Control system for hybrid vehicles

Abstract

To provide a control device of a hybrid vehicle in which an EV travel area is expanded.SOLUTION: A control device 10 of a hybrid vehicle according to the present disclosure is applied to a hybrid vehicle which includes an engine 1 and a motor 2 as drive sources, and a rotary electric machine 3 that performs cranking when the engine 1 is started, and selects the EV mode which travels by using the motor 2 in such a state that the engine 1 is stopped, and the engine travel mode which travels by using at least the engine 1 as the travel modes. The control device 10 has the EV priority mode that can be used in conjunction with the EV mode. In the time when the EV priority mode is set, the transition condition from the EV mode to the engine travel mode is relaxed in comparison to the time when the EV priority mode is not set. The starting speed which is the cranking speed of the engine 1 by the rotary electric machine 3 when starting the engine 1 in the time when the EV priority mode is set is set to be less than the starting speed in the time when the EV priority mode is not set.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a control device for a hybrid vehicle.

Background Art

[0002] Conventionally, in a hybrid vehicle equipped with a motor and an engine as drive sources, there is known a vehicle in which an EV mode in which only the motor is used for running and a hybrid mode in which the motor and the engine are used together for running are automatically selected. In this type of hybrid vehicle, various controls have been proposed to expand the driving range in which the EV mode is selected. For example, a technique has been proposed in which a low-voltage battery for engine starting is provided separately from the high-voltage battery for motor driving to reduce the power load related to engine starting. By such a method, it becomes unnecessary to secure the power for engine starting in the high-voltage battery, and the maximum output of the motor by the high-voltage battery can be increased, and the driving range of the EV mode can be expanded (see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The starting RPM required to start an engine is not always constant and varies depending on the cranking time. For example, if you want to start the engine quickly in a short time, you need to crank the engine at a relatively high starting RPM. Conversely, if it is acceptable to start the engine slowly over time, you can crank the engine at a relatively low starting RPM without any problems. Existing technologies do not adequately consider these characteristics of starting RPM, so in some cases, more power is allocated for engine starting than is actually needed, and there is room for improvement in expanding the operating range of EV mode.

[0005] One of the objectives of this invention is to provide a control device for a hybrid vehicle that expands the EV driving range, as devised in light of the above-mentioned challenges. However, other objectives of this invention include achieving effects and benefits that cannot be obtained with conventional technology, derived from the various configurations described in the "Modes for Carrying Out the Invention" section below. [Means for solving the problem]

[0006] The control device for the disclosed hybrid vehicle can be implemented in the following embodiments (examples of application) and solve at least some of the above-mentioned problems. Each of the embodiments from Embodiment 2 onward is an additional embodiment that can be appropriately selected and each of the embodiments is optional. None of the embodiments from Embodiment 2 onward disclose any embodiments or configurations that are essential to this case.

[0007] Embodiment 1. The control device for a hybrid vehicle disclosed comprises an engine and a motor as drive sources, and a rotating electric machine for cranking the engine when starting the engine, and is a control device for a hybrid vehicle in which either an EV mode in which the vehicle is driven using the motor with the engine stopped, or an engine driving mode in which the vehicle is driven using at least the engine, can be selected as a driving mode. This control device includes an EV priority mode that can be used in conjunction with the EV mode. When the EV priority mode is set, the conditions for transitioning from the EV mode to the engine driving mode are more favorable than when the EV priority mode is not set. It will get tougher Furthermore, when the EV priority mode is set, the starting speed, which is the cranking speed of the engine by the rotating electric machine when starting the engine, is set to be lower than the starting speed when the EV priority mode is not set.

[0008] The engine driving mode includes a hybrid mode in which the engine and the motor are used in combination. 。 The aforementioned hybrid mode includes a parallel mode in which the driving force of the engine and the motor is transmitted to the drive wheels, and a series mode in which the driving force of the engine is transmitted to wheels other than the drive wheels and the driving force of the motor is transmitted to the drive wheels. 。 When the EV priority mode is set, the starting rotation speed when transitioning from the EV mode to the parallel mode is set to be greater than the starting rotation speed when transitioning from the EV mode to the series mode. 。

[0009] manner 2 The above aspects 1 In this case, when the remaining fuel level of the engine is below a predetermined amount, it is preferable that the starting speed when the EV priority mode is set is set to the same value as the starting speed when the EV priority mode is not set. manner 3 .Aspect 1 above or 2 (e.g., embodiment 1)In this case, if the engine is stopped for a predetermined time or longer, it is preferable that the starting speed when the EV priority mode is not set is set to the same value as the starting speed when the EV priority mode is set.

