JPH03246150A - Turning action controlling device for vehicle - Google Patents

Abstract

PURPOSE:To secure the stability of a vehicle while improving the turning ability by providing a steering condition detecting means for detecting the steering condition, a running condition detecting means for detecting a vehicle speed or a lateral acceleration added to the vehicle, and a wheel controlling means. CONSTITUTION:A wheel control means steers rear wheels in the inverse phase through a rear wheel steering means when a detected value by a running condition detecting means is less than a predetermined value in response to signals from a steering condition detecting means and the running condition detecting means for detecting the steering condition, and the vehicle speed or lateral acceleration respectively at the time of turning. When the detected value is more than a predetermined value, wheel braking forces are set different between the inner side and outer side in the turning direction to produce a yaw moment for assisting this turn corresponding to the turning condition for the inner and outer wheels in the turning direction. The improvement of turning ability can thus be realized by reduction of an understeer tendency by inverse phase steering of rear wheels in a range where the vehicle speed or lateral acceleration is less than predetermined value, while if it is more than predetermined, it can be achieved by utilizing the differential braking force for braking the wheels. The stability is also secured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a device for controlling turning behavior of a vehicle, and particularly to a device for controlling vehicle behavior during turning in a rear wheel steered vehicle.

(Prior art) As described in Japanese Patent Application Laid-Open No. 64-90858, a vehicle capable of steering the rear wheels in conjunction with the steering of the front wheels steers the rear wheels in the opposite phase to the front wheels during a turn to prevent understeer tendency. There is a method that improves turning performance by reducing the amount. However, in this case, when the amount of understeer reduction becomes large, the brakes are used to decelerate the vehicle.

(Problem B that the invention seeks to solve) However, in the past, it has not been possible to sufficiently deal with the increase in understeer that occurs when the accelerator pedal is pressed during a turn, and the rear wheels are steered in the opposite phase during a turn. However, when the accelerator pedal is depressed, especially in front-wheel drive or 4WD vehicles, the effectiveness of the rudder changes, resulting in a tendency for understeer.

In the above-mentioned publication, the rear wheels are steered in reverse phase when turning at high speeds, but at high speeds or when lateral acceleration is large, if the rear wheels are reversed in phase to improve turning performance, the turning performance may be improved. The lateral force on the rear wheels decreases accordingly. This reduction in the lateral force of the rear wheels tends to make the vehicle unstable, making it difficult to simultaneously improve turning performance and ensure stability.

On the other hand, in order to suppress the tendency for understeer and improve turning performance, there is a technology that varies the braking force between the inner and outer wheels in the turning direction. , the frequency of braking increases, making brake fade more likely.

The present invention introduces braking control that uses a wheel braking force difference, and by appropriately combining this with rear wheel reverse phase steering, it is possible to improve turning performance while ensuring vehicle stability. An object of the present invention is to provide a turning behavior control device for a vehicle that prevents performance deterioration due to brake fade.

(Means for Solving the Problem) For this purpose, the turning behavior control device of the present invention, as conceptually shown in FIG. 1, steers the rear wheels to a predetermined steering angle in accordance with the front wheel steering angle when the front wheels are steered. In a vehicle equipped with rear wheel steering means, a steering state detection means detects a steering state, a running state detection means detects vehicle speed or lateral acceleration applied to the vehicle, and a signal from the steering state detection means and the running state detection means is provided. Based on this, when the detected value of the driving state detecting means is less than a predetermined value during a turn, the rear wheels are steered in the opposite phase by the rear wheel steering means, and when the detected value is greater than a predetermined value, the vehicle is steered in accordance with the turning state. The vehicle is equipped with wheel control means that varies the braking force of the wheels between the inner and outer sides of the turning direction so as to generate a yaw moment that promotes turning.

