WO2023223488A1 - Internal combustion engine control device and internal combustion engine control method - Google Patents

Abstract

The purpose of the present invention is to suppress the generation of hydrocarbon from an internal combustion engine. This internal combustion engine control device controls an internal combustion engine including an ignition device having an ignition plug and an ignition coil that causes the ignition plug to generate a discharge. The internal combustion engine control device comprises a control unit that outputs an output signal to the ignition device. The output signal includes a multiple-ignition signal for preheating the ignition plug, a main ignition signal for igniting an air-fuel mixture by means of the discharge of the ignition plug, the main ignition signal having a frequency different from that of the multiple-ignition signal, and a pre-charge signal for pre-charging the ignition coil.

Description

Internal combustion engine control device and internal combustion engine control method

The present invention relates to an internal combustion engine control device and an internal combustion engine control method.

Conventionally, it is known that an internal combustion engine generates a large amount of hydrocarbons (HC) when the engine is started cold, when the temperature of each part is about the same as the outside air temperature. There are two main reasons why hydrocarbons are generated during cold engine startup. The first is that due to the low in-cylinder temperature, unvaporized fuel is discharged as hydrocarbons without being oxidized (unburned). The second problem is that due to the low in-cylinder temperature, less fuel is vaporized by the ignition timing, and the air-fuel ratio of the in-cylinder mixture increases (fuel becomes diluted). In this case, the required ignition energy increases, resulting in more ignition failures and extinguishing (misfires), which increases the amount of hydrocarbons.

Furthermore, at the time of cold start, control is performed to increase the fuel injection amount to be greater than the fuel injection amount after warm-up. As a result, the amount of hydrocarbons generated during cold engine startup increases further.

Incidentally, in order to purify hydrocarbons and the like generated from the internal combustion engine, an exhaust catalyst is provided in the exhaust pipe. Exhaust catalysts use expensive precious metals such as platinum. In order to improve exhaust performance, if a larger amount of precious metal than before is used in an exhaust catalyst, the manufacturing cost of the exhaust catalyst will increase significantly. Therefore, attempts have been made to reduce the amount of hydrocarbons generated by controlling the ignition device to reduce ignition failure and flame extinction in response to the increase in required ignition energy during cold engine starts.

For example, Patent Document 1 discloses a control device for an internal combustion engine in which additional ignition is performed immediately after the normal ignition timing (main ignition) near compression top dead center in one combustion cycle of the internal combustion engine. has been done. According to this technique, ignition failure and flame extinction are reduced compared to the case where discharge is performed only once per combustion cycle with normal ignition timing. In addition, the amount of hydrocarbons generated during cold engine startup is reduced.

Japanese Patent Application Publication No. 2020-165352

By the way, when discharge is performed two or more times for the purpose of ignition during one combustion cycle of one cylinder, the amount of heat generated by the ignition coil increases. As a result, the ignition coil may be damaged by heat damage.

In the control device for an internal combustion engine disclosed in Patent Document 1, when a multi-ignition permission condition for performing two or more discharges during one combustion cycle is satisfied, the length of time that the ignition coil is energized is shortened. . As a result, the main ignition energization time, ie, the charging energy to the ignition coil, is reduced compared to when ignition is performed only once during one cycle.

If the charging energy to the ignition coil is reduced in this way, dielectric breakdown may not occur during discharge, or the required ignition energy may not be reached. As a result, ignition failure (extinction) occurs. Therefore, in the control device for an internal combustion engine described in Patent Document 1, ignition failure (extinction) is likely to occur under the multiple ignition permission condition, making it difficult to suppress the generation of hydrocarbons.

In view of the above problems, it is an object of the present invention to provide an internal combustion engine control device and an internal combustion engine control method that suppress the generation of hydrocarbons during cold starting of an internal combustion engine.

In order to solve the above problems and achieve the present object, an internal combustion engine control device of the present invention controls an internal combustion engine that includes an ignition device that has a spark plug and an ignition coil that causes the spark plug to generate discharge. The internal combustion engine control device includes a control section that outputs an output signal to the ignition device. The output signals are a multiple ignition signal for preheating the spark plug, a frequency different from the multiple ignition signal, a main ignition signal for igniting the air-fuel mixture by discharging the spark plug, and a main ignition signal for precharging the ignition coil. and a pre-charging signal for performing.

According to the present invention, it is possible to increase the charging energy to the ignition coil as much as possible to ensure appropriate implementation of ignition control during cold engine startup, and to suppress the generation of hydrocarbons from the internal combustion engine.

FIG. 1 is an overall configuration diagram showing an example of the basic configuration of an internal combustion engine according to an embodiment. FIG. 2 is a partially enlarged view illustrating a spark plug according to an embodiment. FIG. 1 is a functional block diagram illustrating a functional configuration of an internal combustion engine control device according to an embodiment. FIG. 3 is a diagram illustrating the relationship between electrode temperature, minimum ignition energy, and air-fuel ratio. FIG. 2 is a circuit diagram showing an example of an electric circuit including an ignition coil. This is an example of a discharge waveform of multiple ignitions. It is a figure explaining the relationship between the number of misfires and the amount of hydrocarbon emissions. FIG. 3 is a diagram showing the relationship between the number of misfires and the environmental temperature. FIG. 3 is a diagram showing the relationship between hydrocarbons and environmental temperature. FIG. 3 is a diagram showing transitions when multiple ignition and main ignition are executed. FIG. 2 is a conceptual diagram showing the relationship between the amount of heat generated and ignitability with respect to the frequency of an ignition signal. FIG. 2 is a conceptual diagram showing the relationship between the transition time and the temperature of the ignition coil in the case of multiple ignition and the case of no multiple ignition. 2 is a timing chart showing changes in temperature and HC concentration of a conventional ignition coil. FIG. 1 is a circuit diagram showing an example of an electric circuit including an ignition coil according to an embodiment. 7 is a flowchart showing multiple ignition switching processing according to one embodiment. It is a flow chart which shows fuel injection amount switching processing concerning one embodiment. 5 is a timing chart showing multiple ignition switching processing according to one embodiment. It is a flow chart which shows an example of fuel injection amount switching processing concerning one embodiment. 2 is a timing chart showing the relationship between the operating state of an internal combustion engine installed in a general automobile and a multiple discharge permission period. It is a correlation graph showing the relationship between equivalence ratio and minimum ignition energy.

<Embodiment>
An internal combustion engine control device according to an embodiment will be described below. Note that common members in each figure are given the same reference numerals.

[Internal combustion engine system]
First, the configuration of an internal combustion engine system according to an embodiment will be described. FIG. 1 is an overall configuration diagram showing an example of the basic configuration of an internal combustion engine according to an embodiment of the present invention.

Although the internal combustion engine 100 shown in FIG. 1 may have a single cylinder or multiple cylinders, in the embodiment, the internal combustion engine 100 having four cylinders will be described as an example.

As shown in FIG. 1, in the internal combustion engine 100, air (intake) sucked in from the outside flows through an air cleaner 110, an intake pipe 111, and an intake manifold 112. Air that has passed through the intake manifold 112 flows into each cylinder 150 when the intake valve 151 opens. The amount of air flowing into each cylinder 150 is adjusted by the throttle valve 113. The amount of air adjusted by the throttle valve 113 is measured by a flow sensor 114.

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

In this embodiment, an electronic throttle valve driven by an electric motor is used as the throttle valve 113. However, the throttle valve according to the present invention may be of any other type as long as it can appropriately adjust the flow rate of air.

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

A crank angle sensor 121 is provided on the radially outer side of the ring gear 120 attached to the crankshaft 123. Crank angle sensor 121 detects the rotation angle of crankshaft 123. In this embodiment, the crank angle sensor 121 detects the rotation angle of the crankshaft 123 every 10 degrees and every combustion cycle.

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

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

The fuel stored in the fuel tank 130 is sucked and pressurized by the fuel pump 131. The fuel sucked and pressurized by the fuel pump 131 is regulated to a predetermined pressure by a pressure regulator 132 provided in a fuel pipe 133. Then, the fuel adjusted to a predetermined pressure is injected into each cylinder 150 from a fuel injection device (injector) 134. Excess fuel after the pressure is regulated by the pressure regulator 132 is returned to the fuel tank 130 via a return pipe (not shown).

Control of the fuel injection device 134 is performed based on a fuel injection pulse (control signal) from a fuel injection control section 82 (see FIG. 3) of the internal combustion engine control device 1, which will be described later.

A cylinder pressure sensor (also referred to as a combustion pressure sensor) 140 is provided in the cylinder head (not shown) of the internal combustion engine 100. The cylinder pressure sensor 140 is provided inside the cylinder 150 and detects the pressure (combustion pressure) inside the cylinder 150. As the cylinder pressure sensor 140, for example, a piezoelectric pressure sensor or a gauge pressure sensor is applied. Thereby, the cylinder pressure inside the cylinder 150 can be detected over a wide temperature range.

