Control system for hybrid vehicles

Abstract

To provide a control device for hybrid vehicles that can suppress the emission of particulate matter. [Solution] The control device for a hybrid vehicle includes an internal combustion engine mounted on the vehicle, a generator driven by the internal combustion engine to generate electricity, a drive battery for storing the electricity generated by the generator, and a motor that rotates using the electricity generated by the generator to drive the drive wheels of the vehicle. The control device for a hybrid vehicle performs a series mode in which the internal combustion engine drives the generator, and the electricity generated by the generator is used to drive the motor to drive the drive wheels. When the conditions for stopping the internal combustion engine are met during the execution of the series mode, if the conditions for an increase in particulate matter generated from the internal combustion engine are met, the stopping of the internal combustion engine is prohibited.

Description

Technical Field

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

Background Art

[0002] Conventionally, a control device for a hybrid vehicle having a series mode is known (see, for example, Patent Document 1). The control device for the hybrid vehicle of Patent Document 1 prohibits the intermittent operation of the engine when the oil in the engine is diluted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 discloses a control device for a hybrid vehicle that prevents over-rotation of the engine while prohibiting intermittent operation. However, Patent Document 1 does not disclose a control device for a hybrid vehicle that suppresses the emission of particulate matter.

[0005] An object of the present disclosure is to provide a control device for a hybrid vehicle that can suppress the emission of particulate matter.

Means for Solving the Problems

[0006] The control device for a hybrid vehicle according to this disclosure comprises an internal combustion engine mounted on the vehicle, a generator driven by the internal combustion engine to generate electricity, a drive battery for storing the electricity generated by the generator, and a motor that rotates using the electricity generated by the generator to drive the drive wheels of the vehicle. The control device for a hybrid vehicle performs a series mode in which the internal combustion engine drives the generator, and the electricity generated by the generator is used to drive the motor to drive the drive wheels. When the conditions for stopping the internal combustion engine are met during the execution of the series mode, if the conditions for an increase in particulate matter generated from the internal combustion engine are met, the stopping of the internal combustion engine is prohibited. [Effects of the Invention]

[0007] The control system of this hybrid vehicle prohibits the shutdown of the internal combustion engine if the conditions for increased particulate matter are met during series mode operation. This allows the internal combustion engine to continue operating, burning the particulate matter during engine operation. Therefore, the accumulation of particulate matter on the internal combustion engine can be suppressed. As a result, the control system of this hybrid vehicle can reduce particulate matter emissions. [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 flowchart illustrating a control procedure performed by a control device according to one embodiment of the present disclosure. [Figure 4] A timing chart showing 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 the wheels (an example of drive wheels) C1 via the transaxle 8. The engine 2 in this embodiment is an inline four-cylinder gasoline engine. The engine 2 receives fuel from the fuel tank 22 and consumes it by burning it.

[0012] As shown in Figure 2, the engine 2 includes a fuel injector 40, a variable valve timing device 42, a water temperature sensor 44, and an exhaust temperature sensor 46. The fuel injector 40 of this embodiment includes an intake port injector 40a that injects fuel into the intake port 41 and an in-cylinder injector 40b that injects fuel into the cylinder N. The variable valve timing device 42 includes an intake valve timing device 42a and an exhaust valve timing device 42b. The intake valve timing device 42a varies the valve timing of the intake valve 48a by changing the phase of the intake cam 48. The exhaust valve timing device 42b varies the valve timing of the exhaust valve 50a by changing the phase of the exhaust cam 50. The variable valve timing device 42 varies the overlap amount of the intake valve 48a and the exhaust valve 50a (hereinafter referred to as valve overlap amount in this specification). The water temperature sensor 44 detects the temperature of the coolant that cools the engine 2 (hereinafter referred to as water temperature WT in this specification). The exhaust temperature sensor 46 detects the temperature of the exhaust from the engine 2.

[0013] 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.

[0014] 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.

[0015] The transaxle 8 has multiple 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 open, power transmission between the engine 2 and the axle 10 is interrupted, and when the clutch 8a is engaged, power from the engine 2 is transmitted to the axle 10.

[0016] The inverter 12 controls the motor torque of the motor 3 by converting the DC power supplied from the drive battery 6 into AC power and adjusting the power supplied to the motor 3. Furthermore, when the motor 3 is regenerating, the inverter 12 controls the regenerative torque of the motor 3 by converting the AC power supplied from the motor 3 into DC power and adjusting the power supplied to the drive battery 6.

