Electric vehicles

Abstract

To provide an electric vehicle using an electric motor as a travelling power device, and making a user enjoy driving sensation like that of a clutch pedal-less MT vehicle provided with a shifter but no clutch.SOLUTION: An electric vehicle includes an accelerator pedal 22, a shifter 26, and a control device 50. The control device 50 responds to an operation of the accelerator pedal 22 and an operation of the shifter 26 to change a motor torque an electric motor 2 outputs. The shifter 26 generates signals by an operation in a direction of a steering wheel.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an electric vehicle that uses an electric motor as a driving power device.

Background Art

[0002] An electric motor used as a driving power device in an electric vehicle has significantly different torque characteristics from an internal combustion engine that has been used as a driving power device in conventional vehicles. Due to the difference in the torque characteristics of the power device, a conventional vehicle requires a transmission, while an electric vehicle generally does not have a transmission. Of course, an electric vehicle does not have a manual transmission (MT) that switches the gear ratio by manual operation of the driver. Therefore, there is a significant difference in the driving feeling between driving a conventional vehicle with an MT (hereinafter referred to as an MT vehicle) and driving an electric vehicle.

[0003] On the other hand, an electric motor can relatively easily control torque by controlling the applied voltage and field excitation. Therefore, with an electric motor, by implementing appropriate control, it is possible to obtain desired torque characteristics within the operating range of the electric motor. Utilizing this feature, technologies for controlling the torque of an electric vehicle to simulate the torque characteristics unique to an MT vehicle have been proposed in, for example, Patent Document 1 and Patent Document 2. The electric vehicles disclosed in these patent documents are provided with a pseudo shifter and a pseudo clutch pedal so as to obtain a driving feeling similar to that of an MT vehicle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since operating the clutch pedal is unique to manual transmission vehicles, equipping electric vehicles with a simulated clutch pedal would appeal to users who want to enjoy a driving experience similar to a manual transmission vehicle in an electric car. However, for today's drivers accustomed to driving vehicles with automatic transmissions, operating the clutch pedal can sometimes be cumbersome and difficult. Furthermore, if the only operation required is the shifter, it would be possible to achieve faster gear changes.

[0006] It is estimated that there are a certain number of users who want to enjoy the driving feel of a manual transmission (MT) vehicle but are uncomfortable with or do not need to operate a clutch pedal. It is presumed that the driving feel desired by such users is, strictly speaking, the driving feel of a clutchless MT vehicle, which does not have a clutch pedal. Clutchless MT vehicles often use sequential shifters. The driving feel of a clutchless MT vehicle, including the feel of operating a sequential shifter, is different from the driving feel of a normal MT vehicle with a clutch pedal.

[0007] The electric vehicle disclosed in the above-mentioned patent document is designed to simulate the power characteristics of a conventional manual transmission vehicle equipped with a clutch pedal. Therefore, simply removing the simulated clutch pedal from the electric vehicle disclosed in the above-mentioned patent document will not satisfy users who desire a driving feel similar to that of a clutchless manual transmission vehicle with a sequential shifter.

[0008] This disclosure has been made in view of the above-mentioned issues. One of the purposes of this disclosure is to enable electric vehicles that use an electric motor as a power source for driving to enjoy a driving sensation similar to that of a clutchless manual transmission vehicle with a sequential shifter. [Means for solving the problem]

[0009] This disclosure provides an electric vehicle for achieving the above objective. The electric vehicle of this disclosure comprises an accelerator pedal and a sequential shifter. The electric vehicle of this disclosure also comprises a control device that changes the motor torque output by the electric motor in response to the operation of the accelerator pedal and the operation of the sequential shifter. The control device is configured to change the rate of change of the motor torque at least twice during a predetermined shift time in response to the operation of the sequential shifter.

[0010] The sequential shifter may be, for example, a paddle-type shifter or a lever-type shifter. In other words, the sequential shifter may have a similar structure and feel to the sequential shifter found in a clutchless manual transmission vehicle. However, as mentioned above, the operation of the sequential shifter acts on the motor torque of the electric motor, and therefore differs in function from the sequential shifter found in a clutchless manual transmission vehicle. To distinguish it from the sequential shifter found in a clutchless manual transmission vehicle, the sequential shifter found in the electric vehicle of this disclosure will be referred to as a pseudo-sequential shifter below.

[0011] According to the configuration of the electric vehicle described herein, the motor torque changes with output characteristics similar to the drive wheel torque of a clutchless manual transmission vehicle when a sequential shifter is operated, due to the shift operation of the pseudo-sequential shifter. This allows the driver to enjoy a driving sensation in the electric vehicle similar to that of a clutchless manual transmission vehicle with a sequential shifter.

[0012] The control device changing the rate of change of the motor torque at least twice during the shift time may include the control device reducing the motor torque to a minimum value and then increasing it again during the shift time. By temporarily reducing the motor torque, the driving sensation of when the clutch is temporarily released by a sequential shifter shift operation in a clutchless MT vehicle is recreated. In this case, the control device may set the minimum value to zero and maintain the motor torque at zero for a predetermined time within the shift time. Furthermore, the control device may cause the motor torque to overshoot as the shift time elapses. The driving sensation obtained by the shift operation of the pseudo-sequential shifter depends on the setting of the motor torque change characteristics within the shift time.

[0013] The motor torque change characteristics within the shift time exemplified may be applied to the upshift operation of a pseudo-sequential shifter, or to the downshift operation of a pseudo-sequential shifter.

[0014] The control device may, when the accelerator pedal operation is constant, generate a difference in motor torque before and after the shift time has elapsed, corresponding to the shift direction of the sequential shifter. If the operation of the pseudo-sequential shifter is an upshift operation, the motor torque may be decreased before and after the shift time has elapsed. Conversely, if the operation of the pseudo-sequential shifter is a downshift operation, the motor torque may be increased before and after the shift time has elapsed.