An exhaust valve 152 and an exhaust manifold 160 are attached to each cylinder 150. When the exhaust valve 152 opens, exhaust gas is discharged from the cylinder 150 to the exhaust manifold 160. The exhaust manifold 160 discharges 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. The three-way catalyst 161 purifies exhaust gas. Exhaust gas purified by the three-way catalyst 161 is discharged into the atmosphere.

An upstream air-fuel ratio sensor 162 is provided upstream of the three-way catalyst 161. The upstream air-fuel ratio sensor 162 continuously (linearly) detects the air-fuel ratio of exhaust gas discharged from each cylinder 150. The upstream air-fuel ratio sensor 162 of this embodiment is a linear air-fuel ratio sensor.

Further, downstream of the three-way catalyst 161, a downstream air-fuel ratio sensor 163 is provided. The downstream air-fuel ratio sensor 163 outputs a detection signal that changes binary depending on whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio. The downstream air-fuel ratio sensor 163 of this embodiment is an O2 sensor.

A spark plug 200 is provided above each cylinder 150. The spark plug 200 generates a spark by electric discharge (ignition), and the spark ignites the air-fuel mixture in the cylinder 150. This causes an explosion within the cylinder 150, and the piston 170 is pushed down. By pushing down the piston 170, 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 .

Output signals from various sensors such as the aforementioned throttle opening sensor 113a, flow rate sensor 114, crank angle sensor 121, accelerator position sensor 126, water temperature sensor 122, cylinder pressure sensor 140, etc. device 1). Control device 1 detects the operating state of internal combustion engine 100 based on output signals from these various sensors. The control device 1 controls the amount of air sucked into the cylinder 150, the amount of fuel injected from the fuel injection device 134, the ignition timing of the spark plug 200, and the like.

[Spark plug]
Next, the spark plug 200 will be explained with reference to FIG. 2.
FIG. 2 is a partially enlarged view illustrating the spark plug 200.

As shown in FIG. 2, the spark plug 200 has a center electrode 210 and an outer electrode 220. The center electrode 210 is supported by a plug base (not shown) via an insulator 230. Thereby, the center electrode 210 is insulated. The outer electrode 220 is grounded.

When a voltage is generated in the ignition coil 300 (see FIG. 1), a predetermined voltage (for example, 20,000V to 40,000V) is applied to the center electrode 210. 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. Then, the spark generated by the discharge ignites the air-fuel mixture (gas component) in the cylinder 150.

Note that the voltage that causes dielectric breakdown of the gas components in the cylinder 150 and generates discharge (ignition) depends on the state of the gas (air mixture in the cylinder) existing between the center electrode 210 and the outer electrode 220, and the state of the gas component in the cylinder 150. It varies depending on the cylinder pressure. The voltage at which this discharge occurs is called the dielectric breakdown voltage.

Discharge control (ignition control) of the spark plug 200 is performed by an ignition control section 83 (see FIG. 3) of the control device 1, which will be described later.

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

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- It has a ROM (Read Only Memory) 60, an I/O (Input/Output) port 70, and an output circuit 80.

The analog input section 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 cylinder 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 section 10 are converted into digital signals by the A/D conversion section 30. The digital signal converted by the A/D converter 30 is then 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. The digital output signal input to the digital input section 20 is stored in the RAM 40 via the I/O port 70.

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

The MPU 50 executes a control program (not shown) stored in the ROM 60 to process 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, the throttle valve 113, the fuel pump 131, the spark plug 200, etc.) that drives the internal combustion engine 100 according to the control program, and temporarily stores the control value in the RAM 40. remember exactly.

The control value that defines the amount of operation 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 overall control section 81, a fuel injection control section 82, and an ignition control section 83 (see FIG. 3). The overall control unit 81 performs overall control of the internal combustion engine based on output signals from various sensors (for example, the cylinder pressure sensor 140). The fuel injection control unit 82 controls driving of a plunger rod (not shown) of the fuel injection device 134. The ignition control section 83 controls the voltage applied to the spark plug 200.

[Functional block of control device]
Next, the functional configuration of the control device 1 will be explained with reference to FIG. 3.
FIG. 3 is a functional block diagram illustrating the functional configuration of the control device 1. As shown in FIG.

Each function of the control device 1 is realized as various functions in the output circuit 80 by the MPU 50 executing a control program stored in the ROM 60. Various functions in the output circuit 80 include, for example, control of the fuel injection device 134 by the fuel injection control section 82 and control of the ignition coil 300 by the ignition control section 83.

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

[Overall control section]
The overall control unit 81 receives requested torque (acceleration information S1) from the accelerator position sensor 126 and cylinder pressure information S2 from the cylinder pressure sensor 140, which are stored in the RAM 40.

The overall control unit 81 controls the overall control of the fuel injection control unit 82 and the ignition control unit 83 based on the required torque (acceleration information S1) from the accelerator position sensor 126 and the cylinder pressure information S2 from the cylinder pressure sensor 140. control.

[Fuel injection control section]
The fuel injection control unit 82 includes an angle information generation unit 85 that measures the crank angle of the crankshaft 123, and an angle information generation unit 85 that measures the crank angle of the crankshaft 123. It is connected to a cylinder determining section 84 that determines whether the engine is in a compression stroke (compression, intake, or compression stroke), and a rotation speed information generating section 86 that measures the engine speed. The fuel injection control section 82 receives cylinder discrimination information S3 from the cylinder discrimination section 84, crank angle information S4 from the angle information generation section 85, and engine rotation speed information S5 from the rotation speed information generation section 86.

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

The fuel injection control unit 82 calculates the injection amount and injection time of the fuel injected from the fuel injection device 134 based on the received information. The fuel injection control unit 82 then transmits the fuel injection pulse S9 generated based on the calculated fuel injection amount and injection time to the fuel injection device 134.

[Ignition control section]
The ignition control section 83 is connected to the overall control section 81, a cylinder discrimination section 84, an angle information generation section 85, a rotation speed information generation section 86, a load information generation section 88, and a water temperature measurement section 89. We accept information from these sources.

Based on the received information, the ignition control unit 83 determines the amount of current to be applied to the primary coil 310 (see FIG. 5) of the ignition coil 300, the energization start time (energization angle), and the amount of current to be applied to the primary coil 310 of the ignition coil 300 (see FIG. 5). Calculate the time to cut off the applied current (ignition time).

The ignition control unit 83 outputs an ignition signal SA to the primary coil 310 of the ignition coil 300 based on the calculated energization amount, energization start time, and ignition time, thereby controlling the discharge by the ignition plug 200 ( ignition control).

[Electrode temperature, minimum ignition energy, and air-fuel ratio]
Next, the relationship between the temperature of the electrode of the spark plug 200, the minimum ignition energy, and the air-fuel ratio will be described with reference to FIG. 4.
FIG. 4 is a diagram illustrating the relationship between electrode temperature, minimum ignition energy, and air-fuel ratio.

FIG. 4 shows the air-fuel ratio values corresponding to the minimum ignition energy values. In FIG. 4, the vertical direction indicates a voltage scale value corresponding to the minimum ignition energy of the air-fuel mixture, and the left-right direction in FIG. 4 indicates an air-fuel ratio scale value corresponding to the air-fuel ratio of the air-fuel mixture. The air-fuel ratio P1 shown in FIG. 4 is an air-fuel ratio value corresponding to a predetermined value of the minimum ignition energy that can ignite the air-fuel mixture when the electrode temperature of the spark plug is low (for example, -7 degC). On the other hand, the air-fuel ratio P2 is an air-fuel ratio value corresponding to a predetermined value of the minimum ignition energy that can ignite the air-fuel mixture when the electrode temperature of the spark plug is high (for example, 25 degC).

As shown in FIG. 4, in the internal combustion engine 100, the larger the air-fuel ratio (the thinner the fuel), the higher the value of the minimum ignition energy of the air-fuel mixture. It becomes difficult to accomplish. Furthermore, the lower the electrode temperature of the spark plug, the higher the value of the minimum ignition energy of the air-fuel mixture, which makes it more difficult for the air-fuel mixture to be ignited by discharge (ignition) from the spark plug.

For example, assume that a value equivalent to the minimum ignition energy corresponding to the air-fuel ratio P2 when the spark plug electrode temperature is high is obtained when the spark plug electrode temperature is low. In this case, the discharge (ignition) from the spark plug 200 cannot exceed the minimum ignition energy unless the air-fuel ratio is set to the air-fuel ratio P1, which is smaller (fuel richer) than the air-fuel ratio P2. Therefore, conventionally, as a setting with a safety margin that does not cause problems such as misfires in the internal combustion engine 100, a rich air-fuel ratio (P1), which assumes that the temperature of the electrode of the spark plug 200 is always low, is used for fuel injection. It was set in the control unit 82. As a result, in the internal combustion engine 100, as the ratio of fuel in the air-fuel mixture increased, more hydrocarbons (HC) were generated during combustion.