[0010] manner 4 . Any of the above embodiments 1 to 3 (for example, embodiment 1) In this configuration, it is preferable that the rotating electric machine is driven to generate electricity by the engine in series mode, and that the hybrid vehicle comprises a high-voltage battery that supplies power to the motor and the rotating electric machine, and an auxiliary battery that supplies power to the rotating electric machine and auxiliary equipment. Furthermore, it is preferable that when the charge level of the auxiliary battery is below a predetermined charge level, power is supplied from the high-voltage battery to the rotating electric machine to start the engine, and when the charge level of the auxiliary battery is at or above the predetermined charge level, power is supplied from the auxiliary battery to the rotating electric machine to start the engine. Embodiment 5. In Embodiment 4 described above, it is preferable that the hybrid vehicle is equipped with a voltage booster that controls the voltage boost of the auxiliary battery. Furthermore, when power is supplied from the auxiliary battery to the rotating electric machine to start the engine, it is preferable that the voltage boost when transitioning from the EV mode to the parallel mode is set to be greater than the voltage boost when transitioning from the EV mode to the series mode. [Effects of the Invention]

[0011] According to the disclosed hybrid vehicle control device, the power consumption required for engine starting can be reduced by lowering the engine starting speed when EV priority mode is set compared to normal operation (when EV priority mode is not set). Therefore, the power required for engine starting in EV mode can be reduced, and the EV driving range can be expanded. [Brief explanation of the drawing]

[0012] [Figure 1] This is a block diagram showing the configuration of a hybrid vehicle. [Figure 2] This is a list of the various modes. [Figure 3]It is a graph showing the change in the engine speed (starting speed) at engine startup. (A) is a graph when the EV priority mode is not set (off), (B) is a graph when the EV priority mode is set (on) and when shifting from the EV mode to the parallel mode, and (C) is a graph when the EV priority mode is set (on) and when shifting from the EV mode to the series mode. [Figure 4] It is a flowchart related to the adjustment of the starting speed.

Embodiment for Carrying out the Invention

[0013] The disclosed control device is applied to a hybrid vehicle (Hybrid Electric Vehicle, HEV) described in the following embodiments. The hybrid vehicle referred to here includes an engine and a motor as drive sources and a rotating electric machine that cranks when starting the engine. In this hybrid vehicle, as a driving mode (control mode regarding the transmission path of the driving force related to the running of the vehicle and the combination of the driving forces used), an EV mode in which the motor is used for running with the engine stopped and an engine driving mode in which at least the engine is used for running are selected. The EV mode and the engine driving mode are set and selected (automatically or manually) mutually exclusively. The engine driving mode includes a hybrid mode. The hybrid mode is a driving mode in which the engine and the motor are used in combination. Note that the engine driving mode may include an engine mode in which only the engine is used.

Example

[0014] [[ID=I7]] [1. Device Configuration] Figure 1 is a block diagram illustrating the configuration of a hybrid vehicle as an embodiment. This hybrid vehicle comprises an engine 1 and a motor 2 as drive sources, a generator 3 connected to the drive shaft of the engine 1, a high-voltage battery 4, a clutch 5, a booster 6, and an auxiliary battery 7. The hybrid vehicle in this embodiment is a plug-in hybrid vehicle (PHEV) capable of external charging of the high-voltage battery 4 or external power supply from the high-voltage battery 4. This hybrid vehicle is provided with a charging port (inlet) for inserting a charging cable into which power is supplied from an external charging facility, and an outlet for external power supply.

[0015] The high-voltage battery 4 is a relatively high-voltage secondary battery and is electrically connected to the motor 2 and the generator 3. The auxiliary battery 7 is a relatively low-voltage secondary battery (compared to the high-voltage battery 4) and is connected to auxiliary equipment (e.g., cooling system, fuel supply system, ignition system, air conditioning system, lighting system, onboard electrical equipment, etc.), and is also electrically connected to the motor 2 and the generator 3 via the booster 6. The high-voltage battery 4 only needs to be able to supply power to at least the motor 2 and the generator 3, and the auxiliary battery 7 only needs to be able to supply power to at least the generator 3 and the auxiliary equipment. The high-voltage battery 4 is, for example, a lithium-ion secondary battery, a nickel-metal hydride battery, etc., and the auxiliary battery 7 is, for example, a lithium-ion secondary battery, a nickel-metal hydride battery, a lead-acid battery, etc.

