Control device for internal combustion engine and control method for ignition mechanism

Abstract

The purpose of this invention is to suppress hydrocarbon generation during cold starts of an internal combustion engine. The internal combustion engine control device of this invention includes a control unit that outputs an energizing signal (ignition signal) to the ignition coil. The control unit outputs an energizing signal (misignition relief) for a first cycle to the ignition coil at least after fuel injection for the first explosion, and outputs an energizing signal (HC in-cylinder aftertreatment) for a second cycle, shorter than the first cycle, to the ignition coil after successful ignition (first explosion).

Description

Technical Field

[0001] This invention relates to an internal combustion engine control device and a control method for an ignition mechanism. Background Technology

[0002] In recent years, with increasingly stringent emissions regulations, the industry has been seeking to improve the performance of emission catalysts (three-way catalysts) in internal combustion engines. Expensive precious metals such as platinum are used in these catalysts. Therefore, the increasing stringency of emissions regulations necessitates the use of large quantities of precious metals to improve emission performance, leading to a rise in the manufacturing cost of emission catalysts.

[0003] In this type of internal combustion engine, a large amount of hydrocarbons (HC) are produced during cold starts when the temperature is lower than the outside air temperature. There are two main reasons for hydrocarbon production during cold starts. First, the low cylinder temperature delays fuel vaporization, with some fuel vaporizing only after combustion is complete. This vaporized fuel remains unoxidized and is emitted as hydrocarbons. Second, the amount of vaporized fuel decreases by ignition time, increasing the air-fuel ratio in the cylinder (lean fuel). Under these conditions, higher ignition energy is required, leading to increased misfires and consequently, increased hydrocarbon production. Therefore, by suppressing hydrocarbon production during cold starts, the amount of precious metals used in emission catalysts can be reduced, thus lowering the manufacturing cost of emission catalysts.

[0004] However, in internal combustion engines, to prevent misfires (missed combustion) during cold starts, the fuel injection quantity is increased. As a result, hydrocarbon production increases during cold starts, making it difficult to reduce the cost of emission catalysts.

[0005] Patent document 1 discloses an ignition device for an internal combustion engine that performs multiple ignitions at times different from the normal ignition timing (before fuel injection begins) during one combustion cycle of the internal combustion engine, thereby preventing the temperature of the spark plug electrodes from dropping.

[0006] [Existing technical documents]

[0007] [Patent Literature]

[0008] [Patent Document 1] International Publication No. 2019 / 087748 Summary of the Invention

[0009] [The problem the invention aims to solve]

[0010] However, the ignition device for internal combustion engines disclosed in Patent Document 1 cannot heat the gas inside the cylinder. Therefore, it cannot improve fuel vaporization delay, thus failing to reduce misfires or the generation of hydrocarbons. Consequently, it cannot suppress hydrocarbon generation during cold starts of the internal combustion engine, making it difficult to reduce the manufacturing cost of emission catalysts.

[0011] The present invention takes into account the above-mentioned problems and aims to suppress the generation of hydrocarbons during cold start of an internal combustion engine.

[0012] [Technical means to solve the problem]

[0013] To solve the above problems and achieve the objective, the internal combustion engine control device of the present invention controls an internal combustion engine comprising an injector, a spark plug, an ignition coil, and a control unit. The injector injects fuel into the cylinder, the spark plug has an ignition electrode disposed in the cylinder, the ignition coil is connected to the spark plug, and the control unit outputs an energizing signal to the ignition coil. The control unit outputs an energizing signal for a first cycle to the ignition coil at least after fuel injection for the first ignition, and outputs an energizing signal for a second cycle, shorter than the first cycle, to the ignition coil after successful ignition.

[0014] [The effects of the invention]

[0015] According to the present invention, the generation of hydrocarbons during cold starting of an internal combustion engine can be suppressed. Attached Figure Description

[0016] Figure 1 This is an overall configuration diagram illustrating a basic configuration example of an internal combustion engine according to one embodiment.

[0017] Figure 2 A partially enlarged view illustrating one embodiment of the spark plug.

[0018] Figure 3 A functional block diagram illustrating the functional configuration of the control device for an internal combustion engine according to one embodiment.

[0019] Figure 4 A graph illustrating the relationship between emission concentration and air-fuel ratio.

[0020] Figure 5 A circuit diagram illustrating an example of a circuit including an ignition coil according to one embodiment.

[0021] Figure 6 Example of discharge waveform for multi-point ignition.

[0022] Figure 7 A graph illustrating the relationship between air-fuel ratio and required ignition energy.

[0023] Figure 8 An example of a timing diagram for ignition signal control aimed at preventing misfire.

[0024] Figure 9 An example of a timing diagram for ignition signal control aimed at reducing HC generated in the cylinder.

[0025] Figure 10A graph illustrating the relationship between the number of discharges and the amount of HC emitted.

[0026] Figure 11 An example of a time diagram for discharge cycle switching control aimed at resolving the trade-off between preventing misfire and reducing HC.

[0027] Figure 12 A flowchart illustrating an example of the discharge cycle switching process of the present invention.