[0017] The control device 20 is electrically connected to the engine 2 and the motor 3 via the inverter 12, and controls the engine 2 and the motor 3. In reality, the control device 20 is an ECU (Electronic Control Unit) composed of a microcomputer including an arithmetic unit, memory, and input / output buffers. The control device 20 controls the vehicle C based on maps and programs stored in memory.

[0018] Vehicle C in this embodiment has driving modes such as EV mode, series mode, and parallel mode. In EV mode, with the engine 2 stopped, vehicle C drives the motor 3 with power from the drive battery 6. In series mode, vehicle C disengages the clutch 8a, drives the generator 4 with the engine 2, and uses the power generated by the generator 4 to drive the motor 3 and drive the wheels C1. In parallel mode, vehicle C engages the clutch 8a and uses the power of the engine 2 to drive the wheels C1 via the axle 10. In vehicle C, the control device 20 switches between each driving mode according to the depression state of the accelerator pedal 14, and controls the motor 3 and generator 4 via the inverter 12, as well as the engine 2.

[0019] Furthermore, the vehicle C of the present embodiment has an external power supply mode. In the external power supply mode, when the connector 18a is connected to an external device, the control device 20 supplies power from the drive battery 6 to the external device using the external power supply device 18. When the state of charge (SOC) of the drive battery 6 becomes less than or equal to the minimum SOC (SOCmin) during the external power supply mode, the control device 20 disconnects the clutch 8a, starts the engine 2 to drive the generator 4, stores the power generated by the generator 4 in the drive battery 6, and supplies it to the external device, thereby executing an engine power generation external power supply mode.

[0020] Next, the control procedure executed by the control device 20 will be described. In the present embodiment, the control device 20 starts the control procedure when an ignition switch (not shown) is turned on.

[0021] In step S1, the control device 20 determines whether or not the series mode is being executed. If the control device 20 determines that the series mode is being executed (step S1: YES), the process proceeds to step S2. If the control device 20 determines that the series mode is not being executed, the control device 20 returns.

[0022] In step S2, the control device 20 determines whether or not there is a stop request for the engine 2. During the series mode, for example, when the required power generation amount Q becomes zero or less (an example of a stop condition), the control device 20 instructs a stop request for the engine 2. When the required power generation amount Q becomes zero or less, for example, when the motor 3 is in a regenerative state and charging of the drive battery is unnecessary. In such a state, the control device 20 stops the engine 2 and stops power generation by the generator 4. As shown by the broken line from time t2 to time t3 in FIG. 4, in the present embodiment, when the control device 20 instructs a stop request for the engine 2, the stop request flag is turned on. If the control device 20 determines that there is a stop request for the engine 2 (step S2: YES), the process proceeds to step S3.

[0023] In step S3, the control device 20 determines whether the PN (PN stands for Particle Number) increase condition has been met. The PN increase condition is a condition in which the amount of particulate matter generated from the engine 2 increases. More specifically, it is a condition in which the number of particulate matter generated from the engine 2 increases. That is, when the PN increase condition is met, the number of particulate matter generated from the engine 2 increases compared to when the increase condition is not met. A condition in which the number of particulate matter increases is, for example, a condition in which fuel is likely to adhere to the cylinder N of the engine 2. In this embodiment, the control device 20 determines that the PN increase condition has been met when the water temperature WT of the engine 2 is less than a predetermined water temperature WT1 and the engine 2 is operated between a medium load and a high load. The predetermined water temperature WT1 is, for example, about 40°C. A medium load is, for example, 30 percent or more and less than 70 percent of the maximum output of the engine 2. A high load is, for example, 70 percent or more of the maximum output of the engine 2. If the control device 20 determines that the PN increase condition has been met (step S3 YES), it proceeds to step S4.

[0024] In step S4, the control device 20 prohibits stopping the engine 2. If the PN increase condition is met, there is a risk that fuel is adhering to cylinder N. If the engine 2 is stopped with fuel adhering to cylinder N, when the engine 2 is started again, particulate matter will be mixed with the exhaust and discharged. This will worsen the exhaust. However, if stopping the engine 2 is prohibited, the adhering fuel will be burned by the engine 2. As a result, the amount of particulate matter discharged from the engine 2 will decrease. If the control device 20 prohibits stopping the engine 2, it proceeds to step S5.

