Restart control method and control device for spark ignition internal combustion engine

Abstract

To make a restart at a lean air-fuel ratio and also to prevent an HC increase due to insufficient flame spreading when a cylinder wall temperature is low.SOLUTION: An internal combustion engine 2 for electric power generation in a series hybrid vehicle is restarted in response to a request for electric power generation etc., accompanied by motoring by a motor generator 1 for electric power generation. At the restart, an air amount control part 51 controls an air amount control device such as a throttle valve 22 so as to obtain a target air amount. A target air-fuel ratio at the restart is determined by correcting, by a correction air-fuel ratio computation part 61, a target air-fuel ratio which is a lean air-fuel ration that a basic air-fuel ratio output part 60 outputs at the restart according to a cylinder wall temperature, and supplied to a fuel flow rate computation part 59. The fuel flow rate computation part 59 finds a fuel injection amount so as to obtain the target air-fuel ratio to the target air amount.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a restart control method and control device for a spark ignition internal combustion engine that performs lean burn. [Background technology]

[0002] From the viewpoint of fuel consumption rate and exhaust composition, spark ignition internal combustion engines have been proposed that are capable of lean burn with a significantly lean air-fuel ratio (for example, an air-fuel ratio of 20 or more) assuming supercharging. Even in such lean burn internal combustion engines, when starting (cranking) the internal combustion engine, it is common to start by injecting an appropriate amount of fuel so that the air-fuel ratio is close to the stoichiometric air-fuel ratio, rather than using lean burn.

[0003] Although Patent Document 1 does not specify the air-fuel ratio value, it discloses an internal combustion engine that performs lean burn with a target air-fuel ratio set to lean in the medium-speed medium-load range, and operates at the stoichiometric air-fuel ratio in the high-speed high-load range and during idling. This engine starts by injecting an appropriate amount of fuel according to the coolant temperature during start-up cranking to achieve a stoichiometric or rich air-fuel ratio. Once the engine starts, the air-fuel ratio is set to lean from immediately after startup until catalyst warm-up is complete, thereby suppressing HC emissions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-184421 Summary of the Invention [Problem to be solved by the invention]

[0005] As disclosed in Patent Document 1, in conventional general starting methods, the air-fuel ratio during cranking is not strictly controlled, and an appropriate amount of fuel is injected to enable complete combustion and self-sustaining operation within a relatively short cranking time. As a result, as is well known, exhaust emissions temporarily worsen.

[0006] Patent Document 1 does not mention restarting the engine after warming up the catalyst, but if the engine is restarted at a stoichiometric air-fuel ratio after continuing lean combustion, the catalyst will be in an oxygen-saturated state due to the lean combustion up to that point, and the NOx in the exhaust will hardly be processed, resulting in excessive NOx emissions.

[0007] On the other hand, according to new findings by the inventors, when the engine is restarted under a lean air-fuel ratio after continued lean combustion, HC emissions actually increase when the air-fuel ratio is high (for example, around 30). This tendency is particularly pronounced when the cylinder wall temperature is low. This is thought to be because the lean air-fuel mixture leads to insufficient flame propagation, making it more likely that fuel adhering to the cylinder wall surface or present near the cylinder wall surface will remain unburned. [Means for solving the problem]

[0008] This invention is This spark-ignition internal combustion engine uses liquid fuel and has a stoichiometric combustion mode in which combustion is performed at a near-stoichiometric air-fuel ratio, and a lean combustion mode in which combustion is performed at a lean air-fuel ratio. The target air-fuel ratio in the stoichiometric combustion mode and the target air-fuel ratio in the lean combustion mode are discontinuous, and when restarting, the engine is restarted by fuel injection and ignition while motoring in the lean combustion mode. A restart control method or control device for a spark ignition internal combustion engine, The air-fuel ratio is in the range of 24 to 26, which is smaller than the target air-fuel ratio in the lean combustion mode after the start is completed. Lean air-fuel ratio at restart Basic Set as the target air-fuel ratio Determine At the same time, Cylinder wall temperature The cylinder wall temperature is estimated or detected. The lower the value, the less lean the fuel is. Within the range of air-fuel ratio 20 or more Correct the target air-fuel ratio above The amount of fuel injected during motoring is then controlled in accordance with this target air-fuel ratio.

