JP6881274B2 - Vehicle drive - Google Patents

Description

The present invention relates to a vehicle drive device that controls the operation of an electric motor as a vehicle drive source.

A vehicle such as an electric vehicle having an electric motor for driving a drive wheel is provided with a motor control unit that controls the operation of the electric motor, a storage battery that supplies electric power to the electric motor and the motor control unit, and the like (see Patent Document 1). ).

When driving such a vehicle, the control target value (torque indicated value) of the output torque of the electric motor is calculated based on the vehicle operating state such as the vehicle speed and the accelerator operation amount, and the output corresponding to the torque command value is calculated. The operation of the electric motor is controlled so that torque is obtained.

Japanese Unexamined Patent Publication No. 7-2129111

Here, when the vehicle is traveling on a downhill road, the vehicle tends to accelerate, so that the vehicle speed tends to increase. From this, when the vehicle speed exceeds a predetermined predetermined speed, the torque command value is set to negative torque (direction of decelerating the vehicle [reverse rotation direction]] even when the accelerator operating member is turned on. It is conceivable to implement a vehicle speed limit such as setting the torque to act on the vehicle. By executing such a vehicle speed limit, it is possible to limit the maximum speed of the vehicle so that the vehicle speed does not become too high.

However, when such a vehicle speed limit is executed, a so-called hunting phenomenon may occur in which the decelerating state (hereinafter [state A]) and the accelerating state (same [state B]) are repeatedly switched in a short cycle. ..

[State A] When the vehicle speed exceeds the specified speed as the vehicle accelerates, the output torque of the electric motor is forcibly negative torque, and then the vehicle decelerates.
[State B] When the vehicle decelerates and the vehicle speed falls below the specified speed by setting the output torque of the electric motor to a negative torque, the output torque of the electric motor becomes a positive torque according to the vehicle operating state (direction of accelerating the vehicle [direction to accelerate the vehicle]. The torque acts in the forward rotation direction], and then the vehicle accelerates.

Then, the occurrence of such a hunting phenomenon may cause a vibration that causes the vehicle to rattle in small steps, thereby lowering drivability.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicle drive device capable of suppressing a decrease in drivability due to execution of a vehicle speed limit.

The vehicle drive device for solving the above problems includes an electric motor for driving the vehicle drive wheels and a motor control unit for controlling the operation of the electric motor so that an output torque according to the vehicle operating state can be obtained. In the vehicle driving device, when the condition that the accelerator operating member is turned on and the vehicle speed is equal to or higher than a predetermined predetermined speed is satisfied, the motor control unit of the electric motor The output torque is set to a negative torque, and the switch of the output torque to a positive torque is restricted during the period from when the condition is satisfied until the vehicle speed falls below the return speed lower than the specified speed. Is.

The vehicle drive device for solving the above problems includes an electric motor for driving the vehicle drive wheels and a motor control unit for controlling the operation of the electric motor so that an output torque according to the vehicle operating state can be obtained. In the vehicle driving device, when the condition that the accelerator operating member is turned on and the vehicle speed is equal to or higher than a predetermined predetermined speed is satisfied, the motor control unit of the electric motor The output torque is set to a negative torque, and the switching of the output torque to a positive torque is restricted during a period from the establishment of the above conditions to the elapse of a predetermined fixed time.

In the above configuration, when the vehicle speed exceeds the specified speed while the accelerator operating member is turned on, a negative torque is output from the electric motor in order to limit the vehicle speed. Then, in the predetermined period immediately after that, the switching of the output torque of the electric motor to the positive torque is restricted, so even if the vehicle speed falls below the specified speed due to the vehicle deceleration at this time, the output of the negative torque from the electric motor is output. It will be continued. As a result, it is possible to suppress the occurrence of a hunting phenomenon in which a negative torque is output from the electric motor to decelerate the vehicle and a positive torque is output to accelerate the vehicle in a short cycle. It is possible to suppress the occurrence of vehicle vibration. Therefore, according to the above configuration, it is possible to suppress a decrease in drivability when the vehicle speed is limited.

In the vehicle drive device, it is preferable that the motor control unit controls the operation of the electric motor so that a predetermined constant torque is output as the negative torque.