[0015] The characteristics of the motor torque change during the shift time may be modifiable. For example, if the electric vehicle of this disclosure is equipped with a drive mode selection switch, the control device may change the characteristics of the motor torque change during the shift time according to the drive mode selected by the drive mode selection switch. With this configuration, the driver can arbitrarily obtain a driving sensation that suits their mood or driving situation by appropriately selecting a drive mode.

[0016] The driving sensation experienced by the driver depends on visual information. Therefore, it is expected that visually representing the behavior unique to clutchless manual transmission vehicles will provide the driver with a more realistic driving sensation. The electric vehicle of this disclosure may be equipped with a simulated engine speed meter as a device for visually representing the behavior unique to clutchless manual transmission vehicles. The simulated engine speed meter displays the virtual engine speed of the clutchless manual transmission vehicle that the electric vehicle of this disclosure is simulating. As one example, when the simulated sequential shifter is operated upshift, the simulated engine speed meter may display the virtual engine speed that decreases monotonically during the shift time in response to the upshift operation. As another example, when the simulated sequential shifter is operated downshift, the simulated engine speed meter may display the virtual engine speed that increases at a predetermined timing within the shift time in response to the downshift operation.

[0017] The motor torque calculation by the control device may be performed using a clutchless manual transmission vehicle model that simulates the output characteristics of the drive wheel torque in a clutchless manual transmission vehicle. The clutchless manual transmission vehicle model and the method for calculating motor torque using it will be described later in the embodiments of this disclosure. [Effects of the Invention]

[0018] As described above, with the electric vehicle of this disclosure, the driver can enjoy a driving sensation similar to that of a clutchless manual transmission vehicle with a sequential shifter. [Brief explanation of the drawing]

[0019] [Figure 1] This figure schematically shows the configuration of an electric vehicle according to an embodiment of the present disclosure. [Figure 2] Figure 1 is a block diagram showing the configuration of the control system for an electric vehicle. [Figure 3] Figure 1 is a block diagram showing the functions of the control device for an electric vehicle. [Figure 4] It is a block diagram showing an example of a clutch pedal-less MT vehicle model provided in the control device shown in FIG. 3. [Figure 5] It is a diagram showing an example of an engine model constituting the clutch pedal-less MT vehicle model shown in FIG. 4. [Figure 6] It is a diagram showing an example of a clutch model constituting the clutch pedal-less MT vehicle model shown in FIG. 4. [Figure 7] It is a diagram showing an example of a sequential transmission model constituting the clutch pedal-less MT vehicle model shown in FIG. 4. [Figure 8] It is a diagram showing a comparison of the torque characteristics of an electric motor realized by motor control using a clutch pedal-less MT vehicle model with the torque characteristics of an electric motor realized by normal motor control as an electric vehicle. [Figure 9] It is a diagram showing an example of the calculation of motor torque using a clutch pedal-less MT vehicle model performed in response to an upshift operation. [Figure 10] It is a diagram showing another example of the calculation of motor torque using a clutch pedal-less MT vehicle model performed in response to an upshift operation. [Figure 11] It is a diagram showing an example of the calculation of motor torque using a clutch pedal-less MT vehicle model performed in response to a downshift operation. [Figure 12] It is a diagram showing another example of the calculation of motor torque using a clutch pedal-less MT vehicle model performed in response to a downshift operation. [Figure 13] It is a diagram schematically showing a modification example of the configuration of an electric vehicle according to an embodiment of the present disclosure.

Embodiments for Carrying Out the Invention

[0020] 1. Configuration of Electric Vehicle Figure 1 is a schematic diagram showing the configuration of the powertrain of the electric vehicle 10 according to this embodiment. As shown in Figure 1, the electric vehicle 10 is equipped with an electric motor 2 as a power source. The electric motor 2 is, for example, a brushless DC motor or a three-phase AC synchronous motor. The electric motor 2 is provided with a rotational speed sensor 40 for detecting its rotational speed. The output shaft 3 of the electric motor 2 is connected to one end of the propeller shaft 5 via a gear mechanism 4. The other end of the propeller shaft 5 is connected to the drive shaft 7 at the front of the vehicle via a differential gear 6.

[0021] The electric vehicle 10 is equipped with drive wheels 8, which are the front wheels, and driven wheels 12, which are the rear wheels. The drive wheels 8 are located at both ends of the drive shaft 7. Wheel speed sensors 30 are provided on each wheel 8 and 12. In Figure 1, only the wheel speed sensor 30 of the right rear wheel is shown as a representative example. The wheel speed sensors 30 are also used as vehicle speed sensors to detect the vehicle speed of the electric vehicle 10. The wheel speed sensors 30 are connected to a control device 50, which will be described later, via an in-vehicle network such as a Controller Area Network (CAN).

[0022] The electric vehicle 10 is equipped with a battery 14 and an inverter 16. The battery 14 stores electrical energy to drive the electric motor 2. In other words, the electric vehicle 10 is a battery electric vehicle (BEV) that runs on the electrical energy stored in the battery 14. The inverter 16 converts the DC power input from the battery 14 into driving power for the electric motor 2. The power conversion by the inverter 16 is performed by PWM control by the control device 50. The inverter 16 is connected to the control device 50 by an in-vehicle network.

[0023] The electric vehicle 10 is equipped with an accelerator pedal 22 for inputting acceleration requests and a brake pedal 24 for inputting braking requests, which serve as an operation request input device for the driver to input operation requests to the electric vehicle 10. The accelerator pedal 22 is equipped with an accelerator position sensor 32 for detecting the accelerator opening, which is the amount the accelerator pedal 22 is operated on. The brake pedal 24 is equipped with a brake position sensor 34 for detecting the amount the brake pedal 24 is operated on, which is the amount the brake pedal 24 is pressed down on. The accelerator position sensor 32 and the brake position sensor 34 are connected to the control device 50 by an in-vehicle network.