[0009] Note that "becoming leaner" means that the deviation from the stoichiometric air-fuel ratio becomes smaller, in other words, the value of the lean air-fuel ratio becomes relatively smaller. By making the air-fuel ratio leaner when the temperature parameter is low, flame propagation improves and HC generation by the fuel on or near the cylinder wall surface is suppressed. [Effects of the Invention]

[0010] According to the present invention, the air-fuel ratio at the time of restart is correctly controlled to a lean air-fuel ratio, and this target air-fuel ratio is Cylinder wall temperatureBy making corrections according to the engine speed, increases in exhaust emissions including NOx and HC that occur when the engine is restarted are suppressed. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram of the configuration of a series hybrid vehicle. [Figure 2] 1 is a diagram illustrating the configuration of an internal combustion engine according to an embodiment; [Figure 3] FIG. 4 is a block diagram showing control at the time of restarting. [Figure 4] A characteristic diagram showing the HC characteristics after restart, comparing (a) when the wall temperature is high and (b) when the wall temperature is low. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment in which the present invention is applied to an internal combustion engine for generating electricity in a series hybrid vehicle will be described below. FIG. 1 shows a schematic configuration of a series hybrid vehicle. The series hybrid vehicle is configured to include a power-generating motor-generator 1 that operates primarily as a generator, an internal combustion engine 2 used as a power-generating internal combustion engine that drives the power-generating motor-generator 1 in response to power demands, a traction motor-generator 4 that operates primarily as a motor to drive drive wheels 3, and a battery 5 that temporarily stores the generated electricity. The electric power obtained by the internal combustion engine 2 driving the power-generating motor-generator 1 is stored in the battery 5 via an inverter device (not shown). The traction motor-generator 4 is driven and controlled using the electric power from the battery 5. The electric power generated by the traction motor-generator 4 during regeneration is stored in the battery 5 via an inverter device (not shown).

[0013] The operation of the motor generators 1 and 4, the charging and discharging of the battery 5, and the operation of the internal combustion engine 2 are controlled by a controller 6. The controller 6 is composed of multiple controllers connected to each other so that they can communicate with each other, such as a motor controller 7 that controls the motor generators 1 and 4, an engine controller 8 that controls the internal combustion engine 2, and a battery controller 9 that manages the battery 5. Information such as the accelerator pedal position and vehicle speed (not shown) is input to the controller 6. The battery controller 9 also calculates the SOC of the battery 5 based on the voltage and current of the battery 5. When the SOC drops to a predetermined lower limit, the internal combustion engine 2 is started via the engine controller 8 to generate electricity. Such a series hybrid vehicle has two driving modes: an EV mode in which the vehicle runs on power from the battery 5 without combustion operation of the internal combustion engine 2, and an HEV mode in which the vehicle runs while generating electricity through combustion operation of the internal combustion engine 2. However, even if the SOC is above the lower limit, the vehicle will run in the HEV mode if the required driving force of the vehicle is relatively large.

[0014] FIG. 2 shows the system configuration of an internal combustion engine 2. This internal combustion engine 2 is a four-stroke, spark-ignition internal combustion engine equipped with a turbocharger 12. A pair of intake valves 14 and a pair of exhaust valves 15 are arranged on the ceiling wall of each cylinder 13, and an ignition plug 16 is arranged in the center surrounded by these intake valves 14 and exhaust valve 15. A fuel injection valve 17 that supplies fuel into the cylinder 13 is provided below the intake valve 14. The ignition timing of the spark plug 16 and the injection timing and injection amount of fuel by the fuel injection valve 17 are controlled by an engine controller 8. As will be described later, this internal combustion engine 2 is configured to be switchable between a stoichiometric combustion mode in which the target air-fuel ratio is the theoretical air-fuel ratio (λ=1), and a lean combustion mode in which combustion is performed with a lean air-fuel ratio (near λ=2) assuming supercharging.

[0015] The intake valve 14 and the exhaust valve 15 are equipped with variable valve timing mechanisms 18, 19 that can change the opening and closing timings of the valves, respectively. These variable valve timing mechanisms 18, 19 may be of any type, but for example, a mechanism that retards the phase of the camshaft relative to the phase of the crankshaft can be used.

[0016] The intake passage 21 has an intake collector 21a, and upstream of this intake collector 21a is provided an electronically controlled throttle valve 22 whose opening is controlled by a control signal from the engine controller 8. The compressor 12a of the turbocharger 12 is located upstream of the throttle valve 22, and upstream of this compressor 12a are provided an air flow meter 24, for example of a hot wire type, that detects the amount of intake air, and an air cleaner 25. Between the compressor 12a and the throttle valve 22, is provided an intercooler 26, for example of a water-cooled type, to cool the high-temperature, high-pressure intake air. In addition, a recirculation valve 27 is provided to communicate the discharge side and intake side of the compressor 12a.