[0025] In step S5, the control device 20 performs warm-up control. Warm-up control is a control that raises the water temperature WT of the engine 2's coolant. During warm-up control, the control device 20 adjusts the requested power generation Q and continues the operation of the engine 2. As shown by the solid line from time t2 to time t3 in Figure 4, when the control device 20 performs warm-up control, it sets the requested power generation Q to a first predetermined value or a second predetermined value, which will be described later. The first predetermined value or the second predetermined value is a value greater than zero. As a result, the control device 20 continues the operation of the engine 2.

[0026] The control device 20 controls the fuel injector 40 during warm-up control, retarding the fuel injection timing during the intake stroke and advancing it during the compression stroke. This reduces the amount of fuel adhering to the cylinder N. Furthermore, by adjusting the injection timing as described above, more fuel burns, causing the cylinder N to become hotter. This makes it easier for the engine water temperature WT to rise. When the engine water temperature WT rises, the fuel adhering to the cylinder N becomes more likely to volatilize. As a result, the fuel adhering to the cylinder N becomes easier to burn. Consequently, the emission of particulate matter is further suppressed.

[0027] The control device 20 controls the variable valve timing device 42 during warm-up control to increase the valve overlap amount. When the valve overlap amount increases, the amount of internal exhaust circulating gas, which is exhaust gas returning from the exhaust to the cylinder N, increases, and the intake air warms up. This suppresses the adhesion of fuel to the cylinder N. As a result, the emission of particulate matter is further suppressed. When the control device 20 performs warm-up control, it proceeds to step S6.

[0028] In step S6, the control device 20 determines whether the charge level (SOC) is equal to or greater than the first predetermined charge level (SOC1). The first predetermined charge level (SOC1) is a value that provides a margin over the upper limit of the charge level (SOC) that can be accepted by the regeneration of the motor 3 and the power generation of the generator 4. The first predetermined charge level (SOC1) is, for example, about 80 percent of the upper limit (the second predetermined charge level (SOC2), which will be described later). If the control device 20 determines that the charge level (SOC) is equal to or greater than the first predetermined charge level (SOC1) (step S6 YES), it proceeds to step S7.

[0029] In step S7, the control device 20 sets the requested power generation amount Q to a first predetermined value Q1. The first predetermined value Q1 is the requested power generation amount Q at which the engine 2 operates under no load, and is, for example, a value close to zero. That is, the output of the engine 2 is set to the minimum output that the engine 2 can output, suppressing the output of the engine 2 while maintaining combustion of the engine 2. This makes it possible to continue operating the engine 2 while avoiding charging the drive battery 6. Once the requested power generation amount Q is set to the first predetermined value Q1, the control device 20 proceeds to step S8.

[0030] In step S8, the control device 20 determines whether the charge level (SOC) is equal to or greater than the second predetermined charge level (SOC2). The second predetermined charge level (SOC2) is the upper limit of the charge level (SOC) that can be accepted by the regeneration of the motor 3 and the power generation of the generator 4. In other words, if the charge level (SOC) is equal to or greater than the second predetermined charge level (SOC2), the power generated by the regeneration of the motor 3 and the power generated by the generator 4 cannot be accepted by the drive battery 6. Therefore, if the control device 20 determines that the charge level (SOC) is equal to or greater than the second predetermined charge level (SOC2) (step S8 YES), the control device 20 proceeds to step S9 and terminates the warm-up control. The control device 20 returns after terminating the warm-up control.

[0031] In step S2, if the control device 20 determines that there is no request to stop the engine (step S2 NO), the control device 20 returns.

[0032] If the control device 20 determines in step S3 that the PN increase condition is not met (step S3 NO), the control device 20 proceeds to step S10. In step S10, the control device 20 stops the engine 2. After stopping the engine 2, the control device 20 returns.

