JP2008265715A - Steering device, automobile, and steering control method - Google Patents

Abstract

An object of the present invention is to facilitate width adjustment to a road shoulder while ensuring operability close to normal two-wheel steering.
A drive mode A for starting the steering of only the front wheels in response to the steering operation and starting the steering of the rear wheels in a direction opposite to the front wheel steering angle δf when the front wheel steering angle δf is saturated, and depending on the steering operation When the rear wheel steering angle δr is saturated and the rear wheel steering angle δr is saturated, the driving mode B in which the steering of the front wheels is started in the opposite direction to the rear wheel steering angle δr is performed from either one at extremely low speeds. Switch to the other and execute.
[Selection] Figure 3

Description

  The present invention relates to a steering apparatus, an automobile equipped with the steering apparatus, and a steering control method.

Conventionally, when parking with four-wheel steering, the rear wheels are steered in reverse phase with respect to the front wheels so that the turning centers of the front wheels and rear wheels coincide with each other on a predetermined axis, and parking in a narrow space is easy (See Patent Document 1).
JP 2000-128008 A

As described above, if the rear wheels are steered in reverse phase with respect to the front wheels, the small turning performance is improved. However, in a scene where the vehicle is parked in parallel while moving forward, the vehicle is hardly brought close to the shoulder. In particular, a driver who is used to normal two-wheel steering may not be able to reach the shoulder.
An object of the present invention is to facilitate width adjustment to the road shoulder while ensuring operability close to that of normal two-wheel steering.

  In order to solve the above-described problems, a steering apparatus according to the present invention includes a steering mechanism that can steer each of the front and rear wheels, and performs steering control when the steering mechanism is driven and controlled in accordance with a driver's steering operation. The first drive setting that starts turning only the front wheels according to the operation and starts turning the rear wheels in the direction opposite to the front wheel steering angle when the front wheel steering angle is saturated, and only the rear wheels according to the steering operation When the steering is started and the rear wheel steering angle is saturated, the second drive setting for starting the steering of the front wheel in the direction opposite to the rear wheel steering angle is switched from one to the other during extremely low speed driving. It is characterized by performing.

According to the steering device according to the present invention, an operation close to normal two-wheel steering can be performed by switching between the first drive setting and the second drive setting during extremely low speed traveling such as parking and stopping. The width can be easily adjusted to the road shoulder while securing the property.
For example, when turning the steering angle toward the road shoulder while moving forward, by performing the first drive setting, it is possible to ensure steering performance close to normal two-wheel steering, and the front end of the vehicle approaches the road shoulder. When the steering angle is turned in the opposite direction, the rear end of the vehicle can be brought closer to the road shoulder so that the front end of the vehicle does not move away from the road shoulder by switching to the second drive setting.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<< First Embodiment >>
"Constitution"
FIG. 1 is a schematic configuration of a vehicle. The automobile 1 includes a steering angle ratio variable mechanism 3 that can change a steering angle ratio of the front wheels 2FL and 2FR with respect to a driver's steering operation, and a steering that can steer the rear wheels 2RL and 2RR separately from the front wheels 2FL and 2FR. A mechanism 4 and a controller 5 that controls the steering angle ratio variable mechanism 3 and the steering mechanism 4 are mounted. However, illustration of a drive circuit and a drive power supply is omitted.

The controller 5 inputs a signal from the mode switch 6 in which the driver can arbitrarily set the steering angle, the wheel speed, and drive modes A and B described later, and executes the drive control process of FIG.
In step S101, it is determined whether or not the vehicle speed V is an extremely low vehicle speed as when parking or stopping depending on whether or not the vehicle speed V is less than the predetermined value V1.
As shown below, the vehicle speed V calculates an average value for two wheels excluding the maximum value and the minimum value among the wheel speeds. The predetermined value V1 corresponds to an upper limit value at which the vehicle performs geometric motion, and is set to about 7 km / h.