[0024] The electric vehicle 10 is further equipped with a simulated paddle shifter 26 as an input device. A paddle shifter, or paddle-type sequential shifter, is a device used to operate a sequential manual transmission (SMT), but naturally, the electric vehicle 10 does not have an SMT. The simulated paddle shifter 26 is merely a dummy and is different from a real paddle shifter. Generally, MT vehicles equipped with paddle shifters are clutch-less MT vehicles that do not have a clutch pedal. Therefore, although the electric vehicle 10 is equipped with a simulated paddle shifter 26, it does not have a simulated clutch pedal that resembles a clutch pedal.

[0025] The simulated paddle shifter 26 has a structure similar to the paddle shifters found in clutchless manual transmission vehicles. The simulated paddle shifter 26 is mounted on the steering wheel. The simulated paddle shifter 26 is equipped with an upshift switch 26u and a downshift switch 26d. The upshift switch 26u is located on the right side of the steering wheel, and the downshift switch 26d is located on the left side of the steering wheel. The upshift switch 26u and the downshift switch 26d can be operated independently. The upshift switch 26u emits a signal when pulled towards the driver, and the downshift switch 26d also emits a signal when pulled towards the driver. Hereinafter, the operation of pulling the upshift switch 26u towards the driver will be referred to as an upshift operation, and the signal emitted by the upshift switch 26u as a result of the upshift operation will be referred to as an upshift signal. Similarly, the operation of pulling the downshift switch 26d towards the driver will be referred to as a downshift operation, and the signal emitted by the downshift switch 26d as a result of the downshift operation will be referred to as a downshift signal. The upshift switch 26u and the downshift switch 26d are connected to the control unit 50 via the in-vehicle network.

[0026] The electric vehicle 10 is equipped with a drive mode selection switch 42. The drive mode selection switch 42 is a switch for selecting the drive mode of the electric vehicle 10. In the example shown in Figure 1, three drive modes, A mode, B mode, and C mode, can be selected by the drive mode selection switch 42. Each drive mode provides a different driving feel to the driver. Examples of drive modes include sport mode, comfort mode, racing mode, and normal mode. The drive mode is associated with at least the output characteristics of the electric motor 2. The drive mode selection switch 42 is connected to the control device 50 by an in-vehicle network.

[0027] The electric vehicle 10 is equipped with a simulated engine speed meter 44. An engine speed meter is a device that displays the rotational speed of the internal combustion engine to the driver, but naturally, the electric vehicle 10 does not have an engine. The simulated engine speed meter 44 is merely a dummy and is different from a real engine speed meter. The simulated engine speed meter 44 has a structure that resembles the engine speed meter found in conventional vehicles. The simulated engine speed meter 44 may be mechanical or liquid crystal display type. Alternatively, it may be a projected display type using a head-up display. In the case of a liquid crystal display type or a projected display type, the rev limit may be set arbitrarily. The simulated engine speed meter 44 is connected to the control device 50 by an in-vehicle network.

[0028] The control device 50 is typically an electronic control unit (ECU) installed in an electric vehicle 10. The control device 50 may be a combination of multiple ECUs. The control device 50 comprises an interface 52, a memory 54, and a processor 56. An in-vehicle network is connected to the interface 52. The memory 54 includes RAM for temporarily recording data and ROM for storing programs and various data related to programs that can be executed by the processor 56. A program consists of multiple instructions. The processor 56 reads and executes programs and data from the memory 54 and generates control signals based on signals acquired from each sensor.

[0029] Figure 2 is a block diagram showing the configuration of the control system of the electric vehicle 10 according to this embodiment. The control device 50 receives input signals from at least the wheel speed sensor 30, accelerator position sensor 32, brake position sensor 34, upshift switch 26u, downshift switch 26d, rotational speed sensor 40, and drive mode selection switch 42. An in-vehicle network is used for communication between these sensors and the control device 50. Although not shown in the figure, various other sensors are mounted on the electric vehicle 10 and connected to the control device 50 via the in-vehicle network.

[0030] Furthermore, the control device 50 outputs signals to at least the inverter 16 and the simulated engine speed meter 44. An in-vehicle network is used for communication between these devices and the control device 50. Although not shown in the diagram, various other actuators and displays are also mounted on the electric vehicle 10 and connected to the control device 50 via the in-vehicle network.

[0031] The control device 50 also functions as a control signal calculation unit 520. More specifically, the processor 56 functions as at least the control signal calculation unit 520 when the program stored in the memory 54 is executed by the processor 56. Control signal calculation is the function of calculating control signals for actuators and equipment. The control signals include at least a signal for PWM control of the inverter 16 and a signal for displaying information on the simulated engine speed meter 44. The functions of the control device 50 will be described below.

[0032] 2. Functions of the control device 2-1. Motor Torque Calculation Function Figure 3 is a block diagram showing the functions of the control device 50 according to this embodiment, particularly the functions related to calculating the motor torque command value for the electric motor 2. The control device 50 calculates the motor torque command value using the functions shown in this block diagram and generates a control signal for PWM control of the inverter 16 based on the motor torque command value.

[0033] As shown in Figure 3, the control signal calculation unit 520 includes a clutch pedal-less MT vehicle model 530 and a requested motor torque calculation unit 540. The control signal calculation unit 520 receives signals from at least a wheel speed sensor 30, an accelerator position sensor 32, an upshift switch 26u, a downshift switch 26d, and a drive mode selection switch 42. The control signal calculation unit 520 processes the signals from these sensors and switches and calculates the motor torque to be output to the electric motor 2.