According to the above configuration, the output torque of the electric motor when the vehicle speed is limited can be made constant regardless of the vehicle operating state, so that the control structure for controlling the operation of the electric motor can be simplified. Moreover, it is possible to stabilize the driving state of the vehicle by suppressing fluctuations in the output torque of the electric motor when the vehicle speed limit is executed.

In the vehicle drive device, when the motor control unit switches the output torque of the electric motor from the negative torque to the positive torque according to the vehicle operating state when the period elapses, the output torque gradually increases. It is preferable to control the operation of the electric motor so as to change to.

According to the above configuration, when the vehicle speed limit is released due to the elapse of the above period, the output torque of the electric motor is changed from the negative torque for the vehicle speed limit to the positive torque according to the vehicle driving state while suppressing the sudden change. Can be switched to. Therefore, it is possible to suppress a decrease in drivability due to a sudden change in the output torque of the electric motor.

In the vehicle drive device, it is preferable that the motor control unit releases the restriction on switching to the positive torque when the accelerator operating member is turned off during the period.

According to the above configuration, when the accelerator operating member is turned off during the period in which the switching of the output torque of the electric motor to the positive torque is restricted, the driver indicates the intention to change the output torque of the electric motor. If so, the restriction on the switching of the output torque can be lifted. As a result, the execution mode of the operation control of the electric motor can be returned to the execution mode in which the vehicle speed is not limited.

In the vehicle drive device, the motor control unit includes a target value calculation unit that calculates a control target value of the output torque based on the vehicle operating state, and the electric motor so that an output torque corresponding to the control target value can be obtained. It has an operation control unit that controls the operation of the motor, and makes the output torque of the electric motor negative torque by making the control target value negative torque, and to the positive torque of the control target value. By limiting the switching of the output torque, the switching of the output torque to the positive torque is restricted.

According to the above configuration, in a device having a target value calculation unit for calculating the control target value of the output torque of the electric motor, the output torque of the electric motor can be made negative torque or the output torque of the same output torque can be set by setting the control target value. It is possible to limit the switching to positive torque.

According to the vehicle drive device of the present invention, it is possible to suppress a decrease in drivability due to execution of vehicle speed limitation.

The schematic diagram which shows the schematic structure of one Embodiment of a vehicle drive device. The schematic diagram which shows the structure of the map used for the calculation of a torque command value. The explanatory view which shows an example of the transition of the torque command value when the vehicle travels on a downhill road. A timing chart showing an example of the relationship between (a) accelerator operation amount, (b) vehicle speed, and (c) torque command value when the vehicle is traveling on a downhill road. A timing chart showing an example of the relationship between (a) the accelerator operating amount, (b) the vehicle speed, and (c) the torque command value when the accelerator operating member is turned off in a predetermined period. A flowchart showing an execution procedure of switching restriction processing. The flowchart which shows the execution procedure of the switching restriction processing of the modification.

Hereinafter, an embodiment of the vehicle drive device will be described.
As shown in FIG. 1, the vehicle 10 is equipped with an electric motor 11 as a drive source. The electric motor 11 is a three-phase AC motor, and the output shaft of the electric motor 11 is connected to the drive wheels 12 of the vehicle 10. Further, the vehicle 10 is provided with a storage battery 13 and an inverter 14 as a power source. A storage battery 13 is connected to the electric motor 11 via an inverter 14. Then, in the present embodiment, the electric power supplied from the storage battery 13 to the electric motor 11 is adjusted through the operation control of the inverter 14.

The vehicle 10 has various sensors for detecting the driving state of the vehicle. Specifically, the accelerator sensor 15 for detecting the operation amount (accelerator operation amount AC) of the accelerator operation member 15A (for example, the accelerator pedal) and the vehicle speed sensor 16 for detecting the traveling speed (vehicle speed SPD) of the vehicle 10. And so on.

The vehicle 10 is provided with an electronic control device 17 including, for example, a microprocessor. The electronic control device 17 includes a target value calculation unit 18 that calculates a control target value (torque command value T) of the output torque of the electric motor 11, and a command signal output unit 19 that generates an operation command signal (pulse signal) of the inverter 14. And have.

