Control device for hybrid vehicle

Abstract

To provide a technique capable of improving the driving performance of a hybrid vehicle on an uphill road.SOLUTION: In a control device for a hybrid vehicle, a travel mode control unit 12 controls switching between a first travel mode in which an electric motor generates vehicle driving force using electric power supplied from a power storage device and an internal combustion engine is stopped, and a second travel mode in which the electric motor and the internal combustion engine generate vehicle driving force. A detection unit 18 detects an uphill road while the vehicle is traveling in the first travel mode. A determination unit 20 determines, when the uphill road is detected, whether the vehicle can travel on the uphill road in the first travel mode. The travel mode control unit 12 increases a target rotational speed of the electric motor when it is determined that the vehicle can travel on the uphill road in the first travel mode, and switches from the first travel mode to the second travel mode when it is determined that the vehicle cannot travel on the uphill road in the first travel mode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] Patent Document 1 discloses a driving control device for a hybrid vehicle. This technology estimates a uniform deceleration variation chart of deceleration or driving force based on road information, and calculates a first equal division time, which is the time from the start of deceleration control until the integrated value of deceleration or driving force is divided equally. Based on the road information, a non-uniform deceleration variation chart of deceleration or driving force is determined so that a second equal division time, which is the time from the start of deceleration control until the integrated value during non-uniform deceleration is divided equally, is shorter than the first equal division time. The vehicle deceleration is controlled based on the non-uniform deceleration variation chart, and the battery is charged based on the non-uniform deceleration variation chart. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-81358 Summary of the Invention [Problem to be solved by the invention]

[0004] There is room for improvement in hybrid vehicles' running performance on uphill roads.

[0005] An object of the present invention is to provide a technique that can improve the running performance of a hybrid vehicle on an uphill road. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present invention provides a control device for a hybrid vehicle, the control device including: a driving mode control unit that controls switching between a first driving mode in which an electric motor generates vehicle driving force using power supplied from a power storage device and an internal combustion engine is stopped, and a second driving mode in which both the electric motor and the internal combustion engine generate vehicle driving force, a detection unit that detects an uphill road while traveling in the first driving mode, and a determination unit that, when an uphill road is detected, determines whether traveling on the uphill road in the first driving mode is possible. The driving mode control unit increases the target rotation speed of the electric motor when it is determined that traveling on the uphill road in the first driving mode is possible, and switches from the first driving mode to the second driving mode when it is determined that traveling on the uphill road in the first driving mode is not possible. [Effects of the Invention]

[0007] According to the present invention, the driving performance of a hybrid vehicle on an uphill road can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a hybrid vehicle according to an embodiment; [Figure 2] 2 is a diagram showing a functional configuration of a part related to a running mode switching process in the ECU of FIG. 1. FIG. [Figure 3] 4 is a flowchart showing a process performed by the ECU in FIG. 1 regarding traveling on an uphill road. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 shows a schematic configuration of a hybrid electric vehicle (HEV) 1 according to an embodiment. The hybrid vehicle 1 includes an internal combustion engine 100, a first electric motor 110, a second electric motor 120, a power split device 130, a reduction gear 140, an electricity storage device 150, drive wheels 160, an ECU (Electronic Control Unit) 170, and an imaging unit 180.

[0010] The internal combustion engine 100, the first electric motor 110, and the second electric motor 120 are connected to a power split device 130. The hybrid vehicle 1 runs using driving force from at least one of the internal combustion engine 100 and the second electric motor 120. The driving force generated by the internal combustion engine 100 is split into two paths by the power split device 130. One path is transmitted to the drive wheels 160 via a reduction gear 140, and the other path is transmitted to the first electric motor 110. When the hybrid vehicle 1 is running, the power split device 130 functions as a transmission.

[0011] The first electric motor 110 is capable of generating electricity by receiving the driving force of the internal combustion engine 100 that is split by the power split device 130. The power storage device 150 is charged based on the electric power generated by the first electric motor 110.

[0012] The second electric motor 120 generates driving force using at least one of the electric power stored in the power storage device 150 and the electric power generated by the first electric motor 110. The driving force of the second electric motor 120 is then transmitted to the driving wheels 160 via the reduction gear 140.

