JP2008062832A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure feeling of turning stability for a vehicle by a function for controlling a turning posture of the vehicle with braking force, in a vehicular steering device mounted with a steer-by-wire system and a rear-end collision speed reducing system. <P>SOLUTION: A steering control means has a monitoring function for monitoring a correlation between a control input detected by a control input detecting means and a turning condition detected by a turning condition detecting means, a braking control means has an automatic braking function for imparting a braking force onto wheels when a prescribed condition is satisfied, and a steering control means controls a steering actuator by the second relation other than a prescribed relation, when detecting the disturbance in the correlation by the monitoring function after the automatic braking function is actuated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus, and more particularly to a vehicle steering apparatus for a vehicle equipped with a steer-by-wire system and a rear-end collision speed reduction system.

The vehicle includes a steering wheel that is an operation member that is manually operated, a steering angle sensor that serves as an operation amount detection unit that detects a steering angle that is an operation amount of the steering wheel, and a steering angle of the wheel. A steering motor that is a steering actuator that is driven so as to change a tire steering angle, and a steer-by-wire controller that is a steering control means for controlling the steering motor based on an operation amount detected by a steering angle sensor Some have a so-called steer-by-wire system.
Some vehicles are provided with a so-called rear-end collision speed reduction system that predicts a collision with a preceding vehicle using an external sensor such as a radar and avoids the collision using an automatic brake. This rear-end collision speed reduction system detects obstacles ahead by radar, determines the possibility of a collision from the distance and relative speed, and if it is determined that the collision is unavoidable, automatically applies a brake. This reduces the collision speed and reduces damage.

2. Description of the Related Art Conventionally, some vehicle motion control devices maintain the stability of a vehicle by controlling a braking force applied to the vehicle when the vehicle is turning.
Some vehicle behavior control devices control the behavior of a vehicle using a plurality of actuators to reduce the operating frequency of the braking means, thereby reducing the load on the braking means.
Some vehicle steering devices include a steer-by-wire system that controls the yaw rate to stabilize the vehicle behavior when the friction coefficient between the road surface and the wheels decreases.
A by-wire steering device (steer-by-wire system) outputs a drive signal according to the location and content of the abnormality to notify the driver quickly when an abnormality occurs in the running state of the vehicle. There is something that prevents the occurrence.
Some road surface estimation devices estimate a road surface state while the vehicle is traveling with high accuracy and good timing as a grip degree or a friction coefficient in a vehicle equipped with a steer-by-wire system.
Japanese Patent No. 2932589 Japanese Patent No. 3225766 JP 2001-213342 A Japanese Patent Application Laid-Open No. 2003-019996 JP 2004-130965 A

Conventionally, in a vehicle steering apparatus equipped with a rear-end collision speed reduction system, a high deceleration is generated by automatic braking, so that a so-called nose dive occurs and the front wheel load increases rapidly. Therefore, when the steering wheel is steered when the automatic brake for reducing the rear-end collision is applied, the front wheel load is increased by the automatic brake, so that the turning performance is rapidly increased and yaw is generated in the vehicle (see FIG. 4). ). At this time, since the driver does not change the steering angle before and after the application of the automatic brake, it is considered that the driver originally demands the same turning performance. However, the sudden increase in turning performance generated by the applied automatic brake, not the intention of the driver, is not the intention of the driver, and thus there is a disadvantage that the maneuverability is lowered.
Further, in braking intended for quick deceleration, it is very difficult to control the yaw rate by the braking means. First, the application of braking force during the turning of the vehicle affects the yaw rate of the vehicle, and the yaw rate always changes depending on the vehicle speed and the way of turning. On the other hand, only the wheels have a ground contact surface, and the braking force and the driving force are transmitted within a range where the transmission efficiency is good due to the friction of the wheels. It is very difficult to optimally control the constantly changing yaw rate by changing the brake distribution on the front, rear, left and right sides of the vehicle within this efficient range. Even if a high-function and high-cost system having such a function is constructed, it is difficult to mount the system on a small general public vehicle.

  Accordingly, an object of the present invention is to provide a vehicle steering system that ensures a feeling of turning stability of a vehicle by a function of controlling the turning posture of the vehicle with a braking force in a vehicle equipped with a steer-by-wire system and a rear-end collision speed reduction system. To provide an apparatus.

