Hybrid vehicles

Abstract

This hybrid vehicle (60) has a series travel mode and a parallel travel mode. In the series travel mode, the air-fuel mixture to be introduced into a combustion chamber (C) of an engine (10) is set to a first air-fuel ratio, and the ignition timing is set to a first ignition timing. In the parallel travel mode, the air-fuel mixture to be introduced into the combustion chamber (C) is set to a second air-fuel ratio that is richer in fuel than the first air-fuel ratio, and the ignition timing is set to a second ignition timing that is more retarded than the first ignition timing.

Description

[Technical Field]

[0001] The present invention relates to hybrid vehicles. [Background technology]

[0002] Lean-burn engines have been proposed in the past, which burn a mixture with a leaner fuel ratio (excess air relative to fuel) than the stoichiometric air-fuel ratio. To achieve better combustion of this lean mixture, a pre-chamber engine has been proposed, which has a main combustion chamber and a pre-chamber as combustion chambers. In a pre-chamber engine, a communication passage is provided in the partition wall separating the main and pre-chambers. A mixture formed by fuel injected into the main combustion chamber is supplied to the pre-chamber through the communication passage and ignited by a spark plug in the pre-chamber. When a flame is formed in the pre-chamber, the flame propagates to the main combustion chamber through the communication passage and ignites the mixture in the main combustion chamber. This allows the engine to operate at a leaner air-fuel ratio, which is believed to improve fuel economy (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4389777 [Patent Document 2] International Publication No. 2020 / 196206 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, hybrid vehicles equipped with an engine that supplies driving force for driving and a motor (rotating electric machine) that supplies driving force for driving have various driving conditions, such as electric driving mode, series driving mode, and parallel driving mode.

[0005] In conventional engines, when knocking occurs under high load, the ignition timing is retarded to reduce the pressure inside the cylinder, thereby preventing knocking. However, in the case of a pre-chamber engine, retarding the ignition timing creates a lean environment inside the pre-chamber, which can lead to unstable ignition in the pre-chamber. Even in hybrid vehicles equipped with other types of engines, there is a need to find ways to avoid knocking while ensuring good combustion under a variety of constantly changing driving conditions.

[0006] Therefore, an object of the present invention is to ensure good combustion under various driving conditions in an engine mounted on a hybrid vehicle. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a hybrid vehicle equipped with an engine, a storage battery, a generator driven by the engine to generate electricity, and a rotating electric machine that supplies driving force for traveling using electricity supplied from the storage battery or the generator, and having at least a series driving mode in which the engine is operated to supply electricity to the storage battery or the rotating electric machine, and a parallel driving mode in which the engine is operated to supply driving force to the drive wheels, wherein in the series driving mode, the mixture introduced into the combustion chamber of the engine is set to a first air-fuel ratio and the ignition timing is set to a first ignition timing, and in the parallel driving mode, the mixture introduced into the combustion chamber is set to a second air-fuel ratio that is richer in fuel than the first air-fuel ratio and the ignition timing is set to a second ignition timing that is retarded from the first ignition timing.

[0008] Here, in addition to the above aspect, an engine start mode is provided for operating the engine that is not operating, and in the engine start mode when the engine is in a cold state, the mixture introduced into the combustion chamber is set to a third air-fuel ratio that is richer in fuel than the second air-fuel ratio, and the ignition timing is set to a third ignition timing that is retarded from the second ignition timing.

[0009] It is further preferable that the ignition energy when the second ignition timing is set is greater than the ignition energy when the first ignition timing is set, and it is further preferable that the ignition energy when the third ignition timing is set is greater than the ignition energy when the second ignition timing is set.

[0010] The engine may also include a direct injection fuel injection device that injects fuel into the combustion chamber, and the fuel injection amount per combustion cycle of the direct injection fuel injection device may be greater when the second air-fuel ratio is set than when the first air-fuel ratio is set.Furthermore, the engine may also include a direct injection fuel injection device that injects fuel into the combustion chamber, and the fuel injection amount per combustion cycle of the direct injection fuel injection device may be greater when the third air-fuel ratio is set than when the second air-fuel ratio is set.