The output signals of various sensors are taken into the target value calculation unit 18. Then, the target value calculation unit 18 calculates the torque command value T from the map based on the accelerator operation amount AC and the vehicle speed SPD. As the structure of the map is conceptually shown in FIG. 2, the torque command value T is basically a value that increases as the accelerator operation amount AC increases (specifically, a value that increases the output torque of the electric motor 11). ) Is calculated, and the lower the vehicle speed SPD, the larger the value is calculated.

Further, a torque command value T is input to the command signal output unit 19. The command signal output unit 19 generates an operation command signal for the electric motor 11 to output a torque corresponding to the torque command value T, and outputs the operation command signal to the inverter 14. Then, the inverter 14 operates in response to this operation command signal.

In the present embodiment, by controlling the operation of the inverter 14 in this way, the operation of the electric motor 11 is performed so that an output torque corresponding to the vehicle operating state (accelerator operation amount AC and vehicle speed SPD) at that time can be obtained. Is now controlled.

In this embodiment, the inverter 14 and the command signal output unit 19 correspond to an operation control unit that controls the operation of the electric motor 11 so that the output torque corresponding to the torque command value T can be obtained, and the inverter 14 and the target value are calculated. The unit 18 and the command signal output unit 19 correspond to the motor control unit.

Further, in the present embodiment, in the operation control of the electric motor 11, control for limiting the maximum speed of the vehicle 10 (vehicle speed limit control) is executed. Specifically, as shown in FIG. 2, when the following (condition A) and (condition B) are both satisfied, a predetermined negative torque Ta (for example, -2.0) is set as the torque command value T. [Nm]) is calculated.

(Condition A) The accelerator operating member 15A is turned on (accelerator operating amount AC> 0).
(Condition B) The vehicle speed SPD is equal to or higher than a predetermined predetermined speed ωa (for example, 75 km / h).

Here, in the device of the comparative example in which the torque command value T is set to a predetermined negative torque Ta when the vehicle speed SPD is simply equal to or higher than the specified speed ωa, the vehicle 10 is decelerated as described above (see [State A] above). ) And the accelerating state (see [State B] above) are repeatedly exchanged in a short cycle (for example, several tens of milliseconds), that is, a so-called hunting phenomenon may occur. Then, the occurrence of such a hunting phenomenon causes a vibration that causes the vehicle 10 to rattle and rattle, resulting in a decrease in drivability.

In the present embodiment, the return speed ωb (for example, 72 km / h), which is a speed lower than the specified speed ωa, is defined in the operation control of the electric motor 11. Then, in a predetermined period from when both (Condition A) and (Condition B) are satisfied and the execution of the vehicle speed limit control is started until the vehicle speed SPD falls below the return speed ωb, the torque command value T is predetermined. Switching from negative torque Ta to positive torque is restricted. Specifically, in the predetermined period, a predetermined negative torque Ta is calculated as the torque command value T.

Hereinafter, the action and effect of limiting the switching of the torque command value T in this way will be described with reference to FIGS. 3 and 4. Note that FIG. 3 shows an example of the transition of the torque command value T when the vehicle 10 is traveling on a downhill road in a state where the accelerator operation amount AC is constant (AC> 0). Further, FIG. 4 shows the accelerator operation amount AC (FIG. 4 (a)) and the vehicle speed SPD (FIG. 4 (FIG. 4)) when the vehicle 10 is traveling on a downhill road in a state where the accelerator operation amount AC is constant (AC> 0). An example of the relationship between b)) and the torque command value T (FIG. 4 (c)) is shown.

As shown in FIG. 3, when the vehicle speed SPD is lower than the specified speed ωa (operating point A in FIG. 3), the torque command value T is a positive torque corresponding to the vehicle driving state. At this time, the vehicle 10 is accelerating because it is traveling on a downhill road (same operating point A → operating point B).

Then, when the vehicle speed SPD becomes equal to or higher than the specified speed ωa (operating point B), the torque command value T becomes a predetermined negative torque Ta (operating point C). As a result, negative torque is output from the electric motor 11, so that the vehicle 10 is decelerated. As described above, in the present embodiment, when the vehicle speed SPD becomes the specified speed ωa or more in the state where the accelerator operating member 15A is turned on (accelerator operating amount AC> 0), the electric motor is used to limit the vehicle speed SPD. Negative torque comes to be output from 11.

