Electric vehicle control device

Abstract

To suppress a feeling of strangeness of a driver due to switching between a first mode and a second mode.SOLUTION: A running mode of an electric vehicle that is selected by a driver includes a first mode in which a vehicle driving device is controlled in accordance with first required driving force based on an accelerator aperture and a second mode in which the vehicle driving device is controlled in accordance with second required driving force based on the accelerator aperture and a gear stage in accordance with operation of a simulation speed-change operating tool. A control device is configured to be able to execute first forcible reject for forcibly switching the second mode to the first mode in order to secure a cruising distance when SOC decreases and second forcible reject for forcibly switching the second mode to the first mode in order to protect hardware of the electric vehicle. When executing the first forcible reject, the control device changes torque from torque required in the second mode to torque required in the first mode, at a change rate of torque which is lower than when executing the second forcible reject.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a control device for an electric vehicle. [Background technology]

[0002] Patent Document 1 discloses an electric vehicle that can switch between an MT mode, in which the electric motor is controlled with torque characteristics similar to those of a manual transmission (MT) vehicle having an internal combustion engine, and an EV mode, in which the electric motor is controlled with normal torque characteristics. When the driving mode is changed, the control device of this electric vehicle controls the motor torque so that it gradually changes from the motor torque calculated in the driving mode before the change to the motor torque calculated in the driving mode after the change. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-035224 Summary of the Invention [Problem to be solved by the invention]

[0004] The technique described in Patent Document 1 can prevent vehicle behavior from being disrupted by a step in motor torque (driving force) that is not intended by the driver when switching between EV mode and MT mode. However, with a technique that simply gradually changes the motor torque during the drive mode change, the more gradual the change in motor torque, the longer it takes to switch the drive mode. This can cause the driver to feel uncomfortable.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a control device for an electric vehicle that can suppress the discomfort felt by the driver due to switching between a first mode (EV mode) and a second mode (simulated manual shift mode). [Means for solving the problem]

[0006] A control device for an electric vehicle according to the present disclosure controls an electric vehicle equipped with a vehicle drive device including an electric motor and a simulated gear change operating device operated by a driver for simulated gear changes. The driving modes of the electric vehicle selected by the driver include a first mode in which the vehicle drive device is controlled according to a first required driving force based on an accelerator pedal position, and a second mode in which the vehicle drive device is controlled according to a second required driving force based on an accelerator pedal position and a gear position corresponding to operation of the simulated gear change operating device. When switching between the first mode and the second mode, the control device allows the switching to be performed when the difference in driving force before and after the switching is equal to or less than a threshold value. A control device for an electric vehicle according to another aspect of the present disclosure controls an electric vehicle including a vehicle drive device including an electric motor and a simulated gear change operating device operated by a driver for simulated gear changes. The driving modes of the electric vehicle selected by the driver include a first mode in which the vehicle drive device is controlled according to a first required drive force based on an accelerator pedal position, and a second mode in which the vehicle drive device is controlled according to a second required drive force based on an accelerator pedal position and a gear position corresponding to operation of the simulated gear change operating device. The control device is configured to be able to execute a first forced reject that forcibly switches from the second mode to the first mode when the SOC drops in order to ensure range, and a second forced reject that forcibly switches from the second mode to the first mode in order to protect the hardware of the electric vehicle. When executing the first forced reject, the control device changes the torque from the required torque in the second mode to the required torque in the first mode at a lower torque change rate than when executing the second forced reject. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to suppress the discomfort felt by the driver due to switching between the first mode and the second mode. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram schematically illustrating a configuration of an electric vehicle according to an embodiment. [Figure 2] 4 is a diagram showing the driving force characteristics of an electric vehicle in an EV mode and a simulated MT mode. FIG. [Figure 3] 4 is a flowchart showing a process related to switching of a driving mode according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0010] 1. Electric vehicle configuration FIG. 1 is a diagram schematically illustrating the configuration of an electric vehicle 10 according to an embodiment. As shown in FIG. 1, the electric vehicle 10 is equipped with a "vehicle drive device" including an electric motor 2. An output shaft 3 of the electric motor 2 is connected to one end of a propeller shaft (or "propeller shaft") 5 via a gear mechanism 4. The propeller shaft 5 is provided with a rotational speed sensor 40 for detecting its rotational speed (propeller shaft rotational speed Np). The propeller shaft rotational speed Np corresponds to the output shaft rotational speed of the "vehicle drive device." The other end of the propeller shaft 5 is connected to a drive shaft 7 via a differential gear 6. The electric vehicle 10 is equipped with drive wheels 8 and driven wheels 12. The drive wheels 8 are provided at both ends of the drive shaft 7. Each wheel 8, 12 is equipped with a wheel speed sensor 30. In FIG. 1, only the wheel speed sensor 30 for the right rear wheel is illustrated as a representative example. The wheel speed sensor 30 is also used as a vehicle speed sensor for the electric vehicle 10.

