Control system for hybrid vehicles

Abstract

This system provides a control system for hybrid vehicles that enables appropriate fuel injection according to the driving mode. [Solution] The control system for a hybrid vehicle comprises an internal combustion engine mounted on the vehicle and having an in-cylinder injection device that injects fuel into the cylinder, a generator driven by the internal combustion engine that generates electricity, a drive battery that stores the electricity generated by the generator, a motor that rotates using the electricity generated by the generator and drives the drive wheels of the vehicle, and a control device that controls the vehicle, wherein the control device has a series mode in which the generator is driven by the internal combustion engine and the motor is driven using the electricity generated by the generator to drive the drive wheels, and a parallel mode in which the drive wheels are driven by the internal combustion engine, and the number of injection stages of the in-cylinder injection device changes when switching from the series mode to the parallel mode.

Description

Technical Field

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[0001] The present disclosure relates to a control system for a hybrid vehicle.

Background Art

[0002] Conventionally, a control system for a hybrid vehicle equipped with a diesel engine has been known (see, for example, Patent Document 1). The control system for the hybrid vehicle of Patent Document 1 monitors the combustion pressure waveform of the diesel engine and stops the diesel engine when white smoke generation is predicted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, fuel injection devices for diesel engines can execute fuel injection control more finely. As a result, the increase or decrease in the number of injection stages can be made finer. Therefore, it is preferable to vary the number of injection stages in consideration of fuel consumption and exhaust gas according to the driving mode. Patent Document 1 does not disclose control of the number of injection stages.

[0005] An object of the present disclosure is to provide a control system for a hybrid vehicle capable of appropriate fuel injection according to the driving mode.

Means for Solving the Problems

[0006] The hybrid vehicle control system according to this disclosure comprises an internal combustion engine mounted on the vehicle and having an in-cylinder injection device for injecting fuel into the cylinder; a generator driven by the internal combustion engine to generate electricity; a drive battery for storing the electricity generated by the generator; a motor that rotates using the electricity generated by the generator to drive the drive wheels of the vehicle; and a control device for controlling the vehicle. The control device has a series mode in which the internal combustion engine drives the generator and uses the electricity generated by the generator to drive the motor and drive the drive wheels, and a parallel mode in which the internal combustion engine drives the drive wheels. When switching from the series mode to the parallel mode, the number of injection stages of the in-cylinder injection device changes. [Effects of the Invention]

[0007] Increasing the number of injection stages results in faster combustion and higher combustion temperatures. As a result, fuel efficiency is improved and soot is reduced. According to the hybrid vehicle control system of this disclosure, the number of injection stages is increased in parallel mode compared to series mode. Parallel mode is a higher load than series mode. Therefore, by making combustion faster and the combustion temperature higher in parallel mode than in series mode, fuel efficiency and exhaust emissions in parallel mode can be improved. As a result, the hybrid vehicle control system of this disclosure can perform appropriate fuel injection according to the driving mode. [Brief explanation of the drawing]

[0008] [Figure 1] A system diagram of a hybrid vehicle according to one embodiment of the present disclosure. [Figure 2] A system diagram of an engine according to one embodiment of the present disclosure. [Figure 3] A diagram showing the engine's injection pattern. [Figure 4] A diagram showing the series mode region and the parallel mode region according to one embodiment of the present disclosure. [Figure 5] A flowchart illustrating the control performed by a control device according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings.

[0010] As shown in Figures 1 and 2, the control system 1 of vehicle (an example of a hybrid vehicle) C comprises an engine (an example of an internal combustion engine) 2, a motor (FrM) 3, a generator (GEN) 4, a drive battery (BT) 6, a transaxle 8, an inverter 12 that controls the motor 3 and generator 4, an accelerator pedal 14 operated by the user of vehicle C, a charger 16 that can be connected to an external power source, an external power supply device 18 that can supply power to external devices such as home appliances, a control device 20, and a fuel tank 22. Vehicle C in this embodiment is a plug-in hybrid electric vehicle (PHEV) equipped with external charging, which allows power from an external power source to be stored in the drive battery 6 by the charger 16, and external power supply, which allows power from the drive battery 6 to be supplied to external devices by the external power supply device 18.

