JP2007329982A - Drive force controller for electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive force controller of an electric vehicle in which controllability of the vehicle can be enhanced when a motor is locked or unlocked on an uphill slope. <P>SOLUTION: In the drive force controller of an electric vehicle where lock of a drive motor is determined and the drive force of the motor is set to a limit value lower than a normal value dependent on a drive force request when lock of motor is determined, and the drive force is reset to the normal value when unlock of motor is determined, drive force change rate (torque reduction rate, torque reset rate) for varying the drive force between the normal value and the limit value is set based on the slope of road surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention belongs to the technical field of driving force control devices for electric vehicles.

In a conventional driving force control device for an electric vehicle, if the state where the driver stops the vehicle by accelerator control on an uphill road continues beyond the allowable time, it is determined that the motor is locked, and the driving force of the motor is set to the accelerator opening. By changing the normal value from the corresponding value to the limit value, overheating of the motor is suppressed (see, for example, Patent Document 1).
JP-A-9-56182

  If the driving force is limited by the motor lock determination while the vehicle is stopped on the ramp with the accelerator control, the stopped state cannot be maintained, and the vehicle slides down the ramp. At this time, in the above prior art, the driving force of the motor is changed from the normal value to the limit value at one time regardless of the road surface gradient and the motor state. There was a problem that the amount of descending changed and the controllability of the vehicle deteriorated.

  The present invention has been made paying attention to the above-mentioned problem, and an object of the present invention is to drive an electric vehicle capable of improving vehicle controllability at the time of motor lock and motor lock release on an uphill road or the like. To provide a force control device.

In order to achieve the above object, the present invention provides:
When the motor lock is determined, the motor driving force is set to a lower limit value than the normal value according to the driving force request, and when the motor lock is determined to be released, the driving force is returned to the normal value. In the driving force control device,
Driving force change rate setting means for setting a driving force change rate when changing the driving force between the normal value and the limit value based on at least one of a road surface gradient, a driving force request, or a motor state. It is characterized by that.

In the driving force control device for an electric vehicle according to the present invention, the rate of change in driving force when changing the driving force between the normal value and the limit value at the time of motor lock determination or motor lock release determination is calculated as road gradient, road surface Varying based on at least one of gradient, driving force demand or motor condition. Therefore, for example, the larger the road gradient, the smaller the driving force change rate when changing the driving force of the motor from the normal value to the limit value. The amount can be kept constant. Further, the smaller the road gradient, the smaller the driving force change rate when returning the driving force of the motor from the limit value to the normal value, whereby the fluctuation of the driving torque at the start can be suppressed.
As a result, it is possible to improve vehicle controllability when the motor is locked and when the motor lock is released on an uphill road or the like.

  Hereinafter, the best mode for carrying out the present invention will be described based on Examples 1 and 2.

First, the configuration will be described.
FIG. 1 is a configuration diagram illustrating a drive system of a hybrid vehicle to which a drive force control device for an electric vehicle according to a first embodiment is applied. 1 and an electric motor (a driving motor, hereinafter abbreviated as a motor) 2, a power split mechanism 3 using a planetary gear mechanism, a generator 4, a battery 5, and inverters 6a and 6b. And a controller 7.

  The integrated controller 7 generates a target engine torque command value and a target motor torque command value based on the accelerator opening, the vehicle speed, the battery SOC, the engine speed, and the like, and drives and controls the engine 1 and the motor 2.

In the hybrid vehicle of the first embodiment, the fuel is cut off in a region where the engine efficiency is poor, such as when starting, running at a low speed, or going down a gentle slope, and the engine 1 is stopped and the motor 2 is driven.
During normal travel, the power split mechanism 3 splits the engine power into two, and one drives the drive wheels 8 and 8 directly. The other side drives the generator 4 to generate electric power, and drives the motor 2 with this electric power to assist the driving force.
At the time of full open acceleration, power is also supplied from the battery 5 and further driving force is added.
At the time of deceleration and braking, the drive wheels 8 and 8 drive the motor 2 to operate as a generator to generate regenerative power and store it in the battery 5.