[0028] Figure 13 A diagram illustrating the charging and discharging time distribution of a typical passive ignition coil. Detailed Implementation

[0029] <Implementation Method>

[0030] The internal combustion engine control device of the embodiment example will now be described. Furthermore, in each figure, the same components are labeled with the same symbol.

[0031] [Internal Combustion Engine System]

[0032] First, the configuration of an internal combustion engine system according to one embodiment will be described. Figure 1 This is an overall configuration diagram illustrating a basic configuration example of an internal combustion engine according to an embodiment of the present invention.

[0033] Figure 1 The internal combustion engine 100 shown can be a single cylinder or have multiple cylinders. In this embodiment, an internal combustion engine 100 with four cylinders is illustrated.

[0034] like Figure 1 As shown, in the internal combustion engine 100, air drawn in from the outside flows through the air filter 110, intake manifold 111, and intake manifold 112. Air passing 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 the flow sensor 114.

[0035] A throttle valve opening sensor 113a is provided on the throttle valve 113 to detect the opening degree of the throttle valve. The opening degree information of the throttle valve 113 detected by the throttle valve opening sensor 113a is output to the control unit (Electronic Control Unit: ECU) 1.

[0036] In this embodiment, an electronic throttle valve driven by an electric motor is used as the throttle valve 113. However, other types of throttle valves can also be used as the throttle valve of the present invention, as long as the airflow can be properly adjusted.

[0037] The temperature of the gas flowing into each cylinder 150 is detected by the intake air temperature sensor 115.

[0038] A crankshaft angle sensor 121 is disposed radially outside the gear ring 120 mounted on the crankshaft 123. The crankshaft angle sensor 121 detects the rotation angle of the crankshaft 123. In this embodiment, the crankshaft angle sensor 121 detects the rotation angle of the crankshaft 123 every 10° and every combustion cycle.

[0039] A water temperature sensor 122 is installed on the water cooling jacket (not shown) of the cylinder head. The water temperature sensor 122 detects the temperature of the cooling water in the internal combustion engine 100.

[0040] In addition, the vehicle is equipped with an accelerator pedal position sensor (APS) 126 that detects the displacement (depression) of the accelerator pedal 125. The accelerator pedal position sensor 126 detects the torque requested by the driver. The torque requested by the driver detected by the accelerator pedal position sensor 126 is output to the internal combustion engine control unit 1, which will be described later. The internal combustion engine control unit 1 controls the throttle valve 113 according to the requested torque.

[0041] Fuel stored in fuel tank 130 is drawn and pressurized by fuel pump 131. The fuel, after being drawn and pressurized by fuel pump 131, is adjusted to a specified pressure by pressure regulator 132 installed on fuel line 133. Subsequently, the fuel, adjusted to the specified pressure, is injected from fuel injection device (injector) 134 into each cylinder 150. Excess fuel, after pressure adjustment by pressure regulator 132, is returned to fuel tank 130 via return line (not shown).

[0042] The control of the fuel injection device 134 is based on the fuel injection control unit 82 of the internal combustion engine control device 1, which will be described later (see reference). Figure 3 It is carried out by fuel injection pulses (control signals).

[0043] A combustion pressure sensor (CPS, also known as an in-cylinder pressure sensor) 140 is installed on the cylinder head (not shown) of the internal combustion engine 100. The combustion pressure sensor 140 is located within each cylinder 150 and detects the pressure (combustion pressure) within the cylinder 150. The combustion pressure sensor 140 is, for example, a piezoelectric or gauge-type pressure sensor. Therefore, the combustion pressure (in-cylinder pressure) within the cylinder 150 can be detected over a wide temperature range.

[0044] Each cylinder 150 is equipped with an exhaust valve 152 and an exhaust manifold 160. When the exhaust valve 152 is open, exhaust gas is discharged from the cylinder 150 to the exhaust manifold 160. The exhaust manifold 160 discharges the combusted gases (exhaust gas) to the outside of the cylinder 150. A three-way catalytic converter 161 is installed on the exhaust side of the exhaust manifold 160. The three-way catalytic converter 161 purifies the exhaust gas. The exhaust gas purified by the three-way catalytic converter 161 is discharged into the atmosphere.

[0045] An upstream air-fuel ratio sensor 162 is provided on the upstream side of the three-way catalyst 161. The upstream air-fuel ratio sensor 162 continuously detects the air-fuel ratio of the exhaust gas discharged from each cylinder 150.

[0046] Furthermore, a downstream air-fuel ratio sensor 163 is provided downstream of the three-way catalyst 161. The downstream air-fuel ratio sensor 163 outputs a switching detection signal near the stoichiometric air-fuel ratio. In this embodiment, the downstream air-fuel ratio sensor 163 is an O2 sensor.

[0047] Spark plugs 200 are respectively installed on the upper part of each cylinder 150. The spark plugs 200 generate a spark through discharge (ignition), which ignites the air-fuel mixture inside the cylinder 150. This causes an explosion within the cylinder 150, pushing the piston 170 downwards. The downward movement of the piston 170 causes the crankshaft 123 to rotate. Ignition coils 300, which generate electrical energy (voltage) to be supplied to the spark plugs 200, are connected to the spark plugs 200.