In the example shown in FIG. 3, immediately after the vehicle speed SPD becomes equal to or higher than the specified speed ωa, the vehicle speed SPD becomes lower than the specified speed ωa as the vehicle decelerates. However, after that, the torque command value T is held at a predetermined negative torque Ta for a predetermined period (operating point C → operating point D) until the vehicle speed SPD falls below the return speed ωb. At this time, the output of the negative torque from the electric motor 11 is continued.

Then, when the vehicle speed SPD falls below the return speed ωb due to the further deceleration of the vehicle 10 (operating point D), the execution of the vehicle speed limit control is stopped, and the torque command value T is set based on the accelerator operation amount AC and the vehicle speed SPD. It returns to the control (normal control) calculated from FIG. 2). In the example shown in FIG. 3, since the accelerator operating member 15A is turned on at this time (accelerator operating amount> 0), the positive torque is calculated as the torque command value T.

As shown in FIG. 4, also in the present embodiment, the output torque of the electric motor 11 becomes a negative torque and the vehicle 10 decelerates due to the execution of the vehicle speed limit control (time t11 to FIG. 4 in FIG. 4). The state in which the same output torque becomes a positive torque and the vehicle 10 accelerates (before the same time t11 and after the time t12) is periodically and repeatedly replaced with t12).

However, in the present embodiment, the vehicle speed SPD is set immediately after the vehicle speed SPD (the figure (b)) becomes the specified speed ωa or more and the torque command value T (the figure (c)) becomes the predetermined negative torque Ta. Even if the speed falls below the specified speed ωa, the torque command value T is maintained at the predetermined negative torque Ta for a predetermined period (same time t11 to t12) until the vehicle speed SPD falls below the return speed ωb.

Therefore, as compared with the device of the comparative example, the time from when the vehicle speed SPD becomes equal to or higher than the specified speed ωa and the output torque of the electric motor 11 becomes negative torque until the same output torque is switched to positive torque (in FIG. 3). The time required for the transition from the operating point C to the operating point D) can be lengthened.

Moreover, as compared with the device of the comparative example, the vehicle speed SPD becomes the specified speed ωa or more again after the restriction on switching the torque command value T is lifted and the torque command value T becomes a positive torque commensurate with the vehicle operating state. It is also possible to lengthen the time until the torque command value T becomes a predetermined negative torque Ta (the time required for the transition from the operating point E to the operating point B in FIG. 3).

As a result, it is possible to suppress the occurrence of a hunting phenomenon in which a negative torque is output from the electric motor 11 to decelerate the vehicle 10 and a positive torque is output to accelerate the vehicle 10 in a short cycle. Specifically, as compared with the device of the comparative example, the cycle in which the decelerating state and the accelerating state of the vehicle 10 are switched can be lengthened (for example, several seconds), so that the vehicle 10 is shaken in small steps. It is possible to suppress the occurrence of vehicle vibration with a short cycle (for example, several tens of milliseconds). Therefore, it is possible to suppress a decrease in drivability due to the execution of vehicle speed limit control. In this embodiment, based on the results of various experiments and simulations, a vehicle speed SPD that can appropriately suppress a decrease in drivability by removing the restriction on switching the torque command value T is required in advance. Therefore, the same vehicle speed SPD is defined as the return speed ωb.

Further, in the present embodiment, the output torque of the electric motor 11 during execution of the vehicle speed limit control (the above-mentioned predetermined period) becomes constant regardless of the vehicle operating state. Therefore, the process of calculating the torque command value T can be simplified, and the control structure for controlling the operation of the electric motor 11 can be simplified. Moreover, it is possible to stabilize the driving state of the vehicle 10 by suppressing fluctuations in the output torque of the electric motor 11 during execution of the vehicle speed limit control.

Here, when driving the vehicle 10, the driver operates the accelerator operating member 15A in order to change the vehicle acceleration and the vehicle speed SPD. Therefore, when the output torque of the electric motor 11 changes in accordance with the operation of the accelerator operating member 15A by the driver, it is unlikely that the change will give the driver a sense of discomfort, and it is unlikely that the drivability will be reduced. I can say.