[0011] In each of these aspects, the combustion chamber may include a main chamber surrounded by the inner circumferential surface of the cylinder, the inner surface of the cylinder head, and the top surface of the piston, an auxiliary chamber separated from the main chamber and formed at the end of the main chamber facing the cylinder head, and a communication passage connecting the main chamber with the auxiliary chamber, as well as an ignition device that ignites the air-fuel mixture in the auxiliary chamber, the direct injection fuel injection device being positioned within the combustion chamber to inject fuel directly toward the auxiliary chamber, and a port injection fuel injection device that injects fuel into an intake passage leading to the combustion chamber.

[0012] At this time, when the ignition timing is set to be retarded from the first ignition timing, fuel injection by the direct fuel injection device can be performed intermittently a plurality of times. [Effects of the Invention]

[0013] According to the present invention, good combustion can be ensured under various driving conditions of a hybrid vehicle. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a longitudinal cross-sectional view of a pre-combustion chamber engine. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3A] FIG. 2 is a vertical cross-sectional view showing the combustion state of a pre-combustion chamber engine. [Figure 3B] FIG. 2 is a vertical cross-sectional view showing the combustion state of a pre-combustion chamber engine. [Figure 3C] FIG. 2 is a vertical cross-sectional view showing the combustion state of a pre-combustion chamber engine. [Figure 4] FIG. 4 is a graph showing the control of the present invention. [Figure 5] FIG. 4 is a graph showing the control of the present invention. [Figure 6] 1 is a schematic diagram showing an example of a hybrid vehicle according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described with reference to the drawings. This embodiment is a hybrid vehicle 60 (hereinafter simply referred to as vehicle 60). The main parts of an engine 10 mounted on the vehicle 60 are shown in FIGS.

[0016] The vehicle 60 includes a battery 50 that is used primarily as a power source for traveling, and two rotating electric machines 30, 40. One of the rotating electric machines 30 (hereinafter referred to as the first rotating electric machine 30) functions as a starter, and the engine 10 starts when the first rotating electric machine 30 operates. The other rotating electric machine 40 (hereinafter referred to as the second rotating electric machine 40) is a motor that supplies driving force for traveling. The first rotating electric machine 30 also functions as a generator that generates electricity using the driving force of the engine 10 (see FIG. 6).

[0017] The vehicle 60 is a hybrid vehicle that has three drive modes: an electric drive mode (EV mode), a series drive mode, and a parallel drive mode. An electronic control unit 20 provided in the vehicle 60 selects the optimum drive mode depending on the current state and drive condition of the vehicle 60, the driver's request, etc. The engine 10, the first rotating electric machine 30, the second rotating electric machine 40, etc. are controlled depending on the selected drive mode. In this embodiment, the vehicle 60 is assumed to be a plug-in hybrid car that can be externally charged to the battery 50 directly using a plug from a household outlet or the like.

[0018] The first rotating electric machine 30 is a motor-generator that functions both as an electric motor (motor) and as a generator. When starting the engine 10, the first rotating electric machine 30 functions as a starter electric motor. At this time, the first rotating electric machine 30 uses power from a battery (storage battery) 50 or a separately installed auxiliary battery. When the engine 10 is running, the first rotating electric machine 30 functions as a generator that generates power using the driving force of the engine 10. The power generated by the first rotating electric machine 30 is supplied to the second rotating electric machine 40, the battery 50, etc. The rotating shaft of the first rotating electric machine 30 is connected to the crankshaft of the engine 10 via an endless member such as a belt, gears, etc. During operation of the engine 10, the first rotating electric machine 30 is normally rotated in conjunction with the rotation of the crankshaft.

[0019] The second rotating electric machine 40 is provided as a drive source for propelling the vehicle 60. The second rotating electric machine 40 is driven using electric power stored in the battery 50 and electric power generated by the first rotating electric machine 30. As shown in FIG. 6, in some examples, only one second rotating electric machine 40 is provided on the front side, and in other examples, one is provided on the front side and one is provided on the rear side, and the number and locations of the second rotating electric machine 40 vary. The second rotating electric machine 40 also functions as a generator that generates regenerative electric power, mainly during coasting.

[0020] A control unit (not shown) including an inverter that converts DC current and AC current is provided between the first rotating electric machine 30, the second rotating electric machine 40 and the electronic control unit 20. The rotation speeds of the first rotating electric machine 30 and the second rotating electric machine 40 when they are driven are controlled by the electronic control unit 20 via the inverter.

[0021] The engine 10 is a gasoline engine. Depending on the driving mode, the rotation of the crankshaft of the engine 10 is switched between a state in which it is transmitted to the drive wheels via a torque converter, a continuously variable transmission, a clutch, a differential, etc., and a state in which the transmission is cut off.