[0048] The output signals from various sensors, including the throttle opening sensor 113a, flow sensor 114, crankshaft angle sensor 121, accelerator pedal position sensor 126, coolant temperature sensor 122, and combustion pressure sensor 140, are output to the internal combustion engine control unit 1 (hereinafter referred to as "control unit 1"). The control unit 1 detects the operating state of the internal combustion engine 100 based on the output signals from these sensors. Therefore, the control unit 1 controls the amount of air supplied to the cylinder 150, the amount of fuel injected from the fuel injection device 134, and the ignition timing of the spark plug 200, etc.

[0049] [spark plug]

[0050] Next, refer to Figure 2 The following is an explanation of spark plug 200.

[0051] Figure 2 A magnified view of a section of spark plug 200 is shown for illustration.

[0052] like Figure 2As shown, the spark plug 200 has a center electrode 210 and an outer electrode 220. The center electrode 210 is supported on the spark plug seat (not shown) via an insulator 230. Thus, the center electrode 210 is insulated. The outer electrode 220 is grounded.

[0053] When the ignition coil is 300 (reference) Figure 1 When a voltage is generated in the cylinder 150, a specified voltage (e.g., 20,000V to 40,000V) is applied to the center electrode 210. When the specified voltage is applied to the center electrode 210, a discharge (ignition) occurs between the center electrode 210 and the outer electrode 220. The spark generated by the discharge then ignites the air-fuel mixture in the cylinder 150.

[0054] Furthermore, the voltage that causes the insulation breakdown of the gas components within cylinder 150, resulting in a discharge (ignition), varies depending on the state of the gas (mixture) present between the center electrode 210 and the outer electrode 220 and the cylinder pressure within cylinder 150. This voltage that generates the discharge is called the insulation breakdown voltage.

[0055] The discharge control (ignition control) of spark plug 200 is provided by the ignition control unit 83 of control device 1, which will be described later (see reference). Figure 3 )conduct.

[0056] [Hardware Configuration of the Control Device]

[0057] Next, the overall hardware configuration of control device 1 will be described.

[0058] like Figure 1 As shown, the control device 1 includes an analog input unit 10, a digital input unit 20, an A / D (Analog / Digital) converter 30, a RAM (Random Access Memory) 40, an MPU (Micro-Processing Unit) 50, a ROM (Read Only Memory) 60, an I / O (Input / Output) port 70, and an output circuit 80.

[0059] Analog output signals from various sensors, such as throttle opening sensor 113a, flow sensor 114, accelerator pedal position sensor 126, upstream air-fuel ratio sensor 162, downstream air-fuel ratio sensor 163, cylinder pressure sensor 140, and water temperature sensor 122, are input to the analog input unit 10.

[0060] The A / D converter 30 is connected to the analog input unit 10. Analog output signals from various sensors input to the analog input unit 10 are converted into digital signals by the A / D converter 30 after signal processing such as noise reduction. Subsequently, the digital signals converted by the A / D converter 30 are stored in the RAM 40.

[0061] The digital output signal from the crankshaft angle sensor 121 is input to the digital input unit 20.

[0062] I / O port 70 is connected to digital input unit 20. Digital output signals input to digital input unit 20 are stored in RAM 40 via I / O port 70.

[0063] The output signals stored in RAM 40 are processed in MPU 50.

[0064] MPU 50 executes the control program (not shown) stored in ROM 60, and thereby processes the output signals stored in RAM 40 according to the control program. MPU 50 calculates the prescribed control values ​​for the workload of each actuator (e.g., throttle valve 113, pressure regulator 132, spark plug 200, etc.) driving the internal combustion engine 100 according to the control program, and temporarily stores the control values ​​in RAM 40.

[0065] The control values ​​storing the specified workload of the actuator in RAM 40 are output to the output circuit 80 via I / O port 70.

[0066] The output circuit 80 includes functions such as an overall control unit 81, a fuel injection control unit 82, and an ignition control unit 83 (see reference). Figure 3 The overall control unit 81 performs overall control of the internal combustion engine based on output signals from various sensors (e.g., cylinder pressure sensor 140). The fuel injection control unit 82 controls the drive of the plunger rod (not shown) of the fuel injection device 134. The ignition control unit 83 controls the voltage applied to the spark plug 200.

[0067] [Functional blocks of the control device]

[0068] Next, refer to Figure 3 The functional structure of control device 1 will be explained.

[0069] Figure 3 A functional block diagram illustrating the function of control device 1.

[0070] The control device 1 implements various functions in the output circuit 80 by executing the control program stored in the ROM 60 through the MPU 50. Examples of the various functions in the output circuit 80 include the control of the fuel injection device 134 by the fuel injection control unit 82 or the discharge control of the spark plug 200 by the ignition control unit 83.

[0071] like Figure 3 As shown, the output circuit 80 of the control device 1 includes an overall control unit 81, a fuel injection control unit 82, and an ignition control unit 83.

[0072] [Overall Control Department]

[0073] The overall control unit 81 is connected to the accelerator pedal position sensor 126 and the cylinder pressure sensor 140 (CPS). The overall control unit 81 receives the requested torque (acceleration signal S1) from the accelerator pedal position sensor 126 and the output signal S2 from the cylinder pressure sensor 140.