[0016] Engine 1 is an internal combustion engine, such as a gasoline engine or a diesel engine. Generator 3 is an electric motor and generator that combines the functions of a rotating electric machine that cranks when starting engine 1 and a generator that generates electricity when driven by engine 1 after it has started. The electricity generated by generator 3 is used to drive motor 2 and to charge the high-voltage battery 4 and auxiliary battery 7. A transmission mechanism (not shown) may be interposed in the power transmission path connecting engine 1 and generator 3.

[0017] The motor 2 is an electric motor兼generator that has the function of driving a hybrid vehicle using the power of the high-voltage battery 4 and the accessory battery 7 and the generated power of the generator 3, and the function of charging the high-voltage battery 4 and the accessory battery 7 by regenerative power generation. The drive shaft of the motor 2 is connected to the drive wheels of the hybrid vehicle. A transmission mechanism (not shown) may be interposed on the power transmission path connecting the motor 2 and the drive wheels.

[0018] A clutch 5 is interposed on the power transmission path connecting the engine 1 and the motor 2. The engine 1 is connected to the drive wheels via the clutch 5, and the motor 2 is disposed on the drive wheel side of the clutch 5. Also, the generator 3 is connected on the engine 1 side of the clutch 5. When the clutch 5 is disengaged (released), the engine 1 and the generator 3 become disconnected from the drive wheels, and the motor 2 becomes connected to the drive wheels. On the other hand, when the clutch 5 is engaged (fastened), the three components of the engine 1, the motor 2, and the generator 3 become connected to the drive wheels.

[0019] The booster 6 is a DC-DC converter that converts the voltage between the high-voltage circuit connecting the motor 2, the generator 3, and the high-voltage battery 4 and the low-voltage circuit on the accessory battery 7 side. Various electrical components mounted on the hybrid vehicle are connected to the low-voltage circuit. The booster 6 can, for example, boost the power stored in the accessory battery 7 and supply it to the motor 2 or the high-voltage battery 4, and can also step down the power generated by the motor 2 or the generator 3 and supply it to the accessory battery 7 or various electrical components.

[0020] [2. Control Configuration] In this embodiment, the operating state of each component of the drivetrain (engine 1, motor 2, generator 3, high-voltage battery 4, clutch 5) in the hybrid vehicle is controlled by the control device 10. The control device 10 is a computer (electronic control unit, ECU) for controlling the operating state of the drivetrain according to the driving state of the hybrid vehicle. The control device 10 incorporates a processor (arithmetic processing unit) and memory (storage device). The content of the control performed by the control device 10 (control program) is stored in memory and executed by appropriately reading that content into the processor.

[0021] The control device 10 is connected to an EV priority mode switch 11 and a fuel sensor 12, as well as a vehicle speed sensor, accelerator position sensor, brake fluid pressure sensor, etc. (not shown). Furthermore, a battery voltage sensor, battery current sensor, battery temperature sensor, etc. (not shown) are connected to each of the high-voltage battery 4 and the auxiliary battery 7. The EV priority mode switch 11 is a switch for switching the EV priority mode setting (on, off) and is operated by the driver or passenger. The fuel sensor 12 is a sensor that detects the remaining fuel level of the engine 1 (the amount of fuel present in the fuel tank) and is attached to the fuel tank where the engine 1's fuel is stored.

[0022] The EV priority mode refers to the control method for the "conditions for switching between EV mode and hybrid mode." Switching the EV priority mode changes the conditions for switching the driving mode from EV mode to hybrid mode, and the conditions for switching the driving mode from hybrid mode to EV mode. The control device 10 controls the operating state of the drive system based on information input from various sensors and various selectors.

[0023] Figure 2 is a table listing the various modes in the hybrid vehicle of this embodiment. This hybrid vehicle is equipped with three driving modes, an EV priority mode with two states (on or off), and a maintenance mode, which also has two states (on or off). The driving modes include EV mode and hybrid mode, and hybrid mode includes series mode and parallel mode. EV mode is a driving mode in which only motor 2 is used, while hybrid mode is a driving mode in which engine 1 and motor 2 are used in combination. In EV mode, the hybrid vehicle runs using only motor 2's power, with engine 1 and generator 3 stopped.

