JP2984724B2 - Electric car - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electric vehicle in which wheels are driven by a motor, and more particularly to an improvement in running performance.

(Conventional technology) With the recent advancement of automobile technology, technologies that improve the driving performance of automobiles include 4WS (four-wheel steering), 4WD (four-wheel drive), ABS (anti-skid brake), traction control, etc. New technologies have been proposed.

However, these new technologies involve the driving force of each wheel, so to implement them, add a new mechanical configuration to the conventional vehicle configuration and control it appropriately based on the required conditions. is necessary.

(Problems to be Solved by the Invention) In a conventional vehicle, a driving system that distributes the power of an engine as a single driving source to a plurality of driving wheels is configured. The mechanism to be provided and the mechanical configuration accompanying the addition of a new mechanism tend to be complicated due to the relationship with the configuration of the drive system, and the same applies to electric vehicles.

An object of the present invention is to provide an electric vehicle that can easily and safely turn the vehicle by appropriately controlling the steering.

(Means for Solving the Problems) To this end, a first aspect of the present invention is to provide four drive wheels on a vehicle body, install an independent drive motor for each drive wheel, and operate a front wheel by operating a steering handle. An electric vehicle provided with a steering device that steers the steering wheel, and provided with four wheel rotation sensors that detect a rotation speed of each drive wheel, and a steering angle sensor that detects a steering angle of the steering wheel; High-speed running determining means for determining that the vehicle is running at high speed based on a rotation speed signal output by a rotation sensor; and when the vehicle turns by operating the steering wheel, the high-speed running determining means performs high-speed running. When it is determined that the steering angle is detected, based on the steering angle detected by the steering angle sensor and the rotation speed signal Driving force of the two drive wheels as the inside, characterized in that a control means for controlling each drive motor to be greater than the driving force of the driving wheels as the outside during turning.

Claim 2 includes a brake sensor installed on a brake pedal, and deceleration determining means for determining that the vehicle is decelerating based on the rotation speed signal, wherein the control means determines that the deceleration determining means decelerates. When it is determined that the required braking force and the required wheel angular acceleration are determined from the brake signal output by the brake sensor and the rotation speed signal, the braking force is calculated so as not to exceed a previously stored limit braking force. Each drive motor is controlled.

Claim 3 provides an accelerator sensor installed on an accelerator pedal, an accelerator signal output by the accelerator sensor, the rotational speed signal, and a required driving force and a required wheel angular acceleration based on a previously stored limit driving force. And controlling each of the drive motors.

(Operation) According to claim 1, when the high-speed traveling determining means determines that the vehicle is traveling at a high speed when the vehicle turns, the control means sets the driving forces of the two inner driving wheels to the outer side during the turning. Since each drive motor is controlled so as to be larger than the drive force of the drive wheels, the excessive yawing moment of the vehicle center of gravity generated at the time of turning can be offset, and the stability of turning at high speed running can be improved. Can be planned. Also,
Since it is sufficient to control the drive motor, the control is easy. That is, turning at the time of high-speed running can be performed safely and easily.

According to the second aspect, when the deceleration determining unit determines that the vehicle is decelerating, the turning unit obtains the required braking force and the required wheel angular acceleration from the brake signal output by the brake sensor and the rotation speed signal, Since each of the drive motors is controlled so as not to exceed the limit braking force stored in advance, it is possible to prevent a side slip occurring at the time of sudden braking, and to ensure that each drive motor does not exceed the limit braking force. Is controlled to provide an anti-skid function.

According to the third aspect, a required driving force and a required wheel angular acceleration are obtained from an accelerator signal output from an accelerator sensor, a rotation speed signal, and a previously stored limit driving force, and each drive motor is controlled. Therefore, in cooperation with the anti-skid function, it is possible to reliably prevent the occurrence of slip on a road surface having a small friction coefficient.

According to the fourth aspect, since each drive motor is controlled so that the braking phenomenon does not occur at the time of turning, the braking phenomenon that occurs at the time of turning can be prevented.

Hereinafter, the present invention will be described with reference to an embodiment shown in the drawings. This embodiment is a four-wheel electric vehicle (hereinafter, referred to as 4WD) type, and has a four-wheel steering ( Below, 4W
S) function, anti-skid brake (ABS) function,
And a traction control function.