On the other hand, the higher the temperature of the electrode of the spark plug 200 at the time of cold start (see the thick arrow in FIG. 4), the lower the minimum ignition energy for igniting the air-fuel mixture. Therefore, even if the air-fuel ratio is increased (the fuel is made thinner), the discharge (ignition) from the spark plug exceeds the minimum ignition energy, making it possible to ignite the air-fuel mixture. As a result, generation of hydrocarbons (HC) in internal combustion engine 100 can be reduced. Therefore, in the internal combustion engine 100, as will be described later, the temperature of the electrode of the spark plug 200 during cold start is raised before discharge (ignition). This makes it possible to increase the air-fuel ratio during cold engine startup and suppress the generation of hydrocarbons (HC).

[Electrical circuit including ignition coil]
Next, an electric circuit including the ignition coil will be explained with reference to FIG.
FIG. 5 is a diagram illustrating an electric circuit including an ignition coil.

The electric circuit 500 shown in FIG. 5 includes an ignition coil 300. The ignition coil 300 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.

One end of the primary coil 310 is connected to a DC power source 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 a drain (D) terminal of an igniter (energization control circuit) 340 and grounded via the igniter 340. For the igniter 340, a transistor, a field effect transistor (FET), or the like is used.

The gate (G) terminal of the igniter 340 is connected to the ignition control section 83 via the temperature switch section 350. The temperature switch section 350 is installed for the purpose of preventing damage to the ignition coil 300 due to overheating. The temperature switch section 350 includes a temperature detection section 351. Temperature detection section 351 detects the temperature of ignition coil 300 via igniter 340. The temperature switch section 350 cuts off the ignition signal SA output from the ignition control section 83 to the igniter 340 when the temperature detected by the temperature detection section 351 becomes equal to or higher than a predetermined threshold value A (first temperature).

When the temperature switch section 350 cuts off the ignition signal SA, the power supply to the primary coil 310 is stopped, so overheating of the igniter 340 can be avoided. The ignition signal SA output from the ignition control unit 83 when the temperature detected by the temperature detection unit 351 is less than the first temperature is input to the gate (G) terminal of the igniter 340.

When the ignition signal SA is input to the gate (G) terminal of the igniter 340, the drain (D) terminal and the source (S) terminal of the igniter 340 become energized, and the drain (D) terminal and the source (S) terminal become energized. A current flows through. As a result, the ignition signal SA is output from the ignition control section 83 to the primary coil 310 of the ignition coil 300 via the igniter 340. As a result, 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 section 83 stops, the current flowing through the primary coil 310 is cut off. As a result, a high voltage is generated in the secondary coil 320 according to the ratio of turns of the coil to the primary coil 310.

The high voltage generated in the secondary coil 320 is applied to the center electrode 210 (see FIG. 2) of the spark plug 200. This generates a potential difference between the center electrode 210 and the outer electrode 220 of the spark plug 200. When the potential difference generated between the center electrode 210 and the outer electrode 220 exceeds the dielectric breakdown voltage Vm of the surrounding gas (air mixture in the cylinder 150), the gas component undergoes dielectric breakdown and the center electrode 210 and the outer electrode 220 A discharge occurs between the As a result, the fuel (air mixture) is ignited (ignition). An electric circuit 500 having a spark plug 200 and an ignition coil 300 corresponds to an ignition device according to the present invention.

The discharge path generated between the center electrode 210 and the outer electrode 220 reaches a high temperature of several thousand degrees Celsius. Since the discharge path is in contact with the surrounding gas and the electrodes 210 and 220, the exothermic energy of the discharge is distributed to the surrounding gas and the electrodes 210 and 220. The exothermic energy distributed to the surrounding gas heats (preheats) the surrounding gas and the electrodes 210 and 220 to promote ignition.

[Multiple ignition discharge waveform]
Next, the discharge waveform of multiple ignition will be explained with reference to FIG. 6.
FIG. 6 is an example of a discharge waveform of multiple ignitions.

As shown in FIG. 6, multiple ignitions are performed by adding multiple discharges by repeating ON and OFF of the ignition signal. Thereby, the temperature of the electrodes 210 and 220 of the spark plug 200 can be increased before the discharge (ignition) that preheats the electrodes of the spark plug 200. Multiple ignition by this additional discharge can be performed at a timing that does not overlap with the ignition timing of the main ignition. That is, multiple ignition by additional discharge can be performed at least during the period from the ignition (start of discharge) of the main ignition until the start of fuel injection (the period from the expansion stroke to the intake stroke in the embodiment of FIG. 6).

[Air-fuel ratio and required ignition energy]
Next, the number of misfires and the amount of hydrocarbon emissions will be explained with reference to FIGS. 7 to 9.
FIG. 7 is a diagram illustrating the relationship between the number of misfires counted in 15 seconds and the amount of hydrocarbon discharged (integrated mass) in the same 15 seconds. FIG. 8 is a diagram showing the relationship between the number of misfires counted during a period of 60 seconds from the start of the internal combustion engine and the multiple ignition period (heating period) due to additional discharge performed within the period. FIG. 9 is a diagram showing the relationship between the cumulative mass of hydrocarbons discharged from the start of the internal combustion engine until 60 seconds have elapsed and the heating period.

As shown in FIG. 7, there is a one-dimensional correlation between the number of misfires and the amount of hydrocarbon emissions. In other words, the main cause of hydrocarbon generation is misfire. A misfire occurs when a flame kernel generated by ignition is unable to grow and is extinguished. In order to grow the flame kernel and suppress the generation of hydrocarbons (HC), it is necessary to suppress misfires.

In order to grow the flame kernel and suppress misfires, it is necessary to suppress the amount of heat that is transmitted (escaped) from the surrounding gas and flame kernel of the discharge path facing between the electrodes 210 and 220 of the spark plug 200 to the electrodes 210 and 220. . For example, if the ignition device performs multiple ignitions to preheat the electrodes 210 and 220 of the spark plug 200, the temperature difference between the discharge path and the flame kernel and the electrodes 210 and 220 will be reduced. As a result, the amount of heat transmitted from the discharge path or flame kernel to the electrodes 210, 220 can be suppressed.

As shown by the broken line in FIG. 8, there is an inversely proportional relationship between the heating period of the electrodes 210 and 220 and the number of misfires, and the longer the heating period, the more the number of misfires can be reduced. Note that the temperature of the electrodes 210 and 220 changes depending on the environmental temperature. Therefore, the higher the environmental temperature, the higher the temperature of the electrodes 210 and 220 of the spark plug 200. Therefore, as shown in FIG. 8, the number of misfires when the environmental temperature is 80 degC is smaller than the number of misfires when the environmental temperature is 20 degC. As shown by the broken line in FIG. 9, the longer the heating period and the higher the environmental temperature, the more the amount of hydrocarbon emissions can be reduced.

[Ignition signal frequency and ignition coil temperature]
Next, the relationship between the frequency of the ignition signal SA and the temperature of the ignition coil will be explained with reference to FIGS. 10 to 13.
FIG. 10 is a diagram showing the transition when performing multiple ignition and main ignition. FIG. 11 is a conceptual diagram showing the relationship between the calorific value and ignitability with respect to the frequency of the ignition signal. FIG. 12 is a conceptual diagram showing the relationship between the transition time and the temperature of the ignition coil in the case of multiple ignition and the case of no multiple ignition. FIG. 13 is a timing chart showing changes in temperature and HC concentration of a conventional ignition coil.

The purpose of the multiple ignition performed in this embodiment is to preheat the electrode of the spark plug 200 before main ignition. Therefore, multiple ignitions are performed before the main ignition. Moreover, multiple ignition can also be called preheating ignition. As shown in FIG. 10, the ignition performance of the main ignition can be improved by increasing the ignition energy per discharge. On the other hand, preheating by multiple ignitions can improve the amount of electrode heating by increasing the discharge duration per unit time.

As shown in FIG. 10, the main ignition is set so that the ignition energy per discharge is equal to or higher than the above-mentioned dielectric breakdown voltage Vm. Thereby, a discharge is generated between the center electrode 210 and the outer electrode 220, and the air-fuel mixture is ignited (flame kernel formation). On the other hand, in the multiple ignition (preheat ignition) performed in this embodiment, electric discharge is generated between the center electrode 210 and the outer electrode 220 before the main ignition, and the electrodes 210 and 220 of the spark plug 200 can be preheated. It is a purpose. Therefore, multiple ignition (preheat ignition) is performed at a time point before main ignition in time series.

