JP3399940B2 - Vehicle turning behavior control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial applications)   The present invention relates to a vehicle turning behavior control device, particularly a rear-wheel steering vehicle.
And a device for controlling the behavior of the vehicle at the time of turning. (Conventional technology)   As a vehicle that can steer the rear wheels along with the steering of the front wheels,
As described in Japanese Unexamined Patent Publication No.
Steering in reverse phase with the wheels to reduce the tendency to understeer
In some cases, turning performance is improved. But this
When the amount of understeer reduction is large,
The rake slows down. (Problems to be solved by the invention)   However, in such rear-wheel steered vehicles,
Even if such control is performed, for example, a low friction road (low μ
Road), the understeer tendency is not sufficiently reduced.
There is a case. When turning on low μ road, the rear wheels
If the understeer tendency does not decrease sufficiently,
The traces will bulge outward in the turning direction, and the driver wishes
It is not easy to trace the turning trajectory
No.   Here, if the steering amount in the opposite phase is increased,
It is possible to increase the rear wheel maximum reverse steering angle.
Must be set. Therefore, by increasing the amount of reversed phase
Is limited due to layout restrictions around the rear fender.
There are certain limitations (thus,
If the tendency does not decrease sufficiently,
Can not deal with it). In addition, turning performance (small turning performance) is more important
If you look at it, the layout freedom around the rear wheel is narrower
Can be Therefore, the improvement of turning performance is mainly used for reverse-phase steering of the rear wheels.
In the method that depends on it, a higher turning
We cannot expect to have sex.   The present invention combines rear wheel steering and braking control to achieve low friction
Understeer tendency is sufficiently reduced even when turning on the road
To provide a vehicle turning behavior control device capable of
aimed to. (Means for solving the problem)   For this purpose, the turning behavior control device of the present invention is shown in FIG.
As shown in the concept, when steering the front wheels, the rear wheels correspond to the front wheel steering angle.
Vehicle equipped with rear wheel steering means for steering the vehicle to a predetermined steering angle
Turning state detecting means for detecting a turning state of the vehicle;
Based on the signal from the turning state detecting means,
When the rear wheels are steered in the opposite phase to the front wheels by the wheel steering means
In both cases, the yaw motor assists the vehicle in turning according to the turning state.
The braking force on the inner wheel side in the turning direction is
Wheel control means for controlling the braking force to be greater than the braking force
Thus, the control for providing the wheel braking force difference is performed at the time of the front wheel steering.
When the steering rudder angle is more than a predetermined value that turns in the reverse
Wheel control, including means for executing when the vehicle speed is below a predetermined value
Means. (Operation)   When steering the front wheels, the vehicle determines the rear wheels according to the front wheel steering angle.
Equipped with rear wheel steering means that steers to the steering angle,
Based on the signal from the turning state detecting means that detects the turning state
The wheel control means operates the rear wheel steering means and turns the rear wheels in reverse phase.
At least, the inner and outer wheels in the turning direction depend on the turning condition.
Rotation to generate a yaw moment that promotes this rotation
The braking force on the inner wheel side in the turning direction is greater than the braking force on the outer wheel side
Control and make the wheel braking force difference
The control is based on the assumption that the steering angle at the time of the front wheel steering
Executes when the vehicle speed is lower than the predetermined value and the vehicle turns in the direction.
I do.   As a result, the rear wheel steering means for turning the rear wheels in reverse phase is provided.
The steering angle used to determine the rear wheel steering angle
When the vehicle speed is not lower than the predetermined value that is more than the predetermined value that turns in the phase direction
In this regard, this control is performed for the wheel braking force difference.
On the other hand, the steering angle of the steering wheel
If the vehicle speed is lower than a predetermined value and the vehicle speed is lower than a predetermined value, the braking force
Differentiating and thus performing the wheel braking
By using the force difference, the turning property is also increased, and on low μ roads
Can also provide sufficient small turning performance, and
In this case, the maximum rear steering angle of the rear wheels
, Improved turnability and flexibility in layout around the rear wheels
Can be achieved. As mentioned at the beginning of the specification
The control in the conventional case that relies exclusively on the reverse steering of the rear wheels
Approximately, that is, the rear wheels are out of phase, but the understeer tendency is satisfactory.