[0024] In series mode of the hybrid system, the engine 1 operates with the clutch 5 disengaged, the generator 3 generates electricity, and the driving force of the motor 2 is transmitted to the drive wheels, causing the hybrid vehicle to move. In parallel mode of the hybrid system, the engine 1 and motor 2 operate with the clutch 5 engaged, and the driving force of the engine 1 and motor 2 is transmitted to the drive wheels, causing the hybrid vehicle to move. In this case, the generator 3 may be kept stopped or may be allowed to generate electricity.

[0025] One of these three driving modes is automatically selected and set according to predetermined conditions (e.g., vehicle speed, State of Charge (SOC) of the high-voltage battery 4, battery temperature of the high-voltage battery 4, accelerator opening, rate of change of accelerator opening, etc.). The EV mode is selected, for example, when the vehicle speed is relatively low and the SOC of the high-voltage battery 4 is sufficiently high. On the other hand, if the SOC of the high-voltage battery 4 decreases or the vehicle speed increases slightly, the series mode is selected, and power generation is performed by the engine 1 and generator 3. Furthermore, during high-speed driving where the fuel efficiency and performance of the engine 1 are good, the parallel mode is selected, and driving is performed primarily using engine output (motor-assisted driving where motor output is used secondarily).

[0026] The EV priority mode is a mode that is set according to the operation state of the EV priority mode switch 11. When the EV priority mode is set (when the EV priority mode switch 11 is ON), the operating range of the EV driving mode is expanded compared to when the EV priority mode is not set (when the EV priority mode switch 11 is OFF). In other words, when the EV priority mode is set, it is more difficult to start the engine 1 compared to when the EV priority mode is not set. Therefore, if we focus on the conditions for starting the engine 1 when the motor 2 is operating and the engine 1 is not operating (engine start conditions), the engine start conditions when the EV priority mode is set are stricter than the engine start conditions when the EV priority mode is not set.

[0027] Furthermore, various known conditions can be applied as specific engine starting conditions. For example, whether or not to start engine 1 is determined based on parameters such as the battery's charge / discharge output, state of charge (SOC), battery voltage, battery temperature, driver-requested torque, vehicle speed, and accelerator opening. The threshold for this determination is set to a stricter value (a value that makes it less likely for the engine starting conditions to be met) when EV priority mode is set, compared to the threshold when EV priority mode is not set.

[0028] The maintenance mode is automatically set according to the time the engine 1 has been stopped. For example, it is turned on when the elapsed time since the engine 1 last stopped operating exceeds a predetermined fuel degradation period (e.g., several hundred hours to several months). The elapsed time determined here is reset (or shortened) when, for example, the operation of the engine 1 or refueling is detected.

[0029] When maintenance mode is activated (when maintenance mode is on), engine 1 is automatically forced to start, and the consumption of old fuel is accelerated. At this time, if charging of the high-voltage battery 4 is possible, power generation by generator 3 is also performed. This control terminates when termination conditions (conditions for turning off maintenance mode) are met, for example, based on the duration of maintenance mode or the remaining fuel level.

[0030] [3. Engine start control] The control device 10 has a function to set the starting speed of engine 1 according to the state (on, off) of the EV priority mode when the driving mode transitions from EV mode to engine driving mode [specifically, hybrid mode (parallel mode, series mode)]. When the EV priority mode is off (i.e., when the EV priority mode is not set), as shown in Figure 3(A), the starting speed of engine 1 (the cranking speed by the generator 3) is set to the first rotational speed N1. This setting applies whether the destination driving mode is series mode or parallel mode. The expected starting time by cranking at the first rotational speed N1 (the expected time until engine 1 is fully ignited) is the first time T1. In this embodiment, it is determined that engine 1 has "fully ignited" when it exceeds a predetermined starting completion rotational speed N0.

[0031] When EV priority mode is on (i.e., when EV priority mode is set), the starting speed of engine 1 is set lower, at least compared to when EV priority mode is off. In this case, the starting time will be longer than when EV priority mode is off. On the other hand, because the cranking speed of generator 3 is reduced, power consumption by generator 3 is reduced. Therefore, the amount of power that needs to be reserved for engine starting in EV mode is reduced, and the EV driving range is expanded.

[0032] When the EV priority mode of the control device 10 in this embodiment is on, it has a function of setting the starting rotational speed of the engine 1 according to the type of the traveling mode to be shifted to. When the traveling mode to be shifted to is the parallel mode, as shown in Fig. 3(B), the starting rotational speed of the engine 1 is set to a second rotational speed N2 which is slightly lower than the first rotational speed N1 (N2 < N1). The predicted starting time by cranking at the second rotational speed N2 is the second time T2 (T1 < T2).