First, a schematic configuration of an electric vehicle will be described with reference to FIGS. 1 and 2. The electric vehicle 1 has two front wheels 2a and 2b and two rear wheels 3a and 3b arranged on both sides in the vehicle traveling direction (arrow F). The vehicle body 4 is supported on the vehicle body 4, and a front seat 6 and a rear seat 7 are installed in a vehicle compartment 5 formed in the vehicle body 4.

A steering handle 8 is provided in front of the front seat 6, and front wheels 2a and 2b are connected to the steering handle 8 via a steering device (not shown) composed of, for example, an Ackerman mechanism, so that the function of the steering wheel is provided. Is given.

In front of the front seat 6, front and rear wheels 2a, 2b, 3a, 3
An accelerator pedal 11 for adjusting the rotation speed of b and a brake pedal 12 for operating a hydraulic brake device (not shown) are provided.

Below the rear seat 7, front wheels 2a, 2b and rear wheels 3a,
A drive battery 13 for each drive motor to be described later that drives the 3b is disposed, and a controller 14 for each drive motor to be described below is installed behind the rear seat 7.

The drive device of the electric vehicle 1 is configured as shown in FIG.

That is, the respective drive systems of the left and right front wheels 2a, 2b and the left and right rear wheels 3a, 3b are similarly formed, and the drive motors as the drive sources of the respective front wheels 2a, 2b and rear wheels 3a, 3b.
Via drive shafts 23a, 23b, 24a, 24b extending from 21a, 21b, 22a, 22b, gear boxes 25a, 25b, which are configured with bevel gears or the like.
After passing through 26a, 26b, the axles 27a, 27b, 28a, 28b of these front and rear wheels
Are configured to be rotationally driven.

Here, the drive motors 21a, 21b, 22a, and 22b are driven by a current supplied from the drive battery 13, and these are controlled by signals from the controller 14 to be driven independently of each other. I have.

The controller 14 for controlling the drive motors 21a, 21b, 22a, 22b of the electric vehicle 1 is configured as shown in FIG.

That is, the controller 14 is composed of the computer 31 and four motor controllers 32a, 32b, 33a, 33b, and the drive motors 21a, 21b, 22a corresponding to the output signals from these motor controllers 32a, 32b, 33a, 33b respectively. ,
22b is independently controlled.

In addition, the computer 31 includes drive motors 21a, 21b, 22
a, 22b, a rotation speed signal from a wheel rotation sensor 34 (hereinafter referred to as a wheel rotation signal), and a steering angle signal from a steering angle sensor 35 installed on a steering shaft of the steering handle 8 (hereinafter, referred to as a wheel rotation signal). A steering signal), an acceleration command signal detected by an accelerator sensor 36 provided on the accelerator pedal 11 (hereinafter, referred to as an accelerator signal), and a braking command signal detected by a brake sensor 37 provided on the brake pedal 12 (hereinafter, referred to as (Referred to as a brake signal).

These signals are stored in the ROM (Rea
d Only Memory) or the like, is calculated in accordance with a program stored in a storage medium, is compared with the stored traveling data of the electric vehicle 1, and a required output is supplied to each motor controller 32a, 32b, 33a, 33b. Thus, the drive motors 21a, 21b, 22a, and 22b are brought into appropriate rotation states, and the drive force and the braking force of each wheel are controlled.

Hereinafter, the 4WS function, the 4WD function, the ABS function, and the traction control function in this embodiment will be described.

First, the 4WS function will be described with reference to FIGS. 4 and 5. First, referring to FIG.
The S function will be described.

The turning center of the vehicle involved in operating the steering device with the steering handle 8 is M0, and the front wheels 2a, which are inside the turn, from the driving forces △ F1, △ F3 of the front wheels 2b and the rear wheels 3b, which are outside the turn. , 3a, or by controlling the corresponding drive motors of the respective wheels to generate the braking forces △ R2, △ R4, the left and right rear wheels 3a, 3b
Since the same steering effect as that of the caterpillar vehicle is generated, the turning center is located at the position M closer to the vehicle than the above-described M0, and the 4WS effect in which the turning radius of the vehicle is reduced is generated.

In this case, it is preferable from the viewpoint of running stability of the vehicle that the driving force generated in each wheel is equal to the resultant force in the front-rear direction of the vehicle because no acceleration occurs in the traveling direction of the vehicle.