Based on this point, in the present embodiment, in a predetermined period immediately after the vehicle speed SPD becomes equal to or higher than the specified speed ωa and the torque command value T becomes a predetermined negative torque Ta (for example, times t11 to t12 in FIG. 4). When the accelerator operating member 15A is turned off (accelerator operating amount AC = 0), the restriction on switching the torque command value T to the positive torque is released.

Hereinafter, the action and effect of releasing the restriction on switching the torque command value T to the positive torque in this way will be described with reference to FIG. FIG. 5 shows the accelerator operating amount AC (FIG. 5 (a)), the vehicle speed SPD (FIG. 5 (b)), and the torque command value T (FIG. 5 (c)) when the accelerator operating member 15A is turned off during the predetermined period. )) Is shown as an example of the relationship.

As shown in FIG. 5, when the vehicle speed SPD reaches the specified speed ωa (time t21) with the accelerator operating member 15A turned on (accelerator operating amount AC> 0), the torque command value T becomes a predetermined negative torque Ta. Become. Immediately after that (time t21 to t22), since the vehicle speed SPD is equal to or higher than the return speed ωb, the torque command value T is held at a predetermined negative torque Ta.

In the present embodiment, when the accelerator operating member 15A is turned off in this state (time t22), the execution of the vehicle speed limit control is forcibly stopped, and the restriction on switching the torque command value T to the positive torque is released. Will be done. As a result, the operation control of the electric motor 11 is switched to an execution mode in which the torque command value T is calculated based on the vehicle driving state (accelerator operation amount AC and vehicle speed SPD). Specifically, since the accelerator operating member 15A is turned off at this time (accelerator operating amount AC = 0), the torque command value T according to the off operating state of the accelerator operating member 15A is calculated based on the vehicle speed SPD. .. After that, when the accelerator operating member 15A is turned on (time t23), the torque command value T is calculated from the map (see FIG. 2) based on the accelerator operating amount AC and the vehicle speed SPD. At this time, a positive torque corresponding to the on-operation state of the accelerator operating member 15A is calculated as the torque command value T.

As described above, in the present embodiment, it is assumed that the driver indicates the intention to change the output torque of the electric motor 11 when the accelerator operating member 15A is turned off during the predetermined period. , The restriction on the switching of the torque command value T) can be released. Therefore, the execution mode of the operation control of the electric motor 11 can be returned to the execution mode in which the vehicle speed is not limited while suppressing the decrease in drivability.

Hereinafter, the execution procedure of the process for limiting the switching of the torque command value T described above (switching limiting process) will be described in detail with reference to FIG. FIG. 6 shows a specific execution procedure of the switching restriction process, and the series of processes shown in the flowchart of the figure are interrupt processes at predetermined cycles (for example, several tens of milliseconds), and the target value calculation unit 18 Is executed by.

As shown in FIG. 6, in this process, first, it is determined whether or not the accelerator operating member 15A is turned on (step S101). Then, when the accelerator operating member 15A is turned off (step S101: NO), a torque command value T corresponding to the state in which the accelerator operating member 15A is turned off is calculated based on the vehicle speed SPD (step S101: NO). Step S102).

On the other hand, when the accelerator operating member 15A is turned on (step S101: YES), the calculation mode of the torque command value T is switched according to the vehicle speed SPD (steps S103 to S107).

When the vehicle speed SPD is equal to or higher than the specified speed ωa (step S103: YES), a predetermined negative torque Ta is calculated as the torque command value T (step S104). In this case, vehicle speed limit control that limits the maximum speed of the vehicle 10 is executed.

When the vehicle speed SPD is less than the specified speed ωa and is greater than or equal to the return speed ωb (step S103: NO and step S105: YES), the torque command value Ti calculated at the previous execution of this process is a predetermined negative torque. If it is Ta (step S106: YES), a predetermined negative torque Ta is calculated as the torque command value T (step S104). In this case, although the vehicle speed SPD once becomes equal to or higher than the specified speed ωa and the torque command value T becomes a predetermined negative torque Ta, the vehicle speed SPD falls below the specified speed ωa, but the vehicle speed SPD increases. Assuming that the return speed is not lower than ωb, the torque command value T is held at a predetermined negative torque Ta in order to continue the execution of the vehicle speed limit control.

