JP7512766B2 - Electric vehicles - Google Patents

Description

The present invention relates to an electric vehicle.

Patent document 1 discloses that in an electric vehicle powered by an electric motor, in order to create a sense of shifting, control is performed to vary the torque of the electric motor according to the vehicle speed, accelerator opening, and brake depression.

JP 2018-166386 A

In the configuration described in Patent Document 1, there is no clutch pedal or shift lever at the driver's seat, so the shift control is pseudo, with no shift operation by the driver himself. This creates a sense of discomfort for drivers who want the same driving pleasure as operating a manual transmission vehicle. In order to achieve the driving sensation desired by the driver, it is therefore conceivable to provide the electric vehicle with a clutch pedal and shift lever. In this electric vehicle, a manual shift driving mode can be selected in which shift control is performed in response to the operation of the clutch pedal and shift lever.

However, in the manual gear shift driving mode, in order to simulate multiple gear shifts, a limit value is set for the motor's driving force for each gear shift mode. Therefore, when the driving force required for the vehicle (required driving force) is large while driving in the manual driving mode, a driving force greater than the limit value for the driving force in that gear shift mode is required, and there is a risk of a driving force shortage relative to the requested driving force.

The present invention was made in consideration of the above circumstances, and aims to provide an electric vehicle that can suppress a shortage of driving force relative to the required driving force while realizing the driving feel desired by the driver.

The present invention is an electric vehicle equipped with a driving motor, a clutch device operated by a driver, a shift device that selects one of a plurality of gear modes in which the torque characteristics relative to the rotation speed of the motor are gradually different, and a control device having a torque control unit capable of executing a manual gear shift driving mode that controls the torque of the electric motor so that the torque characteristics correspond to the gear mode selected by the driver's operation of the clutch device and the shift device. The control device has a determination unit that, while traveling in the manual gear shift driving mode, compares the driving force that can be output with the torque characteristics of the currently selected gear shift mode with the required driving force to determine whether or not a driving force shortage occurs with respect to the required driving force, and the torque control unit increases the upper limit value of the driving force in the currently selected gear shift driving mode when the determination unit determines that a driving force shortage occurs with respect to the required driving force.

In the present invention, when traveling in a manual gear shift driving mode, if it is determined that the driving force that can be output with the torque characteristics of the current gear shift mode is insufficient for the required driving force, the upper limit of the driving force in that gear shift mode can be raised. This makes it possible to suppress the occurrence of a driving force shortage while realizing the driving feel desired by the driver.

FIG. 1 is a skeleton diagram that illustrates an electric vehicle according to an embodiment. FIG. 2 is a functional block diagram for explaining the configuration of the control device. FIG. 3 is a diagram showing a calculation map of the virtual engine output torque. FIG. 4 is a diagram showing a calculation map for the torque transmission gain. FIG. 5 is a diagram showing a gear ratio calculation map. FIG. 6 is an operational flow diagram showing the procedure of a pseudo manual gear shift operation executed by a driver. FIG. 7 is a diagram showing an example of motor torque characteristics corresponding to a plurality of gear shift modes. FIG. 8 is a flow chart showing a driving force determination flow that is executed while the vehicle is traveling in the manual gear shift traveling mode.

The following describes an electric vehicle according to an embodiment of the present invention in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below.

FIG. 1 is a skeleton diagram showing a schematic diagram of an electric vehicle according to an embodiment. As shown in FIG. 1, an electric vehicle 10 includes a motor 2 as a power source for driving. The motor 2 is, for example, a three-phase AC motor. An output shaft 3 of the motor 2 is connected to one end of a propeller shaft 5 via a gear mechanism 4. The other end of the propeller shaft 5 is connected to a drive shaft 7 at the front of the vehicle via a differential gear 6. The electric vehicle 10 includes driving wheels 8 as front wheels and driven wheels 12 as rear wheels. The driving wheels 8 are provided at both ends of the drive shaft 7. In addition, a shaft rotation speed sensor 40 for detecting a shaft rotation speed Np is disposed on the propeller shaft 5. A wheel rotation speed sensor 42 for detecting a wheel rotation speed Nw is disposed on the drive wheel 8. Signals detected by the shaft rotation speed sensor 40 and the wheel rotation speed sensor 42 are output to the control device 50.