[0011] The electric vehicle 10 includes a battery 14 and an inverter 16. The battery 14 stores electric energy for driving the electric motor 2. That is, the electric vehicle 10 is, for example, a battery electric vehicle (BEV) that runs on the electric energy stored in the battery 14. The inverter 16 converts DC power input from the battery 14 during acceleration into drive power for the electric motor 2. The inverter 16 also converts regenerative power input from the electric motor 2 during deceleration into DC power, which charges the battery 14. Note that the "electric vehicle" according to the present disclosure may be any vehicle that includes at least an electric motor as a vehicle drive device, and may be, for example, a hybrid electric vehicle (HEV) or a fuel cell electric vehicle (FCEV) that has a mode in which it runs using only the drive power of the electric motor.

[0012] The electric vehicle 10 is equipped with an accelerator pedal 22 for the driver to input an acceleration request to the electric vehicle 10, and a brake pedal 24 for inputting a braking request. The accelerator pedal 22 is provided with an accelerator position sensor 32 for detecting the accelerator opening amount. In addition, the brake pedal 24 is provided with a brake position sensor 34 for detecting the amount of brake depression.

[0013] The electric vehicle 10 further includes a paddle-type sequential shifter (or simply, a paddle shifter) 26, but does not include a transmission that is included in a manual transmission (MT) vehicle. In other words, the paddle shifter 26 is a dummy that is different from an actual paddle shifter and is an example of a "simulated gear change operating device" operated by the driver for a "simulated gear change" described below. The paddle shifter 26 allows the driver to select a gear for the simulated gear change (one of multiple simulated gears). The paddle shifter 26 is attached to the steering wheel. The paddle shifter 26 includes an upshift switch 26u and a downshift switch 26d that determine the operating position. The upshift switch 26u outputs an upshift signal, and the downshift switch 26d outputs a downshift signal. Note that the "simulated gear change operating device" according to the present disclosure may be another type of sequential shifter, such as a lever-type, or may be a combination of an H-type shifter and a clutch pedal.

[0014] The electric vehicle 10 is equipped with a mode selection device 42. The mode selection device 42 is a switch that selects the driving mode of the electric vehicle 10. The driving modes of the electric vehicle 10 include, for example, an EV mode and a simulated manual transmission mode (simulated MT mode). The EV mode (first mode) is a control mode that changes the output of the electric motor 2 in response to the operation of the accelerator pedal 22, regardless of the operating position of the paddle shifters 26. The simulated MT mode (second mode) is a control mode for driving the electric vehicle 10 as if it were a manual transmission vehicle, and is programmed to change the output characteristics of the electric motor 2 in response to the operation of the accelerator pedal 22 in response to the operating position of the paddle shifters 26.

[0015] The electric vehicle 10 is equipped with a control device 50. Each sensor and device to be controlled mounted on the electric vehicle 10 is connected to the control device 50 via an information and communication network. The control device 50 is, for example, an electronic control unit (ECU) mounted on the electric vehicle 10. The control device 50 may be a combination of multiple ECUs. The control device 50 is equipped with an interface 52, a memory 54, and a processor 56. The processor 56 reads and executes programs and data from the memory 54, and generates control signals based on signals acquired from each of the above-mentioned sensors.

[0016] 2. Process for switching driving modes As described above, the driving modes of the electric vehicle 10 include the EV mode and the simulated MT mode. FIG. 2 is a diagram showing the driving force characteristics of the electric vehicle 10 in each of the EV mode and the simulated MT mode. The vertical axis of FIG. 2 is the propeller shaft torque Tp, and the horizontal axis is the propeller shaft rotation speed Np. The propeller shaft torque Tp corresponds to the output torque of the propeller shaft 5, i.e., the output shaft torque of the "vehicle drive device." Note that the propeller shaft torque Tp correlates with the driving force of the electric vehicle 10, and the propeller shaft rotation speed Np correlates with the vehicle speed.