[0074] The overall control unit 81 performs overall control of the fuel injection control unit 82 and the ignition control unit 83 based on the required torque (acceleration signal S1) from the accelerator pedal position sensor 126 and the output signal S2 from the cylinder pressure sensor 140.

[0075] [Fuel Injection Control Unit]

[0076] The fuel injection control unit 82 is connected to the cylinder discrimination unit 84 that discriminates each cylinder 150 of the internal combustion engine 100, the crankshaft angle information generation unit 85 that measures the crankshaft angle of the crankshaft 123, and the engine speed information generation unit 86 that measures the engine speed. The fuel injection control unit 82 receives cylinder discrimination information S3 from the cylinder discrimination unit 84, crankshaft angle information S4 from the angle information generation unit 85, and engine speed information S5 from the engine speed information generation unit 86.

[0077] Furthermore, the fuel injection control unit 82 is connected to an intake air volume measuring unit 87 that measures the intake air volume drawn into the cylinder 150, a load information generation unit 88 that measures the engine load, and a coolant temperature measuring unit 89 that measures the engine coolant temperature. The fuel injection control unit 82 receives intake air volume information S6 from the intake air volume measuring unit 87, engine load information S7 from the load information generation unit 88, and coolant temperature information S8 from the coolant temperature measuring unit 89.

[0078] The fuel injection control unit 82 calculates the injection quantity and injection time of the fuel to be injected from the fuel injection device 134 based on the received information. Then, the fuel injection control unit 82 sends the fuel injection pulse (INJ signal) S9 generated based on the calculated fuel injection quantity and injection time to the fuel injection device 134.

[0079] [Ignition Control Unit]

[0080] In addition to being connected to the overall control unit 81, the ignition control unit 83 is also connected to the cylinder discrimination unit 84, the angle information generation unit 85, the speed information generation unit 86, the load information generation unit 88, and the water temperature measurement unit 89, and receives information from these units.

[0081] The ignition control unit 83 calculates the primary coil 310 of the ignition coil 300 (reference) based on the received information. Figure 8 The amount of current supplied (current angle), the start time of energization, and the time to cut off the current supplying the primary coil 310 (ignition time).

[0082] The ignition control unit 83 outputs an ignition signal SA to the primary coil 310 of the ignition coil 300 based on the calculated charge, ignition start time and ignition time, thereby performing discharge control (ignition control) using the spark plug 200.

[0083] [Emission concentration and air-fuel ratio]

[0084] Next, refer to Figure 4 The relationship between emission concentration and air-fuel ratio is explained.

[0085] Figure 4 A graph illustrating the relationship between emission concentration and air-fuel ratio.

[0086] like Figure 4 As shown, near the stoichiometric air-fuel ratio, the combustion temperature is high, resulting in a high NOx concentration. On the other hand, the HC concentration is low near the stoichiometric air-fuel ratio where the fuel is fully combusted. When the air-fuel ratio increases (the fuel becomes lean), the combustion temperature decreases, thus reducing the NOx concentration. However, the HC concentration increases as the combustion temperature decreases.

[0087] [Circuit including ignition coil]

[0088] Next, refer to Figure 5 The circuit containing the ignition coil will be described.

[0089] Figure 5 A diagram illustrating a circuit containing an ignition coil.

[0090] Figure 5The circuit 500 shown has an ignition coil 300. The ignition coil 300 is composed of a primary coil 310 wound with a specified number of turns and a secondary coil 320 wound with more turns than the primary coil 310.

[0091] One end of the primary coil 310 is connected to a DC power supply 330. A specified voltage (e.g., 12V) is thus applied to the primary coil 310. The other end of the primary coil 310 is connected to the drain (D) terminal of an igniter (power-on control circuit) 340, and grounded via the igniter 340. The igniter 340 uses a transistor or a field-effect transistor (FET).

[0092] The gate (G) terminal of the igniter 340 is connected to the ignition control unit 83. The ignition signal SA output from the ignition control unit 83 is input to the 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 current flows between the drain (D) terminal and the source (S) terminal. Therefore, the ignition signal SA is output from the ignition control unit 83 via the igniter 340 to the primary coil 310 of the ignition coil 300. As a result, current flows to the primary coil 310, accumulating electrical energy.

[0093] When the output of the ignition signal SA from the ignition control unit 83 stops, the current flowing to the primary coil 310 is cut off. As a result, a high voltage corresponding to the turns ratio of the coil relative to the primary coil 310 is generated in the secondary coil 320.

[0094] The high voltage generated in the secondary coil 320 is applied to the center electrode 210 of the spark plug 200 (reference). Figure 5 This creates a potential difference between the center electrode 210 and the outer electrode 220 of the spark plug 200. When this potential difference between the center electrode 210 and the outer electrode 220 exceeds the insulation breakdown voltage Vm of the gas (the mixture in the cylinder 150), the gas components undergo insulation breakdown, resulting in a discharge between the center electrode 210 and the outer electrode 220. As a result, ignition (start-up) of the fuel (mixture) is achieved. The circuit 500, including the spark plug 200 and the ignition coil 300, corresponds to the ignition mechanism of the present invention.

[0095] The discharge path generated between the central 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 electrodes 210 and 220, the heat energy generated by the discharge is distributed to the surrounding gas and electrodes 210 and 220. Furthermore, the heat energy distributed to the surrounding gas heats the surrounding gas, promoting ignition.

[0096] [Discharge waveform of multi-key ignition]

[0097] Next, refer to Figure 6 The discharge waveforms of multi-key ignition are explained.

[0098] Figure 6 Example of discharge waveform for multi-point ignition.

[0099] like Figure 6 As shown, by repeatedly switching the ignition signal on and off after the discharge at the normal ignition time (discharge start), multiple additional discharges can be performed to achieve multi-key ignition. This multi-key ignition under additional discharges can continue until fuel injection begins.

[0100] [Air-fuel ratio and required ignition energy]

[0101] Next, refer to Figure 7 The air-fuel ratio and required ignition energy are explained.

[0102] Figure 7 A graph illustrating the relationship between air-fuel ratio and required ignition energy.

[0103] like Figure 7 As shown, near the stoichiometric air-fuel ratio, the minimum ignition energy required for ignition is low. On the other hand, when the air-fuel ratio increases relative to the stoichiometric air-fuel ratio (fuel becomes leaner), the required ignition energy increases. Furthermore, when the air-fuel ratio decreases relative to the stoichiometric air-fuel ratio (fuel becomes richer), the required ignition energy increases.

[0104] [Ignition signal control to prevent misfire]

[0105] Next, refer to Figure 8 This section explains the ignition signal control in case of misfire prevention.

[0106] Figure 8 An example of a timing diagram for ignition signal control aimed at preventing misfire.

[0107] During a cold start, the fuel vaporization is delayed due to the low temperature inside the cylinder. As a result, some fuel vaporizes only after combustion is complete. Because less fuel vaporizes by the ignition timing, the air-fuel ratio inside the cylinder increases at that time. As mentioned above, when the air-fuel ratio increases, the required ignition energy increases (see reference). Figure 7 ).

[0108] When increased ignition energy is required, insufficient ignition energy can lead to de-ignition, resulting in the discharge of unburned gas. To prevent de-ignition, discharge is performed during a period when the air-fuel ratio between the electrodes is low (fuel rich). This reduces the required ignition energy, preventing insufficient ignition energy and thus preventing de-ignition.

[0109] However, the air-fuel ratio distribution in the cylinder is difficult to predict. Therefore, it is effective to increase the ignition probability by repeatedly performing additional discharges (misignition relief) without reducing the ignition energy. Furthermore, additional discharges refer to multiple discharges following the initial discharge after fuel injection (initial ignition). The additional discharges are needed around the top dead center of piston 170, when the combustion chamber volume decreases, resulting in high cylinder pressure.

[0110] To ignite in such a high-pressure and rarefied gas environment, an ignition energy exceeding a specified value must be ensured. Furthermore, to prevent a decrease in ignition energy, the charging time must be ensured. And to ensure the charging time, the discharge cycle of the ignition signal must be set to a specified discharge cycle. That is, to prevent misfires, it is necessary to... Figure 8 As shown, the discharge cycle of the ignition signal is set to a specified cycle (hereinafter referred to as "Cycle 1") so that the ignition energy of each discharge in the additional discharge reaches or exceeds the specified value.

[0111] [Reduce HC ignition signal control]

[0112] Next, refer to Figure 9 The ignition signal control under reduced HC conditions is explained.

[0113] Figure 9 An example of a timing diagram for ignition signal control aimed at reducing HC generated in the cylinder.

[0114] As described above, during a cold start, fuel vaporization is delayed due to the low temperature inside the cylinder. As a result, some fuel vaporizes only after combustion is complete. The unburned gas in the cylinder due to this delayed vaporization is further vaporized by the heat generated during combustion. Consequently, the unburned gas increases in size after the expansion stroke. Furthermore, after the expansion stroke, the combustion chamber volume increases, thus reducing the cylinder pressure.

[0115] Unburned gas is part of the overall fuel injected into the cylinder, so its concentration is low. Therefore, the heat generated by igniting unburned gas is small, and a chain reaction of oxidation caused by additional discharge will not occur. To promote the oxidation of unburned gas, it is advisable to increase the contact opportunities between the unburned gas dispersed in the cylinder and the discharge path generated between electrodes 210 and 220.

[0116] However, the in-cylinder environment after the expansion stroke is characterized by low flow rate. That is, the in-cylinder tumble generated during the intake stroke decreases due to the passage of time and the reduction in combustion chamber volume. Therefore, in an environment with low in-cylinder flow rate, even if the discharge path is extended, it is difficult to increase the contact opportunity between the discharge path and unburned gas.

[0117] Furthermore, the additional discharge (HC in-cylinder aftertreatment) required to promote the oxidation of unburned gases occurs after combustion, resulting in low in-cylinder pressure. Moreover, the ignition energy required for discharge in a low-pressure environment is lower than that under high-pressure conditions. Therefore, to reduce HC production through oxidation, it is advisable to... Figure 9 As shown, the discharge period of the ignition signal is set to be longer than the first period ( Figure 8 The prescribed cycle for fire suppression (shown as a short second cycle) is used to increase the number of discharges.