V _MAX : Maximum wheel speed [m / sec]
V _MIN : Minimum wheel speed [m / sec]
V: Estimated vehicle speed [m / sec]
ω _{FL to} ω _RR : Wheel speed [rpm]
R: tire moving radius length [m]
Here, if it exceeds the extremely low vehicle speed, the process proceeds to step S102, and if it is the extremely low vehicle speed, the process proceeds to step S103.

In step S102, the steering angle ratio variable mechanism 3 and the steering mechanism 4 are driven and controlled in the normal mode according to the steering operation, and then the routine returns to a predetermined main program. Although not described in detail here, the direction of the vehicle body may be made to coincide with the traveling direction, for example, by turning the rear wheels in opposite phases during low-speed cornering and turning the rear wheels in phase during high-speed cornering.
In step S103, it is determined whether or not the flag F has been reset to “0”. If the determination result is F = 0, it is determined that the drive mode A is being executed, and the process proceeds to step S104. On the other hand, if the determination result is F = 1, it is determined that the drive mode B is being executed, and the process proceeds to step S109 described later.

In the drive mode A, as shown in FIG. 3, when the steering of only the front wheels is started in the same direction as the steering angle θ _H and the front wheel steering angle δf is saturated at the maximum value δf _MAX , the rearward direction is reverse to the front wheel steering angle δf. When the steering of the wheels is started and the steering angle θ _H is saturated at the maximum value θ _MAX , the rear wheel steering angle δr is saturated at the maximum value δr _MAX accordingly. Each maximum value θ _MAX , δf _MAX , δr _MAX is an upper limit value determined structurally.

In the drive mode B, as shown in FIG. 3, when the steering of only the rear wheels is started in the direction opposite to the steering angle θ _H and the rear wheel steering angle δr is saturated at the maximum value δr _MAX , the reverse of the rear wheel steering angle δr. The steering of the front wheels is started in the direction, and when the steering angle θ _H is saturated at the maximum value θ _MAX , the front wheel steering angle δf is saturated at the maximum value δf _MAX accordingly.
In step S104, it is determined whether or not the mode switch 6 is set to A. If it is set to A, the process proceeds to step S105, and if it is set to B, the process proceeds to step S106.

In step S105, in the drive mode A, the steering angle ratio variable mechanism 3 and the steering mechanism 4 are driven and controlled, and then the process returns to a predetermined main program.
That is, if the steering angle when the front wheel rudder angle δf reaches the maximum value δf _MAX is θ _L and the steering angle | θ _H | is smaller than θ _L , the front wheels are set according to the steering angle θ _H as shown below. It steers and the rear wheels do not steer. N ₁ is a gear ratio.
δf = θ _H / N ₁
δr = 0
On the other hand, if the steering angle | θ _H | is larger than θ _L , as shown below, the front wheels are steered to δf _MAX and the rear wheels are steered by the shortage of the steering angle θ _H (θ _H −θ _L ). To do. N ₂ and N ₃ are gear ratios.
δf = θ _H / N ₁ − (θ _H −θ _L ) / N ₂ = δf _MAX
δr = (θ _H −θ _L ) / N ₃

In step S106, it is determined whether or not the steering angle | θH | is less than a predetermined value θ1, that is, whether or not the steering angle | θH | The predetermined value θ1 is about 30 deg in consideration of the play of the steering wheel.
Here, if it is outside the neutral region, the process proceeds to step S105, and if it is a neutral region, the process proceeds to step S107.
In step S107, the flag F is set to “1”.
In the subsequent step S108, in the drive mode B, the steering angle ratio variable mechanism 3 and the steering mechanism 4 are driven and controlled, and then the process returns to a predetermined main program.