[0011] As shown in Figure 1, the engine 2 is connected to the generator 4 and drives the generator 4. Furthermore, in this embodiment, the engine 2 can drive a wheel (an example of a drive wheel) C1 via the transaxle 8.

[0012] As shown in Figure 2, the engine 2 has a fuel injector 41. The fuel injector 41 is an in-cylinder injection device that injects fuel directly into the cylinder N. In this embodiment, the engine 2 is a four-cycle, in-line four-cylinder diesel engine. The engine 2 receives fuel from the fuel tank 22 and consumes it by burning it. The fuel tank 22 has a fuel level sensor (not shown) that measures the amount of remaining fuel. The fuel level sensor transmits the amount of remaining fuel in the fuel tank 22 to the control device 20.

[0013] The fuel injector 41 performs fuel injection to supply fuel to cylinder N. In this embodiment, the fuel injector 41 is connected to a fuel injection pump and an accumulator such as a common rail. The fuel injector 41 is electrically connected to a control device 20, which controls the injection amount (fuel injection amount) and the injection stage (number of fuel injections in one cycle). The diesel engine controls the output of engine 2 by the fuel injection amount. In other words, as the injection amount from the fuel injector 41 increases, the output of engine 2 increases.

[0014] As shown in Figure 3, in this embodiment, the fuel injector 41 injects a pilot injection PiI, a pre-injection PrI, a main injection MI, an after-injection AI, and a post-injection PI per cycle, with intake, compression, expansion, and exhaust being considered as one cycle.

[0015] The main injection (MI) is injected from the compression stroke to the expansion stroke. The main injection (MI) delivers the majority of the fuel injected per cycle. The pilot injection (PiI) is injected before the main injection (MI). The pilot injection (PiI) is injected in small amounts and can increase the combustion temperature inside the cylinder N, thereby reducing the ignition delay of the main injection (MI). The pilot injection (PiI) can further suppress the rapid pressure increase of the main injection (MI) and reduce combustion noise. The pre-injection (PrI) is injected immediately before the main injection (MI), i.e., between the pilot injection (PiI) and the main injection (MI). The pre-injection (PrI) is injected in small amounts and can reduce combustion noise and nitrogen oxides. The after-injection (AI) is injected after the main injection (MI). The after-injection (AI) is primarily used to burn any fuel that was not burned by the main injection (MI). The post-injection (PI) is injected after the after-injection. The post-injection (PI) is performed, for example, to increase the temperature of an exhaust gas purification device (not shown).

[0016] In this embodiment, the control device 20 switches between two-stage injection, which performs pre-injection PrI and main injection MI, and three-stage injection, which performs pilot injection PiI, pre-injection PrI, and main injection MI, depending on the driving mode. Two-stage injection has fewer injection stages than three-stage injection, resulting in a slower combustion speed. Therefore, two-stage injection is quieter in terms of engine 2 fuel noise and fuel injection device 41 noise than three-stage injection. On the other hand, two-stage injection has a lower combustion temperature than three-stage injection, making it more prone to soot generation. Furthermore, two-stage injection has lower output per unit injection amount compared to three-stage injection, resulting in worse fuel efficiency. Three-stage injection has a higher combustion temperature and higher output per unit injection amount compared to two-stage injection. Also, because three-stage injection has a higher combustion temperature than two-stage injection, it emits less soot.