Next, the 4WS function during high-speed running will be described with reference to FIG.

In general, when turning during high-speed running, a transient yawing moment causes the vehicle body to take an attitude inward with respect to the instantaneous traveling direction, which may impair the running stability of the vehicle.

On the other hand, in this embodiment, the driving force and the braking force of each wheel are controlled to generate an appropriate yawing moment in the opposite direction to cancel each other, thereby making the instantaneous traveling direction coincide with the direction of the vehicle body, thereby achieving high-speed stable operation. It is intended to improve the performance.

That is, considering a right turn as shown in FIG. 5, a transient yawing moment occurs clockwise around the center of gravity of the center of the vehicle body. In contrast, by controlling each drive motor, the driving force is applied to each wheel. A change ΔF2, ΔF4 or a braking force change ΔR1, ΔR3 is given, whereby a counterclockwise yaw moment is applied to the vehicle body to cancel the clockwise yaw moment, thereby controlling the vehicle body posture.

As the braking force applied in this case, regenerative braking by each drive motor may be used.

In order to prevent the acceleration in the traveling direction of the vehicle from being generated by the force for controlling the vehicle body posture, controlling so that the resultant force in the front-rear direction of the vehicle is equal to that in the case of the above-described 4WS function at the time of low-speed traveling. The same is true.

As described above, in this embodiment, the 4WS function is achieved by appropriately controlling the drive motors of the respective wheels, the running stability can be improved, and it is not necessary to add a special mechanism.

Next, the 4WD function will be described. The electric vehicle 1 has a drive motor 21 for each wheel 2a, 2b, 3a, 3b.
Since a, 21b, 22a, and 22b are installed, if the respective drive motors are controlled so that the rotational speeds of the respective wheels are equal in a straight traveling state, the function of a full-time 4WD is achieved.

Also, in general, when an automobile having a selective 4WD function turns with four-wheel drive, the running distance of the wheel outside the turning and the running distance of the inside wheel are not equal due to the inner wheel difference generated by the turning. In addition, since the differential between the front and rear wheels is not possible, a braking phenomenon occurs.

However, since the electric vehicle 1 of this embodiment has a drive motor for each of the wheels 2a, 2b, 3a, and 3b, the inside of the turn based on the steering signal from the steering angle sensor 35 is provided. The rotation speed of the drive motor (for example, 22a) of a wheel (for example, the shortest rear wheel 3a) whose distance to the turning center is short is set to the rotation speed of the wheel (for example, the front wheel 2b) whose distance to the turning center is longest. Drive motor (for example, 21
The braking phenomenon can be improved by controlling the rotation speed to be lower than the rotation speed of b) by an appropriate amount.

Next, the ABS function will be described. In the electric vehicle of this embodiment, the wheel rotation sensors 34 are respectively installed on the wheels 2a, 2b, 3a, 3b, and the respective wheel rotation signals are obtained from the wheel rotation signals of these sensors 34. In addition to obtaining the angular acceleration, the required braking force and the required wheel angular acceleration are determined from the brake signal, the steering signal, the vehicle speed, and, for example, a previously stored limit braking force, and the braking force and the braking force of each drive motor are determined in consideration of the road surface condition. The driving force is calculated and corrected.

The limit braking force may be a calculated value of a signal from each sensor, and the braking force may be adjusted by adjusting the regenerative braking force and the driving force of each drive motor.

In this way, the driving force and the braking force of each drive motor are corrected, so that the driving force and the braking force of each drive motor do not exceed the limit braking force. Can be played.

Next, a traction control function will be described. A limit value of wheel rotational acceleration which can be taken on a road having a small friction coefficient such as a snowy road of the electric vehicle 1 of this embodiment is stored in a storage medium of the computer 31 in advance. ,
The required driving force and the required wheel angular acceleration are calculated from the accelerator signal, the vehicle speed, and the limit driving force, and the driving of each drive motor is performed in consideration of the road surface condition by the wheel rotational angular acceleration and the required wheel angular acceleration obtained from the wheel rotation signal. The force can be calculated.

The limit driving force may be a calculated value of a signal from each sensor.