That is, if the steering angle when the rear wheel steering angle δr reaches the maximum value δr _MAX is θ _L and the steering angle | θ _H | is smaller than θ _L , the rear wheel has the steering angle θ _H as shown below. It steers accordingly and the front wheels do not steer.
δf = 0
δr = θ _H / N ₃
On the other hand, if the steering angle | θ _H | is larger than θ _L , as shown below, the rear wheels are steered to δr _MAX and the front wheels are steered by the shortage of the steering angle θ _H (θ _H −θ _L ). To do.
δf = (θ _H −θ _L ) / N ₁
δr = θ _H / N ₃ − (θ _H −θ _L ) / N ₂ = δr _MAX
On the other hand, in step S108, it is determined whether or not the mode switch 6 is set to B. If it is set to B, the process proceeds to step S110, and if it is set to A, the process proceeds to step S111.

In step S110, in the drive mode B, the steering angle ratio variable mechanism 3 and the steering mechanism 4 are driven and controlled, and then the process returns to a predetermined main program.
In step S111, it is determined whether or not the steering angle | θH | is less than a predetermined value θ1, that is, whether or not the steering angle | θH | Here, if it is outside the neutral region, the process proceeds to step S110, and if it is a neutral region, the process proceeds to step S112.
In step S112, the flag F is reset to “0”.
In the subsequent step S113, in the drive mode A, the steering angle ratio variable mechanism 3 and the steering mechanism 4 are driven and controlled, and then the process returns to a predetermined main program.

<Action>
Next, the operation of the first embodiment will be described.
Here, consider the scene where the vehicle is brought to the shoulder while moving forward at a very low speed.
Assuming that the mode switch 6 is set to A as an initial state (steps S103 and S104), when the steering angle is turned to the left toward the road shoulder, the drive mode A is executed (step S105). That is, turning of only the front wheels in the same direction as the steering angle θ _H is started. As a result, it is possible to ensure steering performance close to that of normal two-wheel steering.

If the driver switches the mode switch 6 to B when turning the steering angle to the right after the front end of the vehicle body approaches the road shoulder, the drive mode B is executed (steps S104 and S108). That is, to start the turning of only the rear wheel to the steering angle theta _H and reverse. Thereby, the vehicle rear end can be brought close to the road shoulder so that the vehicle front end does not leave the road shoulder. Therefore, the leftward extension of the front end of the vehicle can be suppressed to the minimum, avoiding turning back of the handle and repeated forward and backward movement, and smoothly moving the vehicle to a desired position even in a narrow space. Can be made.

However, switching from drive mode A to B is limited to when the steering angle is in the neutral region (step S106). Thereby, it is possible to prevent a sudden change in the rudder angle of the front wheels and the rear wheels and smoothly shift from the end of the front wheel steering to the start of the rear wheel steering.
FIG. 4 is a simulation result when the rear wheels are steered in reverse phase with respect to the front wheels as in the prior art, and the vehicle is about 0. 0 with respect to the target line corresponding to the road shoulder as the small turning performance is improved. It was only possible to reach up to 4m.

FIG. 5 shows a simulation result when switching from the driving mode A to B as in the present embodiment, and the vehicle can be sufficiently moved toward the target line corresponding to the road shoulder.
Also, when moving away from the shoulder while moving forward at an extremely low speed, switching from the driving mode A to B can be performed, so that it is possible to minimize the vehicle's large turn and the front end of the vehicle. It avoids turning back and repeating forward and backward, and can be smoothly removed even in narrow spaces.
FIG. 6A shows a scene of parking and stopping and leaving in a forward direction that can actually be assumed.