[0013] When braking the vehicle, the second electric motor 120 is driven by the drive wheels 160 via the reduction gear 140, and the second electric motor 120 operates as a generator. This causes the second electric motor 120 to operate as a regenerative brake that converts braking energy into electric power. The power storage device 150 is charged based on the electric power generated by the second electric motor 120.

[0014] The power storage device 150 is a rechargeable DC power supply and includes a secondary battery. The power storage device 150 stores electric power to drive the second electric motor 120 and can also be called a traction battery. The power storage device 150 stores electric power generated by the first electric motor 110 and the second electric motor 120.

[0015] Imaging unit 180 is an in-vehicle camera that periodically captures images of the area ahead of hybrid vehicle 1 at a predetermined frame rate and sends data of the captured images to ECU 170. The captured images include an image of the road ahead.

[0016] As will be described later, the ECU 170 switches the driving mode between the EV mode and the HV mode based on various signals supplied from various sensors (not shown). The various sensors include, for example, an accelerator position sensor and a vehicle speed sensor. The EV mode can also be called the first driving mode. The HV mode can also be called the second driving mode. In the EV mode, the second electric motor 120 generates vehicle driving force using electric power supplied from the power storage device 150, and the internal combustion engine 100 is stopped. In other words, in the EV mode, the hybrid vehicle 1 runs using vehicle driving force generated only by the second electric motor 120. This running can also be called EV running. In the HV mode, the second electric motor 120 and the internal combustion engine 100 each generate vehicle driving force. This running can also be called HV running.

[0017] The ECU 170 derives a required torque to be output to the drive wheels 160 based on the accelerator opening and the vehicle speed, and controls the operations of the internal combustion engine 100, the first electric motor 110, and the second electric motor 120 according to the driving mode so that the hybrid vehicle 1 travels in accordance with a driving force request corresponding to this required torque. The ECU 170 corresponds to a control device of the hybrid vehicle 1.

[0018] The ECU 170 is configured by, for example, a hybrid ECU, an engine ECU, a motor ECU, a battery ECU, etc., and these ECUs are connected to each other so that they can communicate with each other. The configuration of the ECU 170 can be realized by the cooperation of hardware resources and software resources. The ECU 170 has, as hardware resources, a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), etc. The ROM stores, as software resources, various control programs and maps referenced when executing these various control programs. The CPU executes arithmetic processing based on the various control programs and maps stored in the ROM. The RAM is a memory that temporarily stores the results of calculations by the CPU, data input from each sensor, etc.

[0019] Fig. 2 shows a functional configuration of a portion related to a driving mode switching process in ECU 170 in Fig. 1. ECU 170 has a derivation unit 10, a driving mode control unit 12, an electric motor control unit 14, an internal combustion engine control unit 16, a detection unit 18, and a determination unit 20.

[0020] The derivation unit 10 derives the SOC (State Of Charge) of the power storage device 150 based on the voltage and current output from the power storage device 150. The SOC is the ratio of the amount of stored electricity to the total capacity of the power storage device 150, and can also be called the remaining capacity. Various known methods can be used to derive the SOC. The voltage and current are detected by a voltage sensor and a current sensor (not shown).

[0021] The driving mode control unit 12 controls switching between the EV mode and the HV mode based on the SOC derived by the derivation unit 10 and various signals supplied from various sensors. Switching between the EV mode and the HV mode is basically performed according to a driving force source map for selecting a driving mode based on the vehicle speed and required torque. The area lower than a predetermined line in the driving force source map in terms of vehicle speed and required torque is defined as the EV driving region, and the area higher than the predetermined line in terms of vehicle speed and required torque is defined as the HV driving region.

[0022] If the vehicle speed and required torque are within the EV driving range in the driving force source map and the SOC of the power storage device 150 is equal to or greater than a predetermined level, the driving mode control unit 12 sets the vehicle to the EV mode. When the vehicle speed and required torque shift from the EV driving range to the HV driving range in the driving force source map due to a request for vehicle acceleration from the driver or the like in the EV mode, the driving mode control unit 12 switches the vehicle to the HV mode. Switching to the HV mode corresponds to starting the internal combustion engine 100.