  In the first embodiment, the integrated controller 7 determines whether the motor is locked based on the motor state (motor current, motor speed, etc.). If it is determined that the motor is locked, the target motor torque command value of the motor 2 is lowered to a limit value lower than the normal value corresponding to the driving force request (accelerator opening), and the motor 2 and the inverter 6a are protected. Plan. When it is determined that the motor lock is released during the driving force limitation, the target motor torque command value of the motor 2 is returned from the limitation value to the normal value.

  At this time, in the first embodiment, at the time of motor lock determination, the torque reduction rate (driving force change rate) when changing the target motor torque command value from the normal value to the limit value, and at the time of motor lock release determination, the target motor A torque control rate setting control process is performed for setting a torque return rate (driving force change rate) when changing the torque command value from the limit value to the normal value in accordance with the road surface gradient and the accelerator opening.

[Torque control rate setting control processing]
FIG. 2 is a flowchart showing a flow of torque control rate setting control processing executed by the integrated controller 7 of the first embodiment, and each step will be described below. This control process is repeatedly performed at predetermined control cycles (corresponding to the driving force change rate setting means).

  In step S1, on the uphill road, whether the driver stops the vehicle (or travels forward at an extremely constant speed) only by accelerator control without using a brake, or performs torque limitation of the motor 2 described later. It is determined whether or not. If yes, then go to step S2, if no, go to return.

  In step S2, a motor lock determination control process (see FIG. 3) for determining whether or not the motor lock is established is performed, and the process proceeds to step S3. This motor lock determination control process will be described later.

  In step S3, it is determined whether or not it is determined in step S2 that the motor lock has been established. If YES, the process proceeds to step S4. If NO, the process proceeds to step S5.

  In step S4, torque limitation for limiting the target motor torque command value is started, and the process proceeds to step S6. Here, the torque reduction rate when changing the target motor torque command value from the normal value to the limit value is set with reference to the map shown in FIG. As shown in FIG. 4, the torque reduction rate is set to a characteristic that decreases as the road surface gradient (road surface inclination rate [%]) increases.

  In step S5, torque return for canceling the limit of the motor torque is started, and the process proceeds to step S6. Here, the torque return rate when changing the target motor torque command value from the limit value to the normal value is set with reference to the map shown in FIG. As shown in FIG. 5, the torque return rate is set to a characteristic that increases in proportion to the road surface gradient.

  In step S6, a slope detection process is performed to calculate the road surface slope rate [%], and the process proceeds to step S7 (corresponding to road surface slope detection means). In the first embodiment, at least one of a navigation system, an acceleration sensor, a gyro, a running resistance calculation, or a driving force calculation is used as a method for calculating the road surface inclination rate.

  In step S7, the torque control rate (torque reduction rate, torque return rate) of the motor 2 is set according to the gradient value (road slope rate) detected in step S6, and the process proceeds to step S8.

  In step S8, it is determined whether or not the accelerator opening change amount from the accelerator opening when the motor lock is established is less than a predetermined value (for example, 3%). If YES, the process proceeds to return, and if NO, the process proceeds to step S9.

  In step S9, the torque control rate is increased and the process proceeds to return. While the torque is limited, a torque decrease rate is added according to the road surface gradient (FIG. 6), and when the torque is restored, a torque return rate is added according to the road surface gradient (FIG. 7).

[Motor lock determination control processing]
FIG. 3 is a flowchart showing the flow of the motor lock determination control process performed in step S2 of FIG. 2, and each step will be described below.

  In step S2-1, it is determined whether or not the motor temperature is higher than a predetermined value. If YES, the process proceeds to step S2-2. If NO, the process proceeds to step S2-5.

  In step S2-2, it is determined whether or not the absolute value of the motor rotation number is less than a predetermined value. If YES, the process proceeds to step S2-3. If NO, the process proceeds to step S2-5.

  In step S2-3, it is determined whether or not the absolute value of the motor torque is greater than a predetermined value. If YES, the process proceeds to step S2-4. If NO, the process proceeds to step S2-5.

  In step S2-4, it is determined that the motor lock is established, and this control is terminated.

  In step S2-5, it is determined that the motor lock is not established, and this control is terminated.

Next, the operation will be described.
[About driving force drop due to motor lock]
In JP-A-2005-51886, as a measure against vehicle slippage on an uphill road, a vehicle balance torque with respect to a road surface gradient is calculated based on the vehicle acceleration and the motor output torque. A technique is described in which an execution torque is set based on a required torque according to an operation, and control is performed so that the execution torque is output from a motor.