If the steering amount in the opposite phase is increased,
It is possible to improve minute turnability
However, on the other hand, it requires a large rear wheel maximum reverse steering angle.
And therefore also in a way that increases the amount of reversed phase
Is limited due to layout restrictions around the rear fender.
There are certain limitations (thus,
If the tendency does not decrease sufficiently,
On the other hand, but also turnability (small turning performance)
The more freedom you have in the layout around the rear wheels
Turned narrower and therefore higher turning with a small reverse steering angle
Cannot be expected to gain the
It is difficult to achieve both, but the present invention
And the rear wheels are steered in the opposite phase to the front wheels when the vehicle is running at low speed.
Not only the braking force on the inner wheel side in the turning direction
Can be controlled to be greater than the force
Obtaining sufficient small turning performance even on low μ roads such as snowy roads
Besides, even if the rear wheel maximum reverse steering angle is reduced
Small turning performance can be obtained and the ray around the rear fender
Out can be facilitated, increasing design flexibility
If it is possible to obtain excellent effects such as
Close. (Example)   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
You.   FIG. 2 shows an embodiment of the turning behavior control device of the present invention.
(A) is mainly the configuration of the braking control system, and FIG.
Indicates the configuration of the four-wheel steering control system.   In FIG. 2 (a), 1L and 1R are left and right front wheels, 2L and 2R are left and right rear wheels,
3 is a brake pedal, 4 is a tandem master cylinder
Shown respectively. Each wheel 1L, 1R, 2L, 2R is a wheel cylinder 5L, 5
R, 6L, and 6R.
When the hydraulic pressure is supplied from the cylinder 4, each wheel is individually controlled.
Shall be moved.   Here, the master hydraulic system
The front wheel brake system 7F from the compressor 4 includes a pressure response switching valve 8F,
Output chamber 9a of pilot cylinder 9F, pipelines 10F, 11F, 12F,
Left and right front wheel cylinders 5L, via hydraulic pressure control valves 13F, 14F
5R, rear wheel brake from master cylinder 4
System 7R is the output of pressure response switching valve 8R and pilot cylinder 9R.
Left via power chamber 9a, lines 10R, 11R, 12R and hydraulic pressure control valves 13R, 14R
Right rear wheel cylinder 6L, 6R.   In relation to the input chamber 9b of the pilot cylinders 9F and 9R,
Automatic brake including pump 15, reservoir 16 and accumulator 17
A rake hydraulic pressure source is provided, and this is connected to the pilot cylinder input.
An electromagnetic switching valve 18 is inserted between the chamber 9b. This valve 18 is always
The pilot cylinder input chamber 9b to the reservoir 16
The pilot cylinders 9F and 9R are
And set the pilot cylinder input chamber 9b when ON to the pump 15
Through the accumulator 17 maintained at a constant pressure
The pilot pressure of pilot cylinders 9F and 9R
The stone 9c is stroked against the built-in spring 9d, and the output chamber
It is assumed that the liquid in 9a is discharged.   The pressure response switching valve 8F, 8R is the system 7F, 7R
As shown in the figure, and turn on the pilot
When operating cylinders 9F and 9R, switch
Check system 7F and 7R (liquid flow toward master cylinder 4
Block).   The control of the electromagnetic switching valve 18 is performed by a controller described later.
Output as a control signal to the solenoid of the valve.
Style i_FiveThe current i_FiveIs 0A
The switching valve 18 is OFF (that is, normal state), and the current i_FiveIs ON when is 2A
Shall be. Further, at the time of the ON, the system 7F, 7
R is checked and the output chamber 9a of pilot cylinder 9F, 9R
As a result, the system after lines 10F and 10R
Automatic brake fluid pressure regardless of depression of the brake pedal 3
The hydraulic pressure is increased based on the source and therefore the wheels 1L, 1R, 2L, 2R
Will be described later among the respective hydraulic pressure control valves 13F, 14F, 13R, and 14R.