[0022] The battery 50 is a high-voltage power supply that can store (charge) the electric power generated by the first rotating electric machine 30 and the electric power regenerated by the second rotating electric machine 40, and can discharge the stored electric power. The battery 50 is used mainly as a power supply that supplies electric power for traveling. In this embodiment, the battery 50 is compatible with a plug-in hybrid car and can be charged (normal charging) from an external power source to the vehicle, for example, a household AC power source, or from a high-voltage DC power source (rapid charging).

[0023] The vehicle 60 is equipped with a steering wheel, a brake pedal, an accelerator pedal, etc. that are operated by the driver. The brake pedal is provided with a brake sensor that detects the force with which the driver presses the brake pedal. The accelerator pedal is provided with an accelerator position sensor that detects the amount of depression of the accelerator pedal by the driver. Brake information detected by the brake sensor and accelerator information detected by the accelerator position sensor are sent to the electronic control unit 20. The vehicle 60 is also equipped with a vehicle speed sensor that is provided on the axle or the like and detects the traveling speed of the vehicle 60. Vehicle speed information detected by the vehicle speed sensor is also sent to the electronic control unit 20.

[0024] The vehicle 60 is also provided with an engine speed sensor that detects the speed of the engine 10, speed sensors that detect the speeds of the first rotating electric machine 30 and the second rotating electric machine 40, a voltage sensor that detects the cell voltage of the battery 50, and a current sensor that detects the current of the battery 50. The vehicle 60 is also provided with a water temperature sensor that detects the temperature of the coolant for the engine 10 and an oil temperature sensor that detects the temperature of the engine oil. Information from these sensors is also sent to the electronic control unit 20.

[0025] The electronic control unit 20 includes an engine control unit 21 that mainly controls the engine 10, and a vehicle control unit 22 that controls the operation of the entire hybrid vehicle. The electronic control unit 20 is a collection of electronic control devices (computers) that control various devices equipped in the vehicle 60. Inside it are built-in interfaces, processors, memories, etc., which are connected to each other via a bus. The contents of the controls executed by the engine control unit 21 and the vehicle control unit 22 are stored in advance in the memory, and new data is stored as the control progresses, and this data is used for subsequent control.

[0026] Among the traveling modes set in the electronic control unit 20, the electric traveling mode is a traveling mode in which the vehicle 60 is operated (traveled) only by the driving force of the second rotating electric machine 40, while the engine 10 and the first rotating electric machine 30 are stopped. The series traveling mode is a traveling mode in which the engine 10 is operated, the first rotating electric machine 30 is operated with the driving force of the engine 10 to generate electricity, and the second rotating electric machine 40 uses the generated electricity to operate (travel) the vehicle 60. In this case, in addition to the electricity generated by the first rotating electric machine 30, electricity from the battery 50 may also be used. In the series traveling mode, electricity generated by the operation of the engine 10 that is not used for traveling, etc. is supplied to the battery 50. The parallel traveling mode is a traveling mode in which the vehicle 60 is operated (traveled) by the driving force of the engine 10, and the second rotating electric machine 40 assists in the operation (travel) of the vehicle 60 as needed.

[0027] Furthermore, if the engine 10 is stopped (in a non-operating state) when transitioning from electric driving mode to series driving mode or from electric driving mode to parallel driving mode, the engine 10 that is in a stopped state will be started (operated). In other words, in such cases, switching from electric driving mode to series driving mode or from electric driving mode to parallel driving mode is performed after passing through engine start mode. Also, in some cases, the engine 10 is started (operated) when the key (ignition) is turned on for a vehicle 60 that is not powered on. These modes when starting the engine are referred to as engine start modes. Hereinafter, the engine start mode will also be treated as one of the driving modes.

