point and the n+1-th inflection point, and turned off after the n+1-th inflection point. electronic control unit that sends the ignition signal to In the electronic control device according to claim 2,
Let T be an inflection period obtained from the k-th (where k is a natural number satisfying k<n) inflection point and the k+1-th inflection point in the secondary voltage, and is predetermined for the sub primary coil Assuming that the energization time is P, the time point after TP has passed from the n-th inflection point is set as the overlapped discharge start point, and the secondary primary is turned on at the overlapped discharge start point. An electronic control unit that sends the ignition signal to the coil. In the electronic control device according to claim 3,
an inflection point detection 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 period T based on the time interval between the k-th inflection point detected by the inflection point detection unit and the k+1-th inflection point;
an electronic control unit, comprising: a predicting unit that predicts a point in time at which a k+2-th or later inflection point occurs in the secondary voltage, based on the inflection period T calculated by the calculating unit. In the electronic control device according to claim 4,
The electronic control unit, wherein the calculator measures the time intervals for a plurality of values of k and calculates the inflection period T based on each of the measured time intervals. In the electronic control device according to claim 5,
The calculator calculates the inflection period T based on the relationship between the k value obtained by the least squares method and each time interval or a weighted average of each time interval. In the electronic control device according to claim 4,
The calculation unit calculates the inflection period T by excluding an inflection point 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. Electronic controller that calculates. In the electronic control device according to claim 3,
An electronic controller with k=n−1. In the electronic control device according to claim 3,
When the secondary voltage exceeds the first predetermined value before the start of the superimposed discharge, the switch element is turned on at the start of the superimposed discharge. send an ignition signal,
When the secondary voltage exceeds the first predetermined value after the start of the superimposed discharge, the switch element is turned on when the secondary voltage exceeds the first predetermined value. , an electronic control unit that transmits an ignition signal to the secondary primary coil. Detecting an inflection point in the secondary voltage generated on the secondary side of the ignition coil,
calculating the period of the inflection point based on the timing at which the previous inflection point was detected and the timing at which the current inflection point was detected ;
An electronic control unit for predicting the timing of the next inflection point based on the calculated period of the inflection point.

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