(Function) When turning, in response to signals from the steering state detection means and the running state detection means, which respectively detect the steering state and the vehicle speed or lateral acceleration, the wheel control means detects whether the detected value of the running state detection means is a predetermined value. When the detected value is less than a predetermined value, the rear wheel steering means is used to steer the rear wheels in the opposite phase, and when the detected value is greater than or equal to a predetermined value, a yaw moment is generated for the inner and outer wheels in the turning direction to promote the turning according to the turning state. Therefore, the braking force of the wheels is varied between the inside and outside of the turning direction.

As a result, when the vehicle speed or lateral acceleration is less than a predetermined value, the understeer tendency is reduced by reverse-phase steering of the rear wheels, and when the vehicle speed or lateral acceleration is less than a predetermined value, the understeer tendency is reduced. This is achieved by exploiting differences. Retrospective correction using the difference in braking force can improve turning performance and ensure stability even when turning at high speed or with high lateral acceleration without reducing the lateral force of the rear wheels. In this case, the braking force is generated only at high speeds or high lateral accelerations, so braking is not performed too frequently.

(Example) Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Figure 2 shows an embodiment of the turning behavior control device of the present invention.
Figure a) mainly shows the configuration of the braking control system, and figure (b) mainly shows the configuration of the four-wheel steering control system.

IL in Figure 2 (a), II? are left and right front wheels, 2L, 2
R indicates left and right rear wheels, 3 indicates a brake pedal, and 4 indicates a tandem master cylinder. Each wheel IL, IR, 2L,
2R is wheel cylinder 5L, 5R, 6L, 6R
and a master cylinder 4 is attached to these wheel cylinders.
Each wheel shall be braked individually when supplied with hydraulic pressure from.

Here, to explain the brake hydraulic system, the front wheel brake system 7F from the master cylinder 4 is connected to the pressure response switching valve 8F.
, output chamber 9a of pilot cylinder 9F, conduit 10F,
IIF, 12F, and hydraulic pressure control valves 13F and 14F to the left and right front wheel cylinders 5L and 5R, and the rear brake system 7R from the master cylinder 4 is connected to the pressure response switching valve 8R and the output chamber 9 of the pilot cylinder 9R.
a % pipes 10R, IIR, 12R, hydraulic control valve 13
11. Left and right rear wheel cylinder 6L after 14R,
Bring it to 6R.

In relation to the input chambers 9b of the pilot cylinders 9F and 9R, the pump 15, the reservoir 16 and the accumulator 17
An automatic brake hydraulic pressure source including a hydraulic pressure source is provided, and an electromagnetic switching valve 18 is inserted between this and the pilot cylinder input chamber 9b. This valve 18 normally operates in the pilot cylinder input chamber 9b.
The pilot cylinders 9F and 9R are placed in the non-operating position as shown in the figure by communicating with the reservoir 16, and when ON, the pilot cylinder input chamber 9b is communicated with the accumulator 17, which is kept at a constant pressure by appropriately driving the pump 15, so that future liquid is The pressure causes the pistons 9c of the pilot cylinders 9F and 9R to stroke against the built-in spring 9d, and the output chamber 9a
The liquid inside is to be discharged.

In addition, the pressure response switching valves 8F and 8R open the corresponding systems 7F and 7R as shown in the diagram in normal conditions, and when the solenoid switching valve 18 is turned on and the pilot cylinders 9F and 9R are operated, the pressure thereon switches the valves. , systems 7F and 7R will be in a state where they are checked (blocking the liquid flow toward the master cylinder 4).

The control of the electromagnetic switching valve 18 is performed by a current i to the solenoid of the valve, which is output as a control signal from a controller to be described later. When the current i5 is OA, the switching valve 18 is OFF (i.e., in normal state). ) current i is 2
It is assumed that it is ON when A. Furthermore, when it is turned on, the systems 7F and 7R are reverse checked as described above, and the liquid in the output chambers 9a of the pilot cylinders 9F and 9R is discharged, so that the system after the conduit 10F and IOR is activated by the brake pedal 3. The hydraulic pressure is increased based on the automatic brake hydraulic pressure source without stepping on the wheel IL, IR, 2L,
2R is the respective hydraulic pressure control valve 13F.