  The present invention includes an operation member that is artificially operated, an operation amount detection unit that detects an operation amount of the operation member, a steering actuator that is driven to change a steering angle of a wheel, and the operation amount detection. A steering control means for controlling the steering actuator in accordance with a predetermined relationship based on an operation amount detected by the means, a turning state detecting means for detecting a turning state of the vehicle, and applying a braking force to the wheels. In the vehicle steering system, the steering control means includes the operation amount detected by the operation amount detection means and the turning state detection means. A monitoring function for monitoring a correlation with the detected turning state, the braking control means having an automatic braking function for applying a braking force to the wheel when a predetermined condition is satisfied, and the steering control means Serial by said second relationship distinguish it from a predetermined relationship when detecting the disturbance of correlation after the monitoring operation of the automatic braking function of the braking control means and controls the steering actuator.

  The vehicle steering apparatus according to the present invention has a monitoring function for monitoring a correlation between an operation amount and a turning state and an automatic braking function in a vehicle equipped with a steer-by-wire system and a rear-end collision speed reduction system. By detecting and reducing the steering angle of the wheel, it is possible to prevent the deterioration of the feeling of turning stability of the vehicle by automatic braking.

This invention has a monitoring function for monitoring the correlation between the operation amount and the turning state and an automatic braking function for the purpose of preventing the deterioration of the feeling of turning stability of the vehicle by automatic braking. This is realized by detecting and reducing the steering angle of the wheel.
Hereinafter, embodiments of the present invention will be described in detail and specifically based on the drawings.

1 to 8 show an embodiment of the present invention. In FIG. 8, 1 is a vehicle, 2 is a power unit, 3 is a steering wheel, 4L is a left front wheel, 4R is a right front wheel, 5L is a left rear wheel, and 5R is a right rear wheel. The vehicle 1 is equipped with a steer-by-wire system 6 as a steering device and a rear-end collision speed reduction system 7 that applies an automatic brake under predetermined conditions. The steer-by-wire system 6 and the rear-end collision speed reduction system 7 constitute a vehicle steering device 8.
In the power unit 2, an engine 9, a transmission 10, and a front differential 11 are integrally formed, and are mounted horizontally at the front portion of the vehicle 1.
One end of the left front axle 12L is connected to the front differential 11. The other end of the left front axle 12L is connected to the left front wheel 4L via a left front connection member 13L. The left front wheel 4L is provided with a left front brake device 14L which is a braking means for applying a braking force. One end of the right front axle 12R is connected to the front differential 11. The other end of the right front axle 12R is connected to the right front wheel 4R via a right front connection member 13R. This right front wheel 4R is provided with a right front brake device 14R which is a braking means for applying a braking force.
In the vehicle 1, a steering box 15 that houses a steering rack or the like is disposed behind the power unit 2. A left front wheel 4L is connected to the steering box 15 via a left rod 16L, a right front wheel 4R is connected via a right rod 16R, and a steering motor 17 serving as a steering actuator for operating the steering rack is provided. is set up. The steering motor 17 is driven so as to change the tire steering angle as the steering angle of the left front wheel 4L and the right front wheel 4R.

The vehicle 1 is also provided with a rear differential 18 at the rear. One end of the left rear axle 19L is connected to the rear differential 18. The other end of the left rear axle 19L is connected to the left rear wheel 5L via a left rear connection member 20L. The left rear wheel 5L is provided with a left rear brake device 21L which is a braking means for applying a braking force. Further, one end of the right rear axle 19R is connected to the rear differential 18. The other end of the right rear axle 19R is connected to the right rear wheel 5R via a right rear connection member 20R. The right rear wheel 5R is provided with a right rear brake device 21R which is a braking means for applying a braking force.
The steering wheel 3 is an operation member that is manually operated, and is connected to a reaction force motor 23 via a wheel shaft 22.

The steering motor 17 and the reaction force motor 23 communicate with a steer-by-wire controller 24 that is a steering control means. The steer-by-wire controller 24 includes a steering angle as an operation amount detection unit that detects a state in which the steering wheel 3 is steered by the driver and the wheel shaft 22 is rotated as a steering angle that is an operation amount of the steering wheel 3. A sensor 25, a left steering rack sensor 26L and a right steering rack sensor 26R which are provided at the left and right ends of the steering box 15 and detect the moving state of the steering rack, and a yaw rate as a turning state detection means for detecting the turning state of the vehicle 1 A yaw rate sensor 27 to detect and a vehicle speed sensor 28 to detect the speed of the vehicle 1 communicate with each other. As the turning state detection means, in addition to the yaw rate sensor 27, detection means (lateral G sensor) for detecting lateral acceleration may be provided.
The steer-by-wire controller 24 outputs a steering command to the steering motor 17 according to a predetermined relationship based on the steering angle detected by the steering angle sensor 25 based on information from each sensor. To control the tire steering angle. This is because the steering device is a steering-by-wire system 6 and needs to be controlled independently of the steering wheel 3.