When the vehicle speed SPD is less than the specified speed ωa and is greater than or equal to the return speed ωb (step S103: NO and step S105: YES), the torque command value Ti calculated at the previous execution of this process is a predetermined negative torque. If it is not Ta (step S106: NO), the torque command value T is calculated from the map based on the vehicle driving state (step S107). In this case, although the vehicle speed SPD is less than the specified speed ωa and the return speed ωb or more, the torque command value T needs to be set to a predetermined negative torque Ta because the vehicle speed limit control is not executed. If not, the torque command value T is calculated based on the accelerator operation amount AC and the vehicle speed SPD.

When the vehicle speed SPD is less than the return speed ωb (step S103: NO and step S105: NO), the torque command value T is calculated from the map based on the accelerator operation amount AC and the vehicle speed SPD (step S107). .. In this case, the calculation of the torque command value T is executed assuming that the calculation of the torque command value T based on the vehicle driving state is executed regardless of whether or not the vehicle speed limit control is executed.

As described above, according to the present embodiment, the effects described below can be obtained.
(1) In the predetermined period from when the vehicle speed SPD becomes equal to or higher than the specified speed ω and the execution of the vehicle speed limit control is started until the vehicle speed SPD falls below the return speed ωb lower than the specified speed ωa, the torque command value T The switching from the predetermined negative torque Ta to the positive torque is restricted. Therefore, it is possible to suppress a decrease in drivability due to the execution of vehicle speed limit control.

(2) The torque command value T during execution of the vehicle speed limit control is set to a constant torque (predetermined negative torque Ta) regardless of the vehicle operating state. Therefore, the control structure for controlling the operation of the electric motor 11 can be simplified. In addition, it is possible to stabilize the driving state of the vehicle 10 by suppressing fluctuations in the output torque of the electric motor 11 during execution of the vehicle speed limit control.

(3) When the accelerator operating member 15A is turned off in a predetermined period immediately after the vehicle speed SPD becomes equal to or higher than the specified speed ωa and the torque command value T becomes a predetermined negative torque Ta, the driver outputs the electric motor 11. Assuming that the intention to change the torque is indicated, the restriction on the switching of the torque command value T can be lifted. Therefore, the execution mode of the operation control of the electric motor 11 can be returned to the execution mode in which the vehicle speed is not limited while suppressing the decrease in drivability.

<Modification example>
The above embodiment may be modified as follows.
When the torque command value T is switched from the predetermined negative torque Ta to the positive torque according to the vehicle operating state when the predetermined period elapses, the torque command value T may be gradually changed. According to such a configuration, when the restriction on switching the torque command value T is released due to the elapse of the predetermined period, the output torque of the electric motor 11 is reduced from the negative torque for limiting the vehicle speed while suppressing the sudden change. It is possible to switch to positive torque according to the vehicle driving condition. Therefore, it is possible to suppress a decrease in drivability due to a sudden change in the output torque of the electric motor 11.

Hereinafter, a specific example of the switching limiting process including the process of gradually changing the torque command value T in this way (slow change process) will be described. As shown in FIG. 7, in this process, after the torque command value T is calculated based on the vehicle driving state (accelerator operation amount AC and vehicle speed SPD) (step S107), is the vehicle returning from the vehicle speed limit control in progress? Whether or not it is determined (step S108). It should be noted that the fact that the vehicle speed limit control is being restored means that, for example, after the execution of the vehicle speed limit control is stopped, the torque command value Ti at the time of the previous execution of this process and the torque command calculated by the process of step S107 at the time of this process execution are being executed. Judgment is made based on the fact that there is no history that the difference (= T—Ti) from the value T is equal to or less than a predetermined value. Then, when it is determined that the vehicle is recovering from the vehicle speed limit control (step S108: YES), a process of gradually changing the torque command value T is executed (step S109). In this process, for example, a value (Ti + ΔT) obtained by adding a predetermined value ΔT (> 0) to the torque command value Ti at the time of the previous execution is calculated as the final torque command value T. On the other hand, when it is determined that the vehicle is not returning from the vehicle speed limit control (step S108: NO), the process of step S109 is jumped, and the value calculated in step S107 is set as the final torque command value T. To be done.