In multiple ignition (preheat ignition), ignition (discharge) is repeated multiple times to increase the power conversion amount of the ignition coil 300 and increase the discharge duration per unit time. Thereby, the amount of heating (preheating) of the electrodes 210 and 220 can be increased. Therefore, in multiple ignition (preheat ignition), it is necessary to set the switching frequency of the ignition signal SA higher than that in main ignition. That is, the ignition control unit 83 (see FIG. 3) outputs a low-frequency main ignition signal for performing main ignition and a high-frequency multiple ignition signal for performing multiple ignition (preheat ignition). Thus, as shown in FIG. 11, when the frequency of the ignition signal SA is increased, the amount of heat generated by the electrodes 210 and 220 of the spark plug 200 increases. As a result, the ignitability of the spark plug 200 is improved.

As mentioned above, in order to reduce hydrocarbons during cold engine starting, multiple ignitions (preheating ignition ) to preheat the electrodes 210, 220. However, as shown in FIG. 12, the amount of heat generated by the ignition coil 300 due to multiple ignition (preheat ignition) is larger than that during main ignition. Therefore, when performing multiple ignition (preheat ignition), as shown in FIG. 13, the temperature of the ignition coil 300 detected by the temperature detection section 351 (see FIG. When a predetermined threshold value A (first temperature) is reached, it is preferable to cut off the multiple ignition signal from the ignition control unit 83 to the igniter 340 to adjust the amount of heat generated.

[Electrical circuit including ignition coil]
Next, an electric circuit including an ignition coil according to the present invention will be described with reference to FIG. 14.
FIG. 14 is a circuit diagram showing an example of an electric circuit including an ignition coil according to the present invention.

As shown in FIG. 14, an electric circuit 501 according to the present invention includes an ignition coil 300. The ignition coil 300 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.

One end of the primary coil 310 is connected to a DC power source 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 a drain (D) terminal of an igniter (energization control circuit) 340 and grounded via the igniter 340. For the igniter 340, a transistor, a field effect transistor (FET), or the like is used.

The gate (G) terminal of the igniter 340 is connected to the ignition control section 83 via the temperature switch section 360 or the temperature switch section 360 and the filter section 370. Filter section 370 is, for example, a low-pass filter. Filter section 370 passes the main ignition signal having a low frequency. The filter section 370 then blocks the multiple ignition signal, which is a high frequency signal.

The temperature switch section 360 is installed for the purpose of adjusting the temperature of the ignition coil 300. The temperature switch section 360 includes a temperature detection section 351. The temperature switch unit 360 switches the connection destination according to the coil temperature range (low temperature range, medium temperature range, high temperature range) detected by the temperature detection unit 351.

The medium temperature range is a region above the threshold A (first temperature) described above and below the predetermined threshold B (second temperature). When the coil temperature is in the medium temperature range, the temperature switch section 360 connects the ignition control section 83 and the igniter 340 via the filter section 370. As a result, the high frequency multiple ignition signal output from the ignition control section 83 is blocked by the filter section 370. On the other hand, the low-frequency main ignition signal output from the ignition control section 83 passes through the filter section 370 and is transmitted to the igniter 340.

The high temperature range is a range above the threshold B (second temperature) described above and below the upper limit of the design rated temperature of the ignition coil 300. When the coil temperature is in the high temperature range, the temperature switch section 360 disconnects the ignition control section 83 and the igniter 340. As a result, the multiple ignition signal and the main ignition signal output from the ignition control section 83 are not transmitted to the igniter 340.

The low temperature region is a region below the threshold value A (first temperature) described above. When the coil temperature is in the low temperature range, the temperature switch section 360 directly connects the ignition control section 83 and the igniter 340. Thereby, the multiple ignition signal and the main ignition signal output from the ignition control section 83 are transmitted to the igniter 340.

That is, in the low temperature range, the coil temperature is lower than in the medium temperature range or the high temperature range, and the temperature difference (temperature margin) from the upper limit of the design rated temperature of the ignition coil 300 is large. Therefore, in addition to main ignition for igniting the air-fuel mixture, multiple ignition (preheating ignition) in which the ignition coil 300 generates a large amount of heat can be performed. Moreover, in the present embodiment, the temperature detection unit 351 accurately detects the coil temperature and performs multiple ignition (preheat ignition) until the coil temperature reaches a medium temperature range equal to or higher than the threshold value B (second temperature). As a result, the temperature margin with respect to the upper limit of the rated temperature can be minimized, and the period for performing multiple ignitions can be extended, rather than performing multiple ignitions (preheating ignition) in the estimated low temperature range without providing the temperature detection unit 351. It can be set as long as possible.

In this way, when the coil temperature detected by the temperature detection section 351 is less than the threshold value B (second temperature), the ignition signal SA (main ignition signal only, or main ignition signal and multiple signals) output from the ignition control section 83 is The main ignition signal) is input to the gate (G) terminal of the igniter 340 via the temperature switch section 360. When the ignition signal SA is input to the gate (G) terminal of the igniter 340, the drain (D) terminal and the source (S) terminal of the igniter 340 become energized, and the drain (D) terminal and the source (S) terminal become energized. A current flows through. As a result, the ignition signal SA is output from the ignition control section 83 to the primary coil 310 of the ignition coil 300 via the igniter 340. As a result, 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 section 83 stops, the current flowing through the primary coil 310 is cut off. As a result, a high voltage is generated in the secondary coil 320 according to the ratio of turns of the coil to the primary coil 310.

The high voltage generated in the secondary coil 320 is applied to the center electrode 210 (see FIG. 2) of the spark plug 200. This generates a potential difference between the center electrode 210 and the outer electrode 220 of the spark plug 200. When the potential difference generated between the center electrode 210 and the outer electrode 220 exceeds the dielectric breakdown voltage Vm of the surrounding gas (air mixture in the cylinder 150), the gas component undergoes dielectric breakdown and the center electrode 210 and the outer electrode 220 A discharge occurs between the As a result, the fuel (air mixture) is ignited (ignition). An electric circuit 500 having a spark plug 200 and an ignition coil 300 corresponds to an ignition device according to the present invention.

The ignition control section 83 has an energization control circuit 831 and an output monitor circuit 832. The energization control circuit 831 controls the output of the ignition signal SA. The output monitor circuit 832 has a return detection function that detects the ignition signal SA output from the energization control circuit 831 as a return signal, and transmits the detection result of the return signal to the energization control circuit 831.

The energization control circuit 831 transmits the output state of the ignition signal SA and the detection result of the return signal corresponding to the ignition signal SA to the overall control unit 81 (see FIG. 3). The overall control unit 81 compares the output state of the ignition signal SA and the detection result of the return signal, and if the states of the ignition signal SA and the return signal are different, the filter unit 370 outputs a multiple ignition signal or an overheat detection signal to be described later. is determined to have been blocked. Furthermore, when the ignition signal SA and the return signal are the same, the overall control section 81 determines that the multiple ignition signal and the overheat detection signal are not blocked in the filter section 370.

Note that, as described above, in cold engine starting, in order to reduce hydrocarbons, it is necessary to perform multiple ignitions until warm-up of the internal combustion engine is completed (for example, in a period of about 60 seconds). However, in multiple ignition (preheat ignition), the amount of heat generated by the ignition coil 300 is larger than that in normal ignition, so the actual temperature of the ignition coil 300 reaches the intermediate temperature range in a relatively short time. Then, when the actual temperature of the ignition coil 300 reaches the intermediate temperature range, the temperature switch section 360 cuts off the transmission of the multiple ignition signal to the igniter 340.

Therefore, in this embodiment, as described above, the filter section 370 determines whether the main ignition signal or the multiple ignition signal is blocked. Furthermore, based on the determination result, the actual temperature of the ignition coil 300 reaches the medium temperature range and only the multiple ignition signal is cut off, or the actual temperature of the ignition coil 300 returns to the low temperature range and the main ignition is started. The point in time when the signal and the multiple ignition signal are transmitted to the igniter 340 again is detected. Then, the coil temperature of the temperature detection unit 351 is calibrated by assuming that the coil temperature at the time of detection is the threshold value A (first temperature).

When the multiple ignition (preheat ignition) of the ignition plug 200 is stopped, the ignition coil 300 is cooled due to the temperature difference with its surroundings (see FIG. 13). As a result, the temperature detected by the temperature detection section 351 returns to the low temperature range. In the low temperature range, the temperature switch section 360 selects a path in which the ignition signal SA is transmitted to the igniter 340 without passing through the filter section 370. Thereby, the main ignition signal and the multiple ignition signal are transmitted to the igniter 340 again. Therefore, multiple ignitions can be repeated while suppressing misfires, and generation of hydrocarbons can be suppressed.