The electric vehicle 10 includes a battery 14, an inverter 16, and a control device 50. The battery 14 stores electric energy to be used to drive the motor 2. The inverter 16 converts the direct current stored in the battery 14 into a three-phase alternating current, for example, by performing pulse width modulation (PWM). This inverter 16 has a function of controlling the drive torque of the motor 2 based on a target drive torque input from the control device 50. In other words, the motor 2 is controlled by the control device 50.

The electric vehicle 10 also includes an accelerator pedal 22 for inputting an acceleration request and a brake pedal 24 for inputting a braking request, as operation request input devices for the driver to input operation requests to the electric vehicle 10. The accelerator pedal 22 is provided with an accelerator position sensor 32 for detecting the accelerator opening Pap (%). The brake pedal 24 is provided with a brake position sensor 34 for detecting the pedal depression amount. The signals detected by the accelerator position sensor 32 and the brake position sensor 34 are each output to the control device 50.

The electric vehicle 10 further includes a shift lever 26 and a clutch pedal 28 as operation request input devices for gear shifting. However, since the electric vehicle 10 is a vehicle driven by a motor 2 and does not include an engine as a power source, it does not include the transmission and clutch mechanism that MT vehicles include. Therefore, the shift lever 26 and clutch pedal 28 are given the following functions instead of the function of mechanically operating the actual transmission and clutch mechanism.

The shift lever 26 functions as a shift device for the driver to select one of a plurality of gear modes in which the torque characteristics relative to the rotation speed of the motor 2 are specified in stages. The plurality of gear modes here are shift modes that simulate the gears (gear stages) of an MT vehicle, and include, for example, the first gear (1st), second gear (2nd), third gear (3rd), fourth gear (4th), fifth gear (5th), sixth gear (6th), and neutral (N) gear modes. The torque characteristics of each gear mode are preset to the torque characteristics that simulate the gear stages of an MT vehicle, as shown in FIG. 7, for example. That is, a limit value (upper limit value) is set for the driving force of the motor 2 for each gear mode. However, since each of these gear modes is merely a simulation of the gear stages of an MT vehicle, there is no restriction on the torque characteristics to correspond to an actual fixed gear ratio. That is, the torque characteristics of each of the plurality of gear modes can be freely preset as long as they are within the output range of the motor 2.

The shift lever 26 has a structure that mimics a shift lever equipped in an MT vehicle. The arrangement and operation feel of the shift lever 26 are the same as those of an actual MT vehicle. The shift lever 26 has positions that correspond to multiple gear modes with different torque characteristics. The shift lever 26 is provided with a shift position sensor 36 that detects the shift position Gp, which indicates the position of the gear mode. The signal detected by the shift position sensor 36 is output to the control device 50.

The clutch pedal 28 functions as a clutch device having a structure simulating that of a clutch pedal equipped in an MT vehicle. The clutch pedal 28 is depressed when the driver operates the shift lever 26. The layout and operation feel of the clutch pedal 28 are the same as those of an actual MT vehicle. The clutch pedal 28 is provided with a clutch position sensor 38 for detecting the clutch pedal depression amount Pc (%), which is the amount of operation of the clutch pedal 28. The signal detected by the clutch position sensor 38 is output to the control device 50.

In this electric vehicle 10, multiple driving modes can be realized by the control of the control device 50. The multiple driving modes include a manual shift driving mode and an electric driving mode. The manual shift driving mode is a driving mode in which the drive torque of the motor 2 is controlled in response to the operation of the shift lever 26 and the clutch pedal 28 by the driver. The electric driving mode is a driving mode in which the drive torque of the motor 2 is controlled without the operation of the shift lever 26 and the clutch pedal 28. In other words, the manual shift driving mode realizes an operation feel like that of an MT vehicle. The electric driving mode provides an operation feel like that of an AT vehicle, and does not require the operation of the shift lever 26 and the clutch pedal 28 by the driver, but controls the drive torque of the motor 2 in response to the operation of the accelerator pedal 22 and the brake pedal 24 by the driver.