[0028] The engine 10 equipped in the vehicle 60 of this embodiment is a pre-chamber engine. FIGS. 1 and 2 show the main parts of one cylinder 2 of the engine 10. The engine 10 is configured with an intake passage (intake port) 5 that sends air into the combustion chamber C, an exhaust passage (exhaust port) 6 that leads out from the combustion chamber C, and an injector 9 that supplies fuel to the combustion chamber C. An opening 5a of the intake passage 5 to the combustion chamber C is opened and closed by an intake valve 7. An opening 6a of the exhaust passage 6 to the combustion chamber C is opened and closed by an exhaust valve 8. In this embodiment, the injector 9 is a direct injection fuel injection device that injects fuel directly into the combustion chamber C, but it may also be a port injection fuel injection device that injects fuel into the intake passage 5. The engine 10 may also use both a direct injection and a port injection injector 9. The figures show only components and means directly related to the present invention, and other components are omitted. The number of cylinders provided in engine 10 can be freely set according to the specifications of vehicle 60 and engine 10, and may be, for example, three cylinders, four cylinders, or any other number of cylinders.

[0029] As shown in Figure 1, the combustion chamber C includes a main chamber 1, which is surrounded by the inner peripheral surface 2a of the cylinder (cylinder block) 2, the inner surface (lower surface) of the cylinder head 13, and the top surface 3a of the piston 3, and an auxiliary chamber 11, which is separated from the main chamber 1 and is formed at the end of the main chamber 1 on the cylinder head 13 side. The main chamber 1 and the auxiliary chamber 11 are separated by a partition wall 14, and the spaces of the main chamber 1 and the auxiliary chamber 11 are connected by a communication passage 12 made up of a small hole that penetrates the partition wall 14. The auxiliary chamber 11 is also provided with an ignition device 4 that ignites the air-fuel mixture in the auxiliary chamber 11 by generating an electric spark.

[0030] To explain the operating state of the engine 10, first, as shown in FIG. 3A, air is introduced into the main combustion chamber 1 from the intake passage 5, and a lean mixture is formed in the main combustion chamber 1 by the injection of fuel from the injector 9. As shown in FIG. 3B, the lean mixture is forced from the main combustion chamber 1 into the auxiliary combustion chamber 11 during the compression stroke in which the piston 3 rises. Then, as shown in FIG. 3C, a spark is generated at the electrode 4a of the ignition device 4, igniting the mixture introduced into the auxiliary combustion chamber 11. When the mixture is ignited in the auxiliary combustion chamber 11, the resulting flame is injected toward the main combustion chamber 1 through the connecting passage 12, ejecting a high-speed flame. This flame promotes combustion even when the mixture is lean (including when a large amount of exhaust gas recirculation gas is introduced). The burned gas is discharged to the outside through the exhaust passage 6.

[0031] The electronic control unit 20 includes a means for detecting or predicting the occurrence of knocking based on the relationship between the current rotation speed and engine load of the engine 10. As the means for detecting or predicting the occurrence of knocking, a device that detects torque fluctuations or combustion fluctuations based on changes in vibrations or in-cylinder pressure of the engine 10, or changes in the rotational angular velocity of the crankshaft, may also be used.

[0032] As mentioned above, in conventional engines, when knocking occurs under high load, the ignition timing is retarded to reduce in-cylinder pressure and prevent knocking. However, in a pre-chamber engine, retarding the ignition timing creates a leaner environment in the pre-chamber 11, which can lead to unstable ignition and increased susceptibility to knocking. Figure 4 shows the air-fuel ratio curve G, which represents the expected change in the air-fuel ratio in the pre-chamber 11, the fuel injection timing C (by direct injection), and the optimal ignition timing D. The air-fuel ratio in the pre-chamber 11 begins to decrease (increase in fuel amount) from injection timing C. The air-fuel ratio reaches its minimum (maximum fuel amount) at approximately optimal ignition timing D. As the piston 3 approaches top dead center E, the air-fuel ratio gradually increases (decreases in fuel amount). The point at which the air-fuel ratio in the pre-chamber 11 reaches its minimum (richest) value is the optimal ignition timing D. As shown in FIG. 4, the range surrounded by the upper limit line A of the amount of fuel in the pre-chamber that can be ignited and the air-fuel ratio curve G in the pre-chamber 11, that is, the range L from point s to point a A Only then can stable ignition be ensured.