[0034] The clutchless manual transmission vehicle model 530 is a model that calculates the drive wheel torque that should be obtained by operating the accelerator pedal 22 and the simulated paddle shifter 26, assuming that the electric vehicle 10 is a clutchless manual transmission vehicle. The clutchless manual transmission vehicle is a manual transmission vehicle equipped with an engine, an SMT, and a clutch connecting the engine and the SMT, but the clutch is operated automatically and therefore does not have a clutch pedal. The drive wheel torque in the clutchless manual transmission vehicle is determined by operating the gas pedal, which controls the fuel supply to the engine, and operating the paddle shifter, which switches the gear position of the SMT. The engine may be a spark-ignition engine or a diesel engine. Hereinafter, the engine, clutch, and SMT that are virtually realized by the clutchless manual transmission vehicle model 530 will be referred to as the virtual engine, virtual clutch, and virtual SMT, respectively.

[0035] In the clutchless MT vehicle model 530, the accelerator opening Pap detected by the accelerator position sensor 32 is input as the amount of operation of the gas pedal of the virtual engine. In addition, the clutchless MT vehicle model 530 receives the upshift signal Su transmitted from the upshift switch 26u and the downshift signal Sd transmitted from the downshift switch 26d as inputs for operation of the paddle shifter that determines the gear position of the virtual SMT. Furthermore, the clutchless MT vehicle model 530 also receives the vehicle speed Vw (or wheel speed) detected by the wheel speed sensor 30 as a signal indicating the load state of the vehicle.

[0036] The clutchless MT vehicle model 530 receives a mode selection signal from the drive mode selection switch 42. The clutchless MT vehicle model 530 includes multiple models that simulate clutchless MT vehicles with different output characteristics. Each model is associated with the drive mode selected by the drive mode selection switch 42. In the example shown in Figure 3, the clutchless MT vehicle model 530 includes a model for mode A corresponding to mode A, a model for mode B corresponding to mode B, and a model for mode C corresponding to mode C. Depending on the drive mode selected by the drive mode selection switch 42, one of these models is selected and used to calculate the drive wheel torque Tw.

[0037] The required motor torque calculation unit 540 converts the drive wheel torque Tw calculated in the clutchless MT vehicle model 530 into a required motor torque Tm. The required motor torque Tm is the motor torque required to achieve the drive wheel torque Tw calculated in the clutchless MT vehicle model 530. The reduction ratio from the output shaft 3 of the electric motor 2 to the drive wheels 8 is used to convert the drive wheel torque Tw into a required motor torque Tm.

[0038] 2-2. Clutch pedal-less manual transmission vehicle models 2-2-1. Overview Next, a clutchless manual transmission vehicle model 530 will be described. Figure 4 is a block diagram showing an example of a clutchless manual transmission vehicle model 530. The clutchless manual transmission vehicle model 530 consists of an engine model 531, a clutch model 532, an SMT model 533, an axle / drive wheel model 534, and a PCU model 535. In the engine model 531, a virtual engine is modeled. The virtual engine in this embodiment is a spark-ignition engine whose torque is controlled by the throttle opening. In the clutch model 532, a virtual clutch is modeled. In the SMT model 533, a virtual SMT is modeled. In the axle / drive wheel model 534, a virtual torque transmission system from the axle to the drive wheel is modeled. And in the PCU model 535, some functions of a virtual plant control unit (PCU) that integrates and controls the virtual engine, virtual clutch, and virtual SMT are modeled. Each model may be represented, for example, by a calculation formula or by a map.

[0039] Input and output of calculation results are performed between each model. In addition, the accelerator opening Pap, upshift signal Su, and downshift signal Sd input to the clutchless MT vehicle model 530 are used in the PCU model 535. The vehicle speed Vw (or wheel speed) is used in multiple models. In the clutchless MT vehicle model 530, the drive wheel torque Tw and virtual engine speed Ne are calculated based on these input signals.

[0040] 2-2-2. PCU Model The PCU model 535 calculates the virtual throttle opening of the virtual engine, the virtual clutch opening of the virtual clutch, and the virtual gear position of the virtual SMT. The PCU model 535 consists of a throttle opening model for calculating the virtual throttle opening, a clutch opening model for calculating the virtual clutch opening, and a gear position model for calculating the virtual gear position.

[0041] The throttle position model receives the accelerator position Pap, the upshift signal Su, and the downshift signal Sd as inputs and outputs a virtual throttle position TA. In the throttle position model, the virtual throttle position TA is associated with the accelerator position Pap, and as the accelerator position Pap increases, the virtual throttle position TA increases. However, when the upshift signal Su and the downshift signal Sd are input, the virtual throttle position TA is temporarily reduced regardless of the accelerator position Pap. This means that when a shift operation is performed on the pseudo-paddle shifter 26, the virtual throttle is temporarily closed. The virtual throttle position TA output from the throttle position model is input to the engine model 531.

[0042] The clutch opening model receives the upshift signal Su and the downshift signal Sd as inputs and outputs a virtual clutch opening CP. The virtual clutch opening CP is basically set to zero percent. That is, the basic state of the virtual clutch is engaged. When the upshift signal Su and the downshift signal Sd are input, the virtual clutch opening CP is temporarily set to 0%. This means that when a shift operation is performed on the pseudo paddle shifter 26, the virtual clutch is temporarily released. The vehicle speed Vw and the virtual engine speed are used to calculate the virtual clutch opening CP when the virtual clutch is engaged. The clutch opening model calculates the virtual clutch opening CP based on the rotational speed difference so that the rotational speed of the input shaft of the virtual SMT calculated from the vehicle speed Vw and the virtual engine speed are smoothly matched. The virtual clutch opening CP output from the clutch opening model is input to the clutch model 532.