[0017] A turbine 12b of the turbocharger 12 is located in the exhaust passage 30, and a pre-catalyst device 31 is disposed upstream of the turbine 12b, i.e., between the turbine 12b and the exhaust valve 15. The pre-catalyst device 31 is configured by combining, in series from the upstream side, a three-way catalyst 31A, a particulate filter (so-called GPF) 31B for capturing exhaust particulates, and an oxidation catalyst 31C. A main catalyst device 32 is disposed downstream of the turbine 12b. The main catalyst device 32 is typically a selective catalytic reduction (SCR) device that uses urea water to reduce NOx or a NOx adsorption catalyst, mainly to treat NOx during lean combustion. The pre-catalyst device 31 is mounted adjacent to the cylinder head of the internal combustion engine 2, and the main catalyst device 32 is disposed under the vehicle floor.

[0018] An air-fuel ratio sensor 33 for detecting the air-fuel ratio is disposed upstream of the pre-catalyst device 31 in the exhaust passage 30. The turbine 12b is provided with a wastegate valve 34 that bypasses part of the exhaust gas in accordance with the boost pressure in order to control the boost pressure. The wastegate valve 34 is an electrically operated valve whose opening is controlled by the engine controller 8.

[0019] The engine is also provided with an exhaust gas recirculation passage 35 that recirculates a portion of the exhaust gas from the exhaust passage 30 to the intake passage 21, and this exhaust gas recirculation passage 35 is provided with, for example, a water-cooled EGR gas cooler 37 and an EGR valve 38.

[0020] In addition to the air flow meter 24 and air-fuel ratio sensor 33, the engine controller 8 receives detection signals from various sensors, such as a crank angle sensor 41 for detecting engine speed, a water temperature sensor 42 for detecting coolant temperature, a boost pressure sensor 43 for detecting boost pressure, and an atmospheric pressure sensor 44 for detecting atmospheric pressure. Furthermore, in this embodiment, to further improve the accuracy of air-fuel ratio control, an intake air temperature sensor 45 for detecting intake air temperature and a humidity sensor 46 for detecting intake air humidity are provided. In one embodiment, the intake air temperature sensor 45 and humidity sensor 46 are built into the hot-wire air flow meter 24. Based on these detection signals and requests from the other controllers 7 and 9, the engine controller 8 optimally controls the fuel injection amount and injection timing, ignition timing, the opening of the throttle valve 22, the phase of the variable valve timing mechanisms 18 and 19, the boost pressure (i.e., the opening of the wastegate valve 34), and the like.

[0021] In this embodiment, the amount of air in the cylinder 13 is changed by the throttle valve 22, which changes the effective cross-sectional area of the intake passage 21, the variable valve timing mechanism 18, which changes the opening and closing timing of the intake valve 14, and the wastegate valve 34, which controls the boost pressure. In other words, in this embodiment, these three devices correspond to the "air amount control device."

[0022] The internal combustion engine 2 is basically started when the SOC of the battery 5 drops to a predetermined lower limit SOC value and stopped when the SOC recovers to a predetermined level. When the internal combustion engine 2 drives the power-generating motor-generator 1 to generate electricity, the internal combustion engine 2 is basically operated at a predetermined first operating point near the best fuel efficiency point. When the power generation demand is large, the internal combustion engine 2 is operated at a predetermined second operating point for high-output power generation that is set on the high-speed, high-load side of the first operating point.

[0023] The first operating point is set on the relatively low load side and corresponds to the best fuel economy point of the internal combustion engine 2. The second operating point is set on the high-speed, high-load side of the first operating point, and in one embodiment, is set near the point where the highest speed and highest load is achieved. Note that these operating points are not strictly one point, but each includes an appropriate range of rotation speed and load, although it is a relatively narrow range.

[0024] As described above, the operating point of the internal combustion engine 2 is primarily determined by the power generation demand, with the first operating point being selected when the power generation demand is steady, and the second operating point being selected when the power generation demand is large. The final operating point is determined based on the power generation demand as well as the cooling water temperature and other demands, but operating points not included in the first and second operating points are generally not used. Furthermore, the first and second operating points are discontinuous, and therefore, when the operating point transitions between the first and second operating points, the rotational speed and load change stepwise.