Next, fuel injection control will be explained. For example, let T be the fuel injection amount after warming up the internal combustion engine, which is not at the time of cold start. During a cold engine start, the amount of fuel vaporized by the main ignition timing decreases due to the low in-cylinder temperature, so the amount of fuel involved in combustion after ignition decreases. As a result, in order to compensate for the air-fuel ratio of the in-cylinder air-fuel mixture becoming leaner, the fuel injection amount is increased from the injection amount T after warm-up at the time of cold engine startup. Assuming that this amount of increase is a, the fuel injection amount at the time of cold engine start is T+a. By performing multiple ignitions (preheat ignition) in a low temperature range during cold engine startup, the amount of fuel that is vaporized by the main ignition timing and participates in post-ignition combustion is substantially increased. If the contribution of this multiple ignition (preheating ignition) is b1, the fuel injection amount when multiple ignition is executed is T+a−b1.

When the coil temperature reaches the medium temperature range and multiple ignition is stopped and only main ignition is executed, reduce the value of the above-mentioned multiple ignition (preheat ignition) contribution b1, e.g. Let b2 (b2<b1). Then, when multiple ignition is executed, the amount of fuel is increased by the amount reduced, so that the amount of fuel injection becomes T+a−b2. Thereby, it is possible to suppress a rise in the minimum ignition energy of the air-fuel mixture (see FIG. 4) due to a decrease in the temperature of the electrodes 210 and 220, and to prevent misfires. As a result, generation of hydrocarbons can be suppressed as a whole.

Note that the temperature of the electrodes 210 and 220 of the spark plug 200 may be inferred based on the coil temperature detected by the above-mentioned temperature detection unit 351 or the operating state of the internal combustion engine 100 such as water temperature or intake air temperature. be. For example, the temperature of the electrodes 210, 220 at the time when the coil temperature reaches the intermediate temperature range and multiple ignition is interrupted is set based on the above-mentioned threshold value A (first temperature). Then, it is inferred that the temperatures of the electrodes 210 and 220 are sequentially lowered based on the elapse of time after the multiple ignition was interrupted or the elapse of the combustion cycle (such as the number of times main ignition was performed).

[Multiple ignition switching processing]
Next, multiple ignition switching processing according to this embodiment will be described with reference to FIG. 15.
FIG. 15 is a flowchart illustrating an example of multiple ignition switching processing.

When the multiple ignition switching process is started, the temperature detection unit 351 acquires the coil temperature of the ignition coil 300. Then, the temperature switch section 360 determines whether the coil temperature detected by the temperature detection section 351 is equal to or higher than a predetermined threshold value B (second temperature) (S110).

In step S110, when it is determined that the coil temperature is equal to or higher than the predetermined threshold B (YES in S110), the temperature switch section 360 selects a path (circuit) that completely cuts off the ignition signal SA ( S120). As a result, the ignition signal SA output from the ignition control section 83 is not transmitted to the igniter 340, and ignition (ignition) by the spark plug 200 is stopped. After the process in step S120, the ignition device (electric circuit 501) moves the process to step S110.

On the other hand, when it is determined in step S110 that the coil temperature is not equal to or higher than the predetermined threshold B (if NO in S110), the temperature switch unit 360 sets the coil temperature to a predetermined threshold A (first temperature). It is determined whether or not it is the above (S130).

In step S130, when it is determined that the coil temperature is equal to or higher than the predetermined threshold value A (YES in S130), the temperature switch section 360 selects a path for the ignition signal SA to pass through the filter section 370 ( S140). As a result, multiple ignition signals in the ignition signal SA are blocked by the filter section 370, and only the main ignition signal is transmitted to the igniter 340. As a result, in the spark plug 200, multiple ignition for the purpose of preheating is not performed, and only main ignition is performed. After the process in step S140, the ignition device moves the process to step S110.

On the other hand, when it is determined in step S130 that the coil temperature is not equal to or higher than the predetermined threshold A (if NO in S130), the temperature switch section 360 switches the ignition signal SA to the igniter 340 without passing through the filter section 370. A route to be transmitted to is selected (S150). Thereby, the multiple ignition signal and the main ignition signal in the ignition signal SA are transmitted to the igniter 340. As a result, multiple ignition for the purpose of preheating and main ignition are performed in the ignition plug 200. After the process in step S150, the ignition device moves the process to step S110.

[Fuel injection amount switching process]
Next, the fuel injection amount switching process according to this embodiment will be explained with reference to FIG. 16.
FIG. 16 is a flowchart illustrating an example of fuel injection amount switching processing.

When the fuel injection amount switching process is started, the overall control unit 81 (see FIG. 3) acquires the time that has passed since the start of the internal combustion engine. Then, the overall control unit 81 determines whether the time that has passed from the start to the present is within a predetermined value (S210). The predetermined value corresponds to the period until the warm-up described above is completed.

When it is determined in step S210 that the time that has passed from the start to the present is not within a predetermined value (NO in S210), the overall control unit 81 ends the fuel injection amount switching process (S220). .

On the other hand, when it is determined in step S210 that the time that has passed from the start to the present is within a predetermined value (YES in S210), the overall control unit 81 sends an ignition signal including a multiple ignition signal. SA is output (S230). Next, the overall control unit 81 determines whether the ignition signal SA and the return signal obtained from the output monitor circuit 832 are different (S240).

In step S240, when it is determined that the ignition signal SA and the return signal are different (YES in S240), the overall control unit 81 sets the fuel injection amount to the first fuel injection amount (S250). The overall control unit 81 determines that the filter unit 370 has blocked the multiple ignition signal when the ignition signal SA and the return signal are different. When the filter section 370 blocks the multiple ignition signal, the temperature of the ignition coil 300 is equal to or higher than the threshold value A (first temperature). After the process in step S250, the overall control unit 81 moves the process to step S210.

On the other hand, when it is determined in step S240 that the ignition signal SA and the return signal match (if NO in S240), the overall control unit 81 sets the fuel injection amount to the second fuel injection amount (S260). The overall control unit 81 determines that the multiple ignition signal has been transmitted to the igniter 340 when the ignition signal SA and the return signal match. After the process in step S260, the overall control unit 81 moves the process to step S210.

The first fuel injection amount is the fuel injection amount when the multiple ignition signal is cut off during cold start. The first fuel injection amount corresponds to T+a described above. On the other hand, the second fuel injection amount is the fuel injection amount when the multiple ignition signal is transmitted to the igniter 340 during cold engine startup. The second fuel injection amount corresponds to the above-mentioned T+a−bn (n=1, 2). Therefore, the second fuel injection amount is less than the first fuel injection amount.

[Multiple ignition switching processing]
Next, multiple ignition switching processing according to this embodiment will be described with reference to FIG. 17.
FIG. 17 is a timing chart showing multiple ignition switching processing.

In order to improve ignition performance, it is effective to keep the flame core generated by spark discharge warm. In order to keep the flame core warm, it is necessary to raise the temperature of the electrode that comes into contact with the flame core. As described above, preheating by multiple ignitions (discharges) can improve the amount of electrode heating by increasing the discharge duration per unit time. On the other hand, increasing ignition energy through multiple ignitions increases power consumption and affects fuel efficiency.

In order to alleviate the trade-off between improving ignition performance and increasing power consumption, a method is needed to efficiently raise the temperature of the electrode without unnecessarily increasing the ignition energy due to multiple ignitions. As a measure for this, for example, by shortening the interval between multiple ignitions as much as possible within the range where the discharge is sustained (by making the frequency higher), the duration of discharge per unit time can be extended, and in turn, the duration of multiple ignitions can be extended. The time for the electrodes 210, 220 to cool down between the discharges of the main ignition can be shortened as much as possible (see the first stage of FIG. 17). As a result, the heating efficiency due to multiple ignitions can be improved, and the temperature of the electrode after the discharge period can be efficiently raised.

A typical passive ignition coil has the ability to store a certain amount of charge. Therefore, the amount of charge increases until a certain charging time. Then, as the amount of charge increases, the output voltage and output current during discharging increase, and the electrodes 210 and 220 are heated strongly. Therefore, by outputting a low frequency precharge pulse (precharge signal) with sufficient precharging immediately before outputting a high frequency multiple discharge pulse (multiple ignition signal) for performing multiple ignitions, the above-mentioned As shown in FIG. 17, the temperature of the electrodes 210 and 220 can be further increased while making the interval between multiple ignitions as high as possible (see the second row of FIG. 17). That is, the precharge pulse is an energizing waveform that has a lower frequency than the multiple discharge pulse and has an output period such that the capacitive discharge of the ignition coil is reliably activated.

By the way, the electric circuit 501 including the ignition coil 300 described above cuts only the high frequency component of the ignition signal SA when the temperature of the ignition coil 300 is equal to or higher than the threshold value A (first temperature). Therefore, the electric circuit 501 continues the low-frequency precharge signal even when the temperature of the ignition coil 300 is equal to or higher than the threshold value A (first temperature). As a result, high-frequency multiple ignition cannot be performed (the multiple ignition signal is cut), and the heating efficiency of the electrodes 210 and 220 decreases.

