JP2024025551A - Vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which protects components transmitting driving force into front wheels and suppresses deterioration of drive feel when steering angle is large or steering angle cannot be obtained due to failure of a sensor and the like.

SOLUTION: A vehicle comprises: a front-wheel drive device driving a front wheel; a rear-wheel drive device driving a rear wheel; a controller which controls output ratio of the rear-wheel drive device to total output of the front-wheel drive device and the rear-wheel drive device. The controller increases, when a steering angle of the front-wheel exceeds a steering angle threshold value or the steering angle is unknown, the output ratio of the rear-wheel drive device relative to a case that the steering angle is the steering angle threshold value or less, that is, decreases the output ratio of the front-wheel drive device. The vehicle decreases output of the front-wheel drive device and increases output of the rear-wheel drive device, thereby protecting components transmitting driving force into the front-wheels and suppressing deterioration of drive feel.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The technology disclosed herein relates to an automobile that drives front wheels and rear wheels.

Patent Documents 1 and 2 disclose techniques related to power steering devices. A power steering device uses an electric motor to assist the driver in steering. The techniques disclosed in Patent Documents 1 and 2 limit the output of the electric motor when the steering angle exceeds a predetermined threshold value to protect components of the power steering device.

Japanese Patent Application Publication No. 2004-175196 Japanese Patent Application Publication No. 2003-72573

In the case of a front-wheel drive vehicle, when the steering angle of the front wheels is large and the drive torque transmitted to the front wheels is large, a high load is also applied to the parts that transmit the driving force to the front wheels. Therefore, when the steering angle of the front wheels is large, it is conceivable to limit the driving torque of the front wheels to protect the parts. However, as the driving torque of the vehicle decreases, the driving characteristics of the vehicle (so-called drive feel) felt by the driver deteriorate. This specification takes advantage of the characteristics of a four-wheel drive vehicle that drives each of the front wheels and rear wheels, and applies driving force to the front wheels when the steering angle is large or when the steering angle cannot be obtained due to sensor failure. We provide technology that suppresses the deterioration of drive feel while protecting the transmitting parts.

The vehicle disclosed in this specification includes a front wheel drive device that drives the front wheels, a rear wheel drive device that drives the rear wheels, and controls the output ratio of the rear wheel drive device to the total output of the front wheel drive device and the rear wheel drive device. It is equipped with a controller to When the steering angle of the front wheels exceeds a predetermined steering angle threshold, or when the steering angle is unknown, the controller makes the output ratio of the rear wheel drive system higher than when the steering angle is below the steering angle threshold. . Increasing the output ratio of the rear wheel drive system is equivalent to lowering the output ratio of the front wheel drive system. The automobile disclosed in this specification changes the output ratio without changing the total output of the front wheel drive device and the rear wheel drive device. In other words, the output of the front wheel drive device is reduced and the output of the rear wheel drive device is reduced. By increasing the output, it is possible to protect the parts that transmit the driving force to the front wheels while suppressing a decrease in drive feel.

Details and further improvements of the technology disclosed in this specification will be explained in the following "Detailed Description of the Invention".

FIG. 2 is a block diagram of a drive system of an automobile according to an embodiment. It is a flowchart of output ratio control performed by a controller.

An example automobile 2 will be described with reference to the drawings. FIG. 1 shows a block diagram of the drive system of the automobile 2. As shown in FIG. The automobile 2 of the embodiment includes a front motor 11 and a rear motor 21 for driving. Front motor 11 drives front wheels 13 via front wheel drive shaft 12 . A rear motor 21 drives a rear wheel 23 via a rear wheel drive shaft 22. The automobile 2 is an electric four-wheel drive vehicle.

The front wheels 13 can be steered by the driver. The steering wheel 14 is linked to the steering angle of the front wheels 13 via a steering gear mechanism 15 and a steering link 16. A steering motor 17 is attached to the steering gear mechanism 15. The steering motor 17 generates torque in response to the driver's force applied to the steering wheel 14 to assist the driver's steering operation. That is, the automobile 2 is equipped with a power steering function.

The steering angle of the front wheels 13 is measured by a steering angle sensor 18. The steering angle of the front wheels 13 measured by the steering angle sensor 18 is sent to the controller 31. The opening degree of the accelerator pedal 32 and the opening degree of the brake pedal 33 are also sent to the controller 31. The controller 31 determines a target output for driving the automobile 2 based on the opening degree of the accelerator pedal 32 and the vehicle speed. The controller 31 controls the front motor 11 and the rear motor 21 so that the total output of the front motor 11 and the rear motor 21 follows the target output.

The output ratio of the front motor 11 (rear motor 21) to the total output of the front motor 11 and rear motor 21 is determined in advance and stored in the memory of the controller 31. Note that a select switch may be provided at the driver's seat so that the driver can select the output ratio of the front motor 11 (rear motor 21) from among several set values. Note that the sum of the output ratio of the front motor 11 and the output ratio of the rear motor 21 is always 100 [%], and the controller 31 controls so that the total output follows the target output. Once one of the output ratio of the front motor 11 and the output ratio of the rear motor 21 is determined, the other is determined dependently.