Even when the acceleration command from the accelerator sensor 36 exceeds the limit driving force, the calculation result does not exceed the limit value, and the transmission of the acceleration command from the accelerator sensor 36 to the drive motor is limited. Thus, the rotation of the wheels due to the driving force exceeding the limit value is prevented, and the slip on the snowy road or the like having a small friction coefficient is suppressed to perform the traction control function.

At the same time, the braking force is also detected, and the AB
By simultaneously exhibiting the S function, it is possible to reliably prevent the occurrence of slip on a road surface having a small friction coefficient.

In this embodiment, signal processing as shown in FIG. 6 is performed by a program of the computer 31 in order to exert the above functions comprehensively.

First, a wheel rotation signal from a wheel rotation sensor 34 installed on each of the drive motors 21a, 21b, 22a, 22b of the wheels 2a, 2b, 3a, 3b is input to the computer 31, and the vehicle speed is calculated from these. (A).

Then, an accelerator signal from an accelerator sensor 36 installed on the accelerator pedal 11 and a brake signal from a brake sensor 37 installed on the brake pedal 12 are input, and the vehicle is decelerating from the accelerator signal and the brake signal. Is determined (B). If the vehicle is decelerating, the process proceeds to (C). If the vehicle is being driven at a constant speed or accelerated, the process proceeds to (G).

When the vehicle is decelerating and proceeds to (C), the required braking force and the required wheel angular acceleration are calculated from the brake signal, the vehicle speed, and the limiting braking force, and the process proceeds to (D).

In (D), the braking force (torque) and the driving force (torque) of each drive motor in consideration of the road surface condition from each wheel angular acceleration and the required wheel angular acceleration obtained from each wheel rotation signal.
And proceed to (E).

Then, it is determined from the steering signal from the steering angle sensor 35 whether or not the vehicle is turning (E). If YES, the process proceeds to (F). Output.

In (F), the required wheel angular acceleration is corrected by the steering signal and the vehicle speed in comparison with the limit braking force in consideration of the cornering force due to the turning of the vehicle, and the operation result of each motor is output to each motor controller. I do.

 The above (D) to (F) correspond to the ABS function.

On the other hand, if it is determined in (B) that the vehicle is not decelerating,
Proceeding to (G), the required driving force and the required wheel angular acceleration are calculated from the accelerator signal, the vehicle speed, and the critical driving force, and proceeding to (H).

In (H), the braking force and the driving force of each drive motor are calculated from each wheel angular acceleration and the required wheel angular acceleration obtained from each wheel rotation signal in consideration of the road surface condition, and the process proceeds to (J).

Note that these (G) and (H) correspond to the traction control function.

Then, it is determined from the steering signal from the steering angle sensor 35 whether or not the vehicle is turning (J). If YES, the process proceeds to (K), and if NO, the operation amount of each motor is directly changed. The calculation result is output to each motor controller.

In (K), the driving force and the braking force of each drive motor are calculated by taking into account the steering signal and the differential amount of the wheels on both sides from each wheel rotation signal, and a correction value (braking prevention function in 4WD) And proceed to (L).

In (L), it is determined from the vehicle speed whether or not the vehicle is traveling at a high speed. If the vehicle is traveling at a high speed, the process proceeds to (P),
Proceed to (Q) if the vehicle is not running at high speed.

When it is determined in (L) that the vehicle is traveling at high speed,
In (P), a yawing moment of the vehicle is calculated from the steering signal, each wheel rotation signal and the vehicle speed, and a correction value of each driving force for canceling the yawing moment is obtained (4WS function during high-speed running).

On the other hand, when it is determined in (L) that the vehicle is not traveling at high speed, in (Q), a driving force difference between the driving wheels for minimizing the vehicle turning radius is calculated from the steering signal, each wheel rotation signal, and the vehicle speed. Then, a correction value for each driving force of each driving wheel is obtained (4WS function at low speed running).

The correction value of each driving force obtained in this way is input to the motor controller for each driving motor based on the calculation result, and the appropriate wheel driving force and braking force are adjusted.

As described above, in this embodiment, a single computer system is comprehensively configured, and the signals based on the running of the vehicle are utilized in various aspects to control the driving force and the braking force of each wheel. Since the running control and the attitude control of the vehicle are performed, this is preferable from the viewpoint of the running stability of the vehicle.