As described above, the control device (ECU) 1 has a return detection function (output monitor circuit 832) that performs self-diagnosis of the ignition signal SA output to the ignition coil 300. This return detection function allows the control device 1 to detect the cutting of high frequency components performed by the electric circuit 501 in the high temperature range or medium temperature range of the ignition coil 300. By detecting the cut of the high frequency component, the control device 1 recognizes that the temperature state of the ignition coil 300 is equal to or higher than the threshold value A (first temperature), and the control device 1 recognizes that the temperature state of the ignition coil 300 is equal to or higher than the threshold value A (first temperature). The output of the discharge pulse is cut off from the ignition signal SA. That is, the control device 1 outputs only the main ignition signal when the coil temperature is equal to or higher than the threshold value A (first temperature). As a result, the amount of heat generated by the ignition coil 300 can be suppressed.

However, the control device 1 cannot detect the cutting of high frequency components by the electric circuit 501 in a state where only the main ignition signal is output. Therefore, even if the temperature state of the ignition coil 300, which has once increased, converges to below the threshold value A (first temperature), the control device 1 may not be able to resume outputting the multiple ignition signal. Therefore, the control device 1 outputs an overheat detection pulse (overheat detection signal) after the coil temperature becomes equal to or higher than the threshold value A (first temperature) and transitions to a state where only the main ignition signal is output (see FIG. 17). (See third row).

The overheat detection pulse is at least one high frequency pulse (single pulse). This can reduce wasteful charging and wasteful signal output operations. Moreover, the frequency of the overheat detection pulse is within a frequency band that exceeds the rated frequency at which the filter section 370 of the electric circuit 501 blocks the ignition signal SA, and the return detection function (output monitor circuit 832) of the control device 1 allows the ignition signal to be ignited. The return signal of signal SA is set within a detectable range. As a result, the overheat detection pulse is cut by the filter section 370 in the medium temperature range, and is not cut by the filter section 370 in the low temperature range. Therefore, the control device 1 can correctly recognize the temperature state of the ignition coil 300 by using the return detection function to detect whether or not the overheating detection pulse is cut by the filter section 370 (the 4 stages shown in FIG. 17). (see item).

When the control device 1 recognizes that the coil temperature is less than the threshold value A (first temperature), it resumes outputting the ignition signal SA including the precharge signal and the multiple ignition signal (see the fifth stage in FIG. 17). . After restarting the output of the precharge signal and the multiple ignition signal, the output of the overheat detection pulse is stopped (see the fifth stage in FIG. 17). Thereby, the amount of heat generated by the ignition coil 300 can be suppressed while reducing the calculation load on the control device 1 and the load on the ignition control section 83.

The phase of the overheating detection pulse is set at a timing that is later than the previous main ignition signal but before the next precharge signal and that allows the time required for switching the ignition signal of the control device 1 to be secured. Note that the time required to switch the ignition signal is the time required to output the overheat detection pulse of the control device 1, detect the return signal of the overheat detection pulse, and determine whether or not precharging is possible. is the sum of Thereby, the control device 1 can switch the output of the precharge pulse and the multiple discharge pulse within a cycle.

Additionally, the phase of the overheating detection pulse is preferably set as late as possible within the time period necessary for switching the ignition signal described above. In other words, it is preferable to output the overheat detection pulse at a time during the stroke of the internal combustion engine that is earlier than the timing at which the above-mentioned precharge signal is scheduled to be output by the time necessary for switching the ignition signal (see 3 in FIG. 17). (See row 5). As a result, the latest (recent) temperature status of the ignition coil 300 according to the previous main ignition signal is reflected in the return signal of the overheat detection pulse, reducing the delay in switching the ignition signal and increasing the output of the precharge pulse and multiple discharge pulse. It can be carried out without waste.

Furthermore, the overheat detection pulse may be output at every predetermined cycle of the combustion cycle of the internal combustion engine. For example, if the temperature of the ignition coil 300 exceeds the threshold value B (second temperature) (high temperature range) and the main ignition signal is also cut, the precharge pulse, multiple discharge pulse, and main ignition signal control device 1 (not shown), and only an overheat detection pulse is output at regular intervals (intermittently). Thereby, it is possible to quickly detect that the temperature of the ignition coil 300 has decreased and the air-fuel mixture can be ignited again while reducing the calculation load on the control device 1 and the load on the ignition control section 83. Note that such output control of (intermittent) overheating detection pulses at regular intervals may also be performed asynchronously to the combustion cycle when the rotation of the internal combustion engine is stopped due to idle stop control, etc., which will be described later. It is possible.

[Fuel injection amount switching process]
Next, the fuel injection amount switching process according to this embodiment will be explained with reference to FIG. 18.
FIG. 18 is a flowchart illustrating an example of fuel injection amount switching processing.

When the fuel injection amount switching process is started, the overall control unit 81 (see FIG. 3) of the control device 1 acquires the time that has passed from the start of the internal combustion engine to the present. Then, the overall control unit 81 determines whether the time elapsed from the start to the present time is within a predetermined value (S310). The predetermined value corresponds to the period until the warm-up described above is completed.

In step S310, when it is determined that the time that has passed from startup to the present is not within a predetermined value (NO in S310), the overall control unit 81 ends the fuel injection amount switching process (S320). .

On the other hand, when it is determined in step S310 that the time that has passed from the start to the present is within a predetermined value (YES in S310), the overall control unit 81 transmits the precharge signal and the multiple ignition signal. The ignition signal SA including the following is output (S330).

Next, the overall control unit 81 determines whether or not the multiple ignition signal portion of the ignition signal SA is different from the portion corresponding to the multiple ignition signal of the return signal obtained from the output monitor circuit 832. (S340). If it is determined in step S340 that the ignition signal SA and the return signal are different, the overall control section 81 determines that the filter section 370 has blocked the multiple ignition signal. As described above, when the filter section 370 blocks the multiple ignition signal, the coil temperature of the ignition coil 300 is at least equal to or higher than the threshold value A (first temperature).

In step S340, when it is determined that the ignition signal SA and the return signal are different (YES in S340), the overall control unit 81 sets the fuel injection amount to the first fuel injection amount (S350).

Next, the overall control unit 81 turns off the precharge signal and the multiple ignition signal, and turns on the overheat detection pulse (overheat detection signal) (step S360). That is, the overall control unit 81 stops outputting the precharge signal and the multiple ignition signal, and outputs the overheat detection signal. When the overall control unit 81 stops outputting the precharge signal and the multiple ignition signal, it is possible to reduce the amount of heat generated by the ignition coil 300 and lower the coil temperature.

Next, the overall control unit 81 determines whether the overheat detection signal portion of the ignition signal SA is different from the portion of the return signal that corresponds to the overheat detection signal (S370). In step S370, when it is determined that the ignition signal SA and the return signal are different, the overall control section 81 determines that the filter section 370 has cut off the overheat detection pulse. When the filter section 370 cuts off the overheat detection pulse, the coil temperature of the ignition coil 300 is still equal to or higher than the threshold value A (first temperature).

In step S370, when it is determined that the ignition signal SA and the return signal are different (YES in S370), the overall control unit 81 repeats step S370. That is, the overall control unit 81 repeats step S370 until the coil temperature becomes less than the threshold value A (first temperature).

On the other hand, when it is determined in step S370 that the ignition signal SA and the return signal match (if NO in S370), the overall control unit 81 determines that the coil temperature is less than the threshold value A (first temperature). Then, the overall control unit 81 stops outputting the overheat detection pulse and outputs a precharge signal and a multiple ignition signal (S380).

After the processing in step S380, or when it is determined in step S340 that the ignition signal SA and the return signal match (if NO in S340), the overall control unit 81 sets the fuel injection amount to the second fuel injection amount ( S390). After the process in step S390, the overall control unit 81 moves the process to step S310.

[Multiple ignition possible period]
Next, a period during which multiple ignitions can be performed according to this embodiment will be described with reference to FIG. 19.
FIG. 19 is a timing chart showing the relationship between the operating state of an engine (internal combustion engine) installed in a typical automobile and the multiple ignition permission period.

Some modern engine (internal combustion engine) controls are equipped with idle stop control. When implementing idle stop control, the engine also stops when the vehicle stops, so the number of engine starts increases. On the other hand, the lower the temperature of the electrode immediately before multiple ignition is performed, the larger the temperature difference between the electrodes when multiple ignition is performed and when multiple ignition is not performed. Therefore, the lower the temperature of the electrode immediately before performing multiple ignition, the more heat-retaining effect of the flame core can be expected when multiple ignition is performed. Therefore, it is desirable to perform multiple ignitions when the electrode is at a low temperature when starting or restarting the engine.