[0033] On the other hand, when the traveling mode to be shifted to is the series mode, as shown in Fig. 3(C), the starting rotational speed of the engine 1 is set to a third rotational speed N3 which is even lower than the second rotational speed N2 (N3 < N2). The predicted starting time by cranking at the third rotational speed N3 is the third time T3 (T2 < T3). Thus, by making the starting rotational speed at the time of shifting to the parallel mode larger than the starting rotational speed at the time of shifting to the series mode, the predicted starting time of the engine 1 at the time of shifting to the parallel mode becomes shorter than that at the time of shifting to the series mode.

[0034] In principle, the control device 10 sets the starting rotational speed of the engine 1 according to the state of the EV priority mode. However, when the following conditions are satisfied, exceptionally, the starting rotational speed of the engine 1 is set regardless of the state of the EV priority mode. ·Condition 1. When the remaining fuel amount of the engine 1 is less than or equal to a predetermined amount ·Condition 2. When the stop time of the engine 1 is longer than or equal to a predetermined time (when fuel deterioration is a concern)

[0035] If condition 1 is met, even if the EV priority mode is on, the control device 10 sets the starting speed of engine 1 to the same value as when the EV priority mode is off (when the EV priority mode is not set), even if the EV priority mode is on. In other words, reducing the starting speed of engine 1 would prolong the starting time of engine 1 and could potentially lead to a fuel shortage for engine 1, so the control is designed not to reduce the starting speed of engine 1. If we let the total fuel consumption in each of Figures 3(A) to (C) be F1, F2, and F3, their relative sizes are typically "F1 ≤ F2 ≤ F3". When engine 1 starts, fuel injection is performed while cranking, so the shorter the cranking time, the lower the fuel consumption when starting engine 1.

[0036] If condition 2 is met, even if the EV priority mode is off, the control device 10 sets the starting speed of engine 1 to the same value as when the EV priority mode is on (when the EV priority mode is set), which is the case when the EV priority mode is not set. In other words, by actively consuming fuel that is likely to deteriorate, the system makes it less likely to enter maintenance mode, and even if it does enter maintenance mode afterward, the system ensures that the maintenance mode ends in a relatively short time. The specified time in condition 2 is the idle time during which fuel deterioration is a concern (the time corresponding to the state in which the likelihood of entering maintenance mode is increasing), and is shorter than the fuel deterioration period, for example, several tens of hours to several weeks.

[0037] Furthermore, the control device 10 implements control to switch between the high-voltage battery 4 and the auxiliary battery 7 as power sources for starting the engine 1. When the State of Charge (SOC) of the auxiliary battery 7 is below a predetermined charge level, the control device 10 uses the power from the high-voltage battery 4 to start the engine 1. In this case, power is supplied from the high-voltage battery 4 to the generator 3, which is then driven to rotate.

[0038] On the other hand, the control device 10 starts the engine 1 using the power from the auxiliary battery 7 when the State of Charge (SOC) of the auxiliary battery 7 is above a predetermined charge level. In this case, the power from the auxiliary battery 7 is boosted by the booster 6 and supplied to the generator 3, which then rotates. In this way, by utilizing the power from the auxiliary battery 7, it becomes possible to start the engine 1 without consuming the power from the high-voltage battery 4. In other words, the amount of power that needs to be reserved in the high-voltage battery 4 during EV mode is reduced, and the EV driving range is expanded.

[0039] [4. Flowchart] Figure 4 is a flowchart for setting the starting speed of engine 1 when the engine starting conditions are met (when an engine start request is made) during EV mode. In step A1, it is determined whether the remaining fuel level of engine 1 is below a predetermined amount. If this condition is met, the process proceeds to step A10, where it is decided to drive the generator 3 using the high-voltage battery 4, and the process proceeds to step A11. In step A11, the starting speed is set to the normal starting speed (first rotation speed N1), and engine 1 is cranked. The expected starting time due to cranking is the first time T1.

[0040] Thus, if the fuel level of engine 1 is low, step A3, which determines the state of EV priority mode, is skipped, and it is decided to start engine 1 at the normal starting speed (first rotation speed N1). This makes it easier for engine 1 to start in a relatively short time, and the total fuel consumption tends to decrease. On the other hand, if the conditions of step A1 are not met, the system proceeds to step A2.