-The torque command value T during execution of vehicle speed limit control is not limited to calculating a constant value (predetermined negative torque Ta) regardless of the vehicle driving state, but slightly changes based on the accelerator operation amount AC and the vehicle speed SPD. The value to be calculated may be calculated.

-The torque command value T is set to the vehicle operating state for the period from when the vehicle speed SPD becomes equal to or higher than the specified speed ωa with the accelerator operating member 15A turned on until a predetermined fixed time (for example, several seconds) elapses. It may be a predetermined period for limiting switching to the corresponding positive torque. In such a configuration, the time limit (time for limiting the switching of the torque command value T) during which the decrease in drivability can be appropriately suppressed is obtained in advance from the results of various experiments and simulations, and the same time is fixed as described above. The time may be stored in the target value calculation unit 18. Even with the above configuration, the action and effect according to the above embodiment can be obtained. In the above configuration, for example, the processing content of step S105 of the switching restriction processing (FIG. 4) is a processing such as "determining whether or not the elapsed time after the vehicle speed SPD becomes the specified speed ωa or more is less than a certain time". It can be realized by changing the content.

-It is not necessary to release the restriction on switching the torque command value T to the positive torque when the accelerator operating member 15A is turned off during the predetermined period. In other words, even if the accelerator operating member 15A is turned off during the predetermined period, the restriction on switching the torque command value T to the positive torque is continued until the predetermined period elapses. It is also good.

-The vehicle drive device of the above embodiment includes an electric vehicle equipped with only an AC motor as a vehicle drive source, an electric vehicle equipped with only a DC motor as a vehicle drive source, and an electric motor and an internal combustion engine as vehicle drive sources. It can also be applied to hybrid vehicles equipped with and.

10 ... Vehicle, 11 ... Electric motor, 12 ... Drive wheel, 13 ... Storage battery, 14 ... Inverter, 15 ... Accelerator sensor, 15A ... Accelerator operating member, 16 ... Vehicle speed sensor, 17 ... Electronic control device, 18 ... Target value calculation unit , 19 ... Command signal output unit.

Claims (5)

A vehicle drive device comprising an electric motor for driving a vehicle drive wheel and a motor control unit for controlling the operation of the electric motor so that an output torque according to a vehicle driving state can be obtained.
The motor control unit
When the condition that the accelerator operating member is turned on and the vehicle speed is equal to or higher than a predetermined predetermined speed is satisfied, the output torque of the electric motor is set to a negative torque.
In the period from when the condition is satisfied until the vehicle speed falls below the lower return speed than the specified speed state, and are not limiting in that the output torque is changed to a positive torque,
The motor control unit is a vehicle drive device that releases a restriction on switching to positive torque when the accelerator operating member is turned off during the period. A vehicle drive device comprising an electric motor for driving a vehicle drive wheel and a motor control unit for controlling the operation of the electric motor so that an output torque according to a vehicle driving state can be obtained.
The motor control unit
When the condition that the accelerator operating member is turned on and the vehicle speed is equal to or higher than a predetermined predetermined speed is satisfied, the output torque of the electric motor is set to a negative torque.
In a period from a certain time during which the condition is predetermined from the established elapsed state, and are not limiting in that the output torque is changed to a positive torque,
The motor control unit is a vehicle drive device that releases a restriction on switching to positive torque when the accelerator operating member is turned off during the period. The vehicle drive device according to claim 1 or 2, wherein the motor control unit controls the operation of the electric motor so that a predetermined constant torque is output as the negative torque. When the motor control unit switches the output torque of the electric motor from the negative torque to the positive torque according to the vehicle operating state when the period elapses, the output torque is gradually changed. The vehicle drive device according to any one of claims 1 to 3, which controls the operation of an electric motor. The motor control unit
A target value calculation unit that calculates a control target value of the output torque based on the vehicle operating state, and an operation control unit that controls the operation of the electric motor so that an output torque corresponding to the control target value can be obtained. Have
By setting the control target value to negative torque, the output torque of the electric motor is set to negative torque.
The vehicle drive device according to any one of claims 1 to 4 , wherein the switching of the output torque to the positive torque is restricted by limiting the switching of the control target value to the positive torque.

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