[0017] As shown in Figure 1, the motor 3 is connected to the wheel C1 via the transaxle 8 and axle 10, and drives the wheel C1. The motor 3 in this embodiment is a three-phase AC motor having multiple coils and multiple permanent magnets. The motor 3 is also driven by the rotation of the wheel C1 to generate electricity (regenerative power). Therefore, the motor 3 is a motor-generator capable of both powering and generating electricity. The generator 4 is connected to the engine 2 and can drive the engine 2. The generator 4 motorizes the engine 2 while powering with electricity from the drive battery 6. On the other hand, the generator 4 is driven by the engine 2 to generate electricity while the engine 2 is running. Therefore, the generator 4 is a motor-generator capable of both powering and generating electricity.

[0018] The drive battery 6 outputs power to the motor 3 and generator 4, and also receives power generated by the motor 3 and generator 4. Furthermore, the drive battery 6 receives external power via the charger 16. In this embodiment, the drive battery 6 is composed of multiple lithium-ion batteries.

[0019] The transaxle 8 has a plurality of gears and a clutch 8a. The engine 2 is connected to the generator 4 and the axle 10 via the transaxle 8. When the clutch 8a is in the released state, the power transmission between the engine 2 and the axle 10 is interrupted. When the clutch 8a is in the connected state, the power of the engine 2 is transmitted to the axle 10.

[0020] The inverter 12 converts the DC power supplied from the drive battery 6 into AC power and controls the driving torque of the motor 3 by adjusting the power supplied to the motor 3. Further, when the motor 3 regenerates, the inverter 12 converts the AC power supplied from the motor 3 into DC power and controls the regenerative torque of the motor 3 by adjusting the power supplied to the drive battery 6.

[0021] The control device 20 is electrically connected to the motor 3 via the engine 2 and the inverter 12 and is a device that controls the engine 2 and the motor 3. The control device 20 is actually an ECU (Electronic Control Unit) constituted by a microcomputer including an arithmetic unit, a memory, an input / output buffer, etc. The control device 20 controls the vehicle C based on the maps and programs stored in the memory.

[0022] The vehicle C of the present embodiment has driving modes such as an EV mode, a series mode, and a parallel mode. In the EV mode, the vehicle C drives the motor 3 with the power from the drive battery 6 while the engine 2 is stopped. In the series mode, the vehicle C disconnects the clutch 8a, drives the generator 4 with the engine 2, and drives the motor 3 with the power generated by the generator 4 to drive the wheels C1. In the parallel mode, the vehicle C connects the clutch 8a and drives the wheels C1 via the axle 10 using the power of the engine 2. The vehicle C switches each driving mode according to the depression state of the accelerator pedal 14, controls the motor 3 and the generator 4 via the inverter 12, and controls the engine 2.

[0023] In this embodiment, the control device 20 calculates the driver-requested torque DTq based on the opening degree of the accelerator pedal 14 (accelerator pedal opening). As shown in Figure 4, the control device 20 switches between series mode (see series mode region) and parallel mode (see parallel mode region) based on the driver-requested torque DTq and the vehicle speed V. The EV mode is executed in the series mode region when the drive battery 6 can output the power required by the motor 3. In this embodiment, when the driver-requested torque DTq is below a medium load (for example, about 50% of the maximum torque), the control device 20 switches from series mode to parallel mode when the vehicle speed V is above a predetermined speed Vt. In the region where the driver-requested torque DTq is greater than a medium load, the control device 20 switches from series mode to parallel mode at a lower speed the greater the load. Therefore, in parallel mode, a high-load region is used where the torque and rotational speed of the engine 2 are relatively high.

[0024] Furthermore, vehicle C of this embodiment has an external power supply mode. In the external power supply mode, when connector 18a is connected to an external device, the control device 20 uses the external power supply device 18 to supply power from the drive battery 6 to the external device. When the State of Charge (SOC) of the drive battery 6 falls below the minimum charge level SOCmin during the external power supply mode, the control device 20 disengages the clutch 8a, starts the engine 2 to drive the generator 4, and executes an engine-generated external power supply mode in which the power generated by the generator 4 is stored in the drive battery 6 and supplied to the external device.