In this embodiment, the four functions of 4WS, 4WD, ABS and traction control have been described. However, it is needless to say that the present invention can be implemented without necessarily providing four resins. Absent. Above, 2WS (2
Wheel steering), but in the case of 4WS, needless to say, finer control of the steering and the rotation speed of each drive wheel can be performed.

(Effect) According to the first aspect of the present invention, when the high-speed traveling determining means determines that the vehicle is traveling at a high speed when the vehicle turns,
The control means controls each drive motor such that the driving force of the two inner driving wheels becomes larger than the driving force of the outer driving wheel during turning, so that excessive yawing of the vehicle center of gravity occurs during turning. The moment can be offset, and the stability of turning at high speed running can be improved. Further, since it is only necessary to control the drive motor, the control is easy. That is, turning at the time of high-speed running can be performed safely and easily.

According to claim 2, when the deceleration determining means determines that the vehicle is decelerating, the control means obtains the required braking force and the required wheel angular acceleration from the brake signal output by the brake sensor and the rotation speed signal, Since each of the drive motors is controlled so as not to exceed the limit braking force stored in advance, it is possible to prevent a side slip occurring at the time of sudden braking, and to ensure that each drive motor does not exceed the limit braking force. Is controlled to provide an anti-skid function.

According to the third aspect, a required driving force and a required wheel angular acceleration are obtained from an accelerator signal output from an accelerator sensor, a rotation speed signal, and a previously stored limit driving force, and each drive motor is controlled. Therefore, in cooperation with the anti-skid function, it is possible to reliably prevent the occurrence of slip on a road surface having a small friction coefficient.

According to the fourth aspect, since each drive motor is controlled so that the braking phenomenon does not occur at the time of turning, the braking phenomenon that occurs at the time of turning can be prevented.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings relate to an embodiment of the present invention. FIG. 1 is a plan view of the configuration of a drive unit of an electric vehicle, FIG. 2 is a schematic structural view of the electric vehicle, FIG. FIG. 4 is an explanatory diagram of the 4WS function during low-speed running, FIG. 5 is an explanatory diagram of the 4WS function during high-speed running, and FIG. 6 is a flowchart. 1; electric vehicle, 2a, 2b; front wheel, 3a, 3b; rear wheel, 21a, 21b, 22a, 22b; drive motor,

Continued on the front page (72) Inventor Shigenori Matsumura 2-12-26 Kaminomachi, Takamatsu City, Kagawa Prefecture (72) Inventor Kazunobu Sato 52-30 Aihata, Aihata, Ishii-cho, Meishi, Tokushima Prefecture (56) References JP 63-195033 (JP, A) JP-A-53-40929 (JP, A)

Claims (4)

(57) [Claims] A vehicle is provided with four drive wheels, each drive wheel is provided with an independent drive motor, and a steering device for steering a front wheel by operating a steering handle is provided to detect a rotational speed of each drive wheel. An electric vehicle provided with four wheel rotation sensors and a steering angle sensor for detecting a steering angle of the steering wheel, wherein the vehicle travels at high speed based on a rotation speed signal output from the four wheel rotation sensors. High-speed traveling determination means for determining that the steering angle is detected by the steering angle sensor when the vehicle turns by operating the steering wheel, and when the high-speed traveling determination means determines that the vehicle is traveling at high speed. On the basis of the rotation speed signal, a drive in which the driving forces of the two inner drive wheels become outer during turning. Electric vehicle, characterized in that a control means for controlling each drive motor to be larger than the driving force of the wheels. A deceleration judging means for judging that the vehicle is decelerating based on the rotation speed signal, wherein the control means determines that the deceleration judgment means decelerates. When it is determined that the required braking force and the required wheel angular acceleration are determined from the brake signal output by the brake sensor and the rotation speed signal, the braking force is calculated so as not to exceed a previously stored limit braking force. The electric vehicle according to claim 1, wherein each electric motor is controlled. 3. An accelerator sensor installed on an accelerator pedal, an accelerator signal output from the accelerator sensor, the rotational speed signal, and a preliminarily stored limit driving force. 3. The electric vehicle according to claim 2, wherein each of the drive motors is controlled in accordance with the following equation. 4. The electric vehicle according to claim 1, wherein each drive motor is controlled so that a braking phenomenon does not occur during turning.