[0043] The gear stage model receives an upshift signal Su and a downshift signal Sd as inputs and outputs a virtual gear stage GP. The number of gear stages in the virtual SMT is N (where N is a natural number greater than or equal to 2). The virtual gear stage GP is raised by one stage each time an upshift signal Su is input. However, when the virtual gear stage GP is at the Nth stage, it remains at the Nth stage even when an upshift signal Su is input. Also, the virtual gear stage GP is lowered by one stage each time a downshift signal Sd is input. However, when the virtual gear stage GP is at the 1st stage, it remains at the 1st stage even when a downshift signal Sd is input. The virtual gear stage GP output from the gear stage model is input to the SMT model 533.

[0044] 2-2-3. Engine Models Engine model 531 calculates the virtual engine rotational speed Ne and the virtual engine output torque Teout. Engine model 531 consists of a model for calculating the virtual engine rotational speed Ne and a model for calculating the virtual engine output torque Teout. For example, the model represented by equation (1) below is used to calculate the virtual engine rotational speed Ne. In equation (1), the virtual engine rotational speed Ne is calculated from the rotational speed Nw of the wheel 8, the overall reduction ratio R, and the slip ratio Rslip of the virtual clutch.

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[0045] In equation (1), the rotational speed Nw of wheel 8 is detected by the wheel speed sensor 30. The overall reduction ratio R is calculated from the gear ratio (shift ratio) r calculated by the SMT model 533 described later and the reduction ratio specified by the axle / drive wheel model 534. The slip ratio Rslip is calculated by the clutch model 532 described later. The virtual engine rotational speed Ne is displayed on the simulated engine rotational speed meter 44.

[0046] However, equation (1) is the formula for calculating the virtual engine speed Ne when the virtual engine and virtual SMT are connected by a virtual clutch. When the virtual clutch is disengaged, the virtual engine torque Te generated by the virtual engine can be considered to be used to increase the virtual engine speed Ne. The virtual engine torque Te is the torque obtained by adding the torque due to the moment of inertia to the virtual engine output torque Teout. When the virtual clutch is disengaged, the virtual engine output torque Teout is zero. Therefore, when the virtual clutch is disengaged, engine model 531 calculates the virtual engine speed Ne using the virtual engine torque Te and the moment of inertia J of the virtual engine by the following equation (2). A map with the virtual throttle opening TA as a parameter is used to calculate the virtual engine torque Te.

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[0047] In addition, during idling in a clutchless manual transmission vehicle, idle speed control is performed to maintain the engine speed at a constant speed. Therefore, when the virtual clutch is disengaged, the vehicle speed is 0, and the virtual throttle opening TA is 0%, the engine model 531 calculates the virtual engine speed Ne as a predetermined idling speed (for example, 1000 rpm). When the driver depresses the accelerator pedal 22 while stationary to rev the engine, the idling speed is used as the initial value of the virtual engine speed Ne calculated by equation (2).

[0048] Engine model 531 calculates virtual engine output torque Teout from virtual engine rotational speed Ne and virtual throttle opening TA. For example, a map like the one shown in Figure 5 is used to calculate the virtual engine output torque Teout. This map defines the relationship between the virtual throttle opening TA, virtual engine rotational speed Ne, and virtual engine output torque Teout in a steady state. In this map, the virtual engine output torque Teout is given for each virtual throttle opening TA relative to the virtual engine rotational speed Ne. The torque characteristics shown in Figure 5 can be set to represent a naturally aspirated engine or a turbocharged engine. Furthermore, the torque characteristics shown in Figure 5 can also be set to represent a diesel engine by replacing the virtual throttle opening TA with a virtual fuel injection amount. The virtual engine output torque Teout calculated by engine model 531 is input to clutch model 532.

[0049] 2-2-4. Clutch Model The clutch model 532 calculates the torque transmission gain k. The torque transmission gain k is a gain used to calculate the degree of torque transmission of the virtual clutch according to the virtual clutch opening CP. The clutch model 532 has a map, for example, as shown in Figure 6. In this map, the torque transmission gain k is given for the virtual clutch opening CP. In Figure 6, the torque transmission gain k is given such that the virtual clutch opening CP is 1 in the range from CP0 to CP1, decreases monotonically with a constant slope from CP1 to CP2 to 0, and is 0 in the range from CP2 to CP3. Here, CP0 corresponds to a clutch opening of 0%, and CP3 corresponds to a clutch opening of 100%. The range from CP0 to CP1 and the range from CP2 to CP3 are dead zones in which the torque transmission gain k does not change with respect to the virtual clutch opening CP.

[0050] The clutch model 532 calculates the clutch output torque Tcout using the torque transfer gain k. The clutch output torque Tcout is the torque output from the virtual clutch. For example, the clutch model 532 calculates the clutch output torque Tcout from the virtual engine output torque Teout and the torque transfer gain k using the following equation (3). The clutch output torque Tcout calculated by the clutch model 532 is input to the SMT model 533.

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[0051] Furthermore, clutch model 532 calculates the slip ratio Rslip. The slip ratio Rslip is used in the calculation of the virtual engine speed Ne in engine model 531. Similar to the torque transmission gain k, a map can be used to calculate the slip ratio Rslip, where Rslip is given in relation to the clutch pedal depression amount Pc. Alternatively, the slip ratio Rslip may be calculated from the torque transmission gain k using the following equation (4), which expresses the relationship between the slip ratio Rslip and the torque transmission gain.

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[0052] 2-2-5. SMT Model The SMT model 533 calculates the gear ratio (shift ratio) r. The gear ratio r is determined by the virtual gear stage GP in the virtual SMT. The SMT model 533 has a map, for example, as shown in Figure 7. In this map, the gear ratio r is given for the virtual gear stage GP. As shown in Figure 7, the larger the virtual gear stage GP, the smaller the gear ratio r becomes.