[0023] When a predetermined condition related to the state quantity of power storage device 150 is satisfied in EV mode, such as SOC being less than a predetermined amount, running mode control unit 12 switches to HV mode without using the driving force source map.

[0024] In the HV mode, when the driver operates a driving mode selection switch located near the driver's seat and selects the EV driving mode as the driving mode, the driving mode control unit 12 may switch to the EV mode if a predetermined switching condition is satisfied.

[0025] In each of the EV mode and the HV mode, the driving mode control unit 12 derives a target rotation speed for the second electric motor 120 based on signals from the various sensors, the driving conditions, the accelerator opening, etc., and sends a command for the derived target rotation speed to the electric motor control unit 14. The electric motor control unit 14 controls the voltage and frequency of the drive signal supplied to the second electric motor 120 so that the rotation speed of the second electric motor 120 approaches the target rotation speed.

[0026] In the HV mode, the driving mode control unit 12 derives a target rotation speed of the internal combustion engine 100 based on signals from the various sensors, the driving conditions, the accelerator opening, etc., and sends a command for the derived target rotation speed to the internal combustion engine control unit 16. The internal combustion engine control unit 16 controls the internal combustion engine 100 so that the rotation speed of the internal combustion engine 100 approaches the target rotation speed.

[0027] Various known control methods can be used for the control of switching between the EV mode and the HV mode, the control in the EV mode, and the control in the HV mode.

[0028] The detection unit 18 detects an uphill road while the hybrid vehicle 1 is traveling in EV mode. For example, the detection unit 18 obtains an acceleration determination value by subtracting an acceleration derived from the actual vehicle speed from an acceleration that should be generated on a flat road, which is derived from the accelerator pedal position, and detects that the vehicle is traveling on an uphill road if the acceleration determination value is greater than a predetermined determination threshold. The determination threshold can be determined appropriately through experiments or simulations. Known techniques can be used to detect an uphill road based on acceleration.

[0029] When detecting an uphill road, the detection unit 18 acquires the gradient of the uphill road based on the acceleration determination value. The larger the acceleration determination value, the larger the gradient of the uphill road that the detection unit 18 derives.

[0030] When the detection unit 18 detects an uphill road, it obtains the length of the uphill road based on the image of the area in front of the vehicle captured by the imaging unit 180. The detection unit 18 performs image recognition on the captured image to derive an estimate of the length of the uphill road. Known techniques can be used to obtain the length of the uphill road based on the captured image. When the detection unit 18 detects an uphill road, it sends information on the gradient and length of the uphill road to the determination unit 20.

[0031] The detection unit 18 may detect an uphill road and obtain the gradient and length of the uphill road based on road information from a navigation system (not shown) and the current position. The detection unit 18 may also detect an uphill road and obtain the gradient and length of the uphill road using other known techniques.

[0032] When an uphill road is detected by the detection unit 18, the determination unit 20 determines whether or not the hybrid vehicle 1 can travel uphill in EV mode, based on the received gradient and length of the uphill road and the SOC received from the derivation unit 10. The ability to travel uphill in EV mode means that the hybrid vehicle 1 can travel uphill to the end of the uphill road using the vehicle driving force generated only by the second electric motor 120.

[0033] The determination unit 20 estimates the driving time to the end of the uphill road based on, for example, the gradient and length of the uphill road, the speed, acceleration, and vehicle weight of the hybrid vehicle 1, etc. The determination unit 20 estimates the time that can be driven in EV mode based on the SOC. The determination unit 20 may estimate the time that can be driven if the target rotation speed of the second electric motor 120, which will be described later, is increased. Known techniques can be used to derive the driving time on the uphill road and the available driving time. If the estimated driving time is equal to or shorter than the estimated available driving time, the determination unit 20 determines that the vehicle can be driven on the uphill road in EV mode. If the estimated driving time is longer than the estimated available driving time, the determination unit 20 determines that the vehicle cannot be driven on the uphill road in EV mode. Note that the determination unit 20 may use other known techniques to determine whether the vehicle can be driven on the uphill road in EV mode.