Braking is automatically performed on the corresponding wheels that are subject to feedback control among 14F, 13R, and 14R according to the method described later (automatic braking).
.

The hydraulic pressure control valves 13F, 14F, 13R, 14''R are
Wheel cylinders 5L, 5R, 6 for corresponding wheels, respectively
The brake fluid pressure toward L and 6R is individually controlled for anti-skid and turning behavior control of the present invention, and when the brake fluid pressure is at the pressure increase position shown in the figure at F, the brake fluid pressure is directed toward the source pressure. When the first stage is ON, the pressure is increased and the brake fluid pressure is not increased or decreased, and the pressure is maintained, and when the second stage is ON, the brake fluid pressure is partially released to the reservoirs 19F and 19R and is reduced to a reduced pressure position.

The control of these hydraulic pressure control valves is also carried out by applying a current (control valve drive current) L to the solenoid of the corresponding valve from the controller, which will be described later.
``L, current i, ``i.

When is OA, the pressure increase position is reached, when the currents i to i4 are 2A, the pressure holding position is set, and when the current amounts 1 to i4 are 5A, the pressure reduction position is set.

The brake fluid in the reservoirs 19F and 19R is pumped by the pumps 20F and 2OR, which are driven during pressure retention and pressure reduction.
The pipes are returned to the pipes 10F and IOR, and accumulators 21F and 21R are connected to these pipes. The accumulators 21F and 21R accumulate hydraulic pressure due to the stroke of the piston 9C of the pilot cylinder during automatic braking.

The hydraulic pressure control valves 13F, 14F, 13R, 14R and the electromagnetic switching valve 18 are turned on and off by the controller 22, respectively.
OFF control, and this controller 22 receives a signal from a steering angle sensor 23 that detects the steering angle θ, and a signal from the brake pedal 3.
A signal from the brake switch 24 that turns on when the
Rotational peripheral speed V of wheels IL, IR, 2L, 2R, 1 to V
, 4 from the wheel speed sensors 25 to 28, and a signal from the lateral acceleration sensor 29 that detects the lateral acceleration g of the vehicle body. Signals from wheel speed sensors are used for anti-skid and traction control.

The controller 22 also includes a wheel cylinder 5L for each wheel.
, 5R, 6L, 6R hydraulic pressure sensors 31R, 31L, 32L, 32R that detect the hydraulic pressure P a
At the same time, a signal from the hydraulic pressure sensor 33 that detects the hydraulic pressure PM of the master cylinder 4 is input. The output of the hydraulic pressure sensor for each wheel is determined by setting a target value for the wheel cylinder hydraulic pressure so that the deviation between the target value and the actual wheel cylinder hydraulic pressure becomes zero (that is, adjusting the wheel cylinder hydraulic pressure to that target value). It is used as a control signal when performing feedback control of brake fluid pressure (so as to match the brake fluid pressure). Regarding the master cylinder hydraulic pressure sensor, in the illustrated example, the master cylinder hydraulic pressure is represented by the hydraulic pressure of the front wheel brake system 7F.

Furthermore, the controller 22 includes a rear wheel steering angle sensor 3 that detects the actual steering angle δ of the rear wheels, as shown in FIG. 2(b).
4 and a signal from a vehicle speed sensor 35 that detects the vehicle speed V are respectively input. As shown in the figure, in a four-wheel steering vehicle, on the front wheel side, the steering wheel 36
A shaft 37 is incorporated into a rack and pinion gear box 38, and tie rods 40. are attached to the left and right ends of the rack shaft 39.
40 is connected to the knuckle arm 41.40, and the front wheels IL and IR are supported at the outer ends of both tie rods 40.40.
41 are connected to each other, and when the steering wheel is operated, the front wheels IL and IR are steered in the steering direction of the steering wheel 36, as is known in the art. Also on the side, a rack and pinion type gear box 42 similar to that described above is installed laterally.In addition to the gear box 42, the rear wheel steering device includes a motor 43 for steering the rear wheels, and the output shaft of the motor 43 includes a motor 43 for steering the rear wheels. The worm gear 44 attached to the gear box 42 meshes with the worm wheel 45 attached to one end of the pinion shaft of the gear box 42, and tie rods 47.47 are connected to the left and right ends of the rack shaft 46.46 of the gear box 42. tie rod 47
A knuckle arm 48.48 supporting the rear wheels 2L and 2R is connected to the outer end of the rear wheel 47, and the rear wheels 2L and 2R are steered by the drive of the motor 43. The rear wheel steering angle sensor 34 is arranged on the other side of the pinion shaft of the gear box 42 in such a rear wheel steering mechanism to detect the rear wheel steering angle.