[0053] The SMT model 533 calculates the transmission output torque Tgout using the gear ratio r. The transmission output torque Tgout is the torque output from the virtual SMT. The MT model 533 calculates the transmission output torque Tgout from the clutch output torque Tcout and the gear ratio r, for example, using equation (5). The transmission output torque Tgout calculated by the MT model 533 is input to the axle / drive wheel model 534.

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[0054] 2-2-5. Axle and drive wheel model The axle / drive wheel model 534 calculates the drive wheel torque Tw using a predetermined reduction ratio rr. The reduction ratio rr is a fixed value determined by the mechanical structure from the virtual SMT to the drive wheel 8. The value obtained by multiplying the reduction ratio rr by the gear ratio r is the aforementioned overall reduction ratio R. The axle / drive wheel model 534 calculates the drive wheel torque Tw from the transmission output torque Tgout and the reduction ratio rr using, for example, the following equation (6). The drive wheel torque Tw calculated by the axle / drive wheel model 534 is output to the requested motor torque calculation unit 540.

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[0055] 2-3. Torque characteristics of electric motors realized in clutchless manual transmission vehicle models The requested motor torque calculation unit 540 converts the drive wheel torque Tw calculated by the clutchless MT vehicle model 530 into motor torque. Figure 8 is a diagram showing the torque characteristics of the electric motor 2 realized by motor control using the clutchless MT vehicle model 530 in comparison with the torque characteristics of the electric motor 2 realized by normal motor control as an electric vehicle (EV). With motor control using the clutchless MT vehicle model 530, as shown in Figure 8, torque characteristics (solid line in the figure) that simulate the torque characteristics of a clutchless MT vehicle can be realized according to the virtual gear stage set by the pseudo-paddle shifter 26. Note that in Figure 8, the number of gear stages of the virtual SMT is set to 6.

[0056] 3. Example of motor torque control in response to shift operation 3-1. Example of motor torque control in response to upshift operation Figure 9 shows an example of motor torque calculation using a clutchless manual transmission vehicle model 530 in response to an upshift operation of the simulated paddle shifter 26. In the example shown in Figure 9, an upshift operation is performed while maintaining a constant accelerator opening during acceleration of the electric vehicle 10.

[0057] An upshift operation using the simulated paddle shifter 26 triggers an upshift signal from the upshift switch 26u. Upon receiving the upshift signal, the PCU model 535 of the clutchless MT vehicle model 530 decreases the virtual throttle opening at a predetermined speed and simultaneously increases the virtual clutch opening at a predetermined speed. At approximately the same time that the virtual throttle opening becomes 0% and the virtual throttle is completely closed, the virtual clutch opening becomes 100% and the virtual clutch is completely released.

[0058] When the virtual throttle is completely closed and the virtual clutch is completely released, the PCU model 535 increases the virtual gear position of the virtual SMT by one step. Then, after a predetermined time has elapsed since increasing the virtual gear position by one step, the PCU model 535 increases the virtual throttle opening at a predetermined speed and simultaneously decreases the virtual clutch opening at a predetermined speed. At approximately the same time that the virtual throttle opening returns to its original opening before the upshift operation, the virtual clutch opening becomes 0%, and the virtual clutch is fully engaged. This completes the upshift of the virtual SMT. In this specification, the time when an upshift operation of the simulated paddle shifter 26 is detected is defined as the start of the upshift, and the time when the virtual clutch is fully engaged is defined as the completion of the upshift. In this specification, the time from the start of the upshift to the completion of the upshift (time t shown in Figure 9) is defined as the upshift shift time.

[0059] During the shift time, the virtual clutch is released and the virtual throttle is closed, causing the virtual engine to rotate due to inertia. As a result, the virtual engine speed decreases monotonically during the shift time. Then, when the virtual clutch re-engages and the virtual throttle reopens, the virtual engine speed begins to increase again. Since the driving sensation experienced by the driver depends on visual information, the virtual engine speed, which changes in response to the upshift operation, is displayed on the simulated engine speed meter 44, providing the driver with a realistic driving sensation.

[0060] The bottom row of Figure 9 shows the change in motor torque achieved by changing the virtual throttle opening, virtual clutch opening, and virtual gear position as described above in response to an upshift operation. In the example shown in Figure 9, the motor torque decreases as the virtual clutch disengages, and decreases to zero when the virtual clutch is fully disengaged. The motor torque is maintained at zero while the virtual clutch is disengaged. Eventually, when the virtual clutch begins to engage, the motor torque increases as the engagement of the virtual clutch progresses. However, the motor torque at the point when the virtual clutch is fully engaged and the upshift is completed is lower than the motor torque at the start of the upshift. In other words, in the control of motor torque in response to an upshift operation, the motor torque is reduced before and after the shift time has elapsed. By controlling the motor torque in this manner, the driver can enjoy a driving sensation in the electric vehicle 10 that is similar to when performing an upshift operation using paddle shifters in a clutchless manual transmission vehicle.

[0061] After the upshift is complete, the motor torque is calculated according to the virtual gear position and virtual throttle opening. However, immediately after the shift time has elapsed, the motor torque may be overshot by the value determined by the virtual gear position and virtual throttle opening, as shown by the dashed line in Figure 9, to account for the inertia due to the rotation of the virtual engine. Alternatively, the motor torque may be undershot by the value determined by the virtual gear position and virtual throttle opening.

[0062] Figures 10A and 10B show another example of motor torque calculation using a clutchless manual transmission vehicle model 530, performed in response to an upshift operation of the simulated paddle shifter 26.