The steer-by-wire controller 24 communicates with a brake controller 29 that is a braking control means for controlling the braking force applied to each wheel.
The brake controller 29 includes a radar 30 that is an external sensor installed at the front of the vehicle 1, a left front wheel speed sensor 31L and a right front wheel speed sensor 31R provided in the vicinity of the left front wheel 4L and the right front wheel 4R, A left rear wheel speed sensor 32L and a right rear wheel speed sensor 32R provided in the vicinity of the rear wheel 5L and the right rear wheel 5R communicate with each other.
A brake actuator 33 communicates with the brake controller 29. In the brake actuator 33, the left front brake device 14L, the right front brake device 14R, the left rear brake device 21L, and the right rear brake device 21R communicate with each other.
The brake controller 29 outputs a brake operation signal to drive the brake actuator 33 and drives each brake device connected to the brake actuator 33 to control the braking force of each wheel.

As shown in FIG. 7, the steer-by-wire system 6 includes a brake controller 29, a steering angle sensor 25, a yaw rate sensor 27, and a vehicle speed sensor 28 that communicate with the steer-by-wire controller 24 and a steering motor 17 that inputs a steering command. Configured to communicate.
As shown in FIG. 6, the rear-end collision speed reduction system 7 communicates the vehicle speed sensor 28 to the brake controller 29 via the steer-by-wire controller 24, communicates the radar 30, and issues a brake command as a brake operation signal. An input brake actuator 33 is configured to communicate.
The radar 30 is a laser radar or a millimeter wave radar, detects an obstacle ahead, measures a distance to the obstacle and a relative speed, and outputs the measured distance to the brake controller 29.
The brake actuator 33 is a brake drive device that can automatically apply a brake in response to a brake command from the brake controller 29.
The brake controller 29 controls the rear-end collision speed reduction system 7. The brake controller 29 inputs signals from the radar 30 and each sensor, makes a collision determination, outputs an automatic brake command to the brake actuator 33, and automatically brakes. , The brake activation signal is transmitted to the steer-by-wire controller 24.

The steer-by-wire controller 24 as the steering control means monitors the correlation between the operation amount detected by the steering angle sensor 25 as the operation amount detection means and the turning state detected by the yaw rate sensor 27 as the turning state detection means. Has a monitoring function.
The brake controller 29, which is a braking control means, has an automatic braking function that applies a braking force to the wheel when a predetermined condition is satisfied.
When the steer-by-wire controller 24 detects the disorder of the correlation by the monitoring function after the automatic braking function of the brake controller 29 is activated, the steer-by-wire controller 24 uses the second relationship (refer to the map in FIG. 5) different from the predetermined relationship. The steering motor 17 is controlled.
The disorder of the correlation is a tendency that the turning state increases with respect to the operation amount. The second relationship is a relationship in which a tire steering angle, which is a steering angle of a wheel with respect to an operation amount detected in comparison with the predetermined relationship, is reduced.
The steer-by-wire controller 24 controls the turning state detected in the second relationship so as to substantially match the turning state detected immediately before the correlation is disturbed, the operation of the automatic braking function is continued, and the detected operation amount is If the amount of operation increases immediately before the correlation is disturbed, the tire steering angle is increased according to the amount of operation.

Next, the steering control in this embodiment will be described based on the flowchart of FIG.
In FIG. 1, the steering angle is an angle at which the driver steers the steering wheel 3. The tire steering angle is a tire steering angle that can be controlled independently of the steering wheel 3 by the steer-by-wire system 6. The rear-end collision reduction brake operation signal is a brake operation signal (brake command) indicating that the rear-end collision reduction brake operation is activated and a large deceleration is generated. The front wheel load is a load applied to the left front wheel 4L and the right front wheel 4R, and the turning performance increases as the load increases. The yaw rate is the yaw of the vehicle 1 and represents the turning ability.