The drive of the motor 43 is controlled by the controller 22. That is, the motor 43 includes the steering angle sensor 2 during four-wheel steering.
3. Based on signals from the vehicle speed sensor 35, rear wheel steering angle sensor 34, etc., a current 10 is supplied as a control signal to control the rear wheels to be steered to the target steering angle through the motor driver built into the controller 22; The motor 43 is driven accordingly.

In the above embodiment system, during normal braking,
Braking is performed as follows, and when turning, under certain conditions, the rear wheels are steered in reverse phase and the wheels are braked with a difference in braking force.
The turning behavior control that the present invention aims at is performed.

During normal braking when the brake pedal 3 is depressed, the controller 22 receives a signal from the brake switch 24, which closes in response, and turns the electromagnetic switching valve 18 to 0FF (is-〇).
Leave as is. As a result, pilot cylinder 9F,
9R connects the input chamber 9b to the reservoir 16 and maintains the position shown in the figure, the pressure response switching valves 8F and 8R also maintain the position shown in the figure, and the front and rear wheel brake systems 7F and 7R are opened. Further, the controller 22 controls the wheels IL and IR.

Hydraulic pressure control valve 1 unless brake lock occurs in 2L and 2R.
Turn off 3F, 14F, 13R, 14R (L-L
= O) and maintain the condition as shown.

Therefore, the same hydraulic pressure (master cylinder hydraulic pressure) that is simultaneously output from the master cylinder 4 to the front and rear wheel brake systems 7F and 7R when the brake pedal 3 is depressed is applied to the pressure response switching valves 8F and 8R, and the pilot cylinder 9F, respectively.
It passes through the output chamber 9a of 9R, the conduit 10F, the IOR, and the hydraulic pressure control valves 13F, 14F, 13R, 14R, and is applied as brake fluid pressure to the wheel cylinders 5L, 5R, 6L,
6R is reached, and each wheel IL, IR, 2L, and 2R is braked individually.

During this time, the controller 22 calculates a pseudo vehicle speed by a well-known calculation from the rotational circumferential speeds (wheel speeds) ■1 to ■ and 44 of the wheels IL, IR, 2L, and 2R detected by the sensors 25 to 28, and calculates the pseudo vehicle speed from this and the individual wheel speeds. The braking slip rate of each wheel is calculated from Then, the controller 22 determines whether or not the brakes of each wheel are locked based on this slip ratio, and when the brake is about to lock, the hydraulic pressure control valves 13F and 14F of the corresponding wheel are activated.

By turning on 13R or 14R one step to set the pressure holding position, further increase in brake fluid pressure of the corresponding wheel is prevented. If a brake lock occurs despite this, the controller 22 turns the hydraulic pressure control valve of the corresponding wheel into a pressure-reducing position by turning on the hydraulic pressure control valve of the corresponding wheel in two steps, thereby lowering the brake hydraulic pressure of the corresponding wheel and preventing the brake lock. As a result, when the corresponding wheel starts to recover its rotation (spinnerve), the controller 22 sets the hydraulic pressure control valve of the corresponding wheel to the pressure holding position and stops any further decrease in the brake hydraulic pressure. