Engine control device and engine control method

Abstract

To provide an engine control device capable of sufficiently heating an ignition plug electrode while suppressing an increase in system cost.SOLUTION: An ECU 20 controls output of an engine 100 having an ignition device for controlling ignition timing of an ignition plug 17 igniting an air-fuel mixture present in a main combustion chamber 14a by injecting a flame jet generated through ignition of the air-fuel mixture by using an electrode within an auxiliary chamber 8 to the main combustion chamber 14a. The ECU 20 includes a control section continuing supply of preliminary ignition signal for causing the ignition plug 17 to perform preliminary ignition that does not involve generation of combustion of the air-fuel mixture until main ignition that enables the air-fuel mixture to reach a spark generated in the electrode.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an engine control device and an engine control method.

Background Art

[0002] Conventionally, a gasoline engine that forms an air-fuel mixture in a combustion chamber and burns it by ignition or auto-ignition is known. As a technique for improving the thermal efficiency of this type of engine, there is a sub-chamber type flame jet ignition (hereinafter also referred to as "sub-chamber combustion") system in which the air-fuel mixture is ignited in a sub-combustion chamber (also referred to as a "sub-chamber"), which is a minute space of several cc, and a flame jet is injected into the main combustion chamber.

[0003] In a general gasoline engine, a spark plug is fixed in such a manner that the tip of the spark plug provided in the upper part of the main combustion chamber is exposed to the combustion chamber. At the start of combustion, a spark is generated by discharge from the spark plug to directly ignite the air-fuel mixture in the main combustion chamber. On the other hand, in sub-chamber combustion, a sub-chamber is provided in the upper part of the main combustion chamber, and the spark plug is fixed in such a manner that it is exposed in the sub-chamber. The sub-chamber is provided with sub-chamber injection holes communicating with the main combustion chamber. At the start of combustion, first, ignition of the air-fuel mixture is performed inside the sub-chamber. After combustion occurs in the sub-chamber, a jet containing high-temperature and unburned air-fuel mixture is ejected from the sub-chamber injection holes toward the main combustion chamber side, and the air-fuel mixture on the main combustion chamber side is ignited by this jet. In the main combustion chamber, ignition occurs simultaneously at multiple points, and combustion progresses rapidly compared to the case where the sub-chamber is not used, so the combustion stability is improved.

[0004] By sub-chamber combustion, lean combustion in which an air-fuel mixture with less fuel than the stoichiometric air-fuel ratio is burned can be performed at a higher dilution state. Due to an increase in the specific heat ratio of the air-fuel mixture, the theoretical thermal efficiency is improved, and due to a reduction in pump loss, the thermal efficiency is improved. In addition, before abnormal combustion such as knocking occurs, combustion gas can reach the abnormal combustion generation region, and as a result, a knocking suppression effect can also be obtained. Thereby, an optimal ignition timing can be taken even in the high load region, and the exhaust loss is reduced and the thermal efficiency is further improved compared to the case where the sub-chamber is not used.

[0005] On the other hand, during low flow such as at engine startup, exhaust gas remains inside the auxiliary chamber, and ignition in the auxiliary chamber is likely to be inhibited. Combustion stability during cold start is a major issue in auxiliary chamber engines. As technologies for improving cold start performance in auxiliary chamber engines, for example, the technologies described in Patent Documents 1 and 2 are known.

[0006] Patent Document 1 describes an internal combustion engine including a main combustion chamber, an auxiliary chamber communicating with the main combustion chamber via a plurality of communication holes, a spark plug provided to perform ignition inside the auxiliary chamber, and a heating unit for raising the temperature of the wall of the auxiliary chamber at low temperatures.

[0007] Patent Document 2 describes a spark ignition internal combustion engine having an ignition control unit that controls the discharge of a spark plug provided in a cylinder. The ignition control unit is configured to perform the discharge of the spark plug in a state where fuel is not injected into the cylinder from a fuel injection valve in the first combustion cycle after the start of operation of the internal combustion engine. That is, it is described that pre-ignition for heating the electrode portion of the spark plug is performed before igniting the air-fuel mixture containing fuel.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in the technology described in Patent Document 1, a glow plug or the like for heating the auxiliary chamber is required, which increases the system cost. In addition, in the technique described in Patent Document 2, in order to prevent early ignition of the air-fuel mixture by pre-ignition, the timing of pre-ignition is limited to before fuel injection. For this reason, in a port fuel injection type engine, pre-ignition during the intake and compression strokes cannot be performed. Further, in a direct in-cylinder fuel injection type engine, pre-ignition cannot be performed mainly after the fuel injection timing set in the intake stroke. For this reason, it becomes impossible to secure a pre-ignition period for sufficiently heating the electrodes during extremely low temperature starting or the like, and the occurrence of misfires and the emission amount of unburned hydrocarbons (HC) increase.

[0010] The present invention has been made in view of such circumstances, and an object thereof is to maximize the heating amount of an ignition plug while suppressing early ignition of an air-fuel mixture.

Means for Solving the Problems

[0011] An engine control device according to the present invention includes a cylinder in which an air-fuel mixture in which fuel injected by a fuel injection device and air taken in from an intake system are mixed burns in a main combustion chamber facing a piston, a sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber, and an electrode attached inside the sub-combustion chamber, and controls the output of an engine including: an ignition plug that injects a flame jet generated by igniting the air-fuel mixture by the electrode inside the sub-combustion chamber into the main combustion chamber to ignite the air-fuel mixture in the main combustion chamber; and an ignition device that controls the ignition timing of the ignition plug. This engine control device includes a control unit that continues to supply a pre-ignition signal for causing the ignition plug to perform pre-ignition without combustion occurrence of the air-fuel mixture until main ignition at which the air-fuel mixture reaches a spark generated by the electrode. Further, the engine control device according to the present invention controls the output of an engine including: a cylinder in which an air-fuel mixture formed by mixing fuel injected by a fuel injection device and air taken in from an intake system burns in a main combustion chamber facing a piston; a sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber; an electrode attached inside the sub-combustion chamber; a spark plug that injects into the main combustion chamber a flame jet generated by igniting the air-fuel mixture by the electrode inside the sub-combustion chamber to ignite the air-fuel mixture in the main combustion chamber; and an ignition device that controls the ignition timing of the spark plug. This engine control device has a control unit that: the timing at which the air-fuel mixture reaches the spark plug is the timing at which the pressure in the sub-combustion chamber becomes lower than the pressure in the main combustion chamber; continues to supply a pre-ignition signal for causing the spark plug to perform pre-ignition without combustion of the air-fuel mixture until main ignition at which the air-fuel mixture reaches a spark generated by the electrode; and when the closing timing of an intake valve provided in the intake system is set in the intake stroke, continues pre-ignition from after the combustion of the air-fuel mixture in the combustion cycle until the start timing of the compression stroke in the combustion cycle. Further, the engine control device according to the present invention controls the output of an engine including: a cylinder in which an air-fuel mixture formed by mixing fuel injected by a fuel injection device and air taken in from an intake system burns in a main combustion chamber facing a piston; a sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber; an electrode attached inside the sub-combustion chamber; a spark plug that injects into the main combustion chamber a flame jet generated by igniting the air-fuel mixture by the electrode inside the sub-combustion chamber to ignite the air-fuel mixture in the main combustion chamber; and an ignition device that controls the ignition timing of the spark plug. This engine control device has a control unit that: the timing at which the air-fuel mixture reaches the spark plug is the timing at which the pressure in the sub-combustion chamber becomes lower than the pressure in the main combustion chamber; continues to supply a pre-ignition signal for causing the spark plug to perform pre-ignition without combustion of the air-fuel mixture until main ignition at which the air-fuel mixture reaches a spark generated by the electrode; and sets the timing at which the air-fuel mixture reaches the spark plug to the timing obtained by adding a mixture arrival delay period determined by the engine rotation speed, the intake pressure of the air-fuel mixture, and the shape of the sub-combustion chamber to the actual compression start timing at which the air-fuel mixture is actually compressed in the compression stroke. Further, an engine control device according to the present invention controls the output of an engine including: a cylinder in which an air-fuel mixture, in which fuel injected by a fuel injection device and air taken in from an intake system are mixed, burns in a main combustion chamber facing a piston; a sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber; and an electrode attached inside the sub-combustion chamber. The engine control device includes an ignition plug that injects a flame jet generated by igniting the air-fuel mixture by the electrode inside the sub-combustion chamber into the main combustion chamber to ignite the air-fuel mixture in the main combustion chamber, and an ignition device that controls the ignition timing of the ignition plug. This engine control device continues to supply a pre-ignition signal for causing the ignition plug to perform pre-ignition without combustion of the air-fuel mixture until main ignition at which the air-fuel mixture reaches a spark generated by the electrode, and includes a control unit that determines the end time of the spark based on a primary voltage, a secondary current, a secondary voltage of an ignition coil, or a map value stored in advance for each operating condition.

Effects of the Invention

[0012] According to the present invention, by performing pre-ignition without combustion occurrence of the air-fuel mixture until main ignition at which the air-fuel mixture reaches a spark, early ignition of the air-fuel mixture is suppressed and the heating amount of the ignition plug is maximized, so that stable combustion can be achieved at the time of main ignition. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

Brief Description of the Drawings

[0013]

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Figure 20

Mode for Carrying Out the Invention

[0014] Hereinafter, a mode (engine control device) for carrying out the present invention will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same function or configuration are denoted by the same reference numerals, and redundant descriptions are omitted.

[0015] <1. First Embodiment Example> First, a configuration example of an engine control device according to the first embodiment example (hereinafter referred to as "this example") will be described.

[0016] <1-1. Configuration Example of Engine> First, a configuration example of the engine will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram showing a system configuration example of the engine 100 of this example. FIG. 2 is a schematic configuration diagram showing a configuration example around the cylinder 14 of the engine 100. FIG. 3 is an enlarged view of the spark plug 17.

[0017] The engine 100 shown in FIG. 1 is an example of an in-cylinder injection type internal combustion engine (direct injection internal combustion engine) that directly injects fuel made of gasoline into the cylinder (also referred to as "in-cylinder"). The engine 100 is a four-cycle engine that repeats four strokes: an intake stroke, a compression stroke, a combustion (expansion) stroke, and an exhaust stroke. Further, the engine 100 is, for example, a multi-cylinder engine having four cylinders. Note that the number of cylinders of the engine 100 is not limited to four, and it may have six or eight or more cylinders.

[0018] As shown in FIG. 1, the engine 100 includes an air flow sensor 1, an electronic control throttle valve 2, an intake pressure sensor 3, a supercharger 4, an intercooler 7, and a cylinder 14. The air flow sensor 1, the electronic control throttle valve 2, the intake pressure sensor 3, the compressor 4a of the supercharger 4, and the intercooler 7 are arranged at positions up to the cylinder 14 in the intake pipe 6.

[0019] The air flow sensor 1 measures the intake air volume and the intake air temperature. The electronic control throttle valve 2 is drivably opened and closed by a drive motor (not shown). Then, based on the accelerator operation of the driver, the opening degree of the electronic control throttle valve 2 is adjusted, and the air volume taken into the intercooler 7 and the cylinder 14 is adjusted.

[0020] The compressor 4a is a supercharger that supercharges the intake air. This compressor 4a has a rotational force transmitted thereto by a turbine 4b described later. The intercooler 7 is disposed upstream of the cylinder 14 and downstream of the electronic control throttle valve 2 and the air flow sensor 1. And the intercooler 7 cools the intake air.

[0021] Also, as shown in FIGS. 1 and 2, the engine 100 is provided with an injector 13 that injects fuel into the cylinder 14, an ignition device including an ignition coil 16 and an ignition plug 17 that supplies ignition energy, a sub chamber 8, and a knock sensor 47 for each cylinder 14. The ignition coil 16 generates a high voltage under the control of the ECU 20 and applies it to the ignition plug 17. The ignition plug 17 generates a spark by the applied high voltage.

[0022] Here, as shown in FIGS. 2 and 3, an engine (engine 100) includes a cylinder (cylinder 14) in which an air-fuel mixture, which is a mixture of fuel injected by a fuel injection device (injector 13) and air taken in from an intake system, burns in a main combustion chamber (main combustion chamber 14a) facing a piston (piston 18). The engine (engine 100) also has a sub-combustion chamber (sub-chamber 8) that communicates with the main combustion chamber (main combustion chamber 14a) and takes in the air-fuel mixture from the main combustion chamber (main combustion chamber 14a), and an electrode attached inside the sub-combustion chamber (sub-chamber 8). An ignition plug (ignition plug 17) that injects a flame jet generated by the electrode igniting the air-fuel mixture inside the sub-combustion chamber (sub-chamber 8) into the main combustion chamber (main combustion chamber 14a) to ignite the air-fuel mixture in the main combustion chamber (main combustion chamber 14a), and an ignition device that controls the ignition timing of the ignition plug (ignition plug 17). The main combustion chamber 14a is formed inside the cylinder 14. The ignition plug 17 is disposed inside a sub-chamber 8 provided in the cylinder 14. The hollow sub-chamber 8 is inserted into the cylinder 14. Therefore, the region where the air-fuel mixture can burn is divided into the main combustion chamber 14a formed inside the cylinder 14 and the sub-chamber 8. The sub-chamber 8 is fixed to the cylinder head with its tip exposed inside the main combustion chamber 14a. A sub-chamber injection hole 8a that communicates with the main combustion chamber 14a is formed at the tip of the sub-chamber 8. The sub-chamber 8 and the main combustion chamber 14a communicate with each other through the sub-chamber injection hole 8a. And the air-fuel mixture is taken into the sub-chamber 8 from the main combustion chamber 14a through the sub-chamber injection hole 8a.

[0023] Also, when the ignition plug 17 generates a spark, a spark 51 is formed between the side electrode 17a and the ground electrode 17b shown in FIG. 3. Note that the side electrode 17a and the ground electrode 17b are collectively referred to as the "ignition plug electrode". When the spark 51 occurs, the side electrode 17a and the ground electrode 17b are heated. In pre-ignition, the voltage between the electrodes of the ignition plug (ignition plug 17) exceeds the breakdown voltage, accompanied by the generation of discharge. However, since there is no air-fuel mixture in the auxiliary chamber 8, even if the spark 51 occurs, it does not burn. On the other hand, in main ignition, the spark 51 ignites the air-fuel mixture, causing the air-fuel mixture in the auxiliary chamber 8 to burn. The flame generated in the auxiliary chamber 8 passes through the auxiliary chamber injection holes 8a and jets into the main combustion chamber 14a as a plurality of flame jets. The flame jets ignite the air-fuel mixture in the main combustion chamber 14a, causing main combustion to occur. Hereinafter, the flame jets injected from the auxiliary chamber injection holes 8a are simply referred to as "jets". In the main combustion chamber 14a, ignition occurs simultaneously at multiple points with the ejection of the jets. Therefore, the engine 100 provided with the auxiliary chamber 8 burns more rapidly compared to an engine without the auxiliary chamber 8, improving the combustion stability.

[0024] Also, a voltage sensor (not shown) is attached to the ignition coil 16. The voltage sensor measures the primary side voltage or the secondary side voltage of the ignition coil 16. Then, the voltage information measured by the voltage sensor is sent to an ECU (Engine Control Unit) 20, which is an example of an engine control device.

[0025] Also, as shown in FIG. 1, a variable valve 5 is provided on the cylinder head of the cylinder 14. As shown in FIG. 2, the variable valve 5 has an intake side timing mechanism 5a, an exhaust side timing mechanism 5b, an intake valve 31, and an exhaust valve 32. The intake valve 31 is disposed at an intake port to which an intake pipe 6 in the cylinder 14 is connected, and the exhaust valve 32 is disposed at an exhaust port to which an exhaust pipe 15 (described later) in the cylinder 14 is connected.

[0026] The variable valve 5 adjusts the valve opening and closing times of the intake valve 31 and the exhaust valve 32 by means of an intake-side timing mechanism 5a and an exhaust-side timing mechanism 5b. Thereby, the flow rate of the air-fuel mixture flowing into the cylinder 14 or the exhaust gas discharged from the cylinder 14 is adjusted. The ECU 20 can adjust the intake air amount and the internal EGR amount of all the cylinders 14 by adjusting the variable valve 5.

[0027] Furthermore, a piston 18 is slidably disposed in the cylinder 14. The piston 18 compresses the air-fuel mixture of fuel and gas flowing into the cylinder 14. Then, the piston 18 reciprocates in the cylinder 14 by the combustion pressure generated in the cylinder 14.

[0028] A crankshaft 48 is connected to the piston 18 via a connecting rod. Also, a crank angle sensor 49 for detecting the angle of the crankshaft 48 is provided in the vicinity of the crankshaft 48. The crank angle sensor 49 detects teeth provided at predetermined angular intervals (for example, 6 deg) in the circumferential direction of the crankshaft 48.

[0029] Also, as shown in FIG. 1, the knock sensor 47 is attached to the side surface portion or the cylinder head of the cylinder 14. The knock sensor 47 is an acceleration sensor that detects the vibration of the cylinder 14. The position where the knock sensor 47 is provided is not limited to the side surface portion of the cylinder 14, and may be a position where the vibration of the cylinder 14 such as the upper part of the cylinder head can be detected. The vibration signal (acceleration information) of the cylinder 14 detected by the knock sensor 47 is output to the ECU 20. Then, when the ECU 20 determines that the vibration signal from the knock sensor 47 exceeds a preset knock threshold value, it detects the occurrence of knocking.

[0030] The injector 13 is controlled by the ECU 20 to inject fuel into the cylinder 14. As a result, in the main combustion chamber 14a of the cylinder 14, a mixed gas in which air and fuel are mixed is generated. Further, a high-pressure fuel pump (not shown) is connected to the injector 13. The fuel whose pressure has been increased by the high-pressure fuel pump is supplied to the injector 13. Furthermore, a fuel pressure sensor for measuring the fuel injection pressure is provided in the fuel pipe connecting the injector 13 and the high-pressure fuel pump.

[0031] In addition, a port injection injector 13A is attached to the intake pipe 6. The port injection injector 13A is controlled by the ECU 20 to inject fuel into the intake pipe 6. The fuel injected by the port injection injector 13A into the intake pipe 6 is taken into the cylinder 14 during the intake stroke.

[0032] In FIG. 1, an engine 100 including the injector 13 and the port injection injector 13A is shown, but it may be configured as an engine 100 provided with only either the injector 13 or the port injection injector 13A. Hereinafter, it will be described assuming that fuel is injected from the injector 13.

[0033] As shown in FIG. 1, a turbine 4b, an electronically controlled wastegate valve 11, a three-way catalyst 10, and an air-fuel ratio sensor 9 are provided in the exhaust pipe 15. The turbine 4b is rotated by the exhaust gas passing through the exhaust pipe 15 and transmits the rotational force to the compressor 4a. The electronically controlled wastegate valve 11 adjusts the exhaust gas flow path flowing into the turbine 4b.

[0034] The three-way catalyst 10 purifies harmful substances contained in the exhaust gas by an oxidation-reduction reaction. The air-fuel ratio sensor 9 is disposed upstream of the three-way catalyst 10. And the air-fuel ratio sensor 9 detects the air-fuel ratio of the exhaust gas passing through the exhaust pipe 15.

[0035] Further, the engine 100 is provided with an EGR flow path pipe 40 that recirculates exhaust gas (EGR gas) from a position downstream of the three-way catalyst 10, upstream of the compressor 4a, and downstream of the air flow sensor 1. The EGR flow path pipe 40 is provided with an EGR cooler 42, an EGR valve 41, and a differential pressure sensor 43.

[0036] The EGR cooler 42 cools the EGR gas. The EGR valve 41 controls the flow rate of the EGR gas passing through the EGR flow path pipe 40 (EGR flow rate). A differential pressure sensor 43 for detecting the differential pressure before and after the EGR valve 41 is attached near the EGR valve 41. Here, the differential pressure before and after the EGR valve 41 is the difference between the pressure on the upstream side and the pressure on the downstream side of the EGR valve 41 in the EGR flow path pipe 40. The EGR temperature sensor 44 is arranged downstream of the EGR valve 41. The EGR temperature sensor 44 detects the temperature of the EGR gas flowing through the EGR flow path pipe 40.

[0037] A part of the exhaust gas purified by the three-way catalyst 10 does not flow out to the outside but flows into the EGR flow path pipe 40 and is used as EGR gas. The EGR gas passes through the EGR cooler 42 and the EGR valve 41 and then merges with the fresh air sucked in upstream of the compressor 4a. The mixed gas of the EGR gas and the fresh air flows into the cylinder 14 after passing through the intercooler 7 and the electronic control throttle valve 2.

[0038] Further, signals detected by various sensors such as the air flow sensor 1, the intake pressure sensor 3, and the knock sensor 47 are sent to the ECU 20. Also, a signal detected by an accelerator opening sensor 12 that detects the amount of depression of the accelerator pedal, that is, the accelerator opening, is also sent to the ECU 20.

[0039] The ECU 20 calculates the required torque based on the output signal of the accelerator opening sensor 12. That is, the accelerator opening sensor 12 is used as a required torque detection sensor for detecting the required torque for the engine 100. Further, the ECU 20 calculates the rotational speed of the engine 100 based on the output signal of the crank angle sensor 49. Then, the ECU 20 optimally calculates the main operating amounts of the engine 100, such as the air flow rate, the fuel injection amount, the ignition timing, and the fuel pressure, based on the operating state of the engine 100 obtained from the outputs of various sensors.

[0040] The fuel injection amount calculated by the ECU 20 is converted into an opening valve pulse signal and output to the injector 13. Further, the ignition timing calculated by the ECU 20 is output to the spark plug 17 as an ignition signal. Furthermore, the throttle opening calculated by the ECU 20 is output to the electronic control throttle valve 2 as a throttle drive signal. Also, the EGR valve opening calculated by the ECU 20 is output to the EGR valve 41 as an EGR valve opening drive signal.

[0041] <1-2. Configuration Example of ECU 20> Next, a configuration example of the ECU 20 will be described with reference to FIG. 4. FIG. 4 is a block diagram showing the configuration of the ECU 20.

[0042] As shown in FIG. 4, the ECU 20 includes an input circuit 21, an input / output port 22, a CPU (Central Processing Unit) 23a, a ROM (Read Only Memory) 23b, and a RAM (Random Access Memory) 23c. Further, the ECU 20 has an ignition control unit 24.

[0043] The input circuit 21 receives information measured by various sensors such as the accelerator opening which is the output signal of the accelerator opening sensor 12, the rotational speed, the humidity in the air detected by a humidity sensor (not shown), the air quantity which is the output signal detected by the air flow sensor 1, the crank angle which is the output signal of the crank angle sensor 49, ignition device information output from the ignition device (including the coil primary voltage or secondary voltage from a voltage sensor not shown), and knock sensor information which is the output signal of the knock sensor 47.

[0044] The input circuit 21 performs signal processing such as noise removal on the input signals and sends the values of each piece of information to the input / output port 22. The values input to the input port of the input / output port 22 are stored in the RAM 23c.

[0045] The ROM 23b stores a control program describing the content of various arithmetic processes executed by the CPU 23a, MAPs and data tables used in each process, etc. The RAM 23c is provided with a storage area for storing the values input to the input port of the input / output port 22 and the values representing the operation amounts of each actuator calculated according to the control program. Also, the values representing the operation amounts of each actuator stored in the RAM 23c are sent to the output port of the input / output port 22.

[0046] The ignition signal set to the output port of the input / output port 22 is sent to the ignition coil 16 via the ignition control unit 24. The ignition control unit 24 controls the energization timing and energization time to the ignition coil 16. Further, the ignition control unit 24 performs discharge energy control at the spark plug 17. And the control unit (control unit 500) continues to supply a pre-ignition signal for causing the spark plug (spark plug 17) to perform pre-ignition without combustion of the air-fuel mixture until the main ignition when the air-fuel mixture reaches the spark (spark 51) generated at the electrode. And the control unit (control unit 500) performs pre-ignition at the start of the engine (engine 100) or before the cycle in which fuel injection is started by the fuel injection device (injector 13).

[0047] In addition, in this example, an example in which the ignition control unit 24 is provided in the ECU 20 has been described, but the present invention is not limited to this. For example, part of the ignition control unit 24, or all of the ignition control unit 24, may be implemented in a control device different from the ECU 20.

[0048] Further, the ECU 20 calculates a pre-ignition and a main ignition profile for heating the spark plug based on output signals from various sensors, and controls the discharge at the spark plug 17.

[0049] <1-3. Configuration Example of Pre-Ignition Profile Correction Process in ECU 20> Next, with reference to FIG. 5, a configuration example of each functional unit that performs the pre-ignition profile correction process in the ECU 20 will be described. FIG. 5 is a functional block diagram showing an internal configuration example of the ECU 20. Among the functional units in the ECU 20, the part that controls the periods of pre-ignition and main ignition according to the present embodiment is used as an example of the control unit according to the present embodiment.

[0050] As shown in FIG. 5, the ECU 20 includes an engine temperature acquisition unit 501, a target spark plug heating amount calculation unit 502, an engine sensor value acquisition unit 503, a calculation unit 504 for the arrival time of the combustible mixture at the plug portion, an ignition coil information acquisition unit 505, a discharge end time calculation unit 506, a pre-ignition end crank angle calculation unit 507, a fuel injection notice signal acquisition unit 508, a fuel injection signal acquisition unit 509, a pre-ignition and main ignition profile calculation unit 510, and an ignition signal output unit 511.

[0051] The engine temperature acquisition unit 501, the target spark plug heating amount calculation unit 502, the engine sensor value acquisition unit 503, and the calculation unit 504 for the arrival time of the combustible mixture at the plug portion perform processes for calculating the time when the mixture reaches the spark plug 17 in the auxiliary chamber 8. Here, the timing at which the mixture reaches the spark plug (spark plug 17) is the timing at which the pressure in the auxiliary combustion chamber (auxiliary chamber 8) becomes lower than the pressure in the main combustion chamber (main combustion chamber 14a) during the compression stroke.

[0052] The engine temperature acquisition unit 501 acquires temperature information (including the engine coolant temperature, engine oil temperature, and fuel temperature) detected by an engine coolant temperature sensor, an engine oil temperature sensor, and a fuel temperature sensor. The engine coolant temperature sensor detects the coolant temperature at the outlet of a water pump (not shown). The temperature of the auxiliary chamber 8 is a value reflected by the engine coolant temperature. The engine oil temperature sensor detects the oil temperature at the outlet of an oil pump (not shown). The fuel temperature sensor is installed in a fuel tank (not shown) and detects the temperature of the fuel. In particular, immediately after refueling, since the temperature of the fuel refueled into the fuel tank changes, the engine oil temperature and the fuel temperature may be different.

[0053] The target ignition plug heating amount calculation unit 502 calculates a target ignition plug heating amount required to raise the temperature of the ignition plug 17 to a temperature at which stable combustion is possible, based on the temperature information (engine coolant temperature, engine oil temperature, and fuel temperature) acquired by the engine temperature acquisition unit 501. For example, if the engine oil temperature is 80°C, control of pre-ignition by the ECU 20 is unnecessary. However, if the fuel temperature is low, it is necessary to perform control of pre-ignition by the ECU 20 to raise the electrode temperature of the ignition plug 17. For example, if the fuel temperature is -7°C, since it is necessary to raise the engine oil temperature to +60°C, the target ignition plug heating amount calculation unit 502 calculates this temperature increase amount as the target ignition plug heating amount.

[0054] The engine sensor value acquisition unit 503 acquires the engine speed, intake pressure, EGR valve opening degree, valve timing, target A / F, and fuel octane number detected by various sensors as engine sensor values (hereinafter collectively referred to as "various sensor values"). In the case of a hybrid vehicle, after the motor rotates at a constant speed, combustion of the engine 100 is performed. Therefore, at the time of cold start of the engine 100, the engine sensor value acquisition unit 503 can acquire various sensor values.

[0055] The combustible mixture plug arrival time calculation unit 504 calculates the time when the combustible mixture reaches the ignition plug 17 based on the engine coolant temperature, engine oil temperature, and fuel temperature detected by the engine temperature acquisition unit 501 and various sensor values detected by the engine sensor value acquisition unit 503.

[0056] The ignition coil information acquisition unit 505 acquires the current or voltage detected by the ignition coil 16. When pre-ignition is performed in the auxiliary chamber 8, the ignition coil information acquisition unit 505 acquires information related to the pre-ignition. The discharge end time calculation unit 506 calculates the time when the discharge of the ignition plug 17 ends (referred to as the "discharge end time") based on the current, voltage detected by the ignition coil 16, or a value stored in advance. Here, the control unit (discharge end time calculation unit 506) may determine the end time of the spark (spark 51) based on the primary voltage, secondary current, secondary voltage of the ignition coil, or a map value stored in advance for each operating condition.

[0057] The pre-ignition end crank angle calculation unit 507 calculates the crank angle (pre-ignition execution period) for ending the pre-ignition of the ignition plug 17 based on the target ignition plug heating amount calculated by the target ignition plug heating amount calculation unit 502, the time when the combustible mixture reaches the ignition plug calculated by the combustible mixture plug arrival time calculation unit 504, and the discharge end time calculated by the discharge end time calculation unit 506. Thereafter, the pre-ignition start timing is calculated by the pre-ignition and main ignition profile calculation unit 510.

[0058] The fuel injection warning signal acquisition unit 508 acquires a fuel injection warning signal generated when the vehicle control device determines that fuel injection will start within a predetermined time from the current time. The fuel injection warning signal acquisition unit 508 can acquire, for example, a fuel injection warning signal that can predict that a fuel injection signal will be applied to the injector 13 several cycles before the first explosion. By the fuel injection warning signal acquisition unit 508 acquiring the fuel injection warning signal, the timing of fuel injection by the injector 13 can be determined even before the injector 13 actually injects fuel.

[0059] The fuel injection signal acquisition unit 509 acquires a fuel injection signal indicating that the injector 13 has actually injected fuel from the injector 13. For example, the fuel injection signal acquisition unit 509 acquires the fuel injection signal applied at the time of the first explosion from the injector 13.

[0060] The pre-ignition and main ignition profile calculation unit 510 calculates the pre-ignition and main ignition profiles so that the time when the combustible mixture calculated by the combustible mixture plug arrival time calculation unit 504 reaches the ignition plug 17 and the discharge end time calculated by the discharge end time calculation unit 506 are not the same time. This process is performed at the timing when the fuel injection signal acquisition unit 509 acquires the fuel injection signal at the time of the first explosion or the fuel injection prediction signal acquisition unit 508 acquires the fuel injection prediction signal. Then, the pre-ignition and main ignition profile calculation unit 510 calculates the pre-ignition and main ignition profiles within one cycle combining the pre-ignition and the main ignition based on the fuel injection prediction signal detected by the fuel injection prediction signal acquisition unit 508, the fuel injection signal detected by the fuel injection signal acquisition unit 509, and the pre-ignition end crank angle calculated by the pre-ignition end crank angle calculation unit 507.

[0061] The ignition signal output unit 511 outputs an ignition signal to the ignition coil 16 based on the pre-ignition and main ignition profiles calculated by the pre-ignition and main ignition profile calculation unit 510 to perform ignition control. Therefore, the ignition signal output unit 511 and the ignition control unit 24 shown in FIG. 4 have substantially the same function. Note that the detailed processing methods of each processing unit will be described later.

[0062] <1-4. Relationship between pre-ignition and ignition plug electrode temperature> Next, with reference to FIG. 6, the relationship between pre-ignition and the ignition plug electrode temperature will be described. FIG. 6 is a graph showing the in-cylinder pressure, ignition signal, and the electrode temperature of the ignition plug 17 under motoring conditions without fuel injection.

[0063] The graph (a) in Fig. 6 shows the crank angle [deg] on the horizontal axis and the in-cylinder pressure [MPa] on the vertical axis. Due to the motoring conditions, the in-cylinder pressure has a symmetric pressure waveform with the top dead center of compression as the peak. The ignition pattern (b) in Fig. 6 shows three types of ignition patterns P1, P2, and P3 of the ignition signal. The ignition pattern P1 shows the case where the ECU 20 performs only the main ignition. The ignition pattern P2 shows the case where the ECU 20 performs the pre-ignition from the expansion stroke to the exhaust stroke. The ignition pattern P3 shows the case where the ECU 20 performs the pre-ignition in the intake stroke. And the pre-ignition implementation periods indicated by a large number of ignition pulses after the application of the pre-ignition signals for the ignition patterns P2 and P3 are the same.

[0064] The graph (c) in Fig. 6 shows the time change of the ignition plug electrode temperature corresponding to each ignition pattern P1 - P3. Here, the temperature change of the ignition plug 17 due to the compression and expansion of air during motoring is ignored. Also, in the expansion stroke, let the crank angle at which the pre-ignition of P2 starts be θini, the ignition plug electrode temperature be Tini, and the ignition plug electrode temperatures at the main ignition timing θend be T1, T2, and T3 respectively.

[0065] At the crank angle θini, in the ignition pattern P2, by performing the pre-ignition, the ignition plug electrode temperature rises from Tini to the peak temperature Tpeak. Since the heat transmitted from the combustion chamber to the ignition plug electrode is constantly dissipated to the cylinder head side, it is considered that the heating amount by the pre-ignition and the heat dissipation amount of the ignition plug 17 itself are balanced and reach an equilibrium state during the pre-ignition period. On the other hand, in the ignition patterns P1 and P3, since the pre-ignition is not performed, the ignition plug electrode temperature remains at Tini.

[0066] After the end of the pre-ignition, in the ignition pattern P2, the ignition plug electrode temperature gradually decreases from Tpeak. More specifically, in the ignition pattern P2, the decrease in the ignition plug electrode temperature starts immediately after the pre-ignition ends in the middle of the exhaust stroke. And the ignition plug electrode temperature at the main ignition timing θend of the next cycle decreases to T2.

[0067] In the case of the ignition pattern P1 without pre-ignition, the temperature of the ignition plug electrode does not change from Tini, and at the main ignition timing θend, the temperature of the ignition plug electrode is T1 = Tini. Therefore, the increase in the electrode temperature ΔT2 (= T2 - T1) at the main ignition timing θend according to the presence or absence of pre-ignition represents the electrode heating effect of pre-ignition.

[0068] In the ignition pattern P3, pre-ignition is carried out during the intake stroke. Then, near the bottom dead center of the intake stroke when the pre-ignition ends, the temperature of the ignition plug electrode reaches Tpeak. After that, the ignition plug 17 is cooled during the compression stroke, and the electrode temperature at the main ignition timing θend drops to T3. Therefore, the increase in the electrode temperature is ΔT3 (= T3 - T1). Here, since T3 > T2, ΔT3 > ΔT2. For this reason, the ignition pattern P3 has a higher electrode heating effect due to pre-ignition than the ignition pattern P2. This is because the electrode temperature after the end of pre-ignition decreases moment by moment, and in P2 where pre-heating is carried out early, the electrode temperature drops by the main ignition timing. Therefore, it is shown that the ignition plug electrode heating by pre-ignition has a higher electrode heating effect when it is carried out closer to the main ignition timing of the next cycle. And the higher the ignition plug electrode temperature, the easier it is to improve the combustion stability at the start of the engine 100.

[0069] <1-5. Limiting period for implementing pre-ignition in a conventional spark ignition engine> Next, with reference to FIG. 7, the relationship between the fuel injection timing and the pre-ignition implementation timing in an ECU that controls a conventional spark ignition engine will be described.

[0070] FIG. 7 is a graph showing an example of the relationship between in-cylinder pressure, fuel injection timing, and pre-ignition execution timing in an ECU that controls a conventional spark ignition engine. Graph (a) of FIG. 7 shows the crank angle [deg] on the horizontal axis and the in-cylinder pressure [MPa] during combustion on the vertical axis. Graph (b) of FIG. 7 shows the fuel injection signal by an in-cylinder direct injection type injector. Graph (c) of FIG. 7 shows two types of ignition patterns P2 and P4. The ignition pattern P2 is the same as the ignition pattern P2 shown in FIG. 6. The ignition pattern P4 is an ignition pattern for explaining the conventional pre-ignition execution limit.

[0071] As described with reference to FIG. 6, from the viewpoint of the ignition plug electrode temperature, in terms of the heating effect of the ignition plug electrode by pre-ignition, it is desirable that it be close to the main ignition timing of the next cycle. However, fuel exists in the combustion chamber immediately after the start of the fuel injection signal shown in graph (b) of FIG. 7. For this reason, depending on the in-cylinder temperature and flow state, early ignition of the fuel may occur due to pre-ignition, leading to deterioration of exhaust due to incomplete combustion and engine damage due to a rapid increase in in-cylinder pressure.

[0072] Therefore, in the prior art, in order to prevent early ignition of the air-fuel mixture by pre-ignition, the timing at which pre-ignition is performed has been limited to before fuel injection. For this reason, in a port fuel injection type engine, pre-ignition during the intake and compression strokes could not be performed. Also, in an in-cylinder direct fuel injection type engine, pre-ignition cannot be performed mainly after the fuel injection timing set in the intake stroke. For this reason, a pre-ignition period for sufficiently heating the electrodes cannot be ensured during extremely low temperature starting, etc., and there has been a problem that misfires occur and the emission amount of unburned hydrocarbons (HC) increases.

[0073] <1-6. Execution time limit of pre-ignition in the auxiliary chamber type spark ignition engine according to the first embodiment example> Next, a control method of the ECU 20 according to the first exemplary embodiment will be described. The ECU 20 is intended to maximize the ignition plug heating amount while suppressing the early ignition in the air-fuel mixture, considering problems such as the occurrence of misfires and the increase in the emission amount of unburned hydrocarbons (HC).

[0074] (Ignition Pattern (1) According to the First Exemplary Embodiment) FIG. 8 is a graph showing an example of the differential pressure between the sub-chamber pressure and the main combustion chamber pressure, valve lift, fuel injection signal, and ignition signal for each ignition pattern when the closing timing of the intake valve 31 is set to the compression stroke in the ECU 20 (also referred to as the "sub-chamber type ECU 20") according to the first exemplary embodiment.

[0075] In the graph (a) of FIG. 8, the horizontal axis represents the crank angle and the vertical axis represents the main combustion chamber pressure [MPa] during combustion. The graph (b) of FIG. 8 represents the differential pressure [MPa] between the sub-chamber 8 and the main combustion chamber 14a. Here, there is a crank angle at which the differential pressure becomes zero or less during the compression stroke. This crank angle corresponds to the closing timing (IVC: Intake Valve Close) of the intake valve 31 shown in the graph (c) of FIG. 8. And in the graph (c) of FIG. 8, the valve lifts [mm] of the intake valve 31 and the exhaust valve 32 are shown.

[0076] Note that since there is an effective valve lift of about 0.1 mm through which air can pass when the intake valve opens, the IVC of the intake valve 31 is a value slightly larger than zero. When the intake valve 31 is in the open state and the differential pressure is positive, the sub-chamber pressure is higher than the main combustion chamber pressure. Therefore, the gas blows out from the sub-chamber 8 into the main combustion chamber 14a, and the inflow of the air-fuel mixture on the main combustion chamber 14a side into the sub-chamber 8 is suppressed. When the intake valve 31 becomes closed, the actual compression starts in the main combustion chamber 14a, the differential pressure becomes negative, and the gas on the main combustion chamber 14a side begins to flow into the sub-chamber 8.

[0077] The timing of the fuel injection signal is shown in the graph (d) of FIG. 8. Fuel is supplied into the main combustion chamber 14a immediately after the fuel injection signal turns on. Graph (e) of FIG. 8 shows an example of a conventional ignition pattern P4 and an ignition pattern P5 according to the first embodiment. In the conventional ignition pattern P4, the addition of the pre-ignition signal ends simultaneously with the start of fuel injection. On the other hand, in the ignition pattern P5 according to the first embodiment, pre-ignition continues until the intake valve 31 reaches IVC, the differential pressure becomes negative, and the inflow of the air-fuel mixture from the main combustion chamber 14a to the auxiliary chamber 8 starts. Thus, when the closing timing of the intake valve (intake valve 31) provided in the intake system is set to the compression stroke, the control unit (control unit 500) continues pre-ignition from after the combustion of the air-fuel mixture in the combustion cycle until the closing timing of the intake valve (intake valve 31) in the compression stroke of the combustion cycle.

[0078] Here, before the actual start of compression in the compression stroke, since the auxiliary chamber pressure is higher than the main chamber pressure, the inflow of the air-fuel mixture into the auxiliary chamber 8 is suppressed, so it is possible to avoid contact between the spark plug 17 during pre-ignition and the air-fuel mixture. For this reason, the continuation limit of pre-ignition for plug heating can be delayed for the period from when the fuel injection signal is turned on until the intake valve 31 reaches IVC, that is, until immediately before the main ignition. As a result, the temperature of the spark plug electrode can be further increased, combustion stability can be improved, and emissions such as unburned hydrocarbons can be reduced. Also, since the continuation period of pre-ignition is included in the compression stroke, the heating effect of the spark plug electrode can be maximally enhanced even with the same number of pre-ignition times.

[0079] (Ignition Pattern (2) According to the First Embodiment Example) FIG. 9 is a graph showing an example of the main combustion chamber pressure, the auxiliary chamber pressure, the differential pressure between the auxiliary chamber pressure and the main combustion chamber pressure, the valve lift, the fuel injection signal, and the ignition signal for each ignition pattern when the closing timing of the intake valve 31 is set to the intake stroke or the bottom dead center (BDC) of the intake stroke in the auxiliary chamber type ECU 20 according to the first embodiment example.