[0063] In the example shown in Figure 10A, the motor torque is reduced to a minimum value during the shift time and then increased again, and the motor torque is reduced before and after the shift time has elapsed. The minimum value is zero. The example in Figure 10A is similar to the example in Figure 9 in that it temporarily reduces the motor torque. By temporarily reducing the motor torque, the driving sensation of performing an upshift operation with the paddle shifter is recreated in a clutchless manual transmission vehicle.

[0064] In the example shown in Figure 10B, the motor torque is reduced at a constant rate from the start to the end of the upshift, and the motor torque is reduced before and after the shift time has elapsed. In the example shown in Figure 10B, a minimum value of the motor torque is not generated during the shift time, as in the examples shown in Figure 9 and Figure 10A. However, the rate of change of the motor torque is changed at the start and end of the upshift. In other words, the example shown in Figure 10A is similar to the examples shown in Figure 9 and Figure 10A in that the rate of change of the motor torque is changed at least twice during the shift time. Note that in the examples shown in Figures 9, 10A, and 10B, the rate of change of the motor torque may be changed after a predetermined delay time has elapsed after the upshift operation is detected.

[0065] In the clutchless MT vehicle model 530, the model used to calculate the motor torque can be switched according to the drive mode selected by the drive mode selection switch 42. For example, the motor torque change characteristics shown in Figure 9 may be used as the change characteristics obtained in mode A, the motor torque change characteristics shown in Figure 10A may be used as the change characteristics obtained in mode B, and the motor torque change characteristics shown in Figure 10B may be used as the change characteristics obtained in mode C. Alternatively, for example, the waveform of the motor torque change characteristics may be common to all drive modes, while the upshift shift time may differ for each drive mode. Different motor torque change characteristics will result in different driving sensations for the driver. By appropriately selecting a drive mode with the drive mode selection switch 42, the driver can arbitrarily obtain a driving sensation that suits their mood or driving situation.

[0066] 3-2. Example of motor torque control in response to downshift operation Figure 11 shows an example of motor torque calculation using a clutchless manual transmission vehicle model 530 in response to a downshift operation of the simulated paddle shifter 26. In the example shown in Figure 11, a downshift operation is performed while maintaining a constant accelerator opening during deceleration of the electric vehicle 10.

[0067] A downshift operation using the simulated paddle shifter 26 triggers a downshift signal from the downshift switch 26d. Upon receiving the downshift signal, the PCU model 535 of the clutchless MT vehicle model 530 decreases the virtual throttle opening at a predetermined speed and simultaneously increases the virtual clutch opening at a predetermined speed. At approximately the same time that the virtual throttle opening becomes 0% and the virtual throttle is completely closed, the virtual clutch opening becomes 100% and the virtual clutch is fully released.

[0068] When the virtual throttle is completely closed and the virtual clutch is completely released, the PCU model 535 reduces the virtual gear position of the virtual SMT by one step. Then, after a predetermined time has elapsed since reducing the virtual gear position by one step, the PCU model 535 temporarily opens the virtual throttle. Subsequently, the PCU model 535 increases the virtual throttle opening at a predetermined speed and simultaneously decreases the virtual clutch opening at a predetermined speed. At approximately the same time that the virtual throttle opening returns to its original opening before the downshift operation, the virtual clutch opening becomes 0%, and the virtual clutch is fully engaged. This completes the downshift of the virtual SMT. In this specification, the time when a downshift operation of the simulated paddle shifter 26 is detected is defined as the start of the downshift, and the time when the virtual clutch is fully engaged is defined as the completion of the downshift. In this specification, the time from the start of the downshift to the completion of the downshift (time t shown in Figure 11) is defined as the downshift shift time.

[0069] The operation of temporarily opening the virtual throttle while the virtual clutch is disengaged is performed to increase the virtual engine speed and match it to the rotational speed of the virtual SMT input shaft, which is determined by the vehicle speed. The virtual clutch engages when the difference between the rotational speed of the virtual SMT input shaft and the virtual engine speed falls within a predetermined threshold. When a downshift operation is performed, the virtual engine speed increases before the virtual clutch engages and the motor torque increases. This change in virtual engine speed is displayed on the simulated engine speed meter 44, allowing the driver to obtain visual information about the driving sensation during a downshift.

[0070] The bottom row of Figure 11 shows the change in motor torque achieved by changing the virtual throttle opening, virtual clutch opening, and virtual gear position as described above in response to a downshift operation. In the example shown in Figure 11, the motor torque decreases as the virtual clutch disengages, and decreases to zero when the virtual clutch is fully disengaged. The motor torque is maintained at zero while the virtual clutch is disengaged. Eventually, when the virtual clutch begins to engage, the motor torque increases as the engagement of the virtual clutch progresses. However, the motor torque at the point when the virtual clutch is fully engaged and the downshift is completed is higher than the motor torque at the start of the downshift. In other words, in the control of motor torque in response to a downshift operation, the motor torque is increased before and after the shift time has elapsed. By controlling the motor torque in this manner, the driver can enjoy a driving sensation in the electric vehicle 10 that is similar to that when performing a downshift operation using paddle shifters in a clutchless manual transmission vehicle.

[0071] After the downshift is complete, the motor torque is calculated according to the virtual gear position and virtual throttle opening. However, immediately after the shift time has elapsed, the motor torque may be overshot by the value determined by the virtual gear position and virtual throttle opening, as shown by the dashed line in Figure 11, to account for the inertia due to the rotation of the virtual engine. Alternatively, the motor torque may be undershot by the value determined by the virtual gear position and virtual throttle opening.

[0072] Figures 12A and 12B show another example of motor torque calculation using a clutchless manual transmission vehicle model 530, performed in response to a downshift operation of the simulated paddle shifter 26.