[0118] The first and second cycles are determined based on factors such as the required ignition energy, the responsiveness of the ignition coil 300, and the performance of the noise filter. When the pulse width decreases, noise and control signals will not be distinguished. Therefore, the minimum pulse width is determined based on the performance of the noise filter. Thus, the minimum discharge cycle is determined when the minimum pulse width is set.

[0119] [Number of discharges and HC emission volume]

[0120] Next, refer to Figure 10 The relationship between the number of discharges and the amount of HC emitted is explained.

[0121] Figure 10 A graph illustrating the relationship between the number of discharges and the amount of HC emitted.

[0122] Figure 10 The results of measurements on the number of discharges and HC emissions with varying discharge cycles are presented. A single-cylinder gasoline engine was used in the measurements. As operating conditions, the engine speed was set to 1500 rpm and the mean effective pressure was set to 6.4 bar. Figure 10 As shown, shortening the discharge cycle and increasing the number of discharges can reduce the amount of HC emitted.

[0123] [Discharge cycle switching control]

[0124] Next, refer to Figure 11 The discharge cycle switching control for preventing flameout and reducing HC is explained.

[0125] Figure 11 An example of a time diagram for discharge cycle switching control aimed at resolving the trade-off between preventing misfire and reducing HC.

[0126] To prevent misfire, a relatively long first-cycle discharge period is required (reference). Figure 8 On the other hand, reducing HC requires a relatively short second-cycle discharge (see reference). Figure 9 In other words, there is a trade-off between preventing misfires and reducing HC.

[0127] To resolve trade-offs, one must be like... Figure 11As shown, the discharge cycle switches the ignition signal after fuel injection and before and after successful ignition (first explosion). Therefore, in this embodiment, discharge cycle switching control is performed to switch the ignition signal before and after successful ignition. The discharge cycle switching of the present invention is performed within either the expansion stroke or the exhaust stroke in the first explosion process.

[0128] By implementing discharge cycle switching control, the trade-off between preventing misfire and reducing HC can be resolved. That is, it is possible to prevent misfire while suppressing the generation of hydrocarbons (HC) during the cold start of the internal combustion engine 100.

[0129] Furthermore, the gas flow within the cylinder exhibits cyclical variations. Therefore, the reproducibility of the time it takes for highly ignitable gases to reach the vicinity of electrodes 210 and 220 is low. Consequently, it is difficult to predict the successful ignition (first explosion) time in advance. Therefore, in this embodiment, the successful ignition time is detected by real-time monitoring of the cylinder pressure and by measuring the absolute value of the cylinder pressure or the amount of change in pressure relative to the first ignition time (pressure change). This allows for high-precision detection of the successful ignition time.

[0130] In-cylinder pressure can be detected, for example, using the combustion pressure sensor 140 described above (reference). Figure 1 In addition, the cylinder pressure can also be detected by a method described in Japanese Patent Application Publication No. 2019-210827, which calculates the cylinder pressure based on the current flowing to the spark plug 200 and the voltage between the electrodes 210 and 220 of the spark plug 200.

[0131] Specifically, the peak values ​​of the secondary voltage and secondary current of the ignition coil 300 during each discharge are detected and calculated using the following formula (1). Furthermore, in formula (1), Vs represents the inter-electrode voltage during discharge, p represents the cylinder pressure, d represents the inter-electrode distance, and A, B, and C represent constants.

[0132] Vs=Bpd / {ln(Apd)+C} ··· (1)

[0133] Thus, by calculating the cylinder pressure based on the peak values ​​of the secondary voltage and secondary current, there is no need to install combustion pressure sensors 140 in each cylinder 150, thereby reducing the cost of the internal combustion engine 100.

[0134] [Discharge cycle switching processing]

[0135] Next, refer to Figure 12 The discharge cycle switching process of this embodiment will be explained.

[0136] Figure 12 This is a flowchart illustrating an example of a discharge cycle switching process.

[0137] Figure 12 The discharge cycle switching process shown begins simultaneously with the start of the discharge for the first ignition after fuel injection, when the ignition signal changes from on to off. Furthermore, the discharge cycle switching process is repeatedly performed between the start of the first ignition discharge and the start of the next fuel injection.

[0138] First, the ignition control unit 83 (reference) Figure 3 The first discharge mode (S101) is set to prevent misfire. The discharge cycle of the first discharge mode is the first cycle described above. That is, the ignition control unit 83 sets the discharge cycle and charging time required for successful ignition in an environment with high pressure and high flow rate in the cylinder.

[0139] Next, the ignition control unit 83 determines whether fuel injection has occurred (S102). That is, if the fuel injection signal is on, the ignition control unit 83 determines that fuel injection has occurred; if the fuel injection signal is off, the ignition control unit 83 determines that fuel injection has not occurred. Furthermore, the ignition control unit 83 obtains the on / off information of the fuel injection signal from the overall control unit 81. In S102, when it is determined that fuel injection has occurred (S102 is the determination case), the ignition control unit 83 stops additional discharge and ends the discharge cycle switching process.