[0080] In the graph (a) of FIG. 9, the horizontal axis represents the crank angle [deg], and the vertical axis represents the main combustion chamber pressure [MPa] during combustion. The graph (b) of FIG. 9 represents the differential pressure [MPa] between the auxiliary chamber 8 and the main combustion chamber 14a. Here, there exists a crank angle at which the differential pressure becomes zero or less near the bottom dead center of the intake stroke. This crank angle corresponds to the bottom dead center shown in the graph (c) of FIG. 9. And in the graph (c) of FIG. 9, the valve lifts [mm] of the intake valve 31 and the exhaust valve 32 are shown. As shown in the graph (c) of FIG. 9, when the closing timing IVC of the intake valve 31 is in the intake stroke, the timing at which the differential pressure becomes zero or less does not coincide with IVC.

[0081] When the differential pressure is positive during the intake stroke, the auxiliary chamber pressure becomes higher than the main combustion chamber pressure, and gas blows out from the auxiliary chamber 8 into the main combustion chamber 14a, so the inflow of the air-fuel mixture on the main combustion chamber 14a side into the auxiliary chamber 8 is suppressed. When the compression stroke is started, actual compression starts in the main combustion chamber 14a, and since the differential pressure becomes negative, the gas on the main combustion chamber 14a side begins to flow into the auxiliary chamber 8.

[0082] In the graph (d) of FIG. 9, the timing of the fuel injection signal is shown. Fuel is supplied into the main combustion chamber 14a immediately after the fuel injection signal turns on. In the graph (e) of FIG. 9, an example of the conventional ignition pattern P4 and the ignition pattern P5 according to the first embodiment is shown. In the conventional ignition pattern P4, the addition of the pre-ignition signal ends simultaneously with the start of fuel injection. On the other hand, in the ignition pattern P5 according to the first embodiment, pre-ignition continues until the piston starts to rise in the compression stroke, the differential pressure becomes negative, and the inflow of the air-fuel mixture from the main combustion chamber 14a into the auxiliary chamber 8 starts. Thus, when the closing timing of the intake valve (intake valve 31) provided in the intake system is set in the intake stroke, the control unit (control unit 500) continues pre-ignition from after the combustion of the air-fuel mixture in the combustion cycle until the start timing of the compression stroke in the combustion cycle.

[0083] In this way, before the actual compression starts, since the pressure in the auxiliary chamber is higher than the pressure in the main chamber, the inflow of the air-fuel mixture into the auxiliary chamber 8 is suppressed, so that contact between the spark plug 17 during pre-ignition and the air-fuel mixture can be avoided. For this reason, the continuous limit of the pre-ignition for plug heating can be delayed for the period from when the intake valve 31 reaches BDC from IVC. As a result, the temperature of the spark plug electrode can be further increased, combustion stability can be improved, and emissions such as unburned hydrocarbons can be reduced.

[0084] Further, the ECU 20 can arbitrarily select the ignition pattern P5 shown in FIGS. 8 and 9 according to the specifications of the engine 100.

[0085] FIG. 10 is an image diagram of the direction in which the gas around the auxiliary chamber 8 flows at each timing A, B, C, and D in the main combustion chamber pressure, the auxiliary chamber pressure, and the differential pressure between the auxiliary chamber pressure and the main combustion chamber pressure when the closing timing of the intake valve 31 is set in the compression stroke in the auxiliary chamber type ECU 20 according to the first embodiment example. Note that the descriptions of graph (a) and graph (b) in FIG. 10 are the same as those in FIG. 8, so they are omitted.

[0086] In the image diagram (c) of FIG. 10, the state of the auxiliary chamber 8 at timings A to D attached to graph (b) of FIG. 10 is shown. Timing A is the compression stroke (before IVC), but since the intake valve 31 is open, even when the piston 18 starts to rise, the fuel (gas) on the main combustion chamber 14a side is blown back into the intake pipe 6. Further, since the pressure in the auxiliary chamber 8 is higher than the pressure in the main combustion chamber 14a, the gas in the auxiliary chamber 8 jets out toward the main combustion chamber side.

[0087] Timing B is during the compression stroke and after the intake valve 31 has closed, and substantial compression occurs. For this reason, the pressure in the main combustion chamber 14a becomes higher than the pressure in the auxiliary chamber 8, and the fuel (gas) in the main combustion chamber 14a flows into the auxiliary chamber 8. If pre-ignition is performed in this state, discharge occurs in a state where an air-fuel mixture containing fuel exists in the auxiliary chamber 8, increasing the likelihood of early ignition of the air-fuel mixture, so pre-ignition is stopped. Since the end of the compression stroke is the timing suitable for main ignition, the ignition timing is set at the end of the compression stroke under many engine and operating conditions. When main ignition is performed, ignition of the air-fuel mixture occurs and combustion starts.

[0088] Timing C is at the beginning of the expansion stroke after main ignition is performed. Since the combustion pressure generated in the auxiliary chamber 8 increases, it is the timing at which the strongest high-temperature and high-pressure jet jets out toward the main combustion chamber 14a. Due to this high-temperature and high-pressure jet, multi-point simultaneous ignition occurs in the air-fuel mixture in the main combustion chamber 14a, and high-speed combustion occurs.

[0089] Timing D is the timing when, immediately after combustion starts on the main combustion chamber 14a side during the expansion stroke, the pressure in the main combustion chamber 14a increases and a reverse flow occurs toward the auxiliary chamber 8. Here, the differential pressure becomes zero or less again, and exhaust gas flows into the auxiliary chamber 8.

[0090] In this way, within one combustion cycle, the pressures in the auxiliary chamber 8 and the main combustion chamber 14a fluctuate in an up-and-down relationship along with piston and valve operations and the generation of combustion gas, and gas flow occurs. Therefore, the inventors of the present invention have found that there is a period near timing A during which an air-fuel mixture containing fuel cannot flow into the auxiliary chamber 8 even during the compression stroke, making it possible to continue pre-ignition until the compression stroke, which was not possible conventionally due to the risk of early ignition.

[0091] <1-7. Example of correction control operation for pre-ignition timing> Next, an example of the correction control of the pre-ignition timing in the ECU 20 having the above-described configuration will be described with reference to FIG. 11. FIG. 11 is a flowchart showing an example of a pre-ignition timing correction control operation in the control unit 500 of the ECU 20 according to the first embodiment example.

[0092] First, the control unit 500 determines whether the ignition switch of the engine 100 is on, that is, whether it is ON (S1). If it is determined that the ignition switch is not ON and the vehicle power supply is not on (NO determination in S1), the control unit 500 repeats the process of step S1 without performing the pre-ignition timing correction process.

[0093] On the other hand, when the control unit 500 determines that the ignition switch is ON (YES determination in S1), it determines whether the warm-up of the engine 100 is completed based on the engine temperature information detected by the engine temperature acquisition unit 501 (see FIG. 5) (S2). When the control unit 500 determines that the warm-up of the engine 100 is completed (YES determination in S2), since there is no need to perform pre-ignition, it merges before step S8.

[0094] Here, when the engine 100 is in a cold state, the ignition plug electrode temperature is low, and the combustion at the time of engine start may become unstable. Therefore, in the process of step S2, when the control unit 500 determines that the warm-up of the engine 100 is not completed (NO determination in S2), it calculates the target heating amount of the ignition plug 17 based on the engine temperature information detected by the engine temperature acquisition unit 501 (S3).

[0095] Next, the combustible mixture plug arrival time calculation unit 504 calculates the time when the combustible mixture reaches the plug part (ignition plug 17) based on the information acquired by the engine temperature acquisition unit 501 and the engine sensor value acquisition unit 503 (S4).

[0096] Next, the discharge end time calculation unit 506 calculates the time when the last discharge of the pre-ignition ends (discharge end time) based on the ignition coil signal (an example of ignition coil information) acquired by the ignition coil information acquisition unit 505 (S5).

[0097] Next, the preliminary ignition end crank angle calculation unit 507 calculates a crank angle at which to end the preliminary ignition in order to suppress early ignition based on the outputs of the target ignition plug heating amount calculation unit 502, the combustible mixture arrival time calculation unit 504 at the plug portion, and the discharge end time calculation unit 506 (S6). Subsequently, the preliminary ignition end crank angle calculation unit 507 determines the execution period of the preliminary ignition and the preliminary ignition frequency (frequency of the ignition pulse) based on the target ignition plug heating amount, and determines a preliminary ignition pattern (S7).

[0098] Subsequently, the preliminary ignition and main ignition profile calculation unit 510 determines whether the fuel injection signal has become ON or is predicted to become ON based on the preliminary ignition pattern determined by the preliminary ignition end crank angle calculation unit 507 and the information detected by the fuel injection advance signal acquisition unit 508 and the fuel injection signal acquisition unit 509 (S8).

[0099] Here, the preliminary ignition may be performed in the first explosion cycle after fuel injection at the start of the engine 100. However, by performing the preliminary ignition several cycles earlier, it becomes possible to surely enter the first explosion cycle with the ignition plug electrode temperature increased. Also, the engine 100 for a hybrid vehicle can drive the vehicle at the time of launch with a motor. Therefore, by using a plurality of cycles until the combustion start of the engine 100 and performing a motoring operation without fuel injection, it is possible to heat the ignition plug electrode by the preliminary ignition.

[0100] Therefore, when the fuel injection advance signal acquisition unit 508 detects that it is necessary to start the engine 100 recently, the control unit 500 may be configured to perform the preliminary ignition to heat the electrode while rotating the engine 100 by motor drive in advance. Here, as the fuel injection advance signal, for example, the timing when the vehicle lock is released, the timing when the driver steps on the brake pedal to turn on the vehicle ignition switch, or the timing when the ignition switch is turned on may be used.

[0101] In the process of step S8, when the preliminary ignition and main ignition profile calculation unit 510 determines that the fuel injection signal is not ON or is not predicted to turn ON (NO determination in S8), it returns to step S2. On the other hand, when the preliminary ignition and main ignition profile calculation unit 510 determines that the fuel injection signal is ON or is predicted to turn ON (YES determination in S8), it determines the ignition pattern during one cycle, combining the preliminary ignition and the main ignition. Then, the ignition signal output unit 511 outputs the preliminary ignition and main ignition signals to the ignition coil 16 (S9).

[0102] Next, the control unit 500 determines whether the engine 100 can stably burn continuously for a predetermined number of cycles (about 20 cycles) in a state where preliminary ignition and main ignition have been performed (S10). If it cannot burn without misfire over the predetermined number of cycles (NO determination in S10), the control unit 500 continues the preliminary ignition and main ignition. On the other hand, if it can stably burn continuously over the predetermined number of cycles (YES determination in S10), the control unit 500 determines that the ignition plug 17 has been maintained at a sufficient temperature. Then, the control unit 500 ends the preliminary ignition and continues to ignite the air-fuel mixture only with the main ignition (S11), thereby ending the preliminary ignition control process shown in FIG. 11.