[0073] In the example shown in Figure 12A, the motor torque is reduced to a minimum value during the shift time and then increased again, and the motor torque is increased before and after the shift time has elapsed. The minimum value is zero. The example in Figure 12A is similar to the example in Figure 11 in that it temporarily reduces the motor torque. By temporarily reducing the motor torque, the driving sensation of a downshift operation using the paddle shifter is recreated in a clutchless manual transmission vehicle.

[0074] In the example shown in Figure 12B, the motor torque is reduced at a constant rate from the start to the end of the downshift, and then increased before and after the shift time has elapsed. Unlike the examples shown in Figures 11 and 12A, the example in Figure 12B does not create a minimum value in the motor torque during the shift time. However, the rate of change of the motor torque is changed at the start and end of the downshift. In other words, the example in Figure 12A is similar to the examples in Figures 11 and 12A in that the rate of change of the motor torque is changed at least twice during the shift time. Note that in the examples shown in Figures 11, 12A, and 12B, the rate of change of the motor torque may be changed after a predetermined delay time has elapsed since the detection of the downshift operation.

[0075] The motor torque change characteristics shown in Figures 11, 12A, and 12B can be associated with the drive modes selectable by the drive mode selection switch 42. For example, the motor torque change characteristics shown in Figure 11 may be the change characteristics obtained in mode A, the motor torque change characteristics shown in Figure 12A may be the change characteristics obtained in mode B, and the motor torque change characteristics shown in Figure 12B may be the change characteristics obtained in mode C. Alternatively, for example, the waveform of the motor torque change characteristics may be common to all drive modes, while the downshift shift time may differ for each drive mode.

[0076] 4. Others Figure 13 schematically shows a modified configuration of the electric vehicle 10 according to the above embodiment. In this modified configuration, a lever-type pseudo-shifter 28 is provided as a pseudo-sequential shifter. The lever-type pseudo-shifter 28 is configured to output an upshift signal when the shift lever 28a is tilted forward and to output a downshift signal when the shift lever 28a is tilted backward. The lever-type pseudo-shifter 28 is connected to the control device 50 by an in-vehicle network.

[0077] The electric vehicle 10 according to the above embodiment is a front-wheel-drive (FF) vehicle in which the front wheels are driven by a single electric motor 2. However, the present invention is also applicable to electric vehicles in which two electric motors are arranged, one at the front and one at the rear, to drive the front wheels and the other at the rear, respectively. Furthermore, the present invention is also applicable to electric vehicles equipped with in-wheel motors for each wheel. In these cases, a clutchless manual transmission (MT) vehicle model can be used that is modeled after an all-wheel-drive vehicle with an SMT (Super Manual Transmission).

[0078] The electric vehicle 10 according to the above embodiment does not have a transmission. However, the present invention is also applicable to electric vehicles equipped with a stepped or continuously variable automatic transmission. In this case, the powertrain consisting of the electric motor and the automatic transmission should be controlled to output the motor torque calculated for the clutchless manual transmission vehicle model.

[0079] The motor torque control technology disclosed herein is not limited to battery electric vehicles, but is broadly applicable to any electric vehicle that uses an electric motor as a power source for driving. For example, the motor torque control technology disclosed herein can be applied to hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs) that have a mode in which they are driven solely by the electric motor. Furthermore, the motor torque control technology disclosed herein can be applied to fuel cell electric vehicles (FCEVs) that supply electric energy generated by a fuel cell to an electric motor. [Explanation of Symbols]

[0080] 2 Electric motor, 8 Drive wheels, 10 Electric vehicle, 16 Inverter, 26 Simulated paddle shifter (simulated sequential shifter), 28 Lever-type simulated shifter (simulated sequential shifter), 42 Drive mode selection switch, 44 Simulated engine speed meter, 50 Control device, 520 Control signal calculation unit, 530 Clutch pedal-less MT vehicle model, 540 Required motor torque calculation unit

Claims

1. An electric vehicle that uses an electric motor as a power source for driving, The accelerator pedal and Shifter and, The system includes a control device that changes the motor torque output by the electric motor in response to the operation of the accelerator pedal and the operation of the shifter, The shifter emits a signal in response to the steering wheel's direction of movement. The control device makes the motor torque different before and after the operation of the shifter. Making the motor torque different before and after the operation of the shifter includes controlling the motor torque in response to the downshift operation of the shifter, thereby increasing the motor torque at a predetermined downshift time elapsed from the start of the downshift operation compared to the motor torque at the start of the downshift operation. An electric vehicle characterized by the following features.

2. In the electric vehicle according to claim 1, The aforementioned shifter is equipped with an upshift switch and a downshift switch, The upshift switch is located on the right side of the steering wheel. The downshift switch is located on the left side of the steering wheel. An electric vehicle characterized by the following features.

3. In the electric vehicle according to claim 2, Making the motor torque different before and after operating the shifter is, The motor torque at the time a predetermined upshift time has elapsed from the time the upshift switch is operated is reduced compared to the motor torque at the time the upshift switch is operated. This includes increasing the motor torque at a predetermined downshift time elapsed from the time the downshift switch is operated, relative to the motor torque at the time the downshift switch is operated. An electric vehicle characterized by the following features.

4. In the electric vehicle according to claim 1, The control device calculates the motor torque using a virtual clutch, which is a computational model, and reduces the opening of the virtual clutch in response to the signal emitted by the shifter. An electric vehicle characterized by the following features.

5. In the electric vehicle according to claim 4, The control device reduces the motor torque to zero when the virtual clutch is released. An electric vehicle characterized by the following features.

6. In an electric vehicle according to any one of claims 1 to 5, It also features a simulated engine speed meter that displays virtual engine rotation speed, The simulated engine speed meter changes the virtual engine speed in response to the signal emitted by the shifter. An electric vehicle characterized by the following features.

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