[0025] Here, at a first operating point where fuel economy is emphasized, the lean burn mode is selected, and lean burn is performed with a lean air-fuel ratio as the target air-fuel ratio, assuming supercharging. For example, the internal combustion engine 2 is operated at a relatively high lean air-fuel ratio (i.e., an air-fuel ratio of approximately 30) where the excess air ratio λ is approximately 2. On the other hand, at a second operating point where output is emphasized, the stoichiometric burn mode is selected, and stoichiometric burn is performed with the theoretical air-fuel ratio (λ=1) as the target air-fuel ratio. Regarding air-fuel ratio control, the target air-fuel ratio in the lean burn mode and the target air-fuel ratio in the stoichiometric burn mode are discontinuous, and intermediate lean air-fuel ratios are not used as the target air-fuel ratio. This is to avoid a deterioration in NOx due to an intermediate lean air-fuel ratio.

[0026] Next, the control of restarting the internal combustion engine 2, which is a key part of the present invention, will be described. As described above, the internal combustion engine 2 is operated intermittently while the vehicle is running, and the internal combustion engine 2 is repeatedly stopped and started (restarted). Restarting is achieved by motoring the internal combustion engine 2 using the power generation motor / generator 1, which is directly or indirectly connected to the crankshaft of the internal combustion engine 2, and performing fuel injection and ignition. Here, since the internal combustion engine 2 is in a somewhat warmed-up state, restarting is performed in a lean combustion mode with a lean air-fuel ratio as the target air-fuel ratio. In particular, the amount of air flowing into the cylinder 13 (in other words, the charging efficiency) and the amount of fuel injection are controlled so that the target air-fuel ratio is correctly obtained.

[0027] The power-generating motor generator 1 motors the crankshaft of the internal combustion engine 2 at a constant rotational speed by controlling the rotational speed. This motoring rotational speed is set to a different value for each restart mode depending on the restart mode, which is determined by the conditions under which restart is requested, etc.

[0028] 3 is a functional block diagram showing one embodiment of control during restart. The portion enclosed by dashed line 51 in the diagram is an air amount control unit that performs control to obtain a target air amount, assuming that motoring is performed at a stable rotational speed. In other words, in one embodiment, the air amount control device is controlled so as to obtain the target air amount, without relying on detection of the intake air amount by the air flow meter 24.

[0029] The air amount control unit 51 includes a target air amount setting unit 52 and a device manipulated variable setting unit 53. The target air amount setting unit 52 sets a target air amount per cycle that should flow into the cylinder 13 at the time of restart, and outputs the target air amount to the device manipulated variable setting unit 53. In other words, this target air amount is a target charging efficiency. The device manipulated variable setting unit 53 also receives as input the atmospheric pressure, intake air temperature, and humidity detected by the atmospheric pressure sensor 44, intake air temperature sensor 45, and humidity sensor 46, respectively. Taking these atmospheric pressure, intake air temperature, and humidity into consideration, the device manipulated variable setting unit 53 controls the opening of the throttle valve 22, the opening of the wastegate valve 34, and the phase angle of the variable valve timing mechanism 18 (VTC), which are air amount control devices, respectively, so as to obtain the target air amount in accordance with predetermined characteristics (blocks 54, 55, 56). For example, the basic control parameters of these air amount control devices are predetermined for a target air amount, and each of these control parameters is corrected by the atmospheric pressure, intake air temperature, and humidity. In other words, in one embodiment, the amount of air to be introduced into the cylinder 13 is controlled in an open-loop manner.

[0030] The intake air temperature may be the outside air temperature, the intake air temperature at the intake air collector 21a, the intake air temperature immediately after passing through the intercooler 26, etc. Corrections based on atmospheric pressure, intake air temperature, or humidity may be omitted.

[0031] Furthermore, the target air amount output by the target air amount setting unit 52 is subjected to delay correction by a primary delay coefficient output unit 58 in a corrected air amount calculation unit 57. The value of the target air amount after delay correction output by the corrected air amount calculation unit 57 is input to a fuel flow rate calculation unit 59.

[0032] On the other hand, the restart basic air-fuel ratio output section 60 outputs a basic air-fuel ratio to be targeted at the time of restart. This is given according to the restart mode described above, in other words, according to the motoring rotation speed of each restart mode. More specifically, this restart basic air-fuel ratio is set to about 24 to 26, which is slightly smaller than the target lean air-fuel ratio (for example, around 30) at the first operating point.