The control device 50 is an ECU (Electronic Control Unit). The processing circuit of the control device (hereinafter referred to as ECU) 50 includes an input/output interface 52, a memory 54, and a CPU 56. The input/output interface 52 receives sensor signals from various sensors attached to the electric vehicle 10 and outputs operation signals to various actuators equipped in the electric vehicle 10. The sensors from which the ECU 50 receives signals include the various sensors described above as well as various sensors necessary for controlling the electric vehicle 10. The actuators from which the ECU 50 outputs operation signals include various actuators such as the motor 2 described above. The memory 54 stores various control programs for controlling the electric vehicle 10, the latest shift position Gp, maps, etc. The CPU 56 reads out and executes the control programs, etc. from the memory 54, and generates operation signals based on the received sensor signals.

The control of the electric vehicle 10 performed by the ECU 50 includes torque control that controls the torque transmitted to the drive wheels 8. In this torque control, the drive torque of the motor 2 is controlled so that the motor drive torque Tp transmitted to the propeller shaft 5 becomes the motor required drive torque Tpreq.

In other words, the ECU 50 has a required driving force calculation unit that calculates the driving force (required driving force) required of the electric vehicle 10 by the driver, and a torque control unit that controls the torque output from the motor 2 so that the driving force of the motor 2 becomes the required driving force.

The required driving force calculation unit calculates the required driving force based on the accelerator opening Pap and the vehicle speed. For example, the ECU 50 detects the vehicle speed using the wheel rotation speed Nw from the wheel rotation speed sensor 42. The required driving force calculation unit then calculates the required driving force based on the accelerator opening Pap and the vehicle speed using a predetermined map. This map is pre-stored in a memory unit provided in the ECU 50. The torque control unit also calculates the driving torque of the motor 2 so as to obtain a driving force that satisfies the required driving force calculated by the required driving force calculation unit. Note that when detecting the vehicle speed, the ECU 50 is not limited to a configuration in which the vehicle speed is detected using the wheel rotation speed Nw from the wheel rotation speed sensor 42, and may calculate the vehicle speed using the shaft rotation speed Np from the shaft rotation speed sensor 40.

In addition, in the torque control of the motor 2, the ECU 50 performs calculations assuming that the driving state of the electric vehicle 10 is realized by a MT vehicle equipped with a virtual engine and transmission during the manual gear shift driving mode. The ECU 50 then calculates the transmission output torque Tgout output from the transmission, and uses the calculated transmission output torque Tgout as the motor required driving torque Tpreq. In the following description, the engine virtually installed in the electric vehicle 10 is referred to as a "virtual engine", the engine output torque of the virtual engine is referred to as a "virtual engine output torque Teout", and the rotation speed of the virtual engine is referred to as a "virtual engine rotation speed Ne".

Figure 2 is a functional block diagram for explaining the configuration of the control device. The ECU 50 includes, as functional blocks related to the torque control of the motor 2, a virtual engine rotation speed calculation unit 500, a virtual engine output torque calculation unit 502, a torque transmission gain calculation unit 504, a clutch output torque calculation unit 506, a gear ratio calculation unit 508, a transmission output torque calculation unit 510, and a determination unit 512.

For example, while the electric vehicle 10 is traveling, the ECU 50 dynamically calculates the virtual engine rotation speed Ne based on the driving state. Specifically, the ECU 50 back-calculates the virtual engine rotation speed Ne during traveling from the following formula (1) using the shaft rotation speed Np of the propeller shaft 5, the gear ratio (speed ratio) r corresponding to the shift position Gp, and the slip rate slip of the clutch mechanism calculated from the clutch pedal depression amount Pc, etc.
Ne = Np × (1 / r) × slip ... (1)

It can be assumed that the kinetic energy that is not used to transmit torque to the propeller shaft 5 among the energy output from the virtual engine is used to increase the virtual engine rotation speed Ne. Therefore, the virtual engine rotation speed Ne may be dynamically calculated based on a motion equation based on kinetic energy.