[0041] In step A2, it is determined whether the engine 1 has been stopped for a predetermined time or longer. If the conditions in step A2 are met, the process proceeds to step A4. From step A4 onward, as described later, the engine 1 is cranked with a starting speed set to at least less than the first rotational speed N1. In other words, if the engine 1 has not been operating for a long time and fuel degradation is a concern, step A3, which determines the state of EV priority mode, is skipped, and it is decided to set the starting speed of the engine 1 to less than the normal starting speed (first rotational speed N1). This promotes the consumption of fuel that is likely to degrade. If the conditions in step A2 are not met, the process proceeds to step A3.

[0042] In step A3, it is determined whether the EV priority mode is on (i.e., the EV priority mode is set). If this condition is met, the process proceeds to step A4; otherwise, it proceeds to step A10. In other words, if the EV priority mode is on, it is decided that the starting speed of engine 1 will be lower than the normal starting speed (first rotation speed N1), and if the EV priority mode is off, it is decided that engine 1 will be started at the normal starting speed (first rotation speed N1).

[0043] In step A4, it is determined whether the State of Charge (SOC) of the auxiliary battery 7 is above a predetermined charge level. If this condition is met, the process proceeds to step A5, where it is decided to use the auxiliary battery 7 to drive the generator 3, and then to step A7. On the other hand, if the condition in step A4 is not met, the process proceeds to step A6, where it is decided to use the high-voltage battery 4 to drive the generator 3, and then to step A7. This control promotes the use of the power stored in the auxiliary battery 7, and makes it easier to conserve the power in the high-voltage battery 4.

[0044] In step A7, it is determined whether the destination driving mode is parallel mode. If this condition is met (transition to parallel mode), the process proceeds to step A8, where the starting speed is set to a second speed N2, which is slightly lower than the first speed N1, and engine 1 is cranked. As a result, the expected starting time due to cranking is a second time T2, which is slightly longer than the first time T1.

[0045] If the conditions in step A7 are not met (when transitioning to series mode), the process proceeds to step A9. In step A9, the starting speed is set to a third speed N3, which is lower than the second speed N2, and engine 1 is cranked. As a result, the expected starting time due to cranking is the third time T3, which is longer than the second time T2.

[0046] Furthermore, if it is decided to drive the generator 3 using the auxiliary battery 7, the voltage boost by the booster 6 (the voltage supplied to the generator 3) may be different in step A8 and step A9. For example, the voltage boost during the transition to parallel mode (step A8) may be greater than the voltage boost during the transition to series mode (step A9). In this way, by making the voltage supplied to the generator 3 in step A8 higher than the voltage supplied to the generator 3 in step A9, the cranking torque supplied from the generator 3 to the engine 1 can be increased, and the starting time of the engine 1 may be shortened.

[0047] However, since the battery capacity of the auxiliary battery 7 is smaller than that of the high-voltage battery 4, increasing the voltage boost by the booster 6 and thus increasing power consumption will easily cause the SOC of the auxiliary battery 7 to decrease. Therefore, considering the need to maintain the SOC of the auxiliary battery 7 at an appropriate level, the voltage boost by the booster 6 may be made the same in step A8 and step A9, or the voltage boost by the booster 6 may be adjusted so that an appropriate cranking torque is obtained to start the engine 1.

[0048] [5. Effects] (1) The control device 10 of this embodiment is applied to a hybrid vehicle that comprises an engine 1 and a motor 2 as drive sources and a generator 3 (rotating electric machine) that cranks when starting the engine 1, and in which either an EV mode (a driving mode in which the vehicle is driven using the motor 2 with the engine 1 stopped) or an engine driving mode (a driving mode in which the vehicle is driven using at least the engine 1) can be selected as the driving mode.

[0049] This control device 10 includes an EV priority mode that can be used in conjunction with EV mode. When the EV priority mode is set (on), the conditions for transitioning from EV mode to engine driving mode are more favorable than when the EV priority mode is not set (off). It will get tougher Furthermore, as shown in Figures 3(A) to (C), the starting rotation speeds of the engine 1 by the generator 3 (second rotation speed N2, third rotation speed N3) when the EV priority mode is set are set to be lower than the starting rotation speed of the engine 1 (first rotation speed N1) when the EV priority mode is not set.