[0033] In step S6, if the control device 20 determines that the charge level (SOC) is less than the first predetermined charge level (SOC1), the control device 20 proceeds to step S11. In step S11, the control device 20 sets the requested power generation Q to the second predetermined value Q2. The second predetermined value Q2 is greater than the first predetermined value Q1 and is a variable value depending on the speed of the vehicle C (hereinafter referred to as vehicle speed V in this specification). The generator 4 generates a load corresponding to the second predetermined value Q2. The engine 2 drives the generator 4 by outputting power according to the load generated by the generator 4. The power generated by the generator 4 during warm-up control is charged to the drive battery 6. The second predetermined value Q2 is larger the higher the vehicle speed V. The higher the vehicle speed V, the greater the power required by the motor 3 when transitioning from deceleration to acceleration (hereinafter referred to as re-acceleration in this specification). Therefore, by increasing the second predetermined value Q2 as the vehicle speed V increases, the amount of electricity charged to the drive battery 6 increases, and more electricity can be output from the drive battery 6 when re-accelerating. As a result, the amount of electricity generated by the generator 4 decreases, and fuel efficiency improves. Furthermore, the higher the second predetermined value, the higher the heat generated by the engine 2. As a result, the water temperature WT of the engine 2 warms up more quickly, and the warm-up time is shortened. When the control device 20 sets the requested power generation amount Q to the second predetermined value, it proceeds to step S8.

[0034] If the control device 20 determines in step S8 that the charge level SOC is less than the second predetermined charge level SOC2 (step S8 NO), the control device 20 proceeds to step S12. In step S12, the control device 20 determines whether the water temperature WT is equal to or greater than the predetermined water temperature WT1. If the water temperature WT is equal to or greater than the predetermined water temperature WT1, the engine 2 has finished warming up. Once warming up is complete, the amount of fuel adhering to cylinder N decreases. Therefore, if the control device 20 determines that the water temperature WT is equal to or greater than the predetermined water temperature WT1 (step S12, YES), it proceeds to step S9 and terminates the warm-up control. In other words, the control device 20 terminates the warm-up control if the water temperature WT of the engine 2 is equal to or greater than the predetermined water temperature WT1 (step S12 YES), or if the charge level SOC of the drive battery 6 is equal to or greater than the second predetermined charge level SOC2 (step S8 YES). If the control device 20 determines that the water temperature WT is equal to or greater than the predetermined water temperature WT1, it returns.

[0035] The dashed line in Figure 4 shows the control state of the control device 20 when warm-up control is not performed. The solid line in Figure 4 shows the control state of the control device 20 when warm-up control is performed. As shown from time t1 to time t2 in Figure 4, the control device 20 configured in this way selects series mode and accelerates vehicle C when the accelerator pedal 14 is pressed. When vehicle C accelerates, the vehicle speed V increases. When accelerating vehicle C, the control device 20 instructs an increase in the requested power generation Q and increases the rotational speed of engine 2. In this embodiment, the load on engine 2 transitions from medium load to high load. As shown by the solid line on the water temperature WT from time t1 to time t2 in Figure 4, if the water temperature WT is less than or equal to a predetermined water temperature WT1 in this state, the control device 20 determines that the PN increase condition has been met (see step S3 YES in Figure 3). Therefore, as shown by the solid line on the engine stop prohibition flag from time t1 to time t2 in Figure 4, the control device 20 prohibits stopping the engine 2 by turning on the engine stop prohibition flag (see step S4 in Figure 3). In this embodiment, the control device 20 maintains the engine stop prohibition flag in the ON state until time t4 when the water temperature WT is equal to or greater than a predetermined water temperature WT1.

[0036] As shown by the dashed line on the water temperature WT from time t1 to time t2 in Figure 4, if the water temperature WT is equal to or greater than the predetermined water temperature WT1, the control device 20 determines that the PN increase condition is not met (see step S3 NO). As shown by the dashed line on the engine stop prohibition flag from time t1 to time t2 in Figure 4, if the PN increase condition is not met, the control device 20 keeps the engine stop prohibition flag off.

[0037] As shown in Figure 4 from time t2 to time t3, when the accelerator pedal 14 is released, the control device 20 regenerates the motor 3. As shown by the solid line for the engine stop request from time t2 to time t3 in Figure 4, when the control device 20 regenerates the motor 3, it turns on the engine stop request flag to stop the engine 2. When the motor 3 regenerates, the vehicle C decelerates and the vehicle speed V decreases. As shown by the dashed line for the engine rotation from time t2 to time t3, when the engine stop prohibition flag is off, the control device 20 stops the engine 2 when the engine stop request flag is turned on.

[0038] On the other hand, as shown by the solid line of engine speed from time t2 to time t3, when the engine stop prohibition flag is on, even if the engine stop request flag is on, the control device 20 sets the requested power generation amount Q to a first predetermined value or a second predetermined value and continues to operate the engine 2, thereby performing warm-up control.