In addition, when assuming an MT vehicle, idle speed control (ISC control) is performed to maintain the engine speed at a constant speed while the MT vehicle is idling. Therefore, taking into account the ISC control in the virtual engine, for example, when the shaft rotation speed Np is 0 (zero) and the accelerator opening Pap is 0%, the ECU 50 assumes that the virtual engine is idling and outputs the virtual engine rotation speed Ne as a predetermined idling rotation speed (for example, 1000 rpm). The calculated virtual engine rotation speed Ne is output to the virtual engine output torque calculation unit 502.

The virtual engine output torque calculation unit 502 executes a process to calculate the virtual engine output torque Teout. The accelerator opening Pap and the virtual engine rotation speed Ne are input to the virtual engine output torque calculation unit 502. The memory 54 of the ECU 50 stores a map in which the virtual engine output torque Teout relative to the virtual engine rotation speed Ne is specified for each accelerator opening Pap. An example of the map is shown in FIG. 3. The virtual engine output torque calculation unit 502 calculates the virtual engine output torque Teout corresponding to the input accelerator opening Pap and virtual engine rotation speed Ne using the map shown in FIG. 3. The calculated virtual engine output torque Teout is output to the clutch output torque calculation unit 506.

The torque transmission gain calculation unit 504 executes a process to calculate the torque transmission gain k. The torque transmission gain k is a gain for calculating the degree of torque transmission according to the depression amount of the clutch for operating the clutch mechanism connected to the virtual engine. The clutch pedal depression amount Pc is input to the torque transmission gain calculation unit 504. The memory 54 of the ECU 50 stores a map in which the torque transmission gain k for the clutch pedal depression amount Pc is specified. An example of the map is shown in FIG. 4. As shown in FIG. 4, the torque transmission gain k is 1 when the clutch pedal depression amount Pc is in the range of pc0 to pc1, and gradually decreases toward 0 as the clutch pedal depression amount Pc increases when the clutch pedal depression amount Pc is in the range of Pc1 to Pc2, and is 0 when the clutch pedal depression amount Pc is in the range of Pc1 to Pc2. Here, Pc0 corresponds to the position where the clutch pedal depression amount Pc is 0%, Pc1 corresponds to the position of the play limit when depressing from Pc0, Pc3 corresponds to the position where the clutch pedal depression amount Pc is 100%, and Pc2 corresponds to the position of the play limit when releasing from Pc3. The torque transmission gain calculation unit 504 calculates the torque transmission gain k corresponding to the input clutch pedal depression amount Pc using the map shown in FIG. 4. The calculated torque transmission gain k is output to the clutch output torque calculation unit 506.

The clutch output torque calculation unit 506 executes a process of calculating a clutch output torque Tcout. The clutch output torque Tcout is a torque output from a clutch mechanism connected to the virtual engine. The virtual engine output torque Teout and the torque transmission gain k are input to the torque transmission gain calculation unit 504. The clutch output torque calculation unit 506 calculates the clutch output torque Tcout using the following formula (2) that multiplies the virtual engine output torque Teout by the torque transmission gain k. The calculated clutch output torque Tcout is output to the transmission output torque calculation unit 510.
Tcout = Teout × k (2)
In addition, an actual clutch mechanism often includes a damping device such as a spring, a damper, etc. Therefore, the clutch output torque Tcout may be calculated as a dynamic transmission torque taking into account the characteristics of each of the devices.

The gear ratio calculation unit 508 executes a process to calculate the gear ratio r. The gear ratio r is a torque characteristic of the motor 2 corresponding to a plurality of shift speed modes, and simulates the gear ratio of the transmission. The shift position Gp is input to the gear ratio calculation unit 508. The memory 54 of the ECU 50 stores a map in which the gear ratio r for the shift position Gp is specified. An example of the map is shown in FIG. 5. As shown in FIG. 5, the gear ratio r is specified so that the gear ratio r is lower as the shift position Gp is a higher gear. The gear ratio calculation unit 508 calculates the gear ratio r corresponding to the input shift position Gp using the map shown in FIG. 5. The calculated gear ratio r is output to the transmission output torque calculation unit 510.