[0050] This configuration reduces the power consumption required for engine starting when the EV priority mode is on. Therefore, the power required for engine starting in EV mode can be reduced, expanding the EV driving range. However, with the above control, while power consumption is reduced, the engine starting time is extended. On the other hand, by turning off the EV priority mode, the effect of reducing engine starting time can be obtained instead of reducing power consumption. Therefore, the control device 10 of this embodiment can balance power consumption and engine starting time, which are in a trade-off relationship, and improve the overall driving feeling.

[0051] (2) The engine driving modes in the above embodiment include a hybrid mode in which engine 1 and motor 2 are used in combination. The hybrid mode includes a parallel mode in which the driving force of engine 1 and motor 2 is transmitted to the drive wheels, and a series mode in which the driving force of engine 1 is transmitted to parts other than the drive wheels and the driving force of motor 2 is transmitted to the drive wheels. Furthermore, as shown in Figures 3(A) to (C), when the EV priority mode is set, the starting speed of engine 1 when transitioning from EV mode to parallel mode (second rotation speed N2) is set to be higher than the starting speed of engine 1 when transitioning from EV mode to series mode (third rotation speed N3).

[0052] This configuration allows the engine start time (second time T2) when transitioning from EV mode to parallel mode to be shorter than the engine start time (third time T3) when transitioning from EV mode to series mode. This allows, for example, the clutch 5 engagement operation performed after engine start in parallel mode to begin earlier, expanding the EV driving range in EV mode while improving driving performance in parallel mode. In addition, since the time it takes for the engine 1's driving force to be transmitted to the drive wheels is shortened, the acceleration response when transitioning from EV mode to parallel mode due to strong pressing of the accelerator pedal can be improved. Therefore, the driving feel can be improved.

[0053] (3) In the above embodiment, if the remaining fuel level of engine 1 is below a predetermined amount, the starting speed of engine 1 is set to the same value as the starting speed of engine 1 when EV priority mode is not set (first rotation speed N1), regardless of the setting of EV priority mode. With this control, the starting time can be shortened compared to when the starting speed of engine 1 is reduced, and the total fuel consumption can be reduced. Therefore, it is possible to prevent engine stalling due to insufficient fuel. Note that if the starting speed of engine 1 is increased when the remaining fuel level of engine 1 is below a predetermined amount when EV priority mode is set, compared to when the remaining fuel level of engine 1 is above a predetermined amount when EV priority mode is set, it is not necessary to set the first rotation speed to N1, but setting it to the first rotation speed N1 can further enhance the effect.

[0054] (4) In the above embodiment, if the engine 1 is stopped for a predetermined time or longer, the starting speed of the engine 1 is set to the same value as the starting speed of the engine 1 when the EV priority mode is set (first rotation speed N1, second rotation speed N2), regardless of the setting of the EV priority mode. This control allows for the active consumption of fuel that is likely to deteriorate, preventing failure and deterioration of the engine 1 and fuel system components (fuel tank, fuel piping, fuel filter, fuel pump, etc.). Furthermore, by reducing the amount of fuel that is likely to deteriorate, it becomes less likely to enter maintenance mode, and even if maintenance mode is entered, the time required for it can be shortened. Note that if the starting speed of the engine 1 is reduced when the engine 1 is stopped for a predetermined time or longer when the EV priority mode is not set, compared to when the engine 1 is stopped for less than a predetermined time when the EV priority mode is not set, it is not necessary to set the first rotation speed to N1 and the second rotation speed to N2, but the effect can be further enhanced by setting the first rotation speed to N1 and the second rotation speed to N2.

[0055] (5) The above-mentioned generator 3 (rotating electric machine) has the function of generating electricity by being rotated by the engine 1 in series mode. The above-mentioned hybrid vehicle also includes a high-voltage battery 4 that supplies power to the motor 2 and generator 3, and an auxiliary battery 7 that supplies power to the generator 3 and auxiliary equipment. The above-mentioned control device 10 starts the engine 1 by supplying power from the high-voltage battery 4 to the generator 3 when the charge level of the auxiliary battery 7 is below a predetermined charge level. On the other hand, when the charge level of the auxiliary battery 7 is above a predetermined charge level, the control device 10 starts the engine 1 by supplying power from the auxiliary battery 7 to the generator 3 instead of the high-voltage battery 4.