《Application example》
When the front wheels are steered, as shown in FIG. 6, the increase rate of the front wheel steering angle may be reduced in a saturated region where the front wheel steering angle is saturated. As a result, even when the steering angle ratio variable mechanism 3 is adopted, a sudden change in the steering reaction force when the front wheel steering angle is saturated is suppressed, and the driver does not feel uncomfortable.
In addition, when the steering of the rear wheels is started when the front wheel steering angle is saturated, as shown in FIG. 6, the rate of increase of the rear wheel steering angle may be reduced in the initial movement region where the steering is started. This suppresses sudden changes in vehicle behavior such as the yaw rate and does not give the driver a sense of incongruity.
Further, although the steering angle ratio variable mechanism 3 is employed for the front wheels, the present invention is not limited to this, and a steering-by-wire in which the steering wheel and the front wheels are not mechanically connected may be employed.

"effect"
From the above, the steering angle ratio variable mechanism 3 and the steering mechanism 4 correspond to the “steering mechanism”, and the processing of steps S101 to S113 corresponds to the “control means”. Further, the switching of the mode switch 6 corresponds to “a predetermined operation different from the steering operation”, the driving mode A corresponds to the “first driving setting”, and the driving mode B corresponds to the “second driving setting”. is doing.
(1) A steering mechanism that can steer each of the front and rear wheels and a control unit that drives and controls the steering mechanism in accordance with the steering operation of the driver. The control unit includes only the front wheels in accordance with the steering operation. When the steering is started and the front wheel steering angle is saturated, the first drive setting to start the rear wheel in the direction opposite to the front wheel steering angle, and the steering of the rear wheels only according to the steering operation When the wheel steering angle is saturated, the second drive setting for starting the steering of the front wheel in the direction opposite to the rear wheel steering angle is executed by switching from one to the other during extremely low speed traveling.

  As a result, it is possible to easily adjust the width to the road shoulder while ensuring operability close to that of normal two-wheel steering. For example, when turning the steering angle toward the road shoulder while moving forward, by performing the first drive setting, it is possible to ensure steering performance close to normal two-wheel steering, and the front end of the vehicle approaches the road shoulder. When the steering angle is turned in the opposite direction, the rear end of the vehicle can be brought closer to the road shoulder so that the front end of the vehicle does not move away from the road shoulder by switching to the second drive setting.

(2) The control means executes the first and second drive settings by switching from one to the other according to a predetermined operation different from the steering operation by the driver.
As a result, it is possible to reliably respond to the driver's intention in any scene.
(3) When the steering angle is in the neutral region, the control means executes the first and second drive settings while switching from one to the other.
Thereby, it is possible to prevent a sudden change in the rudder angle of the front wheels and the rear wheels and smoothly shift from the end of the front wheel steering to the start of the rear wheel steering.

(4) If the vehicle is moving forward, the control means performs switching from the first drive setting to the second drive setting.
As a result, it is possible to easily adjust the width to the road shoulder while ensuring operability close to that of normal two-wheel steering.
(5) The control means relaxes the rate of increase of the steering angle in a saturation region where the steering angle is saturated when either one of the front wheels and the rear wheels is being steered.
Thereby, even when the steering angle ratio variable mechanism 3 is adopted as the steering mechanism for the front wheels, a sudden change in the steering reaction force when the front wheel steering angle is saturated is suppressed, and the driver does not feel uncomfortable. .
(6) When starting the other steering because the steering angle of one of the front wheels and the rear wheels is saturated, the control means relaxes the rate of increase of the steering angle in the initial movement region where the steering is started.
This suppresses sudden changes in vehicle behavior such as the yaw rate and does not give the driver a sense of incongruity.

<< Second Embodiment >>
"Constitution"
In the second embodiment, the mode switch 6 is omitted, and the drive mode is switched and executed when the handle is turned back, and the drive control process of FIG. 8 is executed.
This is obtained by changing the processing of steps S104 and S109 to new steps S204 and S209.
In step S204, it is determined whether or not the sign (direction) of the steering angle is reversed. If the sign of the steering angle is reversed, the process proceeds to step S105, and if not, the process proceeds to step S106.
In step S209, it is determined whether the sign (direction) of the steering angle is reversed. If the sign of the steering angle is reversed, the process proceeds to step S110, and if not, the process proceeds to step S111.