Subject to feedback control according to the method
The corresponding wheels corresponding to are automatically braked
(Automatic braking).   The hydraulic pressure control valves 13F, 14F, 13R, and 14R are respectively provided for the corresponding wheels.
The brake fluid pressure toward the wheel cylinders 5L, 5R, 6L, 6R is
Anti-skid and turning behavior control of the present invention
When OFF, press the
Raise the rake fluid pressure to the original pressure and brake the first stage ON
The holding pressure position does not increase or decrease the fluid pressure.
Partially release the hydraulic pressure to accumulators 19F and 19R to reduce
At the decompression position.   The control of these hydraulic pressure control valves is also performed by a controller described later.
Current to the solenoid of the corresponding valve (control valve drive current)
i₁~ I_FourDone by the current i₁~ I_FourAbove is 0A
Pressure position, current i₁~ I_FourWhen the pressure is 2 A, the pressure holding position and the current i₁
~ I_FourWhen the pressure is 5 A, it is assumed that the pressure reducing position is reached.   The pressure in accumulators 19F and 19R is
Pipelines 10F, 1 by pumps 20F, 20R driven during
0R, and these accumulators 21F, 21
Connect R. The accumulators 21F and 21R
Pilot 9C stroke of pilot cylinder during rake
To accumulate the hydraulic pressure.   The hydraulic pressure control valves 13F, 14F, 13R, 14R and the electromagnetic switching valve 18 are respectively
ON / OFF control is performed by the controller 22.
The signal from the steering angle sensor 23 that detects the steering angle θ
Signal and brakes that turn ON when the brake pedal 3 is depressed
The signal from the switch 24 and the rotation of the wheels 1L, 1R, 2L, 2R
Speed V_W1~ V_W4From the wheel speed sensors 25 to 28
Enter each one. The signal from the wheel speed sensor is
Used for road and traction control.   The controller 22 includes wheel cylinders 5L, 5
R, 6L, 6R hydraulic pressure P₁~ P_FourPressure sensors 31R, 31L, 32
The signals from L and 32R are input and the master
Hydraulic pressure P of da4_MFrom the pressure sensor 33 that detects
Is done. The output of the hydraulic pressure sensor for each wheel is
The target value of the hydraulic pressure is set and the target value and the actual wheel
The deviation from the cylinder fluid pressure is set to zero (that is, the wheel
Brake so that the cylinder fluid pressure matches its target value)
Control signal for feedback control of hydraulic pressure
Used. Also, for the hydraulic pressure sensor for the master cylinder,
In the illustrated example, the hydraulic pressure of the front wheel brake system 7F
Master cylinder fluid pressure is represented.   FIG. 2B also shows the controller 22.
The actual steering angle δ of the rear wheel_rRear steering angle sensor 34 for detecting
From the vehicle speed sensor 35 for detecting the vehicle speed V.
Input each signal. As shown in the figure, a four-wheel steering vehicle
On the front wheel side, the shaft 37 of the steering wheel 36
Is installed in the rack and pinion type gear box 38,
Tie rods 40, 40 are connected to the left and right ends of the rack shaft 39
At the same time, support the front wheels 1L, 1R on the outer ends of both tie rods 40, 40.
Knuckle arms 41, 41 are connected, and stearin
As is well known, the front wheels 1L, 1R are
The steering wheel 36 is turned in the steering direction. On the other hand, the rear wheels 2L and 2R
To enable steering, the same rack
Cupinion type gearbox 42 is installed horizontally.
You. The rear wheel steering device includes a rear wheel steering device in addition to the gear box 42.
Motor 43, and a motor mounted on the output side of the motor 43.
Arm 44 and one end of the pinion shaft of the gear box 42.
The worm wheel 45 attached meshes with the gear
Tie rods 47, 47 are provided at the left and right ends of the rack shafts 46, 46 of the box 42.
Be linked. Rear wheels 2L, 2R are attached to the outer ends of both tie rods 47, 47.
The knuckle arms 48, 48 supported are connected,
The driving of the motor 43 steers the rear wheels 2L and 2R. Rear wheel rudder
The angle sensor 34 is provided in a gearbox in such a rear wheel steering mechanism.