[0103] Next, with reference to FIG. 12, an example of a method for calculating the arrival time of the air-fuel mixture at the ignition plug 17 in the auxiliary chamber 8 (the arrival time of the combustible air-fuel mixture at the plug portion described above) will be described. FIG. 12 is an image diagram of the auxiliary chamber 8 with parameters for calculating the arrival time of the air-fuel mixture at the ignition plug 17 in the ECU 20 according to the first embodiment example.

[0104] When actual compression starts and the pressure in the auxiliary chamber 8 becomes lower than the pressure in the main combustion chamber 14a at the actual compression start time Tcomp, the air-fuel mixture starts to flow into the auxiliary chamber 8. Here, since the inflow rate of the air-fuel mixture is finite, there is a mixture arrival delay period ΔTflow as a time lag until the air-fuel mixture reaches the vicinity of the side electrode 17a, the ground electrode 17b, or the spark 51 of the high-temperature ignition plug 17.

[0105] Then, the control unit (the plug arrival time calculation unit 504 for the combustible mixture) determines the timing (the plug arrival time Tplug of the combustible mixture) at which the mixture reaches the ignition plug (ignition plug 17) as the timing obtained by adding the mixture arrival delay period (mixture arrival delay period ΔTflow) determined by the engine speed, the intake pressure of the mixture, and the shape of the auxiliary combustion chamber (auxiliary chamber 8) to the actual compression start timing (actual compression start time Tcomp) at which the mixture is actually compressed during the compression stroke.

[0106] That is, the plug arrival time Tplug of the combustible mixture is defined by the following equation (1). Tplug = Tcomp + ΔTflow …(1)

[0107] Here, the plug arrival time calculation unit 504 for the combustible mixture may use, as the actual compression start time Tcomp, the timing detected by the pressure sensor as the timing at which the differential pressure between the auxiliary chamber 8 and the main combustion chamber 14a reverses. Further, the plug arrival time calculation unit 504 for the combustible mixture may use, as the actual compression start time Tcomp, the time calculated from the valve timing information acquired by the engine sensor value acquisition unit 503 as the timing at which the effective valve lift becomes a predetermined threshold value, for example, 0.1 mm or less. Further, the plug arrival time calculation unit 504 for the combustible mixture may previously store a map for the differential pressure between the auxiliary chamber 8 and the main chamber, and acquire the mixture arrival delay period ΔTflow by referring to this map. Further, the plug arrival time calculation unit 504 for the combustible mixture may also previously store, as a map based on the engine speed and the throttle opening, a map for the differential pressure, and acquire the differential pressure by referring to this map.

[0108] In this way, by calculating the plug arrival time Tplug of the mixture in consideration of the mixture arrival delay period, the plug arrival time calculation unit 504 for the combustible mixture can more precisely determine the execution limit time of the pre-ignition, and can enhance the electrode heating effect by the pre-ignition.

[0109] Next, with reference to FIG. 13, an example of a method for calculating the end time of the discharge by the pre-ignition will be described. FIG. 13 is an illustrative diagram showing an example of the end time of discharge by pre-ignition in the ECU 20 according to the first embodiment. Here, representative behaviors of the ignition signal output from the ECU 20 and the primary current, primary voltage, secondary current, and secondary voltage of the ignition coil 16 are shown.

[0110] The determining factor for whether early ignition occurs or not is whether contact occurs between the spark plug 17 and the air-fuel mixture during pre-ignition. Therefore, if the timing at which the discharge generated by the last pre-ignition in a plurality of pre-ignition pulses disappears is earlier than the time Tplug at which the air-fuel mixture reaches the plug portion represented by the above formula (1), early ignition does not occur. For this reason, the discharge end time calculation unit 506 defines the discharge end time Tend by the following formula (2). Tend = min (T1, T2, T3) …(2)

[0111] Here, T1, T2, and T3 in the formula (2) represent the detection timing of the feature amount representing the end of discharge, which is detected based on the ignition coil signal. Generally, a high voltage is generated on the secondary side of the ignition coil 16 when the ignition signal turns off. When this high voltage exceeds the breakdown voltage between the electrodes of the spark plug 17, a spark 51 is formed from the side electrode 17a to the ground electrode 17b. During discharge, a secondary current is generated in the negative direction, and as time passes, the secondary current approaches zero. Finally, the secondary current becomes zero and the discharge ends.

[0112] As an example of detecting the discharge end timing using the ignition coil signal, the discharge end time calculation unit 506 sets the earliest time among the three types of timings T1 to T3 as the discharge end time Tend. Here, the timing T1 at which noise is first observed after a certain time, for example, about 1 ms, has elapsed from the discharge start time Tstart in the primary voltage is called the "primary voltage noise occurrence time". Also, the timing T2 at which the absolute value of the secondary current becomes equal to or less than a predetermined threshold value, for example, 5 mA or less, is called the "secondary current detection end time". Further, the timing T3 at which the second minimum value of the secondary voltage is detected is called the "secondary voltage second minimum value". In this way, by obtaining the pre-ignition discharge end time Tend, the discharge end time calculation unit 506 can more precisely determine the implementation limit period of the pre-ignition and enhance the electrode heating effect by the pre-ignition.

[0113] Next, with reference to FIGS. 14 to 18, an example of the correction calculation method for the final pre-ignition implementation time performed by the pre-ignition and main ignition profile calculation unit 510 will be described. The likelihood of early ignition changes with changes in engine conditions.

[0114] In the case of engine conditions where early ignition is likely, in order to end the pre-ignition with sufficient time margin for the inflow of the air-fuel mixture, the final pre-ignition implementation time is advanced. Conversely, in the case of engine conditions where early ignition is unlikely, the final pre-ignition implementation time is retarded to perform more efficient pre-ignition. Examples of changes in engine conditions are shown below.

[0115] FIG. 14 is a graph showing a control method for the pre-ignition duration corresponding to the engine speed and the intake valve closing time.

[0116] The horizontal axis of FIG. 14(a) is the final pre-ignition implementation time, and the vertical axis is the engine speed [r / min]. The higher the engine speed, the higher the gas inflow rate into the auxiliary chamber 8, the decrease in the time delay until the air-fuel mixture reaches the spark plug 17, and the advance of the early ignition limit. Therefore, the control unit 500 advances the final pre-ignition implementation time as the engine speed increases, so that early ignition can be suppressed even under conditions where the gas inflow rate into the auxiliary chamber 8 is large.

[0117] The horizontal axis of Fig. 14(b) represents the timing of the final pre-ignition, and the vertical axis represents the intake valve closing timing [deg. ABDC]. As the intake valve closing timing approaches the middle of the compression stroke, the piston rising speed increases. Therefore, the gas inflow speed into the auxiliary chamber 8 increases, the time delay until the air-fuel mixture reaches the spark plug 17 decreases, and the early ignition limit advances. Thus, the control unit 500 advances the timing of the final pre-ignition as the intake valve closing timing approaches the center of the compression stroke, so that early ignition can be suppressed even under conditions where the gas inflow speed into the auxiliary chamber 8 is high.

[0118] Fig. 15 is a graph showing a control method for the pre-ignition duration corresponding to the intake air temperature, engine oil temperature, coolant water temperature, and fuel temperature. In the figure, it is described as the engine oil temperature and the coolant water temperature, but in this specification, they are collectively referred to as "engine oil and coolant water temperature".

[0119] The horizontal axis of Fig. 15(a) represents the timing of the final pre-ignition, and the vertical axis represents either the intake air temperature, the engine oil and coolant water temperature, or the fuel temperature. The higher any of the intake air temperature, the engine oil and coolant water temperature, or the fuel temperature is, the higher the ignitability of the air-fuel mixture becomes, and the early ignition limit advances. Thus, the control unit 500 advances the timing of the final pre-ignition as any of the intake air temperature, the engine oil and coolant water temperature, or the fuel temperature is higher, so that early ignition can be suppressed even under conditions where the ignitability of the air-fuel mixture is relatively good.

[0120] The horizontal axis of Fig. 15(b) represents the timing of the final pre-ignition, and the vertical axis represents the intake pressure [kPa]. The higher the intake pressure is, the higher the ignitability of the air-fuel mixture becomes, and the early ignition limit advances. Thus, the control unit 500 advances the timing of the final pre-ignition as the intake pressure is higher, so that early ignition can be suppressed even under conditions where the ignitability of the air-fuel mixture is good.

[0121] Fig. 16 is a graph showing a control method for the pre-ignition duration corresponding to the EGR valve opening degree and the intake and exhaust valve overlap.

[0122] The horizontal axis of Fig. 16(a) represents the timing of the final pre-ignition, and the vertical axis represents the EGR valve opening [%]. The larger the EGR valve opening, the lower the ignitability of the air-fuel mixture, and the later the early ignition limit is retarded. Therefore, the control unit 500 retards the timing of the final pre-ignition as the EGR valve opening increases, so that more efficient heating of the ignition plug electrodes can be achieved under conditions where the ignitability of the air-fuel mixture is poor.

[0123] The horizontal axis of Fig. 16(b) represents the timing of the final pre-ignition, and the vertical axis represents the exhaust valve overlap amount or the internal EGR rate [%]. The larger the exhaust-intake valve overlap amount or the internal EGR rate, the lower the ignitability of the air-fuel mixture, and the later the early ignition limit is retarded. Therefore, the control unit 500 retards the timing of the final pre-ignition as the exhaust-intake valve overlap amount or the internal EGR rate increases, so that more efficient heating of the ignition plug electrodes can be achieved under conditions where the ignitability of the air-fuel mixture is poor.

[0124] Fig. 17 is a graph showing a control method for the pre-ignition duration corresponding to the target A / F and the octane number of the fuel.

[0125] The horizontal axis of Fig. 17(a) represents the timing of the final pre-ignition, and the vertical axis represents the target A / F. The larger the target A / F, the lower the ignitability of the air-fuel mixture, and the later the early ignition limit is retarded. Therefore, the control unit 500 retards the timing of the final pre-ignition as the target A / F increases, so that more efficient heating of the ignition plug electrodes can be achieved under conditions where the ignitability of the air-fuel mixture is poor.

[0126] The horizontal axis of Fig. 17(b) represents the timing of the final pre-ignition, and the vertical axis represents the octane number of the fuel. The higher the octane number of the fuel, the lower the ignitability of the air-fuel mixture, and the later the early ignition limit is retarded. Therefore, the control unit 500 retards the timing of the final pre-ignition as the octane number of the fuel increases, so that more efficient heating of the ignition plug electrodes can be achieved for fuels with poor ignitability.