<Action>
Next, the operation of the second embodiment will be described.
Here, consider the scene where the vehicle is brought to the shoulder while moving forward at a very low speed.
When the driving mode is set to A as an initial state and the steering angle is turned to the left toward the road shoulder (steps S103 and S204), the driving mode A is executed (step S105).
When the steering angle is turned back to the right after the front end of the vehicle body approaches the road shoulder, this time, the drive mode is switched to B (steps S204 and S108).
In this way, when the sign (direction) of the steering angle is reversed, the drive mode is automatically switched, so that the operation burden on the driver can be reduced. Moreover, since the mode switch 6 can be omitted, an increase in cost can be prevented.

"effect"
As described above, the processes of steps S204 and S209 are included in the “control unit”.
(1) When the direction of the steering angle is reversed, the control unit executes the first and second drive settings by switching from one to the other.
As a result, the operation burden on the driver can be reduced and the cost can be prevented from increasing.

<< Third Embodiment >>
"Constitution"
In the third embodiment, the initial state of the drive mode is set according to whether the vehicle is moving forward or backward, and the drive control process of FIG. 9 is executed.
This is a process in which new processing in steps S301 and S302 is added.
In step S301, it is determined whether the vehicle is moving forward or backward. Whether the vehicle is moving forward or backward may be determined based on a signal from the inhibitor switch, for example. If it is moving forward, the process proceeds to step S103, and if it is moving backward, the process proceeds to step S302.
In step S302, it is determined whether or not the flag F is set to “1”. If the determination result is F = 1, it is determined that the drive mode B is being executed, and the process proceeds to step S209. On the other hand, if the determination result is F = 0, it is determined that the drive mode A is being executed, and the process proceeds to step S204.

<Action>
Next, the operation of the third embodiment will be described.
Here, consider a scene where the vehicle is brought close to the road shoulder while retreating at a very low speed.
When the driving mode is set to B as an initial state and the steering angle is turned to the left toward the road shoulder (steps S301, S302, S209), the driving mode B is executed (step S110). That is, turning of only the rear wheels in the same direction as the steering angle θ _H is started. Accordingly, the rear end of the vehicle body can be directed to the road shoulder while suppressing the rightward extension of the front end of the vehicle body.

Then, when the steering angle is turned to the right after the rear end of the vehicle body approaches the road shoulder, this time, the drive mode is switched to A and executed (steps S209 and S113). That is, to start turning only the front wheels to the steering angle theta _H and reverse. Thereby, the vehicle front end can be brought close to the road shoulder so that the vehicle rear end is not separated from the road shoulder. Therefore, the leftward extension of the rear end of the vehicle can be suppressed to the minimum, so that turning of the steering wheel and repeated forward and backward movements can be avoided, and the vehicle can be smoothly moved to a desired position even in a narrow space. Can be moved.

As described above, when the vehicle moves forward, the drive mode is switched from A to B for execution, and when the vehicle moves backward, the drive mode is switched from B to A for execution. Can be.
In addition, when the vehicle retreats from the shoulder while retreating at an extremely low speed, switching from the driving mode B to A can be performed, so that it is possible to minimize the vehicle's large turn and the front end of the vehicle. It avoids turning back and repeating forward and backward, and can be smoothly removed even in narrow spaces.
FIG. 6B is a scene of parking and stopping and leaving in a reverse movement that can be actually assumed.

"effect"
As described above, the processes of steps S301 and S302 are included in the “control unit”.
(1) If the vehicle is moving backward, the control means performs switching from the second drive setting to the first drive setting.

Thereby, the width adjustment to the road shoulder can be facilitated even when retreating.
<< 4th Embodiment >>
"Constitution"
Immediately before this fourth embodiment, when executing the process of step S105, S113 (the driving mode A), when increasing the front wheel steering angle delta] f in accordance with an increase in the steering angle theta _H, reaching a maximum value delta] f _MAX Thus, the increase in the front wheel steering angle δf is limited, and the rear wheel steering angle δr is increased from this point.