[0025] Next, the control procedure executed by the control device 20 will be explained using the flowchart in Figure 5. In this embodiment, the control device 20 starts the control procedure when an ignition switch (not shown) is turned on.

[0026] In step S1, the control device 20 determines whether or not it is in series mode. If the control device 20 determines that it is in series mode (step S1 YES), it proceeds to step S2.

[0027] In step S2, the control device 20 performs two-stage injection. In series mode, the sound of the engine 2 is more easily transmitted to the user than in parallel mode. For this reason, the control device 20 performs two-stage injection, which produces quieter combustion noise and fuel injection device 41 noise than three-stage injection. After performing two-stage injection, the control device 20 proceeds to step S3.

[0028] In step S3, the control device 20 determines whether or not it is in external power supply mode. If the control device 20 determines that it is in external power supply mode (step S3 YES), it proceeds to step S4. If the control device 20 determines that it is not in external power supply mode (step S3 NO), it proceeds to step S5.

[0029] In step S4, the control device 20 performs three-stage injection. The external power supply mode may be used in times of disaster. Therefore, in the engine power generation external power supply mode, where engine 2 is operated in external power supply mode, good fuel efficiency and exhaust without soot are required. For this reason, the control device 20 performs three-stage injection to operate engine 2 with good fuel efficiency and low soot. After performing three-stage injection, the control device 20 proceeds to step S5.

[0030] In step S5, the control device 20 determines whether the charge rate SOC (an example of the amount of charge) is less than or equal to a predetermined charge rate SOCt (an example of a predetermined amount of charge) and whether the remaining fuel FT is less than or equal to a predetermined remaining amount FTt. If the control device 20 determines that the charge rate SOC is less than or equal to a predetermined charge rate SOCt and the remaining fuel FT is less than or equal to a predetermined remaining amount FTt (step S5 YES), it proceeds to step S6. If the control device 20 determines that the charge rate SOC is greater than the predetermined charge rate SOCt and the remaining fuel FT is greater than the predetermined remaining amount FTt (step S5 NO), it returns. The predetermined charge rate SOCt is a value that indicates a state in which the drive battery 6 does not have enough power stored to run the vehicle C, such as 30 percent. The predetermined remaining amount FTt is a value that indicates a state in which there is not enough fuel remaining in the fuel tank 22, such as 10 liters.

[0031] In step S6, the control device 20 performs three-stage injection. In other words, if the control device 20 is performing two-stage injection, it switches to three-stage injection. If the control device 20 is performing three-stage injection, it continues with three-stage injection. Three-stage injection is more fuel-efficient than two-stage injection. Therefore, if the charge level (SOC) is not sufficient for driving vehicle C or generating power for external power supply, and the remaining fuel level (FT) is also not sufficient for driving vehicle C or generating power for external power supply, it is preferable to maximize the fuel efficiency of engine 2. The control device 20 returns after performing three-stage injection.

[0032] If the control device 20 determines in step S1 that it is not executing in series mode (step S1 NO), the control device 20 proceeds to step S7.

[0033] In step S7, the control device 20 determines whether or not it is in parallel mode. If the control device 20 determines that it is in parallel mode (step S7 YES), it proceeds to step S8. If the control device 20 determines that it is not in parallel mode (step S7 NO), it returns.

[0034] In step S8, the control device 20 performs three-stage injection. In other words, when the control device 20 switches from series mode to parallel mode, it changes the number of injection stages. More specifically, when the control device 20 switches from series mode to parallel mode, it increases the number of injection stages. That is, parallel mode has more injection stages than series mode. In this embodiment, when the control device 20 switches from series mode to parallel mode, it increases the number of injection stages from two-stage injection to three-stage injection. In parallel mode, the vehicle speed V is high, so the sound of the engine 2 is not easily heard by the user. For this reason, the control device 20 prioritizes fuel efficiency and low snort and performs three-stage injection. After performing three-stage injection, the control device 20 proceeds to step S9.