[0039] As shown in Figure 4 from time t3 to time t5, when the accelerator pedal 14 is pressed again, the control device 20 increases the requested power generation Q and also increases the rotation speed of the engine 2. This increases the vehicle speed V. The control device 20 of this embodiment can suppress the number of particulate matter particles (PN) generated between time t3 and time t5 by performing warm-up control.

[0040] As shown in Figure 4 from time t4 onwards, when the water temperature WT becomes equal to or greater than the predetermined water temperature WT1, the control device 20 turns off the engine stop prohibition flag. As shown in Figure 4 from time t5 onwards, when the accelerator pedal 14 is released, the control device 20 turns on the engine stop flag. Since the engine stop prohibition flag is off, the control device 20 stops engine 2.

[0041] As described above, this disclosure provides a control device 20 for a vehicle C that can suppress the emission of particulate matter.

[0042] <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.

[0043] In the above embodiment, an example was described in which the control device 20 determines that the PN increase condition is met when the engine water temperature WT is less than a predetermined water temperature WT1 and the engine 2 is operated between medium and high load. However, this disclosure is not limited to this. The PN increase condition may be any condition that increases the number of particulate matter generated from the engine 2, such as a condition using the temperature of the lubricating oil of the engine 2.

[0044] In the above embodiment, an example was described in which, in series mode, the vehicle C disengages the clutch 8a, drives the generator 4 with the engine 2, and uses the power generated by the generator 4 to drive the motor 3 and drive the wheels C1. However, the disclosure is not limited to this. The clutch 8a may be, for example, a planetary gear. The series mode can be any system that can drive the generator 4 with the engine 2 and use the power generated by the generator 4 to drive the motor 3 and drive the wheels C1. [Explanation of Symbols]

[0045] 1: Control system, 2: Engine, 3: Motor, 4: Generator, 6: Drive battery 20: Control device 40: Fuel injection system, 42: Variable valve timing system 44: Water temperature sensor, 46: Exhaust temperature sensor, 48: Intake cam 48a: Intake valve, 50: Exhaust cam, 50a: Exhaust valve, C: Vehicle Q: Required power generation, Q1: First predetermined value, Q2: Second predetermined value SOC: Charging rate, SOC1: First predetermined charging rate, SOC2: Second predetermined charging rate V: Vehicle speed, WT: Water temperature, WT1: Predetermined water temperature

Claims

1. A control device for a hybrid vehicle having an internal combustion engine mounted on the vehicle, a generator driven by the internal combustion engine to generate electricity, a drive battery for storing the electricity generated by the generator, and a motor that rotates using the electricity generated by the generator to drive the drive wheels of the vehicle, The internal combustion engine drives the generator, and the electricity generated by the generator is used to drive the motor and drive the drive wheels in a series mode. If the conditions for stopping the internal combustion engine are met during the execution of the series mode, and the conditions for an increase in particulate matter generated from the internal combustion engine are also met, the stopping of the internal combustion engine is prohibited. Control system for hybrid vehicles.

2. A control device for a hybrid vehicle according to claim 1, wherein, when stopping the internal combustion engine is prohibited, a warm-up control is performed to warm up the internal combustion engine.

3. The internal combustion engine has a fuel injection device, In the warm-up control, the injection timing of the fuel injection device is retarded. A control device for a hybrid vehicle according to claim 2.

4. The internal combustion engine has a variable valve timing device that varies the overlap amount of the intake valve and exhaust valve of the internal combustion engine. In the warm-up control described above, the variable valve timing device is controlled to increase the overlap amount. A control device for a hybrid vehicle according to claim 2.

5. In the warm-up control described above, if the charge level of the drive battery is less than a first predetermined charge level, the internal combustion engine is operated with a load corresponding to the vehicle's speed. A control device for a hybrid vehicle according to claim 2.

6. If the charge rate is equal to or greater than the first predetermined charge rate, the load of the internal combustion engine is set to the first predetermined value. A control device for a hybrid vehicle according to claim 5.

7. If the charge rate is less than or equal to the first predetermined charge rate, the load on the internal combustion engine is set to a value greater than the first predetermined value and to a second predetermined value corresponding to the vehicle speed. The control device for a hybrid vehicle according to claim 6.

8. The prohibition against stopping the internal combustion engine ends when the water temperature of the internal combustion engine exceeds a predetermined water temperature, or when the charge level of the drive battery reaches a second predetermined charge level, which is higher than the first predetermined charge level. A control device for a hybrid vehicle according to any one of claims 1 to 6.

Images