[0033] If the ignition timing is retarded from the optimum ignition timing D, the air-fuel ratio in the pre-chamber 11 will gradually become leaner. If the ignition timing is delayed beyond point a in the figure, the air-fuel ratio in the pre-chamber 11 will exceed the upper limit line A of the ignitable pre-chamber air-fuel ratio (below line A on the graph), which may result in poor ignition of the mixture. However, in this invention, the ignition timing can be retarded by controlling the amount of fuel in the pre-chamber 11 by changing the fuel injection amount according to the operating conditions. That is, by increasing the fuel injection amount at the first injection time C, as shown in FIG. 4, the air-fuel ratio curve G in the pre-chamber 11 will shift to the corrected air-fuel ratio curve F1 while keeping the upper limit line A of the ignitable pre-chamber fuel amount. Therefore, the period during which good combustion is achieved is defined as the range L between point s' and point c1, which is the range enclosed by the upper limit line A of the ignitable pre-chamber fuel amount and the corrected air-fuel ratio curve F1. C1This allows the amount of fuel in the pre-combustion chamber 11 to be expanded, making it possible to retard the ignition timing. In this way, by controlling the amount of fuel in the pre-combustion chamber 11, the energy of flame propagation from the pre-combustion chamber 11 to the main combustion chamber 1 is controlled, ensuring good combustion.

[0034] Specific control will now be described. The engine 10 of this embodiment is based on a lean air-fuel mixture with a lower fuel ratio (lean fuel) than the stoichiometric air-fuel ratio (A / F = 14.7). The air-fuel ratio of this lean air-fuel mixture is set as an initial value A1. The air-fuel ratio is the air / fuel ratio, and is expressed as a dimensionless quantity obtained by dividing the air mass by the fuel mass. The electronic control unit 20 has the function of detecting or estimating the air-fuel ratio in the auxiliary combustion chamber 11 and the air-fuel ratio of the entire combustion chamber C, based on information from sensors around the engine 10.

[0035] First, in the series running mode, the engine 10 is rarely subjected to a large load, so it is unlikely that the ignition timing will need to be retarded. Therefore, the air-fuel ratio of the mixture introduced into the combustion chamber C of the engine is set to an initial value A1 (hereinafter referred to as the first air-fuel ratio A1), and the ignition timing is set to the first ignition timing B1. The first ignition timing B1 may be set between points s and a shown in FIG. 5, i.e., a timing at which the air-fuel ratio in the auxiliary combustion chamber 11 is below the upper limit line A of the ignitable air-fuel ratio in the auxiliary combustion chamber (i.e., on the richer side (upper side) than line A on the graph) and the mixture can be smoothly ignited. In this embodiment, the first ignition timing B1 is set to the timing D (optimal ignition timing D) at which the air-fuel ratio in the auxiliary combustion chamber 11 is richest, thereby improving thermal efficiency. Thus, it is desirable that the first ignition timing B1 be as close to the optimal ignition timing D as possible.

[0036] Next, in parallel running mode, a greater load is applied to the engine 10 than in series running mode, and it can be said that this is an environment in which knocking is more likely to occur. For this reason, in parallel running mode, the air-fuel ratio of the mixture introduced into the combustion chamber C is set to a second air-fuel ratio A2 that has a higher fuel ratio (is richer in fuel) than the first air-fuel ratio A1, and the ignition timing is set to a second ignition timing B2 that is retarded from the first ignition timing B1. That is, First air-fuel ratio A1 (lean side) > Second air-fuel ratio A1 (rich side) 1st ignition timing B1 < 2nd ignition timing B2 (retard side) In this way, in the parallel running mode, the ignition timing is retarded and the air-fuel ratio is enriched, thereby ensuring maximum output without exceeding the design limit pressure of the engine 10.

[0037] In addition, in the engine start mode in which the non-operating engine 10 is operated, when the engine 10 is in a cold state, the mixture introduced into the combustion chamber C is set to a third air-fuel ratio A3 that has a higher fuel ratio (richer fuel) than the second air-fuel ratio A2, and the ignition timing is set to a third ignition timing B3 that is retarded from the second ignition timing B2. Second air-fuel ratio A2 (lean side) > Third air-fuel ratio A3 (rich side) 2nd ignition timing B2 < 3rd ignition timing B3 (retard side) In this way, in engine start mode, the ignition timing is retarded and the air-fuel ratio is made rich, which accelerates catalyst warm-up by raising the exhaust temperature early.

[0038] The term "cold state" for engine 10 generally refers to a state in which engine 10 is at the same temperature as or colder than the ambient temperature of the environment in which engine 10 is placed. In an actual vehicle, the cold state can be established, for example, when the temperature of engine coolant is below a predetermined temperature (e.g., 40°C) or when the temperature of engine oil is below a predetermined temperature (e.g., 60°C).