[0127] Fig. 18 is a graph showing a control method for the pre-ignition duration corresponding to the vapor pressure of the fuel and the heat of vaporization of the fuel.

[0128] The horizontal axis of Fig. 18(a) represents the timing of the final pre-ignition, and the vertical axis represents the saturated vapor pressure of the fuel [kPa]. The higher the saturated vapor pressure of the fuel, the easier it is for the fuel to evaporate, the ignition performance of the air-fuel mixture is improved, and the early ignition limit advances. Therefore, the control unit 500 advances the timing of the final pre-ignition as the saturated vapor pressure of the fuel increases, so that even under conditions where the ignition performance of the air-fuel mixture is good, early ignition can be suppressed.

[0129] The horizontal axis of Fig. 18(b) represents the timing of the final pre-ignition, and the vertical axis represents the heat of vaporization of the fuel [kJ / kg]. The higher the heat of vaporization of the fuel, the greater the amount of air-fuel mixture cooling associated with the vaporization of the fuel. For this reason, the air-fuel mixture temperature decreases, the ignition performance of the air-fuel mixture deteriorates, and the early ignition limit retards. Therefore, the control unit 500 retards the timing of the final pre-ignition as the heat of vaporization of the fuel increases, so that more efficient heating of the ignition plug electrodes is possible for fuels with poor ignition performance of the air-fuel mixture.

[0130] Note that the processing for changing the timing of the final pre-ignition and other pre-ignition periods is not limited to the above-described example, and various other modifications are applicable.

[0131] <1-8. Conditions for Performing Pre-ignition> The pre-ignition according to the first embodiment is a pre-ignition that pre-heats the ignition plug electrodes when starting combustion under non-warming conditions in a sub-chamber type engine, thereby improving the combustion stability at the first explosion and start.

[0132] Here, in the control unit 500 according to the modification, since the secondary voltage due to the pre-ignition exceeds the breakdown voltage between the electrodes of the ignition plug 17, a spark 51 is formed between the side electrode 17a and the ground electrode 17b. By performing ignition with spark discharge at a timing other than the main ignition in this way by the control unit 500 according to the modification, the thermal energy due to the discharge can be transmitted to the ignition plug 17, and the temperature of the plug electrodes can be further improved.

[0133] Further, the control unit 500 according to the modification may perform ignition so that the secondary voltage due to pre-ignition is lower than the breakdown voltage between the electrodes of the spark plug 17, and generate corona discharge on the electrode surface to heat the electrode. Therefore, the pre-ignition according to the modification is preferably performed at the start of combustion of the engine 100 or immediately before the start of combustion.

[0134] When starting the operation of the engine 100, for example, in the case of a normal gasoline engine vehicle, the engine rotation starts by the starter, and pre-ignition is performed from the cycle in which the first fuel injection is performed or several cycles before that.

[0135] In addition, in the case of a hybrid engine vehicle equipped with both the engine 100 and the electric motor, and capable of driving the engine 100 and the electric motor in a state separated from the axle, it is possible to perform motoring of the engine 100 by the electric motor for a sufficient period. In this case, the engine 100 is rotated by motoring, and the engine oil temperature and the combustion chamber wall temperature can be increased by using the heat loss due to air compression and the heat generation caused by the friction of the axle portion. After the engine temperature is increased by motoring, a configuration may be adopted in which pre-ignition is performed from the cycle in which the first fuel injection is performed or several cycles before that.

[0136] The control unit 500 according to the first embodiment described above continues to apply the pre-ignition pulse for performing pre-ignition until the start of the actual compression of the air-fuel mixture (immediately before the main ignition) in the auxiliary chamber type engine. Therefore, it is possible to perform at least one or more pre-ignitions without combustion of the air-fuel mixture before the start of the actual compression in the compression stroke. Further, the pre-ignition pulse is applied until the start of the actual compression of the air-fuel mixture, and since the auxiliary chamber pressure is higher than the main combustion chamber pressure before the start of the actual compression, the inflow of the air-fuel mixture into the auxiliary chamber is suppressed. Therefore, the contact between the spark plug 17 and the air-fuel mixture during pre-ignition can be avoided, and the risk of early ignition of the air-fuel mixture can be suppressed.

[0137] In this way, the control unit 500 can achieve both an increase in the electrode temperature of the ignition plug 17 and suppression of early ignition of the air-fuel mixture. Furthermore, since the electrode temperature of the ignition plug 17 rises due to the pre-ignition that is delayed until the limit, it is possible to enhance the combustion stability during the main ignition at the cold start of the engine 100. Also, since the ignition plug 17 ignites the air-fuel mixture with the sufficiently heated electrode, it is possible to reduce the emissions such as unburned hydrocarbons.

[0138] Also, during the expansion stroke, exhaust stroke, and intake stroke after the combustion in the pre-combustion cycle has ended, by performing pre-ignition during the period when combustion of the air-fuel mixture does not occur, the period during which pre-ignition is continued can be made longer compared to the conventional case, and the ignition plug electrode can be sufficiently heated.

[0139] <2. Second Embodiment Example> Next, a configuration example of an engine control device according to a second embodiment example (hereinafter referred to as "this example") of the present invention will be described.

[0140] The pre-ignition according to the second embodiment example is preferably performed at the cold start when the temperature of the engine 100 is low. Here, the target ignition plug heating amount calculation unit 502 calculates the target ignition plug heating amount based on the temperature information acquired by the engine temperature acquisition unit 501 shown in FIG. 5. At this time, the target ignition plug heating amount calculation unit 502 is set such that the lower the engine temperature, the larger the target ignition plug heating amount. FIG. 19 is a graph showing an example of the main combustion chamber pressure, the sub-chamber pressure, the differential pressure between the sub-chamber pressure and the main combustion chamber pressure, the valve lift, and the ignition signal for each ignition pattern.

[0141] The graph (a) of FIG. 19 shows the crank angle on the horizontal axis and the in-cylinder pressure [MPa] on the vertical axis. The graph (b) of FIG. 19 represents the differential pressure [MPa] between the auxiliary chamber 8 and the main combustion chamber 14a. The graph (c) of FIG. 19 represents the intake and exhaust valve lifts. The graph (d) of FIG. 19 shows three types of ignition patterns P5, P6, and P7. The ignition pattern P5 shows an example of the ignition pattern indicating the start and end times of pre-ignition when the engine temperature is 40°C, the ignition pattern P6 shows the start and end times of pre-ignition when the engine temperature is 20°C, and the ignition pattern P7 shows the start and end times of pre-ignition when the engine temperature is -10°C.

[0142] The lower the engine temperature, the greater the target ignition plug heating amount. Therefore, the control unit (control unit 500) increases the electrode heating amount for heating the electrodes of the ignition plug (ignition plug 17) by pre-ignition as the engine coolant temperature at the start of the engine (engine 100) is lower. For example, the control unit 500 increases the temperature of the ignition plug electrodes by expanding the execution period of pre-ignition and widening the period for heating the ignition plug electrodes by pre-ignition. For example, in the ignition pattern P5 at an engine temperature of 40°C, pre-ignition is carried out during the intake stroke, whereas in the ignition pattern P6 at an engine temperature of 20°C, pre-ignition is carried out from the exhaust stroke of the previous cycle, which is before the intake stroke.

[0143] Furthermore, in the ignition pattern P7 at an engine temperature of -10°C, pre-ignition starts from the expansion stroke of the previous cycle. Therefore, the control unit 500 can further heat the surface of the ignition plug electrodes as the engine temperature is lower. As a result, at extremely low temperatures such as below freezing point, the heating amount of the ignition plug electrodes by pre-ignition becomes large, so it is possible to stably raise the temperature of the ignition plug electrodes to a temperature at which the air-fuel mixture can be ignited.

[0144] [Modification Example] Note that the application target of the present invention is not limited to a vehicle equipped only with the engine 100 or a hybrid vehicle equipped with the engine 100 and a motor. The present invention is also applicable to, for example, a power generation engine and a marine engine, etc., which are composed of an engine and a motor having the same configuration as the engine 100.

[0145] The preliminary ignition according to the above-described embodiment is preferably performed during cold start when the temperature of the engine 100 is low. When the target ignition plug heating amount calculating unit 502 calculates the target ignition plug heating amount based on the temperature information acquired by the engine temperature acquisition unit 501, the lower the engine temperature, the larger the target ignition plug heating amount is set. Therefore, at extremely low temperatures such as below freezing, the heating amount by the preliminary ignition increases, and it becomes possible to raise the temperature of the ignition plug electrode to a level where stable ignition is possible.

[0146] Also, in the preliminary ignition according to the above-described embodiment, the power consumption of the battery temporarily increases. When it is determined that there is not enough remaining battery at the start of combustion of the auxiliary chamber type engine, the control unit 500 may control not to perform the preliminary ignition according to the above-described embodiment. Further, even when it is determined that the wear state of the ignition plug 17 has progressed and replacement of the ignition plug 17 is necessary, the control unit 500 may control not to perform the preliminary ignition according to the above-described embodiment. In this case, the control unit 500 may further issue a warning to prompt the driver of the vehicle to replace the ignition plug 17.

[0147] <Configuration example of an active type engine> The engine 100 shown in FIG. 1 is an example of a passive type engine in which the injector 13 is provided on the side surface of the cylinder 14 and only the ignition plug 17 is installed in the auxiliary chamber 8. Note that the engine 100 to which the control unit 500 of the present invention is applied is not limited to the passive type shown in FIG. 1. Next, a modification of the engine 100 will be described with reference to FIG. 20. FIG. 20 is a schematic configuration diagram showing an enlarged view of the periphery of the auxiliary chamber 8A configured in the engine 100A according to the modification.

[0148] As an engine in which the control unit 500 according to the first embodiment can control pre-ignition, an active engine 100A shown in FIG. 20 in which an injector 13B is installed in the auxiliary chamber 8A may be configured. The injector 13B directly injects fuel into the auxiliary chamber 8A. In the active engine 100A, the air-fuel ratio in the auxiliary chamber 8A of the air-fuel mixture supplied from the main combustion chamber 14a side through the auxiliary chamber injection hole 8a and the fuel injected from the injector 13B is controlled so that the ignitability in the auxiliary chamber 8A is good. As a result, it becomes possible to improve combustion stability. Even in the engine 100A configured in this way, since the pre-ignition is performed at the time of cold start, the temperature of the ignition plug electrode rises, so that the combustion stability of the air-fuel mixture in the main ignition can be enhanced.