[0033] The restart basic air-fuel ratio is input to a correction air-fuel ratio calculation unit 61, which corrects it based on the cylinder wall temperature output by a wall temperature estimation unit 62. Here, the target air-fuel ratio is corrected so that the lower the cylinder wall temperature, the less lean it becomes. For example, if the target basic air-fuel ratio is about 26, the target air-fuel ratio will be reduced to about 23 or 21 at low temperatures. However, since an intermediate lean air-fuel ratio increases NOx, the air-fuel ratio is set to a range of 20 or higher.

[0034] The cylinder wall temperature is estimated, for example, from the coolant temperature at that time and the time elapsed since the operation of the internal combustion engine 2 was stopped. Alternatively, the coolant temperature itself may be used as a temperature parameter that substitutes for the cylinder wall temperature. Alternatively, the cylinder wall temperature may be estimated from the time progression of the coolant temperature. Of course, the cylinder wall temperature may also be directly detected by a temperature probe.

[0035] The target air-fuel ratio is further slightly corrected based on the humidity detected by the humidity sensor 46. Humidity affects the oxygen concentration in the air. Note that this correction based on humidity may be omitted.

[0036] The corrected target air-fuel ratio output by corrected air-fuel ratio calculation unit 61 is input to fuel flow rate calculation unit 59. Fuel flow rate calculation unit 59 calculates the fuel flow rate, i.e., the fuel injection amount, required to obtain the target air-fuel ratio from the air amount input from corrected air amount calculation unit 57 and the target air-fuel ratio. This determined fuel injection amount is provided to a fuel injection valve drive unit 63 that drives and controls fuel injection valve 17. A drive pulse signal is provided to fuel injection valve 17 in accordance with this fuel injection amount, and fuel injection is performed.

[0037] In a preferred embodiment, the lean combustion during restart is in the form of homogeneous lean combustion without active stratification. Furthermore, while fuel injection may be single-stage injection, in a preferred embodiment, multi-stage injection is used, where the fuel is injected in multiple stages. For example, three-stage injection is performed, where two injections are performed during the intake stroke and one injection is performed early in the compression stroke. This multi-stage injection reduces spray penetration, resulting in relatively less fuel adhering to the cylinder wall surface or floating near the cylinder wall surface, which is advantageous for reducing HC emissions.

[0038] In this embodiment, the engine is restarted in the lean burn mode, with the target air-fuel ratio significantly leaner. Therefore, especially when the engine transitions to steady-state operation at the first operating point, which provides the best fuel economy, after the restart, the lean burn mode can be maintained, eliminating the need to switch between the lean and stoichiometric burn modes. Furthermore, the air volume in the cylinder 13 is controlled to the target air volume by the air volume control device without relying on flow rate detection by the air flow meter 24, and the fuel injection amount corresponding to the target air volume is set to obtain the target air-fuel ratio. This ensures a highly accurate, appropriate air-fuel ratio from the beginning of motoring. Therefore, a reliable restart is possible at a lean air-fuel ratio of 20 or more.

[0039] Furthermore, the target air-fuel ratio is basically set to a sufficiently lean air-fuel ratio, and when the cylinder wall temperature is low, the target air-fuel ratio is corrected so that the degree of leanness becomes relatively small, thereby suppressing an increase in unburned hydrocarbons near the cylinder wall surface that is caused by insufficient flame propagation.

[0040] FIG. 4 is a characteristic diagram showing the relationship between HC emissions from the internal combustion engine 2 after restart and the target air-fuel ratio at the time of restart. Diagram (a) shows the characteristics when the cylinder wall temperature is relatively high (e.g., when the coolant temperature is around 85°C). Line L1 shows the characteristics when the air-fuel ratio is 24, and line L2 shows the characteristics when the air-fuel ratio is 26. As shown in the diagram, under conditions where the air-fuel ratio is significantly lean, the relatively leaner characteristic L2 results in higher HC emissions than the characteristic L1 when the air-fuel ratio is 24. This is thought to be due to the fact that a significantly lean air-fuel ratio results in insufficient flame propagation, making it more likely that fuel present on or near the cylinder wall surface will remain unburned. In other words, even though there is sufficient oxygen in the cylinder, flame propagation does not reach the cylinder wall surface, resulting in an increase in HC. Therefore, a basic target air-fuel ratio of approximately 24 to 26 is preferable. Note that, under such a sufficiently lean air-fuel ratio, NOx emissions also decrease.