[0039] In the above example, the ignition timing is retarded by controlling the amount of fuel in the pre-chamber 11 by changing the fuel injection amount according to the operating conditions, but instead of or in addition to this, the ignition timing may be retarded by changing the ignition energy. That is, by increasing the ignition energy in one combustion cycle, the upper limit line A of the amount of fuel in the pre-chamber that can be ignited is shifted to the modified upper limit line B on the lean side, as shown in Figure 5, and the period in which good combustion is achieved is extended to the range L from point s' to point b. B This also makes it possible to ensure stable, good combustion even after the ignition timing is retarded.

[0040] Conventionally, ignition energy has been constant regardless of the ignition timing (crank angle). However, in this invention, by increasing the ignition energy when it is necessary to retard the ignition timing, misfires can be prevented even at the ignition timing after the retard, and good combustion can be ensured stably. However, if the ignition energy is constantly increased, it is possible that the ignition device 4 (spark plug) will melt or that the thermal efficiency of the engine 10 will decrease due to the increased electricity consumption. For this reason, when increasing the ignition energy, it is necessary to limit the increase in energy to the minimum necessary.

[0041] Specifically, the ignition energy C2 (referred to as the second ignition energy C2) when the second ignition timing B2 is set can be set to be greater than the ignition energy C1 (referred to as the first ignition energy C1) when the first ignition timing B1 is set. Also, the ignition energy C3 (referred to as the third ignition energy C3) when the third ignition timing B3 is set can be set to be greater than the ignition energy C2 (referred to as the second ignition energy C2) when the second ignition timing B2 is set. Here, (Second ignition energy C2) = (First ignition energy C1) × α (Third ignition energy C3) = (Second ignition energy C2) × β In this case, α>1 and β>1, and the values ​​of α and β can be set to the minimum required values ​​according to the operating conditions, for example, 1.1, 1.2, 1.3, 1.4, etc.

[0042] In addition, when retarding the ignition timing is required, changing the ignition pattern can be considered as a method to prevent misfires at the ignition timing after retarding. Changing the ignition pattern can be, for example, a method to promote ignition by igniting multiple times during one combustion cycle, or a method to overlap sparks by re-discharging using a different coil after one discharge during one combustion cycle. and a method of shortening the discharge time in the ignition device 4 to create a state with a higher current value and promote ignition.

[0043] Furthermore, as a method for making the second air-fuel ratio A2 richer than the first air-fuel ratio A1, for example, the fuel injection amount per combustion cycle when the second air-fuel ratio A2 is set may be increased compared to the fuel injection amount per combustion cycle when the first air-fuel ratio A1 is set. As a method for making the third air-fuel ratio A3 richer than the second air-fuel ratio A2, for example, the fuel injection amount per combustion cycle when the third air-fuel ratio A3 is set may be increased compared to the fuel injection amount per combustion cycle when the second air-fuel ratio A2 is set. In each case, it is desirable that a large amount of fuel remains near the ignition device 4 at the ignition timing after retardation. Furthermore, particularly when the ignition timing is retarded, that is, when the ignition timing is set to a timing retarded from the first ignition timing, it is possible to employ split injection, in which fuel is injected intermittently multiple times during one combustion cycle, or compression stroke injection, in which fuel is injected significantly into the compression stroke by delaying the end of fuel injection. At this time, if the fuel injection amount is increased, or if the fuel is injected in divided injections or in the compression stroke, using a direct injection fuel injection device, it is easy to leave a large amount of fuel near the ignition device 4.

[0044] The second injection timing C' in Fig. 5 indicates a fuel injection that is performed in addition to the first injection timing C. By performing the second injection timing C', the air-fuel ratio curve G in the pre-chamber 11 shifts to the corrected air-fuel ratio curve F2 while the upper limit line A of the amount of fuel in the pre-chamber that can be ignited remains the same. Therefore, the period in which good combustion is achieved is the range surrounded by the upper limit line A of the amount of fuel in the pre-chamber that can be ignited and the corrected air-fuel ratio curve F2, that is, the range L from point s to point c. C2 This allows for retarding the ignition timing.