However, the above prior art has the following problems.
(a) In a hybrid vehicle that uses a motor and an engine as a drive source of the vehicle, it is common to generate a drive force with the motor in order to improve fuel efficiency at low vehicle speeds. Therefore, even in the above-described prior art, when the driver stops on the uphill road by the accelerator control, only the driving force of the motor is relied upon. However, when the driving torque required for maintaining the vehicle stop calculated based on the road surface gradient is equal to or higher than the motor size, the stopped state cannot be maintained, and the vehicle slides down the uphill road.

  (b) Even if the driving force required to maintain the vehicle stopped is within the physique limit, if the system has a proportional relationship between the motor rotation speed and the vehicle drive shaft rotation speed, the shaft rotation speed is near zero rotation. Then, the motor is also near zero rotation, and it is determined that the motor is locked. For the purpose of unit protection, the motor torque is limited when the motor is locked. Therefore, on an uphill road with a certain slope or higher, the stop state cannot be maintained by the accelerator control, and the vehicle slips down.

  (c) When the vehicle moves down the slope, the motor lock is released, and by releasing the torque limit, the drive torque for maintaining the vehicle stop can be obtained. Therefore, the vehicle repeats swinging back and forth.

  (d) While the driving torque is limited by the motor lock, no matter how much the driver depresses the accelerator pedal, the driving torque corresponding to the depression cannot be obtained and the vehicle does not respond to the accelerator. It cannot be removed from the swinging state.

[Torque control rate setting action according to road surface gradient]
On the other hand, in the driving force control apparatus for an electric vehicle according to the first embodiment, the torque reduction rate when the driving force of the motor 2 is limited is made smaller as the road surface inclination rate is larger by the motor lock determination.

  At this time, as shown in FIG. 8 (a), when the driver depresses the accelerator pedal at a constant amount and the vehicle is stopped by the accelerator control, step S1 → step S2 → The flow from step S3 → step S4 → step S6 → step S7 → step S8 is repeated. That is, torque is limited based on the torque reduction rate set according to the road surface inclination rate, and the vehicle slides down (FIG. 8 (b)).

  In the prior art, the torque reduction rate is made constant regardless of the road surface inclination rate. As the road surface inclination rate increases, the amount of sliding and the speed of sliding increase, resulting in variations in vehicle behavior, resulting in poor vehicle controllability. .

  On the other hand, in the first embodiment, the amount of vehicle sliding due to the motor lock and the vehicle sliding speed can be maintained almost constant regardless of the road surface gradient. Improvements can be made.

  Further, in the first embodiment, the torque return rate when releasing the driving force restriction of the motor 2 is increased as the road surface inclination rate increases as a result of the motor lock release determination. At this time, if the driver depresses the accelerator pedal at a fixed amount and the vehicle is stopped by the accelerator control, the procedure goes from step S1, step S2, step S3, step S5, step S6, step S7, step S8. The forward flow is repeated. That is, torque return is performed based on the torque return rate set according to the road surface inclination rate, and the vehicle stops after slightly climbing (FIG. 8 (c)).

  In the prior art, since the torque return rate is constant regardless of the road surface inclination rate, when the road surface inclination rate is small, torque fluctuation occurs due to a sudden rise in driving torque, and the vehicle is likely to jump out. There was a problem of poor controllability.

  On the other hand, in the first embodiment, when the road surface inclination rate is small, the torque return rate is reduced, so that torque fluctuation and vehicle jump-out when the motor lock is released can be suppressed as compared with the prior art.

[Torque control rate setting action according to motor temperature]
In the first embodiment, when the accelerator opening while the motor torque is limited is greater than or equal to a predetermined value, it is determined that the driver has a willingness to start, and both the torque reduction rate and the torque return rate are increased. That is, the flow proceeds from step S1, step S2, step S3, step S4 (or step S5), step S6, step S7, step S8, and step S9. In step S9, the torque reduction rate (torque Return rate) is added.

  That is, when the driver depresses the accelerator, it can be determined that the vehicle is willing to start. Therefore, when the driver performs an operation to start the vehicle, the motor lock is increased by increasing the torque reduction rate. Can be released early. Further, when the driver performs an operation of starting the vehicle, it is possible to quickly escape from the state determined to be motor locked again by increasing the torque return rate.