The transmission output torque calculation unit 510 executes a process of calculating the transmission output torque Tgout. The transmission output torque Tgout is a torque output from the transmission. The clutch output torque Tcout and the gear ratio r are input to the transmission output torque calculation unit 510. The transmission output torque calculation unit 510 calculates the transmission output torque Tgout by using the following formula (3) that multiplies the clutch output torque Tcout by the gear ratio r.
Tgout = Tcout × r (3)

In this way, during torque control in the manual shift driving mode, the ECU 50 sequentially executes processing in the virtual engine output torque calculation unit 502, torque transfer gain calculation unit 504, clutch output torque calculation unit 506, gear ratio calculation unit 508, and transmission output torque calculation unit 510. The calculated transmission output torque Tgout is then output to the inverter 16 as the motor required drive torque Tpreq. The inverter 16 controls the command value to the motor 2 so that the motor drive torque Tp approaches the calculated motor required drive torque Tpreq. In torque control, such processing is repeatedly executed at a predetermined control period, thereby controlling the motor drive torque Tp to the motor required drive torque Tpreq.

The driver of the electric vehicle 10 performs a manual shift operation at any timing during driving with the manual shift driving mode selected. FIG. 6 is an operation flow diagram showing the procedure of the pseudo manual shift operation performed by the driver. As shown in FIG. 6, when the driver performs a pseudo manual shift operation in the electric vehicle 10, the driver first depresses the clutch pedal 28 (step S101). When the clutch pedal depression amount Pc exceeds Pc1, the clutch output torque Tcout changes toward 0 as the clutch pedal depression amount Pc increases. Then, when the clutch pedal depression amount Pc exceeds Pc2, the clutch output torque Tcout becomes 0. According to such a depression operation of the clutch pedal 28, the motor drive torque Tp changes toward 0 in response to the depression operation of the clutch pedal 28, so the driver can feel the sensation of torque being released when depressing the clutch pedal of the MT vehicle.

Next, the driver operates the shift lever 26 with the clutch pedal 28 depressed (step S102). For example, the gear shift mode of the shift lever 26 is changed from 1st gear to 2nd gear. By operating the shift lever 26 while depressing the clutch pedal 28 in this manner, the driver can obtain a feeling similar to the manual gear shifting operation of an MT vehicle.

Then, the driver releases the clutch pedal 28 (step S103). When the clutch pedal depression amount Pc falls below Pc3, the clutch output torque Tcout changes toward the virtual engine output torque Teout as the clutch pedal depression amount Pc decreases. Then, when the clutch pedal depression amount Pc falls below Pc1, the clutch output torque Tcout becomes the virtual engine output torque Teout. With this type of clutch pedal 28 return operation, the motor drive torque Tp changes toward the motor drive torque Tp reflecting the current mode in response to the clutch pedal 28 return operation, so the driver can feel the sensation of torque being connected when releasing the clutch pedal of an MT vehicle.

In this way, with the electric vehicle 10, the torque changes in response to the operation of the clutch pedal 28, allowing the driver to virtually experience the unique shifting sensation of an MT vehicle through manual shifting. In addition, the virtual engine output torque calculation unit 502, the torque transmission gain calculation unit 504, the clutch output torque calculation unit 506, the gear ratio calculation unit 508, and the transmission output torque calculation unit 510 function as a torque control unit that enables the manual shifting driving mode to be executed.

The determination unit 512 executes a process to determine whether or not a driving force shortage occurs relative to the requested driving force while the electric vehicle 10 is traveling. This determination unit 512 compares the driving force that can be output in the currently selected gear shift mode while traveling in the manual gear shift traveling mode with the requested driving force requested by the driver to the electric vehicle 10, and determines whether or not a driving force shortage occurs relative to the requested driving force.

Figure 8 is a flow chart showing the driving force determination flow performed while driving in the manual gear shift driving mode. Note that the control shown in Figure 8 is repeatedly executed by the ECU 50 while the driving mode is selected as the manual gear shift driving mode.