As shown in FIG. 1, when the steering control program is started (step S01), the steering angle and yaw rate are continuously input and monitored (step S02), and there is a brake operation signal output from the brake controller 29. Whether or not (ON) is monitored (step S03). If step S03 is NO, the process returns to step S02.
If this step S03 is YES, the steering angle and the yaw rate are monitored again (step S04), and the yaw rate value is looked up, and this yaw rate value rises suddenly (the sudden yaw due to the operation of the rear-end collision reduction brake). It is determined whether or not a change has occurred (step S05). If step S05 is NO, the process returns to step S04.
If this step S05 is YES and the yaw rate value has a sharp rise, it is confirmed that the current steering rudder angle is equal to or smaller than the steering rudder angle before the brake operation signal is received, that is, the steering wheel 3 is turned off. It is confirmed whether it has not increased (step S06).
When this step S06 is YES, in order to prevent a rapid increase in the yaw rate, the tire steering angle command value is made smaller than the current value and the turning performance is made the same as before the brake operation (step S07).
Then, the steering angle is monitored again, and it is confirmed whether the current steering angle is larger than the steering angle before the tire steering angle command value is reduced in step S07 (the steering angle in step S04). It is confirmed whether the driver desires an increase in turning performance (step S08). That is, in this step S08, after the tire steering angle command value is made smaller than the current value in step S07 to make the turning performance the same as before the brake operation, the driver increases the steering wheel 3 to improve the turning ability. Judge that you want.
If this step S08 is YES and the current steering angle is larger than the steering angle before the tire steering angle command value is reduced, the tire steering angle command value is increased in order to restore turning performance (step S09). ).
After the process of step S09 or when the step S08 is NO, the brake operation signal is monitored (step S10). If step S10 is NO, the process returns to step S08.
If this step S10 is YES, the control of the tire steering angle of the steer-by-wire system 6 is returned to the normal control, that is, the operation of the rear-end collision reduction brake is finished (step S11), and the program is ended (step). S12).
On the other hand, when step S06 is NO, a brake operation signal is monitored (step S13). If this step S13 is NO and the brake operation signal remains (ON), the process returns to step S04. When this step S13 is YES and there is no brake operation signal (OFF), the process proceeds to step S11.

Next, this steering control will be described based on the time chart of FIG.
As shown in FIG. 2, as the steering angle increases by operating the steering wheel 3, the tire steering angle also increases (time t1), and the yaw rate starts to increase gradually (time t2).
Then, when there is a brake operation signal (time t3) and the yaw rate is about to increase suddenly due to an increase in front wheel load accompanying a large deceleration (time t4), the tire steering angle is controlled to be reduced (time t5). As a result, since the turning performance is lowered, the increase in the yaw rate is suppressed, and the yaw rate becomes the same as before the brake operation (time t6). In other words, since the steering angle does not change, the driver wants the same turning performance and returns to the desired turning performance.

FIG. 3 shows a time chart when the steering angle is increased after control for suppressing a rapid increase in the yaw rate.
As shown in FIG. 3, as the steering angle increases by operating the steering wheel 3, the tire steering angle also increases (time t1), and the yaw rate also gradually increases (time t2).
Then, when there is a brake operation signal (time t3) and the yaw rate is about to increase suddenly due to an increase in front wheel load accompanying a large deceleration (time t4), the tire steering angle is controlled to be reduced (time t5). As a result, since the turning performance is lowered, an increase in the yaw rate can be suppressed.
Thereafter, when the steering angle is increased (time t6), the tire steering angle is controlled to increase (time t7), the yaw rate increases again, and the turning performance is recovered (time t8). This determines that the driver has turned the steering wheel 3 and wants the turning ability, and the turning ability is restored.

However, in the case where there is no steering control described above, as shown in FIG. 4, as the steering rudder angle is increased by the operation of the steering wheel 3, the tire steering angle is increased (time t1), and the yaw rate is also gradually increased. Start (time t2). Then, when the rear-end collision reduction brake is activated and there is a brake activation signal with the steering wheel 3 being steered (time t3), the load movement to the front wheels due to the large deceleration occurs and the yaw rate increases rapidly. (Time t4). In other words, since the steering angle is the same as before the brake operation, the driver expects the same turning performance, but the turning performance suddenly increases. As a result, maneuverability deteriorates due to unintended turning performance.
Therefore, by the steering control in this embodiment, it is possible to achieve the turning performance intended by the driver when the rear-end collision reduction brake is operated, and to prevent the steering performance from being lowered.
Further, the steering control in this embodiment can be easily applied to a small general public vehicle as long as the vehicle is equipped with the steer-by-wire system 6 and the rear-end collision speed reduction system 7.