  Therefore, even though the accelerator is depressed while the torque is reduced by the motor lock determination and the torque is restored by releasing the motor lock, the torque is limited by the continuation of the motor lock and the phenomenon that the vehicle continues to slide down is suppressed. be able to. Moreover, the vehicle behavior at the time of start can be made to follow the driver's accelerator work, and drivability can be improved.

  FIG. 9 is a time chart showing the accelerator opening, the motor torque, the motor lock determination, and the motor speed when the torque control rate setting control of the first embodiment is applied. The driver controls the vehicle on the uphill road by the accelerator control. Stopped.

  At time t1, a motor lock determination is made from the motor torque, the motor rotation speed, and the motor temperature, and the motor torque decreases according to the torque reduction rate, so the vehicle slides down the uphill road.

  At time t2, the motor lock release determination is made, and the motor torque increases according to the torque return rate, so that the vehicle climbs slightly and then stops.

  In the section from time t3 to t4, the motor torque is decreased and increased by the motor lock determination and motor lock release determination as in the time t1 to t2, so the vehicle climbs slightly after going down the uphill road, Stop. At this time, the torque decrease rate and the torque return rate are set to the same values as at the time points t1 to t2.

  At time t5, since the driver has stepped on the accelerator, the amount of change in accelerator opening ≧ predetermined value, and the torque return rate is set to a value larger than the values set at times t2 and t4. Therefore, in the section from the time point t5 to t6, the rate of increase of the motor torque is larger than that in the section from the time point t2 to t3 and the section from t4 to t5.

  At time t6, a motor lock determination is made. At this time, since the accelerator opening change amount ≧ predetermined value, the torque reduction rate is set to a value larger than the values set at the time points t1 and t3. Therefore, the section from the time point t6 to t7 is shorter than the section from the time point t3 to t4, so that the vehicle is prevented from sliding down due to the torque limitation, and can follow the accelerator work of the drive.

Next, the effect will be described.
In the driving force control apparatus for an electric vehicle according to the first embodiment, the effects listed below can be obtained.

  (1) Driving force change rate setting means for setting the driving force change rate (torque reduction rate, torque return rate) when changing the driving force between the normal value and the limit value based on the road surface gradient (FIG. 2). ). Thereby, it is possible to improve vehicle controllability when the motor is locked and when the motor is unlocked on an uphill road or the like.

  (2) The driving force change rate setting means keeps the amount of vehicle slip by the motor lock and the rate of slippage almost constant regardless of the road gradient because the torque decrease rate becomes smaller as the road gradient increases. Therefore, the vehicle controllability can be improved.

  (3) Since the driving force change rate setting means increases the torque return rate as the road surface gradient increases, it is possible to suppress torque fluctuation and vehicle jumping when the motor lock is released.

  (4) When the accelerator opening change rate is equal to or greater than the predetermined value, the driving force change rate setting means increases the torque decrease rate and the torque return rate. Even though the accelerator is stepped on during the torque recovery, the torque is limited due to the continuation of the motor lock, and the phenomenon that the vehicle continues to slide down can be suppressed. Moreover, the vehicle behavior at the time of start can be made to follow the driver's accelerator work, and drivability can be improved.

  (5) Since it has road surface gradient detection means (step S6) for detecting the road surface gradient (road surface inclination rate) using at least one of navigation system, acceleration sensor, gyroscope, driving resistance calculation or driving force calculation, high accuracy The vehicle controllability can be improved by detecting the gradient.

The second embodiment is an example in which the torque control rate is increased as the motor temperature is higher.
The configuration is the same as that of the first embodiment shown in FIG.

  In the second embodiment, as shown in FIG. 10, in the torque control rate setting control process, the torque control rate (torque reduction rate, torque return rate) is increased as the motor temperature increases. Inverter temperature may be used instead of motor temperature.

  Next, the operation will be described. Since the motor lock determination is determined based on the motor temperature, the duration of the motor lock determination becomes longer as the motor temperature is higher, and the controllability of the vehicle is deteriorated.

  On the other hand, in Example 2, the torque control rate is increased as the motor temperature is higher. Therefore, even when the motor temperature is high, the duration of the motor lock determination can be kept short. Therefore, the motor life can be improved and torque limitation due to heat can be suppressed. In addition, the controllability of the vehicle with respect to the driver's willingness to move forward or backward is also improved.