The processing in the driving mode A will be described with reference to the flowchart of FIG.
In step S401, the steering angle when the front wheel steering angle δf reaches a predetermined value δf _R that is slightly smaller than the maximum value δf _MAX is θ _R, and it is determined whether the steering angle | θ _H | is smaller than θ _R. . If the steering angle | θ _H | is smaller than θ _R , the process proceeds to step S402. If the steering angle | θ _H | is larger than θ _R , the process proceeds to step S403.
In step S402, as shown below, the rear wheel without turning, after turning according to the front wheel to the steering angle theta _H, it ends the processing of the driving mode A.
δf = θ _H / N ₁
δr = 0
In step S3, as shown below, the front wheels are steered to δf _R , the rear wheels are steered by an insufficiency (θ _H −θ _R ) of the steering angle θ _H , and the processing of the drive mode A is terminated. To do.
δf = θ _H / N ₁ − (θ _H −θ _R ) / N ₂ = δf _R
δr = (θ _H −θ _R ) / N ₃

<Action>
Depending on the structure of the rudder angle ratio variable mechanism 3, there are some cases where the steering wheel cannot be increased when the front wheel rudder angle is saturated. This is because when the rack is locked by a rack stopper or the like, the motor of the steering angle ratio variable mechanism 3 cannot rotate, and the handle does not rotate due to the reaction force. Therefore, when the driving mode A is executed, if the front wheel steering angle δf is saturated to the maximum value δf _MAX , the steering angle θ _H cannot be increased thereafter, and the rear wheels cannot be steered.

Therefore, the steering angle when the front wheel steering angle δf reaches a predetermined value δf _R slightly smaller than the maximum value δf _MAX is θ _R, and the steering angle | θ _H | has reached θ _R as shown in FIG. At this point, the increase in the front wheel steering angle δf is limited, and the rear wheel steering angle δr is increased from this point. That is, as long as the front wheel steering angle δf does not reach the maximum value δf _MAX , the motor of the steering angle ratio variable mechanism 3 can be rotated, so that the steering wheel can be increased. The steering angle δr can be increased. The predetermined value δf _R is determined near the maximum value δf _MAX and a position where the rack and the rack stopper do not come into contact with each other in consideration of structural variations.

On the other hand, it is necessary for the steering feeling that the driver recognizes that the steering angles of the front and rear wheels are saturated (locked). If the front wheel rudder angle δf is limited to the predetermined value δf _R forever, that is, if the front wheel rudder angle δf is not saturated, such a feeling of lock cannot be obtained. Therefore, as shown in FIG. When the steering angle δr saturates to the maximum value δr _MAX , the front wheel steering angle δf may be saturated from the limit value δf _R to the maximum value δf _MAX . The timing at which the front wheel steering angle δf is increased again is the time when the rear wheel steering angle δr reaches a predetermined value δr _R that is slightly smaller than the maximum value δr _MAX . When the front wheel rudder angle δf is saturated in this way, the motor of the rudder angle ratio variable mechanism 3 cannot rotate, and the steering wheel does not rotate due to the reaction force. The person can be surely recognized and a good steering feeling can be obtained.

As shown in FIG. 13, the front wheel steering angle may be gradually and linearly increased from δf _R to the maximum value δf _MAX during the period in which the rear wheel steering angle δr is increased from 0 to the maximum value δr _MAX . This means that the front wheel steering angle increase rate nf2 during the period when the rear wheels are steered is made smaller than the front wheel steering angle increase rate nf1 during the period when the rear wheels are not steered. As shown, it is determined according to the rear wheel steering angle δr and the increase rate nr of the rear wheel steering angle δr.
nf2 = nr (δf _MAX −δf _R ) / δr
Further, as shown in FIG. 14, during the period in which the rear wheel steering angle δr is increased from 0 to the maximum value δr _MAX , the front wheel steering angle is gradually increased from δf _R to the maximum value δf _MAX , and the front wheel steering angle is increased. In the saturated region where saturation occurs, the rate of increase of the front wheel steering angle may be relaxed. This suppresses a sudden change in the steering reaction force when the front wheel steering angle is saturated, and does not give the driver a sense of incongruity.