The rear wheel steering angle is located on the other side of the pinion shaft of
To detect.   The driving of the motor 43 is controlled by the controller 22.
You. That is, the motor 43 includes the four-wheel steering steering angle sensor 23,
Based on signals from the vehicle speed sensor 35 and the rear wheel steering angle sensor 34, etc.,
Look at the rear wheels through the motor driver built into the controller 22.
A control signal for controlling the steering to the target steering angle
The current i₀Is supplied, and the motor 43 is driven accordingly.
You.   In the system of the above embodiment, during normal braking,
Braking is performed in the following manner, and certain
In this case, the rear wheel steering and wheel braking
The turning behavior control aimed at is performed.   During normal braking when the brake pedal 3 is depressed,
Closes upon receiving a signal from the brake switch 24
The controller 22 turns off the electromagnetic switching valve 18 (i_Five= 0)
I do. As a result, the pilot cylinders 9F and 9R
b is connected to reservoir 16 to maintain the position shown and pressure response
The switching valves 8F and 8R also maintain the positions shown, and the front and rear wheel brake systems 7F and 7R
Is open. Further, the controller 22 includes the wheels 1L, 1R, 2
Hydraulic pressure control valves 13F, 14F, 13
Turn off R and 14R (i₁~ I_Four= 0) to keep the state shown.   Therefore, when the brake pedal 3 is depressed, the master system
Simultaneous output from front and rear wheel brake systems 7F and 7R from Linda 4
The same hydraulic pressure (master cylinder hydraulic pressure)
Response switching valve 8F, 8R, output chamber 9a of pilot cylinder 9F, 9R,
Pass through pipes 10F, 10R and hydraulic pressure control valves 13F, 14F, 13R, 14R,
Rake fluid pressure reaches wheel cylinder 5L, 5R, 6L, 6R
Then, each wheel 1L, 1R, 2L, 2R is individually braked.   During this time, the controller 22 detects the vehicle detected by the sensors 25 to 28.
Rotational peripheral speed (wheel speed) V of wheels 1L, 1R, 2L, 2R_W1~ V_W4Well known from
Calculate the pseudo vehicle speed by calculating
Then, the braking slip ratio of each wheel is calculated. And the control
The roller 22 determines the braking lock of each wheel from the slip ratio.
When it is likely to lock, the hydraulic pressure control valve 13F of the corresponding wheel,
Turn on 14F, 13R or 14R for one step to set the pressure-holding position.
Prevents the brake fluid pressure from rising further on the corresponding wheel.
You. Despite this, if a brake lock occurs, the control
Roller 22 is depressurized by turning on the hydraulic control valve of the corresponding wheel in two stages.
Position to reduce brake fluid pressure on the corresponding wheel
To prevent the brake lock. This causes the corresponding wheel to rotate.
When you start recovering the spin (spin-up),
The roller 22 moves the hydraulic pressure control valve of
Stop further drop in fluid pressure. And the rotation of the wheels
Controller recovers the hydraulic pressure of the corresponding wheel.
By turning off the valve to the pressure increase position, the brake fluid
Increase pressure to master cylinder hydraulic pressure. More than
The brake fluid pressure of each wheel becomes
Controlled to a value at which maximum braking efficiency is achieved,
Skid control is performed.   FIG. 3 shows the actual turning behavior executed by the controller 22.
This is a control program for control. This process is illustrated
For a certain period of time (for example, 5m
s) Performed on a periodic interrupt every time.   First, in steps 101 and 102, the steering wheel
Steering angle θ, vehicle speed V, rear wheel steering angle δ_rAnd wheel cylinder
Hydraulic pressure P₁~ P_FourRead each. In the next step 103, the steering
Rear wheel target steering angle δ according to the angle θ_r(S) is determined. 4th
The figure shows the rear wheel target steering angle δ with respect to the steering angle θ._rDetermine (S)
Of the rear wheel target steering angle δ._r(S)
Is a region where the steering angle θ is small, that is, the predetermined value θ₁The following range
In order for the rear wheels to be steered in phase with the front wheels,
Constant value θ₁Over the range above, the rear wheels rotate in the opposite phase to the front wheels.