[0149] The present invention is not limited to the above-described embodiments, and it goes without saying that various other application examples and modification examples can be taken as long as the gist of the present invention described in the claims is not deviated from. For example, each of the above-described embodiments has described the configuration of the device and the system in detail and specifically in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the configurations described. Also, it is possible to replace a part of the configuration of the embodiment described here with the configuration of another embodiment, and furthermore, it is also possible to add the configuration of another embodiment to the configuration of an embodiment. Also, it is possible to add, delete, or replace other configurations for a part of the configuration of each embodiment. In addition, the control lines and information lines show those considered necessary for explanation, and do not necessarily show all the control lines and information lines on the product. In reality, it may be considered that almost all the components are interconnected.

Explanation of Reference Numerals

[0150] 5... Variable valve, 6... Intake pipe, 8... Auxiliary chamber, 8a... Auxiliary chamber injection hole, 13... Injector, 14... Cylinder, 14a... Main combustion chamber, 16... Ignition coil, 17... Spark plug, 17a... Side electrode, 17b... Ground electrode, 18... Piston, 20... ECU, 24... Ignition control unit, 31... Intake valve, 32... Exhaust valve, 51... Spark, 100... Engine

Claims

1. A cylinder in which an air-fuel mixture, which is a mixture of fuel injected by a fuel injection device and air taken in from an intake system, burns in a main combustion chamber facing a piston, a sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber, and an electrode attached inside the sub-combustion chamber, wherein the electrode ignites the air-fuel mixture inside the sub-combustion chamber and a flame jet generated thereby is injected into the main combustion chamber to ignite the air-fuel mixture in the main combustion chamber, and a spark plug; an engine control device for controlling the output of an engine, comprising an ignition device for controlling the ignition timing of the spark plug, wherein the timing at which the air-fuel mixture reaches the spark plug is a timing at which the pressure in the sub-combustion chamber is lower than the pressure in the main combustion chamber, and a pre-ignition signal for causing the spark plug to perform pre-ignition without combustion of the air-fuel mixture until a main ignition at which the air-fuel mixture reaches a spark generated by the electrode is continuously supplied, and when the closing timing of an intake valve provided in the intake system is set to a compression stroke, a control unit is provided which continues the pre-ignition from after the combustion of the air-fuel mixture in a combustion cycle until the closing timing of the intake valve in the compression stroke in the combustion cycle. An engine control device.

2. A cylinder in which an air-fuel mixture, which is a mixture of fuel injected by a fuel injection device and air taken in from an intake system, burns in a main combustion chamber facing a piston, a sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber, and an electrode attached inside the sub-combustion chamber, wherein the electrode ignites the air-fuel mixture inside the sub-combustion chamber and a flame jet generated thereby is injected into the main combustion chamber to ignite the air-fuel mixture in the main combustion chamber, and a spark plug; an engine control device for controlling the output of an engine, comprising an ignition device for controlling the ignition timing of the spark plug, The timing at which the air-fuel mixture reaches the ignition plug is the timing at which the pressure in the sub-combustion chamber becomes lower than the pressure in the main combustion chamber. Until the main ignition at which the air-fuel mixture reaches the spark generated at the electrode, a control unit is provided that continues to supply a pre-ignition signal for causing the ignition plug to perform pre-ignition without combustion of the air-fuel mixture. When the closing timing of the intake valve provided in the intake system is set in the intake stroke, the pre-ignition is continued from after the combustion of the air-fuel mixture in the combustion cycle until the start timing of the compression stroke in the combustion cycle. Engine control device.

3. A cylinder in which an air-fuel mixture formed by mixing fuel injected by a fuel injection device and air taken in from an intake system burns in a main combustion chamber facing a piston, A sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber, an electrode provided inside the sub-combustion chamber, and a flame jet generated by the electrode igniting the air-fuel mixture inside the sub-combustion chamber is injected into the main combustion chamber, and an ignition plug for igniting the air-fuel mixture in the main combustion chamber, An engine control device for controlling the output of an engine, comprising an ignition device for controlling the ignition timing of the ignition plug. The timing at which the air-fuel mixture reaches the ignition plug is the timing at which the pressure in the sub-combustion chamber becomes lower than the pressure in the main combustion chamber. Until the main ignition at which the air-fuel mixture reaches the spark generated at the electrode, a control unit is provided that continues to supply a pre-ignition signal for causing the ignition plug to perform pre-ignition without combustion of the air-fuel mixture. The timing at which the air-fuel mixture reaches the ignition plug is set to the actual compression start timing at which the air-fuel mixture is actually compressed during the compression stroke, plus a mixture arrival delay period determined by the engine speed, the intake pressure of the air-fuel mixture, and the shape of the sub-combustion chamber. Engine control device.

4. A cylinder in which an air-fuel mixture formed by mixing fuel injected by a fuel injection device and air taken in from an intake system burns in a main combustion chamber facing a piston, A sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber, an electrode provided inside the sub-combustion chamber, and a flame jet generated by the electrode igniting the air-fuel mixture inside the sub-combustion chamber is injected into the main combustion chamber, and an ignition plug for igniting the air-fuel mixture in the main combustion chamber, An engine control device for controlling the output of an engine, comprising: an ignition device for controlling the ignition timing of the spark plug. A control unit is provided that continues to supply a pre-ignition signal for causing the spark plug to perform pre-ignition without combustion of the air-fuel mixture until main ignition at which the air-fuel mixture reaches the spark generated at the electrodes, and determines the end time of the spark based on the primary voltage, secondary current, secondary voltage of the ignition coil, or map values stored in advance for each operating condition. Engine control device.

5. The pre-ignition is accompanied by dielectric breakdown voltage exceeding the voltage between the electrodes of the spark plug and the occurrence of discharge. The engine control device according to any one of claims 1 to 4.

6. The control unit performs the pre-ignition at the start of the engine or before the cycle in which fuel injection is started by the fuel injection device. The engine control device according to any one of claims 1 to 4.

7. The control unit increases the amount of electrode heating for heating the electrodes of the spark plug by the pre-ignition as the engine coolant temperature at the start of the engine is lower. The engine control device according to any one of claims 1 to 4.

8. A cylinder in which an air-fuel mixture of fuel injected by a fuel injection device and air taken in from an intake system burns in a main combustion chamber facing a piston. A sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber, and an electrode attached inside the sub-combustion chamber. A spark plug that injects a flame jet generated by igniting the air-fuel mixture by the electrode inside the sub-combustion chamber into the main combustion chamber to ignite the air-fuel mixture in the main combustion chamber, and an ignition device for controlling the ignition timing of the spark plug. An engine control method for controlling the output of an engine, comprising: an ignition device for controlling the ignition timing of the spark plug. The timing at which the air-fuel mixture reaches the spark plug is the timing at which the pressure in the sub-combustion chamber becomes lower than the pressure in the main combustion chamber. Until main ignition at which the air-fuel mixture reaches the spark generated at the electrodes, the supply of a pre-ignition signal for causing the spark plug to perform pre-ignition without combustion of the air-fuel mixture is continued. When the closing timing of the intake valve provided in the intake system is set to the compression stroke, the process includes continuing the pre-ignition from after the combustion of the air-fuel mixture in the combustion cycle to the closing timing of the intake valve in the compression stroke of the combustion cycle. Engine control method. An engine control method for controlling the output of an engine comprising: a cylinder in which an air-fuel mixture formed by mixing fuel injected by a fuel injection device and air taken in from an intake system burns in a main combustion chamber facing a piston; a sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber; and an electrode attached inside the sub-combustion chamber, wherein an ignition plug injects a flame jet generated by igniting the air-fuel mixture by the electrode inside the sub-combustion chamber into the main combustion chamber to ignite the air-fuel mixture in the main combustion chamber; an ignition device for controlling the ignition timing of the ignition plug, the method comprising: The timing at which the air-fuel mixture reaches the ignition plug is a timing at which the pressure in the sub-combustion chamber is lower than the pressure in the main combustion chamber. A pre-ignition signal for causing the ignition plug to perform pre-ignition without combustion of the air-fuel mixture until main ignition at which the air-fuel mixture reaches a spark generated by the electrode is continuously supplied. When the closing timing of an intake valve provided in the intake system is set in the intake stroke, the method includes a process of continuing the pre-ignition from after the combustion of the air-fuel mixture in a combustion cycle until the start timing of the compression stroke in the combustion cycle. Engine control method.

10. An engine control method for controlling the output of an engine comprising: a cylinder in which an air-fuel mixture formed by mixing fuel injected by a fuel injection device and air taken in from an intake system burns in a main combustion chamber facing a piston; a sub-combustion chamber communicating with the main combustion chamber and taking in the air-fuel mixture from the main combustion chamber; and an electrode attached inside the sub-combustion chamber, wherein an ignition plug injects a flame jet generated by igniting the air-fuel mixture by the electrode inside the sub-combustion chamber into the main combustion chamber to ignite the air-fuel mixture in the main combustion chamber; an ignition device for controlling the ignition timing of the ignition plug, the method comprising: The timing at which the air-fuel mixture reaches the ignition plug is the timing at which the pressure in the sub-combustion chamber becomes lower than the pressure in the main combustion chamber. Before the main ignition at which the air-fuel mixture reaches the spark generated at the electrode, the supply of a pre-ignition signal for causing the ignition plug to perform pre-ignition without combustion of the air-fuel mixture is continued. The timing at which the air-fuel mixture reaches the ignition plug is set to the actual compression start timing at which the air-fuel mixture is actually compressed during the compression stroke, plus a mixture arrival delay period determined by the engine speed, the intake pressure of the air-fuel mixture, and the shape of the sub-combustion chamber. The method includes a process of setting the timing in this way. Engine control method.

11. A cylinder in which an air-fuel mixture obtained by mixing fuel injected by a fuel injection device and air taken in from an intake system burns in a main combustion chamber facing a piston, A sub-combustion chamber that communicates with the main combustion chamber and takes in the air-fuel mixture from the main combustion chamber, and an electrode attached inside the sub-combustion chamber. An ignition plug that injects a flame jet generated by the electrode igniting the air-fuel mixture inside the sub-combustion chamber into the main combustion chamber to ignite the air-fuel mixture in the main combustion chamber, An engine control method for controlling the output of an engine, comprising an ignition device that controls the ignition timing of the ignition plug. Before the main ignition at which the air-fuel mixture reaches the spark generated at the electrode, the supply of a pre-ignition signal for causing the ignition plug to perform pre-ignition without combustion of the air-fuel mixture is continued. The method includes a process of determining the end time of the spark based on the primary voltage, secondary current, secondary voltage of the ignition coil, or map values stored in advance for each operating condition. Engine control method.

Images