"effect"
As described above, the processing of steps S401 to S404 is included in the “control unit”.
(1) The steering mechanism has a steering angle ratio variable mechanism that can steer the front wheels by changing the steering angle ratio of the front wheel steering angle to the steering angle, and the control means responds to an increase in the steering angle. When executing the first drive setting, the increase in the front wheel steering angle is limited immediately before the front wheel steering angle is saturated, and the rear wheels are steered.
As a result, the steering angle can be increased, so that the rear wheel steering angle can be increased accordingly.

(2) The control means limits the increase in the front wheel steering angle when the front wheel steering angle reaches a predetermined value that is in the vicinity of the structurally determined maximum value and smaller than the maximum value.
As a result, the steering angle can be reliably increased, so that the rear wheel steering angle can be increased accordingly.
(3) The control means saturates the front wheel rudder angle when the rear wheel rudder angle is saturated.
Thus, the driver can be surely recognized that both the steering angles of the front and rear wheels are saturated, and a good steering feeling can be obtained.
(4) When the rear wheel is steered, the control means makes the increase rate of the front wheel steering angle smaller than when the rear wheel is not steered.
Thereby, the sudden change of the front wheel rudder angle is suppressed, and a good steering feeling can be obtained.

(5) When turning the rear wheel, the control means determines the increase rate of the front wheel steering angle according to the increase rate of the rear wheel steering angle and the rear wheel steering angle.
Thereby, the saturation of the rear wheel rudder angle and the saturation of the front wheel rudder angle are matched, and a good steering feeling can be obtained.
(6) The control means makes the increase rate of the front wheel steering angle constant.
As a result, the front wheel steering angle can be smoothly saturated without causing the driver to feel uncomfortable.
(7) The control means relaxes the increase rate of the front wheel steering angle in a saturated region where the front wheel steering angle is saturated.
This suppresses a sudden change in the steering reaction force when the front wheel steering angle is saturated, and does not give the driver a sense of incongruity.

1 is a schematic configuration of a vehicle. It is a flowchart which shows the drive control process of 1st Embodiment. 6 is a graph showing drive modes A and B. It is a simulation result in the conventional four-wheel steering. It is a simulation result in the four-wheel steering of this application. It is a scene of parking and stopping that can actually be assumed. This is an application example. It is a flowchart which shows the drive control process of 2nd Embodiment. It is a flowchart which shows the drive control process of 3rd Embodiment. It is a flowchart of a 4th embodiment. This is a drive mode A that is limited before the front wheel rudder angle is saturated. This is drive mode A in which the front wheel steering angle is saturated in accordance with the saturation of the rear wheel steering angle. Application example (linear). It is an application example (relaxation curve).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Automobile 2FL-2RR Wheel 3 Steering angle ratio variable mechanism 4 Steering mechanism 5 Controller 6 Mode switch

Claims (17)