In order to steer, the characteristics shown in the figure correspond to the steering angle θ.
Is set. In step 103, execute the step
From the above relationship based on the steering angle θ at the time, the rear wheel steering angle
The target value will be calculated.   Next, in step 104, the rear wheels determined in step 103 above
Target rudder angle δ_r(S) and the actual steering angle δ of the rear wheels_rOr deviation from
e_r, And in the next step 105, the deviation e_rIn response
The current i to be output to the rear wheel steering motor 43₀As
Set the rear wheel to the target steering angle δ_rControl to steer to (S)
Current (current command value) necessary for the operation is calculated. In this embodiment
Is calculated according to the following equation:   i₀= K_c× e_r                              … (1)   Where K_cIs a proportionality constant.   Thus, the motor current i₀And output in step 106
I do.   The control of the rear wheel steering is executed by the above processing,
Area where the steering angle θ is small (0 ≦ θ ≦ θ
₁In), the rear wheels are steered in phase with the front wheels, so that high-speed stability
The steering angle θ increases during low-speed turning, and θ
> Θ₁In the region where
As a result, the turnability is improved and the so-called understeer tendency is low.
Reduce.   Here, as shown in the characteristics of FIG.
Indicates that the steering angle θ is the predetermined value θ₁Larger predetermined value θ₂
In the above area, the angle of inclination of the rear wheels during rear wheel reverse phase steering
Maximum reverse rudder angle δ_rMAXIt can be kept at a constant value. Follow
Thus, the maximum angle of inclination during rear wheel reverse phase steering is δ_rMAXWhen
When the rear wheel angle is reduced,
Steering angle θ is a predetermined value θ₂At this time (in this case, the driver
(This is when turning with a smaller turning radius is intended.)
The effect of further improvement of turning performance by rear wheel reverse phase steering
Can no longer be expected, but in this turning behavior control,
In this case, use the following wheel braking force control together.
Without increasing the amount of reverse phase (thus, for example, existing
Speaking of cases applied to rear-wheel steered vehicles,
Layout, etc. without changing this at all), under
Steering tendency enables further reduction. That is,
In step 107, the steering angle device sets the predetermined value θ.₂Whether or not
Judgment, the steering angle θ becomes θ₁Exceeds θ₂If less than
Judging that further improvement in turning performance is unnecessary, the braking system described later
No yaw rate is generated by using
5 at hydraulic pressure control valve drive current i₁~ I_FourIf all are set to 0,
And the switching valve current i_FiveAlso maintain 0. In this case,
If these are output in step 114, the hydraulic pressure control valve 13
F, 14F, 13R, and 14R are the boosting positions shown in the drawing,
Since the switching valve 18 also maintains the illustrated position, the
Apply brake fluid pressure (wheel cylinder fluid pressure) to brake pedal
Depending on the hydraulic pressure from the master cylinder 4 when the
And normal braking is possible. That is,
Brake braking by the brake pedal 3 can be performed normally.   In the next step 108, the vehicle speed V is further reduced to a predetermined range V_min~ V
_maxJudge whether it is within or not, and if it is out of the predetermined range,
Execute steps 115 and 114 in the same way as
Complete.   On the other hand, each of the conditions in steps 107 and 108 is satisfied.
If the rear wheels are out of phase during turning,
When the tare tendency does not decrease or is not likely to decrease
And the opposite phase of the rear wheels by the above-mentioned rear wheel steering control
In this embodiment, in addition to the turning,
To activate the automatic brake and
Different wheel braking force, which gives the vehicle a yaw rate
A process for controlling the generation is performed. First,
In step 109, the current i to be output to the electromagnetic switching valve 18_Fiveage
To perform braking by the hydraulic pressure source for automatic braking._Five
= 2A, that is, the current for turning on the switching valve 18
I do.   Next, the braking force of the inner wheel in the turning direction is
Each value should be larger than the braking force of the outer wheel in the turning direction.