Specifically, by performing multiple ignitions for a certain period of time before the first explosion in addition to after the first explosion or second first explosion accompanying the start of fuel injection, further temperature rise of the electrode can be expected. Note that since combustion does not occur before the start of fuel injection, it is possible to perform continuous multiple ignition (multiple discharge control) specialized for raising the temperature of the electrode.

However, continuous multiple ignitions generate more heat than multiple ignitions after fuel injection. Therefore, if the execution period of continuous multiple ignition is lengthened, the ignition coil 300 becomes overheated before the start of fuel injection. As a result, multiple ignition cannot be performed after the start of fuel injection. Therefore, the temperatures of the ignition coil 300 and electrodes 210, 220 are estimated from the engine operating history, outside temperature, cooling water temperature, etc., and the periods for performing multiple ignition before and after the start of fuel injection are determined in advance. Good.

Particularly, during a cold start in a cold region, the temperatures of the ignition coil 300 and the electrodes 210, 220 are sufficiently low. Therefore, it is also possible to start multiple ignition before the engine starts rotating. In this case, since there is no air flow within the cylinder, a high temperature-raising effect can be expected due to multiple ignitions.

[Relationship between ignition performance, equivalence ratio and multiple ignitions]
Next, the relationship between ignition performance, equivalence ratio, and multiple ignition according to this embodiment will be described with reference to FIG. 20.
FIG. 20 is a correlation graph showing the relationship between equivalence ratio and minimum ignition energy.

The horizontal axis of the graph shown in FIG. 20 is the equivalence ratio of the air-fuel mixture. Equivalence ratio indicates the mass ratio of air and fuel. When the equivalence ratio is large, the fuel becomes rich, and when the equivalence ratio is small, the fuel becomes lean. When the equivalence ratio is 1, it becomes the stoichiometric air-fuel ratio.

The vertical axis of the graph shown in FIG. 20 is the minimum ignition energy in the main ignition. Minimum ignition energy is a typical indicator of ignition performance. A common unit of minimum ignition energy is the joule. Minimum ignition energy is the minimum discharge energy required to combust a mixture. If the minimum ignition energy is large, the ignition performance will be low, and if the minimum ignition energy is small, the ignition performance will be high.

Here, the main determining factors for ignition performance are the equivalence ratio of the air-fuel mixture and multiple ignitions. As shown in FIG. 20, when the equivalence ratio deviates from the stoichiometric mixture ratio (air-fuel ratio), the minimum ignition energy increases and the ignition performance decreases. In the case of a cold engine start, the vaporization of the fuel is delayed, so the equivalence ratio of the mixture becomes smaller than the stoichiometric mixture ratio. Therefore, in the case of a cold start, the temperature of the engine (internal combustion engine) and the environment decreases, and the minimum ignition energy increases.

On the other hand, in a state where the electrode is heated by multiple ignitions, the ignition performance improves because the electrode absorbs heat from the flame kernel. Therefore, as shown by the dotted line in FIG. 20, it is possible to combust the air-fuel mixture with smaller ignition energy than when multiple ignition is not performed. In other words, if the minimum ignition energy at engine startup can be satisfied even when multiple ignitions are not performed, the improvement in ignition performance due to multiple ignitions is converted into a reduction in the equivalence ratio of the air-fuel mixture. be able to. This makes it possible to satisfy the minimum ignition energy and at the same time reduce the fuel injection amount. As a result, it is possible to improve fuel efficiency and reduce hydrocarbons.

If a situation arises in which the minimum ignition energy cannot be satisfied, a misfire will occur, and unburned air-fuel mixture containing a large amount of hydrocarbons will be exhausted, and exhaust emissions and fuel efficiency will deteriorate. Therefore, it is necessary to switch between the presence and absence of multiple ignition while maintaining a state in which the minimum ignition energy is satisfied. Therefore, it is preferable to stop multiple ignition after increasing the equivalence ratio of the air-fuel mixture (increase the fuel injection amount), or to decrease the equivalence ratio of the mixture (reduce the fuel injection amount) after starting multiple ignition.

In this way, the control device 1 (internal combustion engine control device) according to the present embodiment controls an internal combustion engine including an ignition device having a spark plug 200 and an ignition coil 300 that causes the spark plug 200 to generate discharge. The control device 1 includes an overall control section 81 (control section) that outputs an output signal to the ignition device. The output signal is a multiple ignition signal for preheating the ignition plug 200 and a frequency different from the multiple ignition signal, a main ignition signal for igniting the air-fuel mixture by discharge of the ignition plug 200, and a main ignition signal for igniting the ignition coil 300. and a precharge signal for precharging.
Thereby, the temperature of the electrodes 210, 220 can be increased, and the minimum ignition energy can be reduced as much as possible to improve ignition performance. As a result, the ignitability of the spark plug 200 during main ignition can be improved, and generation of hydrocarbons can be suppressed.

The overall control unit 81 (control unit) according to the present embodiment outputs a multiple ignition signal before outputting the main ignition signal, and outputs a precharge signal before outputting the multiple ignition signal.
Thereby, the electrodes 210, 220 and the intake air around the electrodes 210, 220 can be efficiently warmed before the air-fuel mixture is ignited by the discharge of the spark plug 200.

The precharge signal according to this embodiment has a lower frequency than the multiple ignition signal.
Thereby, the charging energy of the ignition coil 300 can be increased as much as possible.

The overall control unit 81 (control unit) according to the present embodiment outputs a precharge signal when the temperature of the ignition coil 300 is less than the threshold value A (predetermined temperature).
Thereby, when the temperature of the ignition coil 300 is less than the threshold value A and the ignition coil 300 is not in an overheated state, the charging energy of the ignition coil 300 can be increased.

When the temperature of the ignition coil 300 is equal to or higher than the threshold value A (predetermined temperature), the overall control unit 81 (control unit) according to the present embodiment stops outputting the precharge signal, and starts when outputting the precharge signal. also increases the amount of fuel injection.
Thereby, when the temperature of the ignition coil 300 is equal to or higher than the threshold value A and the ignition coil 300 is in an overheated state, it is possible to suppress the temperature of the ignition coil 300 from increasing. Furthermore, by increasing the fuel injection amount, it is possible to prevent the dielectric breakdown voltage from increasing even if the temperature of the ignition coil 300 decreases. As a result, misfires can be suppressed and generation of hydrocarbons can be suppressed.

The overall control unit 81 (control unit) according to the present embodiment reduces the fuel injection amount when outputting the precharge signal than when not outputting the precharge signal.
Thereby, generation of hydrocarbons can be suppressed.

The output signal according to this embodiment includes an overheat detection signal for detecting the state of the ignition coil 300. The ignition device includes a temperature detection unit 351 that detects the temperature of the ignition coil 300, and cuts off a multiple ignition signal and an overheat detection signal among the output signals when the temperature of the ignition coil 300 becomes equal to or higher than a threshold value A (first temperature). It has a filter section 370. The control device 1 (internal combustion engine control device) includes an output monitor circuit 832 (return detection function) that detects a return signal for self-diagnosing the output signal. The overall control section 81 (control section) compares the overheat detection signal and the return signal to determine whether the overheat detection signal is blocked by the filter section. Then, when it is determined that the overheat detection signal is cut off, it is determined that the temperature of the ignition coil 300 is equal to or higher than the threshold value A (first temperature). On the other hand, if it is determined that the overheat detection signal is not interrupted, it is determined that the temperature of the ignition coil 300 is less than the threshold value A (first temperature).
Thereby, the overall control unit 81 can accurately determine whether the temperature of the ignition coil 300 is equal to or higher than the threshold value A (first temperature). As a result, precharging and multiple ignitions can be performed to the maximum extent while avoiding heat damage to the ignition coil 300.

The overall control unit 81 (control unit) according to this embodiment outputs an overheat detection signal at a timing after outputting the main ignition signal.
This allows the ignition signal to be switched within the cycle. Further, the latest status of the temperature of the ignition coil 300 is reflected in the return signal of the overheat detection pulse, so that the delay in switching the ignition signal can be shortened.

The overall control unit 81 (control unit) according to the present embodiment outputs an overheat detection signal for each predetermined cycle among the combustion cycles of the internal combustion engine.
Thereby, for example, when the ignition coil becomes so overheated that the main ignition signal is cut off, the overheat detection pulse can be output intermittently. As a result, it is possible to quickly detect that the temperature of the ignition coil 300 has decreased and the air-fuel mixture is ready to be ignited again.

The overall control unit 81 (control unit) according to the present embodiment outputs a precharge signal when determining that the temperature of the ignition coil 300 is less than the threshold value A (first temperature).
As a result, when the temperature of the ignition coil 300 is less than the threshold value A and the ignition coil 300 is not in an overheated state, the charging energy of the ignition coil 300 is increased to start discharging between the electrodes 210 and 220, and the discharge causes the electrode to The temperature of 210 and 220 can be increased.