A steering mechanism capable of steering each of the front and rear wheels, and a control means for driving and controlling the steering mechanism in accordance with the steering operation of the driver,
The control means starts the steering of only the front wheels according to the steering operation, and when the front wheel steering angle is saturated, the first driving setting starts the steering of the rear wheels in the direction opposite to the front wheel steering angle, and performs the steering operation. In response, the second drive setting for starting the steering of only the rear wheels and starting the steering of the front wheels in the direction opposite to the rear wheel steering angle when the rear wheel steering angle is saturated is set to either one at extremely low speeds. A steering apparatus characterized by being switched from one to the other and executed.   2. The control unit according to claim 1, wherein the first and second drive settings are switched from one to the other in accordance with a predetermined operation different from a steering operation by a driver. A steering device according to claim 1.   3. The control unit according to claim 1, wherein when the direction of a steering angle is reversed, the control unit executes the first and second drive settings by switching from one to the other. 4. Steering device.   4. The control device according to claim 1, wherein when the steering angle is in a neutral region, the control unit executes the first and second drive settings by switching from one to the other. The steering device according to one item.   5. The control unit according to claim 1, wherein if the vehicle is moving forward, the control unit executes the control by switching from the first drive setting to the second drive setting. 6. Steering device.   6. The control unit according to claim 1, wherein the control unit performs switching from the second drive setting to the first drive setting when the vehicle is moving backward. Steering device.   2. The control unit according to claim 1, wherein when the steering wheel is steered on any one of the front wheels and the rear wheels, an increase rate of the steering angle is reduced in a saturated region where the steering angle is saturated. The steering apparatus as described in any one of -6.   The control means is characterized in that when the steering angle of one of the front wheels and the rear wheels is saturated and the other steering is started, the rate of increase in the steering angle is reduced in the initial movement region where the steering is started. The steering device according to any one of claims 1 to 7. The steering mechanism has a steering angle ratio variable mechanism that can steer the front wheels by changing the steering angle ratio of the front wheel steering angle to the steering angle,
When the control means executes the first drive setting in response to an increase in the steering angle, the control means restricts the increase in the front wheel steering angle immediately before the front wheel steering angle is saturated and starts turning the rear wheels. The steering apparatus according to any one of claims 1 to 8, wherein the steering apparatus is characterized.   The control means limits the increase in the front wheel steering angle when the front wheel steering angle reaches a predetermined value in the vicinity of the structurally determined maximum value and smaller than the maximum value. A steering device according to claim 1.   The steering device according to claim 9 or 10, wherein the control means saturates the front wheel steering angle when the rear wheel steering angle is saturated.   The said control means makes the increase rate of a front-wheel steering angle smaller when not turning a rear wheel, when turning a rear wheel, It is any one of Claims 9-11 characterized by the above-mentioned. Steering device.   The said control means determines the increase rate of a front-wheel steering angle according to the increase rate of a rear-wheel steering angle and a rear-wheel steering angle, when turning a rear wheel. Steering device.   The steering device according to claim 13, wherein the control means makes the rate of increase of the front wheel steering angle constant.   The steering device according to claim 13, wherein the control means relaxes the increase rate of the front wheel steering angle in a saturated region where the front wheel steering angle is saturated. In a car equipped with a steering device,
The steering device includes a steering mechanism that can steer each of the front and rear wheels, and a control unit that drives and controls the steering mechanism in accordance with a steering operation of a driver.
The control means starts the steering of only the front wheels according to the steering operation, and when the front wheel steering angle is saturated, the first driving setting starts the steering of the rear wheels in the direction opposite to the front wheel steering angle, and performs the steering operation. In response, the second drive setting for starting the steering of only the rear wheels and starting the steering of the front wheels in the direction opposite to the rear wheel steering angle when the rear wheel steering angle is saturated is set to either one at extremely low speeds. A vehicle characterized by switching from one to the other. It has a steering mechanism that can steer each of the front and rear wheels,
When driving the steering mechanism according to the steering operation of the driver, the steering of the rear wheels is reversed in the direction opposite to the front wheel steering angle when the steering of only the front wheels is started according to the steering operation and the front wheel steering angle is saturated. The first drive setting for starting the steering wheel and the steering of the rear wheels are started according to the steering operation. When the rear wheel steering angle is saturated, the steering of the front wheels is started in the direction opposite to the rear wheel steering angle. A steering control method, wherein drive setting is executed by switching from one to the other during extremely low speed traveling.

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