Wheel hydraulic control valve drive current i₁~ I_FourMake the settings for here
Means that the difference in braking force between the inside and outside of the turning direction is only on the front wheel side
And then go to step 110
Of the front wheels 1L and 1R
Eye of hydraulic pressure of cylinder 5L (when turning left) or 5R (when turning right)
The standard value P (S) is calculated according to the following equation.   P (S) = K_P1× θ / V… (2)   Where K_P1Is a constant.   In the present embodiment, the target value P (S) is manipulated as in equation (2).
Set as proportional to steering angle θ and inversely proportional to vehicle speed V
Like that. In the next step 111, the above step 110
The target value P (S) calculated in step 2 and the wheel to be controlled
Actual cylinder pressure P_in(P when turning left₁, Clockwise
P for time_Two) And deviation e_p, And the following step 11
Deviation e at 2_pHydraulic control valve drive current i according to₁(Left-turn
Time) or i_Two(When turning right) The pattern is determined. Immediately
In order to perform feedback control,
Deviation e_pPressure control valve 13F so that is zero (when turning left)
Or ON / OFF of control valve to operate 14F (during right turn)
Set the pattern. Specifically, for example,
Difference e_pIf the pressure is large, adjust the control valve to
E. E., Increase the percentage of time to keep it at the OFF position (i = 0)
Yiel cylinder hydraulic pressure properly converges to target value P (S)
Set the pattern as follows.   In the next step 113, the step 112 is performed in the turning direction.
The control valve drive current pattern corresponding to the
Difference e_pThe control valve ON-OFF pattern according to
On the other hand, the other wheels, ie, the outer front wheel 1R (turn left
Time) or 1L (right turn), rear wheel 2L, 2R, husband
Each wheel hydraulic control valve drive current i_TwoOr i₁, i_Three, i_FourWith 2A
And turns on the corresponding hydraulic pressure control valve for one stage and switches to the pressure holding position
So that it is held in that position.   As described above, each current i₁~ I_FiveAnd set step 11
The electromagnetic switching valve 18 and the fluid pressure control valve 1
Controls 3F, 14F, 13R, 14R. As a result, the rear wheel
Phase steering alone does not sufficiently reduce the tendency to understeer
Uses braking force difference to cancel understeer tendency
Can be That is, steps 109 to 114 are executed
And the automatic braking system is activated, and
The wheel has its brake fluid pressure controlled to the target value, while the other
The brake fluid pressure of wheels must be prevented from rising.
And braking force is applied only to the front wheel inside the turning direction.
As a result, the braking force difference between the inner and outer wheels in the turning direction (brake
Is automatically generated. With such braking
The vehicle receives the yaw moment in the turning direction to assist turning.
Longer, which can improve the turning performance of the vehicle.
When turning on a low μ road such as a snowy road.
The tendency to dart steer can be sufficiently reduced, and the
Vehicle behavior, such as bulging to the side, to improve safety.
You can also plan.   Also, a combination of the above-described rear wheel reverse phase steering and wheel braking force control.
Causes a yaw moment due to the difference in braking force,
Sufficient turning performance can be obtained even on μ road, and rear wheel
Maximum reverse rudder angle δ_rMAXAround the rear fender
It is also possible to make room for the layout.   As a result of the wheel braking force control, the rear wheel angle during reverse phase steering
Does not need to be too large, which is
Means that the layout is easier.
Also increase the degree of freedom in vehicle design
It becomes. Furthermore, the difference in braking force is used to improve turning performance
However, when using the brakes for this purpose,
Even if there is an increase in turning performance due to rear-wheel reverse-phase steering,
The rake control needs to be performed less frequently, and
Deterioration can be avoided.   In this embodiment, braking is performed between the inner and outer wheels in the turning direction of the front wheels.
Force difference is generated, but both front and rear wheels are targeted
May be controlled, and only for the rear wheel side
It may be.   FIG. 5 is a control program showing another example of the present invention.
Under that occurs when the trojan presses the brake pedal 3
-It is designed to improve the steer tendency.   Steps 151 to 158 correspond to the steering angle in step 151.