While traveling in the manual gear shift traveling mode, the ECU 50 compares the driving force that can be output in the currently selected gear shift mode with the required driving force, and determines whether or not there is a shortage of driving force relative to the required driving force (step S201). In step S201, a determination process is performed by the determination unit 512. For example, when the electric vehicle 10 travels on a steep uphill road, the required driving force becomes large.

In step S201, for example, if the currently selected gear mode is third gear, the determination unit 512 compares the driving force that can be output with the torque characteristics in the third gear mode with the required driving force. That is, using the upper limit value of the driving force of the motor 2 set in the third gear mode, the determination unit 512 compares the upper limit value of the driving force with the required driving force. If the required driving force is greater, it is determined that a driving force shortage will occur in the currently selected third gear mode.

If it is determined that there is no insufficient driving force relative to the requested driving force (step S201: No), this control routine ends.

If it is determined that the driving force is insufficient relative to the required driving force (step S201: Yes), the ECU 50 increases the upper limit of the driving force in the current gear mode (step S202). In step S202, the upper limit of the driving force is changed so that the upper limit of the driving force in the torque characteristic (e.g., as shown in FIG. 7) preset as the currently selected gear mode becomes a larger value.

In the process of step S202, the ECU 50 can raise the upper limit of the driving force of the selected gear mode within the output range of the motor 2 for the torque characteristics in that gear mode. For example, when raising the upper limit of the driving force in the third gear mode, the upper limit of the driving force can be changed to a value close to the torque characteristics of the second gear mode. In this way, the upper limit of the driving force can be changed so as to approach the torque characteristics of the lower gear than the currently set gear. Alternatively, the upper limit can be changed to the maximum of the output range of the motor 2. In short, the upper limit can be changed to a driving force that can satisfy the required driving force or a driving force that can minimize the shortage of driving force. As a result, it becomes possible to run in the selected gear mode even on a steep uphill road by raising the upper limit of the driving force. As a result, drivability is improved. When the process of step S202 is performed, this control routine ends.

As described above, according to the embodiment, when it is determined that the driving force is insufficient relative to the required driving force while traveling in the manual gear shift driving mode, the upper limit value of the driving force in the current gear shift mode can be raised. This makes it possible to suppress the driving force shortage. Furthermore, by selecting the manual gear shift driving mode, it is possible to provide the driver with a driving sensation similar to that of a manual transmission vehicle.

2 Motor 10 Electric vehicle 22 Accelerator pedal 24 Brake pedal 26 Shift lever (shift device)
28 Clutch pedal (clutch device)
50 Control unit (ECU)
512 Determination unit

Claims (1)

A traction motor,
a clutch device that is operated by a driver and is capable of changing an amount of torque applied from the electric motor to the wheels;
a shift device for selecting one of a plurality of gear modes in which torque characteristics with respect to the rotation speed of the motor are gradually changed;
a control device having a torque control unit capable of executing a manual gear shift driving mode that controls the torque of the electric motor so as to have a torque characteristic corresponding to the gear shift mode selected by the driver's operation of the clutch device and the shift device;
Equipped with
The electric motor and the wheels are constantly connected to each other,
An electric vehicle that does not have an engine and does not have a transmission and a clutch mechanism such as those provided in a manual transmission vehicle,
the clutch device is a clutch pedal having a structure simulating a clutch pedal provided in the manual transmission vehicle,
the control device has a determination unit that, while traveling in the manual transmission traveling mode, compares a required driving force with a driving force that can be output based on a torque characteristic of the currently selected gear shift mode, and determines whether or not a driving force shortage occurs with respect to the required driving force,
a torque characteristic of the gear shift mode is set to a torque characteristic simulating a gear shift of the manual transmission vehicle, and an upper limit value is set for the driving force of the electric motor for each gear shift mode;
When the determination unit determines that a driving force shortage occurs with respect to the requested driving force, the torque control unit changes an upper limit value of the driving force in the currently selected gear mode so as to approach a torque characteristic of a gear mode on a lower gear stage side than the currently selected gear mode .
An electric vehicle characterized by:

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