[0017] In FIG. 2, the characteristic line Lev_wot shows the characteristics of the propeller shaft torque Tp obtained when the accelerator pedal 22 is fully opened by the driver while the EV mode is selected. The characteristic line Lev_min is obtained when the accelerator pedal 22 is fully closed while the EV mode is selected. On the other hand, the characteristic line Lmt_wot is obtained when each gear (e.g., first to sixth gears) is selected while the accelerator pedal 22 is fully opened while the simulated MT mode is selected. The characteristic line Lmt_min is obtained when each gear is selected while the accelerator pedal 22 is fully closed while the simulated MT mode is selected.

[0018] The control device 50 controls the inverter 16 so that the propeller shaft torque Tp generated by the electric motor 2 becomes the required propeller shaft torque (or simply required torque) Tpr. For this torque control, the control device 50 calculates the required torque Tpr for each of the EV mode and the simulated MT mode as follows:

[0019] That is, the required torque Tpr_ev in EV mode (corresponding to an example of the "first required driving force" according to the present disclosure) is calculated based on the accelerator opening and rotation speed information (for example, the propeller shaft rotation speed Np) of the electric vehicle 10. The required torque Tpr_ev is calculated as a value within the area surrounded by the two characteristic lines Lev_wot and Lev_min in FIG.

[0020] On the other hand, the required torque Tpr_mt in the simulated MT mode (corresponding to an example of the "second required driving force" according to the present disclosure) is calculated based on the accelerator opening, the propeller shaft rotation speed Np, and the gear selected by operating the paddle shifter 26. The required torque Tpr_mt for each gear is calculated as a value within the region sandwiched between the two characteristic lines Lmt_wot and Lmt_min in FIG. 2.

[0021] When switching between EV mode and MT mode, a step in the propeller shaft torque Tp (driving force) may occur unintentionally by the driver. More specifically, as can be seen from Figure 2, a higher propeller shaft torque Tp can be generated in EV mode compared to simulated MT mode. Therefore, as illustrated in Figure 2, a large torque step may occur when switching modes. In addition, such a torque step occurs more noticeably when simulating a small-displacement MT vehicle in an electric vehicle equipped with a high-output electric motor. The occurrence of a torque step leads to erratic vehicle behavior.

[0022] The torque step described above can be suppressed by performing a process (smoothing process) that gradually changes the propeller shaft torque Tp during a drive mode change. However, with smoothing process, the more gradually the change in the propeller shaft torque Tp during a drive mode change, the longer the time required to switch the drive mode. This can lead to a sense of discomfort for the driver. Furthermore, if the propeller shaft torque Tp is gradually changed by smoothing process during a drive mode change, the driver's operation of the accelerator pedal 22 and the brake pedal 24 is less likely to be reflected in the vehicle behavior. This, too, can cause the driver to feel uncomfortable.

[0023] In view of the above-mentioned problems, in this embodiment, when switching between the EV mode and the simulated MT mode, the control device 50 permits the execution of the switching when the difference ΔTpr in the required torque Tpr before and after the switching (i.e., the difference in driving force) is equal to or less than the threshold value TH. In addition, when the torque difference ΔTpr is greater than the threshold value TH, the control device 50 does not permit the switching.

[0024] 3 is a flowchart showing a process for switching the driving mode according to the embodiment. The process of this flowchart is repeatedly executed by the control device 50 while the system of the electric vehicle 10 is running.

[0025] In step S100, the control device 50 (processor 56) determines whether there is a request to switch the driving mode. Here, the mode switching request includes the following two types of requests. One is a request for "normal switching" based on the driver's operation of the mode selection device 42. The other is a request for forced switching from the simulated MT mode to the EV mode by forced rejection. The forced rejection is performed, for example, to protect the hardware of the electric vehicle 10 or to ensure the cruising distance when the SOC (State Of Charge) of the battery 14 is low.

[0026] If there is no mode switching request in step S100, the process proceeds to RETURN. On the other hand, if there is a mode switching request, the process proceeds to step S102.