[0140] In S102, when it is determined that no fuel injection has been performed (S102 is the case of no determination), the ignition control unit 83 outputs an ignition signal that follows the set discharge mode and repeatedly performs additional discharge (charge and discharge) (S103).

[0141] Next, the ignition control unit 83 detects the cylinder pressure (S104). In this embodiment, the secondary voltage and secondary current during discharge are detected, and the peak values ​​of the secondary voltage and secondary current are substituted into the pressure conversion formula (Equation (1) above) to calculate the cylinder pressure.

[0142] Next, the ignition control unit 83 determines whether ignition has occurred (ignition successful) (S105). In this process, the ignition control unit 83 compares the absolute value of the pressure detected in S104, or the amount of change in pressure relative to the first ignition time, with a predetermined threshold. If the value is above the threshold, it determines that ignition has occurred. On the other hand, if the absolute value of the pressure detected in S104, or the amount of change in pressure relative to the first ignition time, is less than the predetermined threshold, the ignition control unit 83 determines that ignition has not occurred.

[0143] In S105, if it is determined that ignition has not occurred (S105 is a negative determination), the ignition control unit 83 transfers the processing to S102. On the other hand, in S105, if it is determined that ignition has occurred (S105 is a positive determination), the ignition control unit 83 sets a second discharge mode (S106) for the purpose of reducing HC generated in the cylinder.

[0144] The discharge cycle of the second discharge mode is the second cycle described above. That is, it is set to the discharge cycle and charging time required to promote the oxidation of unburned gases in a low-pressure and low-flow-rate environment in the cylinder. After the processing of S106, the ignition control unit 83 outputs an ignition signal following the second discharge mode until fuel injection begins. For example, if ignition is determined to have occurred after one charge-discharge cycle following the ignition signal of the first discharge mode, after one additional discharge for the purpose of preventing misfire, it switches to an additional discharge for the purpose of reducing HC.

[0145] [Ignition signal DUTY ratio]

[0146] Next, refer to Figure 13 The DUTY ratio of the ignition signal is explained.

[0147] Figure 13 A diagram illustrating the charging and discharging time distribution of a typical passive ignition coil.

[0148] In terms of the switching characteristics of the ignition coil 300, the time for discharging is shorter than the time for charging. Therefore, if the DUTY ratio of the ignition signal is set to 50%, the operating rate of the ignition coil 300 will decrease, and it will be unable to efficiently obtain heat energy.

[0149] like Figure 13 As shown, in this embodiment, the DUTY ratio in the additional discharge (first discharge mode and second discharge mode) is set as the charge-discharge time ratio of the ignition coil 300. This maximizes the operating rate of the ignition coil 300, thereby maximizing the heat energy generated during discharge. Furthermore, the DUTY ratio in the initial ignition discharge can also be set as the charge-discharge time ratio of the ignition coil 300.

[0150] Furthermore, by setting the DUTY ratio in the additional discharge to the charge-discharge time ratio of the ignition coil 300, the heat generation of the ignition coil 300 is increased. Therefore, the DUTY ratio can be changed based on the measured or inferred temperature of the ignition coil 300. For example, if the temperature of the ignition coil 300 is above a predetermined temperature, the DUTY ratio can be changed by reducing the operating rate of the ignition coil 300. This prevents overheating of the ignition coil 300. The temperature of the ignition coil 300 can be inferred, for example, from the temperature of the igniter 340.

[0151] Thus, the internal combustion engine control device 1 of this embodiment controls an internal combustion engine 100 equipped with a fuel injection device 134 (injector), a spark plug 200, and an ignition coil 300. The fuel injection device 134 (injector) injects fuel into the cylinder 150. The spark plug 200 has electrodes 210 and 220 (ignition electrodes) disposed within the cylinder 150. The ignition coil 300 is connected to the spark plug 200. The internal combustion engine control device 1 has an ignition control unit 83 (control unit) that outputs an ignition signal (ignition signal) to the ignition coil 300. The ignition control unit 83 outputs an ignition signal for a first cycle to the ignition coil 300 at least after fuel injection for the first explosion, and outputs an ignition signal for a second cycle, shorter than the first cycle, to the ignition coil 300 after successful ignition. This resolves the trade-off between preventing misfires and reducing HC emissions. That is, it can suppress the generation of hydrocarbons (HC) during the cold start of the internal combustion engine 100 while preventing misfire.

[0152] Furthermore, if the pressure inside cylinder 150 (cylinder pressure) exceeds a predetermined threshold, the ignition control unit 83 (control unit) detects successful ignition. This allows for high-precision detection of the ignition success time.

[0153] Furthermore, the ignition control unit 83 (control unit) calculates the pressure inside the cylinder 150 (cylinder pressure) based on the secondary voltage and secondary current values ​​of the ignition coil 300 for each discharge made by the spark plug 200. Therefore, even without installing combustion pressure sensors 140 in each cylinder 150, the pressure inside the cylinder 150 can be detected. As a result, cost reduction of the internal combustion engine 100 can be achieved.