The controller 31 determines the respective output ratios of the front motor 11 and the rear motor 21 according to the steering angle of the front wheels 13. Since the sum of the output ratio of the front motor 11 and the output ratio of the rear motor 21 is always 100%, in other words, the controller 31 adjusts the total output ratio of the front motor 11 and the rear motor 21 according to the steering angle of the front wheels 13. The output ratio of the rear motor 21 to the output is determined. Specifically, when the steering angle of the front wheels 13 exceeds a predetermined steering angle threshold, or when the steering angle is unknown, the controller 31 controls the rear motor 21 to operate more quickly than when the steering angle is below the steering angle threshold. Increase output rate. In other words, if the steering angle of the front wheels 13 exceeds a predetermined steering angle threshold, or if the steering angle cannot be obtained (unknown steering angle), the controller 31 determines whether the steering angle is below the steering angle threshold. The output ratio of the rear motor 21 is increased compared to when the output ratio of the rear motor 21 is increased. In other words, if the steering angle of the front wheels 13 exceeds a predetermined steering angle threshold, or if the steering angle cannot be obtained (unknown steering angle), the controller 31 determines whether the steering angle is below the steering angle threshold. The output ratio of the front motor 11 is lowered than before.

When the steering angle is large and the driving torque transmitted to the front wheels 13 is large, a high load is applied to the parts that transmit the driving torque to the front wheels 13 (front wheel drive shaft 12 or parts related to the front wheel drive shaft 12). Parts are damaged. By lowering the output ratio of the front motor 11, the load applied to the components that transmit drive torque to the front wheels 13 can be lowered. An example of a component to which a high load is applied when the steering angle is large and the drive torque transmitted to the front wheels 13 is large is a bearing that rotationally supports the front wheel drive shaft 12. Further, the steering angle threshold value is set near the end of the movable range of the steering angle. Typically, the steering angle threshold value is set at the end of the movable range of the steering angle (the maximum value of the right steering angle and the maximum value of the left steering angle).

On the other hand, the controller 31 only changes the respective output ratios of the front motor 11 and rear motor 21, but does not change the total output of the front motor 11 and rear motor 21. The controller 31 controls the front motor 11 and the rear motor 21 so that the total output follows the target output. Therefore, the drive feel felt by the driver does not deteriorate. In the automobile 2, when the steering angle is large or when the steering angle is unknown due to sensor failure, etc., it is possible to protect the parts of the drive torque transmission system to the front wheels 13 and suppress a decrease in drive feel.

FIG. 2 shows a flowchart of output ratio control executed by the controller 31. If the steering angle can be acquired and the acquired steering angle is less than or equal to the steering angle threshold (step S2: NO), the controller 31 sets the ratio Rf to the output ratio of the front motor 11 and sets the ratio Rf to the output ratio of the rear motor 21. A ratio Rr is set (step S3). Here, the sum of the ratio Rf and the ratio Rr is 100[%].

For example, both the ratio Rf and the ratio Rr are set to 50[%]. In this case, the output ratio between the front motor 11 and the rear motor 21 is 1:1.

If the steering angle exceeds the steering angle threshold or if the steering angle cannot be obtained (the steering angle is unknown), the controller 31 increases the output ratio of the rear motor 21 compared to when the steering angle is equal to or less than the steering angle threshold. Instead, the output ratio of the front motor 11 is lowered. More specifically, the controller 31 sets the output ratio of the front motor 11 to “ratio Rf−ratio dR”, and sets the output ratio of the rear motor 21 to “ratio Rr+ratio dR”.

For example, if the ratio Rf and the ratio Rr are both 50 [%] and the ratio dR is 25 [%], the respective output ratios after the change are 25 [%] for the front motor 11 and 75 [%] for the rear motor 21. Become. In this way, when the steering angle of the front wheels 13 exceeds the steering angle threshold, or when the steering angle is unknown, the controller 31 controls the output of the rear wheel drive device to be higher than when the steering angle is below the steering angle threshold. Increase the percentage. This process protects the parts of the drive torque transmission system to the front wheels 13 while suppressing a decrease in drive feel.

Points to note regarding the techniques described in the examples will be described. The front motor 11 is an example of a front wheel drive device, and the rear motor 21 is an example of a rear wheel drive device. The front wheel drive device and the rear wheel drive device may each be an engine. Alternatively, one of the front wheel drive and rear wheel drive may be an electric motor and the other may be an engine.

The steering angle does not have to be a value acquired by a steering angle sensor, but may be a value estimated from the difference in rotation speed between the right front wheel and the left front wheel, for example.

Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The techniques described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims as filed. Further, the techniques illustrated in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of the objectives has technical utility in itself.

2: Automobile 11: Front motor 12: Front wheel drive shaft 13: Front wheel 14: Steering wheel 15: Steering gear mechanism 16: Steering link 17: Steering motor 18: Rudder angle sensor 21: Rear motor 22: Rear wheel drive shaft 23: Rear wheel 31: Controller 32: Accelerator pedal 33: Brake pedal

Claims (1)

a front wheel drive device that drives the front wheels;
a rear wheel drive device that drives the rear wheels;
a controller that determines an output ratio of the rear wheel drive device to a total output of the front wheel drive device and the rear wheel drive device;
It is equipped with
The controller makes the output ratio higher when the steering angle of the front wheels exceeds a predetermined steering angle threshold, or when the steering angle is unknown, than when the steering angle is below the steering angle threshold. ,car.

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