Master cylinder hydraulic pressure P together with θ and vehicle speed V_MIs read
Steps 101-108 of the program, except that
Is the same. In step 157 or 158, the steering angle θ becomes the predetermined value θ
₂Is less than or the vehicle speed V is within the predetermined range V_min~ V_maxOutside
For example, the wheel cylinder of each wheel in step 161 described later
The ΔP value applied to the process of calculating the target value P (S) of the hydraulic pressure is
The value is set to 0, and the routine proceeds to step 161. On the other hand,
If all of the conditions in steps 157 and 158 hold,
Is steered in the opposite phase,
In step 160, there is a difference in the wheel braking force between the inside and outside of the turning direction.
Is calculated according to the following equation.   ΔP = K_P2× Q / V… (3)   Where K_P2Is a constant.   In step 161, the master cylinder hydraulic pressure P_MAnd above
Using the hydraulic pressure difference ΔP, the wheel series of each wheel that normally occurs
5L, 5R, 6L, 6R hydraulic pressure, that is, the driver's brake pedal
In the turning direction with respect to the brake fluid pressure
Inside wheel 1L, 2L (when turning left) or 1R, 2R (when turning right) side
High, turning direction outer wheel 1R, 2R (when turning left) or 1L, 2L
(During right turn) is corrected to be lower,
Target value P (S) of the oil cylinder hydraulic pressure_j(J = 1-4)
Is calculated. For example, when turning left,
And correct each target value P (S)_jCan be asked
(However, P (S)_j≧ 0).   P (S)₁= P_M+ ΔP (4)   P (S)₂= P_M−ΔP (5)   P (S)₃= P_M−P₀+ ΔP (6)   P (S)₄= P_M−P₀−ΔP (7)   In this example, the left front wheel 1L is calculated by equation (4),
The brake fluid pressure for each wheel 2L is ΔP according to equation (6).
Only the target pressure is increased, while the right front wheel 1R
According to the formula (5), and the right rear wheel 2R according to the formula (7)
Each brake fluid pressure reduces its target pressure by ΔP.
As a result, the corrected target value P (S)_jSo that
Operate each hydraulic pressure control valve by feedback control.
For example, even when the brake pedal 3 is depressed, the inner wheels in the turning direction
Will be braked with greater braking force than the outer wheels.
You.   When the process of ΔP = 0 in step 159 is executed,
If ΔP becomes 0 in the equations (4) to (7),
Therefore, the normal braking mode, in which the above-mentioned correction is not performed, is used.
You. Also, a target value P (S) for the left and right rear wheels._Three, P (S)₄Calculation
P in equations (6) and (7)₀Is P_MIs below a predetermined value
Is a constant for producing the so-called P-valve effect.
You.   In the next steps 162 and 163, the above-mentioned FIG.
The processing according to steps 111 and 112 of FIG. That is,
For feedback control, each wheel cylinder actual
Hydraulic pressure P_j(J = 1 to 4) deviation e_pjIs calculated for each solution.
Deviation e per pressure control valve_pjON-OFF pattern according to
And the control valve drive current i₁~ I_Four
What is necessary is to output the pattern of.   With the above control, the driver depresses the brake pedal.
When braking based on the
The brake is one-sided as well as during automatic control (automatic braking)
Can be used to cancel the understeer tendency.
As a result, the turnability is improved, so that even when turning on snowy roads,
Even though the turning is increased by turning the wheels in reverse phase, the tune is still
If the driver is unable to
Even if you apply a key, you don't have to worry
The brake pedal can be depressed with ease.   In each of the above examples, the timing for entering the braking force control is
As for the steering angle θ, this is determined by the characteristics shown in FIG.
Value θ₂Although it was the above area, the rear wheel is in opposite phase
Predetermined value θ₁The above areas may be targeted. Also, for example
The predetermined value θ which turns in the opposite phase direction in FIG.₀Timin like
It may be possible to perform the task while capturing the information. (The invention's effect)   Thus, the turning behavior control device of the present invention
Understeer tends to occur when turning the rear wheels in reverse when turning.