Next, the effect will be described.
In the driving force control apparatus for an electric vehicle according to the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment.

  (6) Since the driving force change rate setting means increases the torque control rate as the motor temperature increases, the motor life can be improved and torque limitation due to heat can be suppressed. In addition, the controllability of the vehicle with respect to the driver's willingness to move forward or backward is improved.

(Other examples)
The best mode for carrying out the present invention has been described based on the first and second embodiments. However, the specific configuration of the present invention is not limited to the first and second embodiments. Design changes and the like within a range that does not depart from the gist are also included in the present invention.

  For example, in the first and second embodiments, the example in which the driving force control device of the present invention is applied to a hybrid vehicle having an engine and an electric motor as drive sources is shown. However, the present invention is different from the first and second embodiments. The present invention can be applied to a hybrid vehicle having a configuration. Further, the present invention is not limited to a hybrid vehicle, and can be applied to an electric vehicle using only the motor 2 as shown in FIG.

1 is a configuration diagram illustrating a drive system of a hybrid vehicle to which a drive force control device for an electric vehicle according to a first embodiment is applied. 6 is a flowchart illustrating a flow of torque control rate setting control processing executed by the integrated controller 7 of the first embodiment. It is a flowchart which shows the flow of the motor lock determination control process implemented by step S2 of FIG. 3 is a torque reduction rate setting map according to the road surface gradient of the first embodiment. 3 is a torque return rate setting map according to the road surface gradient of the first embodiment. It is an example of a torque reduction rate setting according to the accelerator opening change amount of the first embodiment. It is an example of a torque return rate setting according to the accelerator opening change amount of the first embodiment. It is explanatory drawing which shows the vehicle behavior according to the motor lock determination and motor lock cancellation | release determination in case the driver has stopped the vehicle by accelerator control. It is a time chart which shows the accelerator opening degree, motor torque, motor lock determination, and motor rotation speed when the torque control rate setting control of the first embodiment is applied. 6 is a torque control rate installation map according to the motor temperature of Example 2. It is a figure which shows the structural example of the electric vehicle which can apply this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Motor 3 Power split mechanism 4 Generator 5 Battery 6a Inverter 6a, 6b Inverter 7 Integrated controller 8, 8 Drive wheel

Claims (7)

When the motor lock is determined, the motor driving force is set to a lower limit value than the normal value according to the driving force request, and when the motor lock is determined to be released, the driving force is returned to the normal value. In the driving force control device,
Driving force change rate setting means for setting a driving force change rate when changing the driving force between the normal value and the limit value based on at least one of a road surface gradient, a driving force request, or a motor state. A driving force control apparatus for an electric vehicle characterized by the above. The driving force control apparatus for an electric vehicle according to claim 1,
The driving force control apparatus for an electric vehicle, wherein the driving force change rate setting means reduces the driving force change rate when changing the driving force from a normal value to a limit value as the road surface gradient increases. In the driving force control device for an electric vehicle according to claim 1 or 2,
The driving force change rate setting means increases the driving force change rate when changing the driving force from a limit value to a normal value as the road surface gradient is larger. The driving force control apparatus for an electric vehicle according to any one of claims 1 to 3,
The drive force control device for an electric vehicle, wherein the drive force change rate setting means increases the drive force change rate when the driver performs an operation of starting the vehicle. The driving force control apparatus for an electric vehicle according to any one of claims 1 to 4,
The driving force change rate setting means increases the driving force change rate as the temperature of the motor or motor drive circuit is higher. The driving force control device for an electric vehicle according to any one of claims 1 to 5,
A driving force control apparatus for an electric vehicle, comprising: road surface gradient detecting means for detecting a road surface gradient using at least one of a navigation system, an acceleration sensor, a gyroscope, a running resistance calculation or a driving force calculation. When the motor lock is determined, the motor driving force is set to a lower limit value than the normal value according to the driving force request, and when the motor lock is determined to be released, the driving force is returned to the normal value. In the driving force control device,
An electric vehicle characterized in that a driving force change rate when changing a driving force between the normal value and the limit value is set based on at least one of a road surface gradient, a driving force request, or a motor state. Driving force control device.

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