[0056] In this way, when there is surplus power in the auxiliary battery 7, using the auxiliary battery 7 to start the engine 1 allows the power of the high-voltage battery 4 to be conserved, thereby expanding the EV driving range. Furthermore, when starting the engine 1 using the auxiliary battery 7, the engine 1 is cranked at a lower starting speed (second rotation speed N2, third rotation speed N3) than the normal starting speed (first rotation speed N1), which suppresses the power consumption of the auxiliary battery 7 and makes it less likely for the State of Charge (SOC) of the auxiliary battery 7 to decrease.

[0057] [6. Others] The above embodiments are merely illustrative examples, and there is no intention to exclude various modifications or applications of techniques not explicitly stated in these embodiments. Each configuration of these embodiments can be modified in various ways without departing from their intended purpose. Furthermore, each configuration of these embodiments can be selected or combined as needed.

[0058] In the above embodiment, a device configuration in which the generator 3 cranks and starts the engine 1 was illustrated, but a starter motor may be used instead of the generator 3. A hybrid vehicle only needs to be equipped with a rotating electric motor that cranks when starting the engine 1. In such a hybrid vehicle, the same effects as in the above embodiment can be obtained by setting the starting rotation speed of the engine 1 when the EV priority mode is set to be lower than the starting rotation speed when the EV priority mode is not set. [Industrial applicability]

[0059] This invention is applicable to the manufacturing industry of control devices for hybrid vehicles, and to the manufacturing industry of hybrid vehicles to which such control devices are applied. [Explanation of Symbols]

[0060] 1 Engine 2 motors 3. Generator (rotating electric machine) 4 High-voltage battery 5. Clutch 6. Step-up transformer 7. Auxiliary battery 10 Control device 11 EV Priority Mode Switch 12. Fuel sensor N0 Starting completion RPM N1 First rotation speed N2 Second rotation speed N3 Third rotation speed T1 first time T2 second time T3 Third Hour

Claims

1. A control device for a hybrid vehicle comprising an engine and a motor as drive sources, and a rotating electric machine for cranking the engine when starting the engine, wherein the control device selects either an EV mode in which the vehicle is driven using the motor with the engine stopped, or an engine driving mode in which the vehicle is driven using at least the engine, The system includes an EV priority mode that can be used in conjunction with the EV mode, and when the EV priority mode is set, the conditions for transitioning from the EV mode to the engine driving mode become stricter than when the EV priority mode is not set. When the EV priority mode is set, the starting rotation speed, which is the cranking speed of the engine by the rotating electric machine when starting the engine, is set to be lower than the starting rotation speed when the EV priority mode is not set. The engine driving mode includes a hybrid mode in which the engine and the motor are used in combination. The aforementioned hybrid mode includes a parallel mode in which the driving force of the engine and the motor is transmitted to the drive wheels, and a series mode in which the driving force of the engine is transmitted to a wheel other than the drive wheels and the driving force of the motor is transmitted to the drive wheels. When the EV priority mode is set, the starting rotation speed when transitioning from the EV mode to the parallel mode is set to be greater than the starting rotation speed when transitioning from the EV mode to the series mode. A control device for a hybrid vehicle, characterized by the following features.

2. When the remaining fuel level of the engine is below a predetermined amount, the starting speed when the EV priority mode is set is set to the same value as the starting speed when the EV priority mode is not set. A control device for a hybrid vehicle according to claim 1, characterized in that

3. If the engine is stopped for a predetermined time or longer, the starting speed when the EV priority mode is not set is set to the same value as the starting speed when the EV priority mode is set. A control device for a hybrid vehicle according to claim 1, characterized in that

4. The aforementioned rotating electric machine is driven to generate electricity by the engine in the series mode, The hybrid vehicle comprises a high-voltage battery that supplies power to the motor and the rotating electric machine, and an auxiliary battery that supplies power to the rotating electric machine and auxiliary equipment. If the charge level of the auxiliary battery is below a predetermined charge level, power is supplied from the high-voltage battery to the rotating electric machine to start the engine. When the charge level of the auxiliary battery is equal to or greater than the predetermined charge level, power is supplied from the auxiliary battery to the rotating electric machine to start the engine. A control device for a hybrid vehicle according to claim 1, characterized in that

5. The hybrid vehicle is equipped with a booster that controls the boost range of the power of the auxiliary battery, In the case where power is supplied from the auxiliary battery to the rotating electric machine to start the engine, the voltage boost when transitioning from the EV mode to the parallel mode is set to be greater than the voltage boost when transitioning from the EV mode to the series mode. A control device for a hybrid vehicle according to claim 4, characterized in that

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