[0034] When the determination unit 20 determines that the vehicle can travel on an uphill road in EV mode, it determines whether an increase in the target rotation speed is necessary. For example, the determination unit 20 determines that an increase in the target rotation speed is necessary when the gradient of the uphill road is equal to or greater than a predetermined gradient threshold. The determination unit 20 determines that an increase in the target rotation speed is not necessary when the gradient of the uphill road is less than the gradient threshold. The gradient threshold can be determined appropriately through experiments or simulations. The determination unit 20 sends the determination result to the driving mode control unit 12. Note that the detection unit 18 may detect an uphill road only when the gradient of the uphill road is equal to or greater than a predetermined gradient threshold. In this case, the determination unit 20 does not need to perform a process of determining whether an increase in the target rotation speed is necessary based on the gradient of the uphill road.

[0035] When the determination unit 20 determines that the vehicle can travel uphill in EV mode and that the target rotation speed needs to be increased, the driving mode control unit 12 maintains the EV mode and increases the target rotation speed of the second electric motor 120 above the target rotation speed determined from the accelerator pedal position. This increases the rotation speed of the second electric motor 120, and therefore the torque of the second electric motor 120 also increases above the torque determined from the accelerator pedal position. This makes it possible to generate a vehicle driving force greater than the required driving force determined from the current accelerator pedal position. This makes it easier to travel uphill using only the driving force of the second electric motor 120 without starting the internal combustion engine 100.

[0036] In a comparative example in which the target rotation speed is not automatically increased on an uphill road, it is assumed that when the vehicle enters an uphill road while traveling in EV mode, the speed will continue to decrease if the accelerator pedal is depressed to a constant amount. The driver, recognizing the decrease in speed, will increase the accelerator pedal depression, but if the accelerator pedal depression amount is too large, the required driving force will become too large, causing the vehicle to switch to HV mode and start the internal combustion engine 100. This will likely result in a decrease in fuel economy.

[0037] In contrast, in the embodiment, the rotation speed of the second electric motor 120 is automatically increased on an uphill road, so the speed is less likely to decrease and the driver is less likely to further depress the accelerator pedal, which prevents the internal combustion engine 100 from starting. This improves fuel efficiency and reduces vibration of the vehicle body. Furthermore, because the target rotation speed is increased only on an uphill road, the EV driving time can be extended.

[0038] When the driving mode control unit 12 increases the target rotation speed of the second electric motor 120 in response to the determination result by the determination unit 20, if the detection unit 18 no longer detects an uphill road, it stops increasing the target rotation speed and controls it to the target rotation speed determined from the accelerator pedal position. In other words, when the vehicle reaches the end of the uphill road, normal control is resumed. This makes it possible to increase the target rotation speed only for a necessary period, thereby extending the EV driving time.

[0039] Even if the determination unit 20 determines that the vehicle can travel uphill in EV mode, if the determination unit 20 determines that an increase in the target rotation speed is not necessary, the driving mode control unit 12 maintains normal control in EV mode and controls the vehicle to the target rotation speed determined from the accelerator pedal position. In other words, in this case, control to automatically increase the target rotation speed of the second electric motor 120 is not executed. If the gradient of the uphill road is less than the gradient threshold, the decrease in vehicle speed due to the uphill road is relatively small, and the vehicle can travel uphill without increasing the target rotation speed. This allows for longer EV driving time.

[0040] When the determination unit 20 determines that the vehicle cannot travel uphill in EV mode, the driving mode control unit 12 switches the vehicle to HV mode and starts the internal combustion engine 100. The internal combustion engine 100 is started when the vehicle enters an uphill road. This allows the vehicle to quickly secure the driving force necessary to travel uphill. It also prevents the internal combustion engine 100 from being switched to HV mode and started due to a drop in SOC while traveling uphill. This prevents sluggish acceleration when the internal combustion engine 100 is started while traveling uphill.

[0041] According to the embodiment, the running performance of the hybrid vehicle 1 on an uphill road can be improved.