When the overall control unit 81 (control unit) according to the present embodiment determines that the temperature of the ignition coil 300 is equal to or higher than a threshold value A (first temperature), the overall control unit 81 (control unit) controls at least one of a precharge signal and a multiple ignition signal. Stop outputting.
Thereby, when the temperature of the ignition coil 300 is equal to or higher than the threshold value A and the ignition coil 300 is in an overheated state, it is possible to suppress the temperature of the ignition coil 300 from increasing.

The overall control unit 81 (control unit) according to the present embodiment outputs an overheat detection signal before outputting the main ignition signal when performing idle stop control (the internal combustion engine is restarted within a predetermined period). do. Then, when it is determined that the temperature of the ignition coil 300 is less than the threshold value A (first temperature), a precharge signal and a multiple ignition signal are output.
Thereby, when the internal combustion engine is restarted and the ignition coil 300 is not in an overheated state, the charging energy of the ignition coil 300 can be increased as much as possible. Furthermore, the temperature of the electrodes 210 and 220 of the spark plug 200 can be increased without increasing the ignition energy due to multiple ignitions. As a result, the ignitability of the spark plug 200 can be improved, and generation of hydrocarbons can be suppressed.

When the overall control unit 81 (control unit) according to the present embodiment determines that the temperature of the ignition coil 300 is equal to or higher than the threshold value A (first temperature), the overall control unit 81 (control unit) stops outputting the precharge signal, and outputs the precharge signal. Increase the fuel injection amount compared to when outputting.
Thereby, when the temperature of the ignition coil 300 is equal to or higher than the threshold value A and the ignition coil 300 is in an overheated state, it is possible to suppress the temperature of the ignition coil 300 from increasing. Furthermore, by increasing the fuel injection amount, it is possible to prevent the dielectric breakdown voltage from increasing even if the temperature of the ignition coil 300 decreases. As a result, misfires can be suppressed and generation of hydrocarbons can be suppressed.

The overheat detection signal according to this embodiment is a single pulse signal.
This can reduce wasteful charging and wasteful signal output operations. Further, it is possible to prevent the overheat detection signal from affecting the temperature rise of the ignition coil 300. Note that the overheat detection signal according to the present invention is not limited to a single pulse, but can be set to a number of pulses within a range that does not affect the temperature rise of the ignition coil.

The overheating detection signal according to this embodiment has a frequency at which the output monitor circuit 832 (return detection function) can detect the return signal and the filter section 370 can cut it off.
Thereby, by detecting that the overheat detection signal is not blocked by the filter section 370, it is possible to detect that the coil temperature is less than the threshold value A (first temperature). Further, even if the overheat detection signal is input to the igniter 340, it is possible to prevent sparks from flying to the electrodes 210, 220. As a result, the overheat detection signal can be prevented from affecting the temperature rise of the ignition coil 300.

The internal combustion engine control method according to the present embodiment is a method for controlling an internal combustion engine including an ignition device having a spark plug 200 and an ignition coil 300 that causes the spark plug 200 to generate discharge. In this internal combustion engine control method, the overall control unit 81 (control unit) generates a multiple ignition signal for preheating the ignition plug 200 and a multiple ignition signal that have different frequencies, and generates a mixture by discharging the ignition plug 200. A main ignition signal for igniting the ignition coil 300 and a precharge signal for precharging the ignition coil 300 are output to the ignition device.
Thereby, the charging energy of the ignition coil 300 can be increased as much as possible. Furthermore, the temperature of the electrodes 210 and 220 of the spark plug 200 can be increased without increasing the ignition energy due to multiple ignitions. As a result, the ignitability of the spark plug 200 can be improved, and generation of hydrocarbons can be suppressed.

The present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be made without departing from the gist of the invention as set forth in the claims.

Furthermore, the embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace some of the configurations of each embodiment with other configurations.

1... Internal combustion engine 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...Overall control section, 82...Fuel injection control section, 83...Ignition control section, 84...Cylinder discrimination section, 85...Angle information generation section, 86...Rotational speed information generation section, 87...Intake amount measurement section, 88... Load information generation section, 89... Water temperature measurement section, 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 device, 140... Cylinder 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... Ignition coil, 310... Primary coil, 320... Secondary coil , 330... DC power supply, 340... Igniter, 350, 360... Temperature switch section, 351... Temperature detection section, 370... Filter section 500, 501... Electric circuit, 831... Energization control circuit, 832... Output monitor circuit

Claims (16)

1. An internal combustion engine control device for controlling an internal combustion engine including an ignition device having a spark plug and an ignition coil that causes the spark plug to generate discharge,
   comprising a control unit that outputs an output signal to the ignition device,
   The output signal includes a multiple ignition signal for preheating the ignition plug, a main ignition signal that has a different frequency from the multiple ignition signal and for igniting the air-fuel mixture by discharge of the ignition plug, and a main ignition signal for igniting the air-fuel mixture by discharge of the ignition plug; A precharge signal for precharging an ignition coil.
2. The internal combustion engine control device according to claim 1, wherein the control unit outputs the multiple ignition signal before outputting the main ignition signal, and outputs the precharge signal before outputting the multiple ignition signal. .
3. The internal combustion engine control device according to claim 1, wherein the precharge signal has a lower frequency than the multiple ignition signal.
4. The internal combustion engine control device according to claim 1, wherein the control unit outputs the precharge signal when the temperature of the ignition coil is less than a predetermined temperature.
5. The control unit stops outputting the precharge signal and increases the fuel injection amount compared to when outputting the precharge signal when the temperature of the ignition coil is equal to or higher than a predetermined temperature. internal combustion engine control device.
6. The internal combustion engine control device according to claim 1, wherein the control unit reduces the fuel injection amount when outputting the precharge signal than when not outputting the precharge signal.
7. The output signal includes an overheat detection signal for detecting a state of the ignition coil,
   The ignition device includes a temperature detection unit that detects the temperature of the ignition coil, and a filter unit that blocks the multiple ignition signal and the overheat detection signal from among the output signals when the temperature of the ignition coil becomes a first temperature or higher. and,
   further comprising a return detection function for detecting a return signal for self-diagnosing the output signal,
   The control unit includes:
   comparing the overheating detection signal and the return signal to determine whether the overheating detection signal is blocked by the filter section;
   If it is determined that the overheating detection signal is interrupted, determining that the temperature of the ignition coil is equal to or higher than the first temperature,
   The internal combustion engine control device according to claim 1, wherein when it is determined that the overheat detection signal is not interrupted, it is determined that the temperature of the ignition coil is lower than the first temperature.
8. The internal combustion engine control device according to claim 7, wherein the control unit outputs the overheat detection signal at a timing after outputting the main ignition signal.
9. The internal combustion engine control device according to claim 8, wherein the control unit outputs the overheat detection signal every predetermined cycle among combustion cycles of the internal combustion engine.
10. The internal combustion engine control device according to claim 7, wherein the control unit outputs the precharge signal when determining that the temperature of the ignition coil is lower than the first temperature.
11. The control unit stops outputting at least one of the precharge signal and the multiple ignition signal when determining that the temperature of the ignition coil is equal to or higher than the first temperature. Internal combustion engine control device.
12. The control unit outputs the overheat detection signal before outputting the main ignition signal when the internal combustion engine is restarted within a predetermined period, and the controller outputs the overheat detection signal when the temperature of the ignition coil is lower than the first temperature. The internal combustion engine control device according to claim 7, wherein the internal combustion engine control device outputs the precharge signal and the multiple ignition signal when it is determined that the precharge signal and the multiple ignition signal exist.
13. When the control unit determines that the temperature of the ignition coil is equal to or higher than the first temperature, the control unit stops outputting the precharge signal and increases the fuel injection amount compared to when outputting the precharge signal. The internal combustion engine control device according to claim 7.
14. The internal combustion engine control device according to claim 7, wherein the overheat detection signal is a single pulse signal.
15. The internal combustion engine control device according to claim 7, wherein the overheat detection signal has a frequency at which the return detection function can detect the return signal and the filter section can cut it off.
16. An internal combustion engine control method for controlling an internal combustion engine including an ignition device having an ignition plug and an ignition coil that causes the ignition plug to generate an electric discharge, the method comprising:
    A control unit includes a multiple ignition signal for preheating the spark plug, a main ignition signal that has a different frequency from the multiple ignition signal, and for igniting the air-fuel mixture by discharge of the spark plug, and a main ignition signal for igniting the air-fuel mixture by discharging the spark plug; An internal combustion engine control method, comprising: outputting a precharge signal to the ignition device to precharge a coil.

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