[0041] Graph (b) shows the characteristics when the cylinder wall temperature is relatively low (for example, when the coolant temperature is around 40°C) during restart in cold regions, etc. Line L3 shows the characteristics when the air-fuel ratio is 21, and line L4 shows the characteristics when the air-fuel ratio is 23. As shown by characteristic L4, when the cylinder wall temperature is low, the increase in HC due to insufficient flame propagation becomes more pronounced. Therefore, when the cylinder wall temperature is low like this, the target air-fuel ratio is corrected to be relatively less lean. This suppresses the deterioration of HC, as shown by characteristic L3 when the air-fuel ratio is 21.

[0042] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible.

[0043] For example, if the detection response of the air flow meter 24 can be ensured to be sufficiently high, the amount of air flowing into the cylinder 13 during motoring may be detected by the air flow meter 24, and the fuel injection amount may be controlled so as to achieve the target air-fuel ratio.

[0044] Furthermore, since the rotational speed can be obtained stably by motoring, the amount of air in the cylinder 13 may be estimated during motoring using the pressure (boost pressure) in the intake collector 21a, the phase angle of the variable valve timing mechanism 18, and the rotational speed.

[0045] The air amount control device is not limited to the above example, and an electric compressor, an electric assisted turbocharger, or the like may also be used.

[0047] Furthermore, in the above embodiment, an example has been described in which the invention is applied to a power-generating internal combustion engine 2 in a series hybrid vehicle, but the invention can also be applied to restarting internal combustion engines in other types of hybrid vehicles or internal combustion engines that serve as a driving source for the vehicle. [Explanation of symbols]

[0048] 1...Power generating motor generator 2...Internal combustion engine 4...Traction motor generator 5. Battery 6...Controller 8...Engine controller 12...Turbocharger 18...Variable valve timing mechanism 22...Throttle valve 24...Air flow meter 34...Wastegate valve

Claims

1. A restart control method for a spark ignition internal combustion engine that uses liquid fuel, has a stoichiometric combustion mode in which combustion is performed near the stoichiometric air-fuel ratio, and a lean combustion mode in which combustion is performed at a lean air-fuel ratio, and the target air-fuel ratio in the stoichiometric combustion mode and the target air-fuel ratio in the lean combustion mode are discontinuous, and at the time of restart, the internal combustion engine is restarted by fuel injection and ignition while motoring in the lean combustion mode, A lean air-fuel ratio in the range of 24 to 26, which is smaller than the target air-fuel ratio in the lean combustion mode after the start is completed, is set as the basic target air-fuel ratio at the time of restarting, a cylinder wall temperature is estimated or detected, and the target air-fuel ratio is corrected within a range of air-fuel ratios of 20 or more so that the degree of leanness decreases as the cylinder wall temperature decreases, and the fuel injection amount during motoring is controlled in accordance with this target air-fuel ratio; A method for controlling restart of a spark ignition internal combustion engine.

2. setting a target air amount and controlling the air amount control device so as to obtain the target air amount; 2. A method for controlling restart of a spark ignition internal combustion engine according to claim 1.

3. The fuel injection amount is controlled using a corrected air amount obtained by performing delay correction processing on the target air amount.

3. The restart control method for a spark ignition internal combustion engine according to claim 2.

4. Detects the amount of air while motoring, The detected air amount is used to control the fuel injection amount.

2. A method for controlling restart of a spark ignition internal combustion engine according to claim 1.

5. The spark ignition internal combustion engine is a power generating internal combustion engine in a series hybrid vehicle, and motoring is performed at the time of restart by a power generating motor generator.

5. A method for controlling restart of a spark ignition internal combustion engine according to claim 1.

6. A restart control device for a spark ignition internal combustion engine that uses liquid fuel, has a stoichiometric combustion mode in which combustion is performed near the theoretical air-fuel ratio, and a lean combustion mode in which combustion is performed at a lean air-fuel ratio, and the target air-fuel ratio in the stoichiometric combustion mode and the target air-fuel ratio in the lean combustion mode are discontinuous, and at the time of restart, restarts by fuel injection and ignition while motoring the internal combustion engine in the lean combustion mode, A lean air-fuel ratio in the range of 24 to 26, which is smaller than the target air-fuel ratio in the lean combustion mode after the start is completed, is set as the basic target air-fuel ratio at the time of restarting, a cylinder wall temperature is estimated or detected, and the target air-fuel ratio is corrected within a range of air-fuel ratios of 20 or more so that the degree of leanness decreases as the cylinder wall temperature decreases, and the fuel injection amount during motoring is controlled in accordance with this target air-fuel ratio; A restart control device for a spark ignition internal combustion engine.

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