[0027] In step S102, the control device 50 determines whether the current mode switching request is a normal switching request. If the current mode switching request is not a normal switching request, that is, if the current mode switching request is based on a forced reject, the process proceeds to step S104. On the other hand, if the current mode switching request is a normal switching request, the process proceeds to step S106.

[0028] In step S104, the control device 50 sets the torque change rate of the smoothing process during forced rejection (i.e., the time change rate of the required torque Tpr when changing from the required torque Tpr in the mode before switching to the required torque Tpr in the mode after switching). Specifically, during forced rejection for hardware protection, a high torque change rate that is determined in advance is set while taking into consideration not to disturb the vehicle behavior, in order to quickly switch the driving mode. On the other hand, during forced rejection due to a decrease in the SOC of the battery 14, a lower torque change rate is set compared to when the purpose is hardware protection.

[0029] In step S106, the control device 50 calculates the torque difference ΔTpr before and after the change of the driving mode. More specifically, the torque difference ΔTpr is the absolute value of the difference between the required torque Tpr_ev in the EV mode at the time when the process proceeds to step S106 and the required torque Tpr_mt in the simulated MT mode at the same time.

[0030] In step S108 following step S106, the control device 50 determines whether the calculated torque difference ΔTpr is equal to or less than a predetermined threshold value TH. If the torque difference ΔTpr is greater than the threshold value TH, the process proceeds to step S110, and if the torque difference ΔTpr is equal to or less than the threshold value TH, the process proceeds to step S112.

[0031] In step S110, the control device 50 disables switching of the driving mode, so that the required torque Tpr of the current (i.e., before switching) driving mode continues to be used to control the propeller shaft torque Tp.

[0032] Meanwhile, in step S112, the control device 50 permits the switching of the traveling mode. As a result, the required torque Tpr used for controlling the propeller shaft torque Tp is switched to the required torque Tpr_mt or Tpr_ev of the traveling mode after the switch, accompanied by smoothing processing using the setting in the next step S114. In addition, as shown in FIG. 2, situations in which the switching is permitted include, for example, when the vehicle is stopped and when the required torque Tpr is close to 0 while traveling.

[0033] In step S114 following step S112, the control device 50 sets the torque change rate for the normal smoothing process. Specifically, the control device 50 sets the torque change rate so that it decreases as the torque difference ΔTpr decreases, for example.

[0034] As described above, according to this embodiment, switching between the EV mode and the simulated MT mode is permitted when the torque difference ΔTpr before and after the switching is equal to or less than the threshold value TH. By performing the switching under such a condition where the torque difference ΔTpr (the step in the driving force) is small, the switching process (e.g., the smoothing process) can be completed in a short time. This reduces the discomfort felt by the driver due to the switching of the driving mode.

[0035] In addition, according to this embodiment, when the torque difference ΔTpr is large, switching is not permitted and the torque calculation in the driving mode before switching is maintained. As a result, under such circumstances, the required torque Tpr is calculated in accordance with the driver's operation of the accelerator pedal 22 and the brake pedal 24 and is reflected in the vehicle behavior. Therefore, the driver does not feel uncomfortable. [Explanation of symbols]

[0036] 2 electric motor, 5 propeller shaft, 10 electric vehicle, 16 inverter, 22 accelerator pedal, 26 paddle shifter, 42 mode selection device, 50 control device

Claims

[Claim 1] A control device for controlling an electric vehicle including a vehicle drive device including an electric motor and a simulated gear shift operating device operated by a driver for simulated gear shifting, The driving mode of the electric vehicle selected by the driver is a first mode in which the vehicle drive device is controlled in accordance with a first required drive force based on an accelerator opening degree; a second mode in which the vehicle drive device is controlled in accordance with a second required drive force based on a gear position corresponding to the accelerator opening and the operation of the simulated gear change operation device; Including, The control device a first forced rejection that forcibly switches from the second mode to the first mode in order to ensure a cruising range when the SOC is reduced; a second forced rejection that forcibly switches from the second mode to the first mode for the purpose of protecting hardware of the electric vehicle; is configured to be executable, When the first forcible reject is executed, the torque is changed from the required torque in the second mode to the required torque in the first mode at a lower torque change rate than when the second forcible reject is executed. A control device for an electric vehicle.

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