[0154] Furthermore, the ignition control unit 83 (control unit) changes the cycle of the energizing signal from the first cycle to the second cycle during either the expansion stroke or the exhaust stroke in the initial explosion process. This allows for additional discharges at appropriate times to prevent misfires and to reduce HC generated in the cylinder.

[0155] Furthermore, the ignition control unit 83 (control unit) adjusts the DUTY ratio of the energizing signal based on the temperature of the ignition coil 300. This prevents overheating of the ignition coil 300, and consequently, prevents malfunctions of the ignition coil 300.

[0156] Furthermore, the ignition mechanism of this embodiment includes a spark plug 200 and an ignition coil 300. The spark plug 200 has electrodes 210 and 220 (ignition electrodes) disposed within the cylinder 150, and the ignition coil 300 is connected to the spark plug 200. The control method of this ignition mechanism is to output a first-cycle energizing signal to the ignition coil 300 at least after the fuel injection for the initial explosion, and to output a second-cycle energizing signal, shorter than the first cycle, to the ignition coil 300 after successful ignition. This resolves the trade-off between preventing misfire and reducing HC. That is, it can prevent misfire while suppressing the generation of hydrocarbons (HC) during cold starting of the internal combustion engine 100.

[0157] The present invention is not limited to the embodiments described above and shown in the accompanying drawings, and various modifications may be made without departing from the spirit of the invention as set forth in the claims.

[0158] Furthermore, the above-described embodiments are provided to illustrate the present invention in an easily understandable manner and are not necessarily limited to all the described configurations. Additionally, a portion of the configuration of one embodiment may be replaced with the configuration of another embodiment, and the configuration of another embodiment may be added to the configuration of one embodiment. Furthermore, other configurations may be added, deleted, or replaced to a portion of the configuration of each embodiment.

[0159] For example, the above embodiment describes an example of discharge cycle switching control after fuel injection for the first explosion. However, the discharge cycle switching control of the present invention can be implemented at least after fuel injection for the first explosion, or it can be implemented after fuel injection at other times.

[0160] Symbol Explanation

[0161] 1…Internal combustion engine control unit, 10…Analog input unit, 20…Digital input unit, 30…A / D converter, 40…RAM, 50…MPU, 60…ROM, 70…I / O port, 80…Output circuit, 81…Overall control unit, 82…Fuel injection control unit, 83…Ignition control unit, 84…Cylinder identification unit, 85…Angle information generation unit, 86…Speed ​​information generation unit, 87…Intake air volume measurement unit, 88…Load information generation unit, 89…Water temperature measurement unit, 100…Internal combustion engine, 110…Air filter, 111…Intake manifold, 112…Intake manifold, 113…Throttle valve, 113a…Throttle valve opening sensor, 114…Flow sensor, 115…Intake air temperature sensor, 120…Ring gear, 121…Crankshaft angle sensor 122…Water temperature sensor, 123…Crankshaft, 125…Accelerator pedal, 126…Accelerator pedal position sensor, 130…Fuel tank, 131…Fuel pump, 132…Pressure regulator, 133…Fuel line, 134…Fuel injection device, 140…Cylinder pressure sensor, 150…Cylinder, 151…Intake valve, 152…Exhaust valve, 160…Exhaust manifold, 161…Three-way catalytic converter, 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…Ignition device, 500…Circuit.

Claims

1. An internal combustion engine control device for controlling an internal combustion engine having an injector, a spark plug, and an ignition coil, wherein the injector injects fuel into a cylinder, the spark plug has an ignition electrode disposed within the cylinder, and the ignition coil is connected to the spark plug, characterized in that... It has a control unit that outputs an energizing signal to the ignition coil. The control unit outputs an ignition signal to the ignition coil at least after the fuel injection for the first explosion. Then, it outputs a first-cycle energizing signal to the ignition coil for misfire relief. After successful ignition, it outputs a second-cycle energizing signal, shorter than the first cycle, to the ignition coil.

2. The internal combustion engine control device according to claim 1, characterized in that, When the pressure inside the cylinder exceeds a predetermined threshold, the control unit detects that the ignition is successful.

3. The internal combustion engine control device according to claim 2, characterized in that, The control unit calculates the pressure inside the cylinder based on the secondary voltage and secondary current values ​​of the ignition coil for each discharge of the spark plug.

4. The internal combustion engine control device according to claim 1, characterized in that, The control unit changes the period of the energizing signal from the first period to the second period during either the expansion or exhaust stroke in the initial explosion process.

5. The internal combustion engine control device according to claim 1, characterized in that, The control unit changes the DUTY ratio of the energizing signal based on the temperature of the ignition coil.

6. A method for controlling an ignition mechanism, the ignition mechanism having a spark plug and an ignition coil, the spark plug having an ignition electrode disposed in a cylinder, the ignition coil being connected to the spark plug, characterized in that... An ignition signal is output to the ignition coil at least after the fuel injection for the first explosion. Then, an energizing signal for the first cycle is output to the ignition coil for misfire relief. After successful ignition, an energizing signal for the second cycle, which is shorter than the first cycle, is output to the ignition coil.

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