In addition to the decrease, the braking force on the inner wheel side in the turning direction is
Enhances turning by controlling to be larger
A yaw moment according to the braking force difference
And rear wheels by rear wheel steering means for turning the rear wheels in reverse phase
The steering angle used to determine the steering angle turns the rear wheels in the opposite phase.
If the vehicle speed is lower than a predetermined value and the vehicle speed is lower than a predetermined value, the braking force
Can make a difference, even when turning on low friction roads,
Understeer tendency can be sufficiently reduced,
The turning performance can be increased and sufficient turning performance can be obtained.
Also, in this case, the maximum rear steering angle of the rear wheels is set to a large value.
It does not need to be fixed, improving turning performance and layout around the rear wheel
Can be achieved simultaneously. Therefore also
The use of the above braking force difference depends solely on the reverse-phase steering of the rear wheels
The constraint in the conventional case can be relaxed, and the present invention
Then, just steer the rear wheels in reverse phase with the front wheels at low speed
And the braking force on the inner wheel side in the turning direction is larger than the braking force on the outer wheel side.
As a result of being able to control
Sufficient turning performance can be obtained even on such low μ roads
Sufficient turning performance even when the maximum reverse steering angle of the rear wheels is reduced
The layout around the rear fender
Can be easier and increase design flexibility
And the like, and excellent effects such as can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram of a turning behavior control device of the present invention, and FIGS. 2 (a) and 2 (b) are respectively a braking control system and a braking control system showing one embodiment of the turning behavior control device of the present invention. FIG. 3 is a flowchart showing an example of a control program of the controller in the example, and FIG. 4 is an example of a characteristic for setting a rear wheel target steering angle applied in the program. FIG. 5 is a flowchart showing another example of the control program of the controller. 1L, 1R… front wheel, 2L, 2R… rear wheel 3… brake pedal 4… tandem master cylinder 5L, 5R, 6L, 6R… wheel cylinder 7F… front wheel brake system, 7R… rear wheel brake system 8F, 8R …… Pressure response switching valve 9F, 9R …… Pilot cylinder 10F, 10R, 11F, 11R, 12F, 12R, 34L, 34R, 37,38 …… Pipe line 13F, 13R, 14F, 14R …… Hydraulic pressure Control valves 15, 20F, 20R, 35 Pumps 16, 36 Reservoirs 17, 19F, 19R, 21F, 21R Accumulator 18 Electromagnetic switching valve 22, Controller 23 Steering angle sensor 24 … Brake switches 25, 26, 27, 28… Wheel speed sensors 31L, 31R, 32L, 32R, 33… Hydraulic pressure sensor… Rear wheel steering angle sensor, 35… Vehicle speed sensor 36… Steering wheel 37… … Axes, 38,42… Gear boxes 39,46 …… Rack shafts, 40,47… Tie rods 41,48 …… Knuckle arms 43 …… Motors, 44 …… Worm gears 45 …… Worm wheels

──────────────────────────────────────────────────続 き Continued on the front page (72) Atsushi Nano, Inventor 2 at Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Nissan Motor Co., Ltd. (72) Inventor Shinji Matsumoto 2 at Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. In-company (56) References JP-A-64-90858 (JP, A) JP-A-49-103325 (JP, A) JP-A-63-279976 (JP, A) (58) Fields investigated (Int. . ^7, DB name) B60T 8/58 B62D 6/00

Claims (1)

(1) When a front wheel is steered, a turning state of the vehicle is detected in a vehicle having rear wheel steering means for steering a rear wheel to a predetermined steering angle corresponding to the front wheel steering angle. A turning state detecting means for turning the rear wheel in the opposite phase to a front wheel by the rear wheel steering means at the time of turning based on a signal from the turning state detecting means, and assisting the vehicle to turn according to the turning state. Wheel control means for controlling the braking force on the inner wheel side in the turning direction to be greater than the braking force on the outer wheel side such that a yaw moment occurs. A wheel control means including means for executing when the vehicle speed is equal to or greater than a predetermined value that is equal to or greater than a maximum steering angle of the rear wheels in the opposite phase direction and equal to or less than a predetermined value. .