[0042] Next, a description will be given of the overall operation of the hybrid vehicle 1 configured as described above. Figure 3 is a flowchart showing the processing related to traveling on an uphill road in the ECU 170 of Figure 1. The processing of Figure 3 is executed repeatedly.

[0043] If the vehicle is in EV mode (Y in S10), and the detection unit 18 detects an uphill road (Y in S12), the detection unit 18 estimates the gradient of the uphill road (S14), estimates the length of the uphill road (S16), and derives the time during which the vehicle can travel in EV mode (S18). If the vehicle can travel on an uphill road in EV mode (Y in S20), and if an increase in the target rotation speed is necessary (Y in S22), the traveling mode control unit 12 increases the target rotation speed of the second electric motor 120 (S24), and the process ends. If an increase in the target rotation speed is not necessary (N in S22), the process ends. If the vehicle cannot travel on an uphill road in EV mode in S20 (N in S20), the traveling mode control unit 12 starts the internal combustion engine 100 (S26), and the process ends.

[0044] In S10, if the vehicle is not in the EV mode (N in S10), the process ends. In S12, if an uphill road is not detected (N in S12), the process ends.

[0045] The present invention has been described above based on the embodiments. However, the embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention.

[0046] For example, the processes of S14, S16, S18, S20, and S26 in FIG. 3 may be omitted. In this case, when an uphill road is detected (Y in S12), the process of S22 is executed. Alternatively, instead of the process of S22, the determination unit 20 may determine whether the target rotation speed of the second electric motor 120 can be increased based on the SOC or the like. For example, the determination unit 20 may determine that the target rotation speed can be increased if the power consumption of the second electric motor 120 when the target rotation speed is increased is equal to or less than the discharge allowable power of the power storage device 150. The determination unit 20 may determine that the target rotation speed cannot be increased if the power consumption of the second electric motor 120 when the target rotation speed is increased is greater than the discharge allowable power of the power storage device 150. The discharge allowable power is derived from the SOC and temperature of the power storage device 150 using a known technique. If it is determined that the target rotation speed can be increased, the running mode control unit 12 may increase the target rotation speed of the second electric motor 120. If it is determined that the target rotation speed cannot be increased, the traveling mode control unit 12 may not increase the target rotation speed of the second electric motor 120. Alternatively, in addition to determining whether the target rotation speed of the second electric motor 120 can be increased, the determination process of S22 may be used in combination, and the traveling mode control unit 12 may increase the target rotation speed of the second electric motor 120 only if it is determined that an increase in the target rotation speed is necessary and that an increase in the target rotation speed is possible. This modification simplifies the process and makes it easier to climb an uphill road using only the driving force of the second electric motor 120.

[0047] Furthermore, the configuration of the power transmission path between the power source such as the internal combustion engine 100 and the drive wheels 160 is not limited to the example shown in Fig. 1. A stepped transmission or a clutch may be provided in the power transmission path. Hybrid vehicle 1 may be a plug-in hybrid electric vehicle (PHEV) in which power storage device 150 can be charged by an external power supply. [Explanation of symbols]

[0048] 1... hybrid vehicle, 10... derivation unit, 12... driving mode control unit, 14... electric motor control unit, 16... internal combustion engine control unit, 18... detection unit, 20... determination unit, 100... internal combustion engine, 110... first electric motor, 120... second electric motor, 150... power storage device, 170... ECU, 180... imaging unit

Claims

[Claim 1] a driving mode control unit that controls switching between a first driving mode in which the electric motor generates vehicle driving force using electric power supplied from the power storage device and the internal combustion engine is stopped, and a second driving mode in which the electric motor and the internal combustion engine generate vehicle driving force; a detection unit that detects an uphill road while traveling in the first traveling mode; a determination unit that, when an uphill road is detected, determines whether the vehicle can travel on the uphill road in the first traveling mode, The driving mode control unit When it is determined that the vehicle can travel uphill in the first traveling mode, the target rotation speed of the electric motor is increased, When it is determined that the vehicle cannot travel on an uphill road in the first traveling mode, the mode is switched from the first traveling mode to the second traveling mode. A control device for a hybrid vehicle.

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