[0045] If the injector 9 is equipped with both a direct injection fuel injector and a port injection fuel injector, it is effective to increase the amount of fuel injected from the direct injection fuel injector, which can inject fuel at a timing closer to the ignition timing. In particular, if the direct injection fuel injector is set to inject fuel directly into the auxiliary combustion chamber 11, it is effective to increase the amount of fuel injected from the direct injection fuel injector in order to leave fuel near the ignition device 4 at the ignition timing. Alternatively, the injector 9 may be equipped with only a direct injection fuel injector, which can separately spray fuel toward the main combustion chamber 1 and the auxiliary combustion chamber 11. In this case, it is effective to increase the amount of fuel injected toward the auxiliary combustion chamber 11 in order to leave fuel near the ignition device 4.

[0046] Furthermore, when the injector 9 is provided with both a direct injection type injector and a port injection type injector, the combined use of fuel injection from the direct injection type injector and fuel injection from the port injection type injector is expected to have the effect of increasing the freedom in setting the injection timing when increasing the amount of fuel.

[0047] In the above embodiment, a pre-combustion engine is used as the engine 10 equipped in the vehicle 60, but the engine 10 is not limited to a pre-combustion engine and may be any other engine that employs a lean combustion system or any other type of engine. However, if the engine has a pre-combustion chamber 11, it is easier to keep fuel near the ignition device 4, and ignition is more stable. Also, in the above embodiment, a plug-in hybrid (PHEV) vehicle equipped with at least three driving modes, namely, electric driving mode, series driving mode, and parallel driving mode, is used as the vehicle 60, but the present invention can also be applied to other types of hybrid vehicles equipped with the above driving modes. [Explanation of symbols]

[0048] 1 Main room 2 cylinders 3 pistons 4 Ignition device 10 Engine 11 Antechamber 12 Communication path 20 Electronic Control Unit 30 First Rotating Electric Machine 40 Second rotating electric machine (rotating electric machine) 50 Battery (storage battery) 60 Hybrid Vehicles (Vehicles) C. Combustion chamber

Claims

1. A hybrid vehicle equipped with an engine, a storage battery, a generator driven by the engine to generate electricity, and a rotating electric machine that supplies driving force for traveling using electric power supplied from the storage battery or the generator, the hybrid vehicle having a series running mode in which at least the engine is operated to supply electric power to the storage battery or the rotating electric machine, and a parallel running mode in which the engine is operated to supply driving force to drive wheels, In the series running mode, the air-fuel mixture introduced into the combustion chamber of the engine is set to a first air-fuel ratio and the ignition timing is set to a first ignition timing; In the parallel running mode, the air-fuel mixture introduced into the combustion chamber is set to a second air-fuel ratio that is richer in fuel than the first air-fuel ratio, and an ignition timing is set to a second ignition timing that is retarded relative to the first ignition timing, the combustion chamber includes a main chamber surrounded by an inner peripheral surface of the cylinder, an inner surface of the cylinder head, and a top surface of the piston; an auxiliary chamber separated from the main chamber and formed at an end of the main chamber on the cylinder head side; and a communication passage connecting the main chamber and the auxiliary chamber, an ignition device that ignites the air-fuel mixture in the auxiliary chamber and a direct fuel injection device that injects fuel directly into the auxiliary chamber, A hybrid vehicle characterized in that when the second air-fuel ratio is set, the amount of fuel injected during the compression stroke of the direct fuel injection device is increased.

2. an engine start mode for operating the engine that is not operating; 2. The hybrid vehicle according to claim 1, wherein in the engine start mode when the engine is cold, the mixture introduced into the combustion chamber has a third air-fuel ratio that is richer in fuel than the second air-fuel ratio, and the ignition timing is set to a third ignition timing that is retarded from the second ignition timing.

3. 2. The hybrid vehicle according to claim 1, wherein the ignition energy when the second ignition timing is set is set to be greater than the ignition energy when the first ignition timing is set.

4. 3. The hybrid vehicle according to claim 2, wherein the ignition energy when the third ignition timing is set is set to be greater than the ignition energy when the second ignition timing is set.

5. a direct injection fuel injection device that injects fuel into the combustion chamber, 3. The hybrid vehicle according to claim 2, wherein the fuel injection amount per combustion cycle of the direct injection fuel injection device is greater when the third air-fuel ratio is set than when the second air-fuel ratio is set.

6. 6. The hybrid vehicle according to claim 5, further comprising a port injection type fuel injection device that injects fuel into an intake passage that communicates with the combustion chamber.

7. 7. The hybrid vehicle according to claim 6, wherein when the ignition timing is set to be retarded from the first ignition timing, fuel injection by the direct fuel injection device is performed intermittently a plurality of times.

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