Although the embodiments of the present invention have been described above, the configuration of the above-described embodiments will be described for each claim.
The steer-by-wire controller 24 has a monitoring function for monitoring the correlation between the operation amount detected by the steering angle sensor 25 and the turning state detected by the yaw rate sensor 27. Yes. The brake controller 29, which is a braking control means, has an automatic braking function that applies a braking force to the wheel when a predetermined condition is satisfied. When the steer-by-wire controller 24 detects the disorder of correlation by the monitoring function after the automatic braking function of the brake controller 29 is activated, the steer-by-wire controller 24 controls the steering motor 17 that is a steering actuator according to a second relationship different from the predetermined relationship. Control.
Thus, after the automatic braking is activated, the turning posture and behavior of the vehicle 1 are not maintained by the braking, and the changing state can be relaxed. Moreover, since it compares with the operation amount which shows a passenger | crew's intention (addition and return), the deterioration of the driving | operation feeling by producing the unintended feeling of entrainment and a feeling of jumping out can be suppressed.

In the invention described in claim 2, the disturbance of the correlation is a tendency that the turning state increases with respect to the operation amount. The second relationship is a relationship in which the steering angle of the wheel with respect to the operation amount detected in comparison with the predetermined relationship becomes small.
Thereby, it can be made to apply broadly to a driver | operator's driving skill level by making it a weaker under tendency than the basic by the 2nd relationship.

Furthermore, in the invention described in claim 3, the steer-by-wire controller 24 controls the turning state detected in the second relationship so as to substantially coincide with the turning state detected immediately before the correlation is disturbed, and the automatic braking function. If the operation amount to be detected is larger than the operation amount detected immediately before the correlation is disturbed, the steering angle of the wheel is increased according to the operation amount.
Thus, the behavior of the vehicle 1 can be changed in accordance with the intention without hindering the driver's operation by the avoidance operation or the like, and the driving feeling is improved.

  It can be applied to other devices to have a monitoring function for monitoring the correlation between the operation amount and the turning state and an automatic braking function, and to detect the disturbance of the correlation to reduce the steering angle of the wheel.

It is a flowchart of steering control. It is a time chart of steering control. It is a time chart in case there is an increase in steering control. It is a time chart when there is no steering control. It is a map of a tire steering angle command value. It is a block diagram of a rear-end collision speed reduction system. It is a block diagram of the steering device for vehicles. 1 is a schematic plan view of a vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 3 Steering wheel 4L Left front wheel 4R Right front wheel 6 Steer-by-wire system 7 Rear-end collision speed reduction system 8 Vehicle steering device 17 Steering motor 24 Steer-by-wire controller 25 Steering angle sensor 27 Yaw rate sensor 28 Vehicle speed sensor 29 Brake controller 30 Radar 33 Brake Actuator

Claims (3)

  An operation member that is artificially operated, an operation amount detection unit that detects an operation amount of the operation member, a steering actuator that is driven so as to change the steering angle of the wheel, and the operation amount detection unit. Steering control means for controlling the steering actuator according to a predetermined relationship based on the manipulated variable, turning state detection means for detecting the turning state of the vehicle, and braking means for applying braking force to the wheels. The vehicle steering system includes a braking control unit that controls a braking force applied to the vehicle, and the steering control unit includes the operation amount detected by the operation amount detection unit and the turning detected by the turning state detection unit. A monitoring function for monitoring the correlation with the state, the braking control means has an automatic braking function for applying a braking force to the wheel when a predetermined condition is satisfied, and the steering control means is the braking control Stage wherein the predetermined vehicle steering apparatus characterized by controlling the steering actuator by another second relationship relationship when detecting the disturbance of correlation by the monitoring function after actuation of the automatic braking functions.   The disturbance of the correlation is a tendency that the turning state increases with respect to the operation amount, and the second relationship is a small steering angle of the wheel with respect to the detected operation amount compared with the predetermined relationship. The vehicle steering apparatus according to claim 1, wherein:   The steering control means controls the turning state detected in the second relationship to substantially coincide with the turning state detected immediately before the correlation is disturbed, the operation of the automatic braking function is continued, and the detected operation amount is The vehicle steering apparatus according to claim 2, wherein the steering angle of the wheel is increased according to the operation amount when the operation amount increases immediately before the correlation is disturbed.

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