[0035] In step S9, the control device 20 determines whether or not the vehicle is in steady-state driving mode. The control device 20 may determine that the vehicle is in steady-state driving mode if the vehicle speed V is constant or does not change much. If the control device 20 determines that the vehicle is in steady-state driving mode (step S9 YES), it proceeds to step S10. If the control device 20 determines that the vehicle is not in steady-state driving mode (step S9 NO), it returns.

[0036] In step S10, the control device 20 performs two-stage injection. That is, the control device 20 reduces the number of injection stages. Even in parallel mode, during steady-state driving, gear noise and other sounds are reduced, and the sound of engine 2 is more easily heard by the user. For this reason, the control device 20 reduces the combustion noise of engine 2 and the noise of the fuel injector 41 by performing two-stage injection. When the control device 20 reduces the number of injection stages in parallel mode, it advances the injection timing. Advancing the injection timing increases the combustion speed and improves fuel efficiency.

[0037] As described above, this disclosure provides a control system 1 for a hybrid vehicle that can perform appropriate fuel injection according to the driving mode.

[0038] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.

[0039] In the embodiments described above, engine 2 was described as a diesel engine, but this disclosure is not limited thereto. Engine 2 may be a gasoline engine capable of multi-stage injection.

[0040] In the embodiments described above, two-stage injection and three-stage injection were used as examples, but this disclosure is not limited thereto. Increasing the number of injection stages includes, for example, increasing from one-stage injection to two-stage injection. In any case, any control that increases the number of injection stages in parallel mode compared to series mode is acceptable.

[0041] In the embodiments described above, examples were given in which a pre-injection PrI and a main injection MI are performed in a two-stage injection, and a pilot injection PiI, a pre-injection PrI, and a main injection MI are performed in a three-stage injection; however, this disclosure is not limited thereto. Two-stage injection may also be achieved by combining a main injection MI and an after-injection AI, or by implementing two-stage injection in other injection configurations. The same applies to three-stage injection. [Explanation of Symbols]

[0042] 1: Control System 2: Engine 3: Motor 4: Generator 6: Power battery 20: Control device 22: Fuel tank 41:Fuel injection device C: Vehicle AI: After-spray MI: Main injection PI: Post-injection PiI: Pilot injection PrI: Pre-injection FTt: Specified remaining amount

Claims

1. An internal combustion engine mounted in a vehicle and having an in-cylinder injection system that injects fuel into the cylinder, A generator that is driven by the aforementioned internal combustion engine and generates electricity, A drive battery for storing the electricity generated by the aforementioned generator, A motor that rotates using electricity generated by the aforementioned generator and drives the drive wheels of the vehicle, A control device for controlling the vehicle, Equipped with, The control device has a series mode in which the internal combustion engine drives the generator, and the power generated by the generator drives the motor to drive the drive wheels, A parallel mode in which the drive wheels are driven by the internal combustion engine, It has, When switching from the series mode to the parallel mode, the number of injection stages of the in-cylinder injection device changes. Control system for hybrid vehicles.

2. The parallel mode has more injection stages than the series mode. A control system for a hybrid vehicle according to claim 1.

3. The control device increases the number of injection stages when the vehicle is running at a steady pace during the parallel mode. A control system for a hybrid vehicle according to claim 1.

4. The control device advances the injection timing when reducing the number of injection stages. A control system for a hybrid vehicle according to claim 3.

5. The series mode includes an external power supply mode for supplying power to equipment outside the vehicle. The control device reduces the number of injection stages during the external power supply mode. A control system for a hybrid vehicle according to claim 1.

6. The vehicle further comprises a fuel tank for storing the aforementioned fuel, The control device increases the number of injection stages, even in series mode, when the charge level of the drive battery is below a predetermined charge level and the fuel tank is below a predetermined remaining amount. A control system for a hybrid vehicle according to any one of claims 1 to 5.

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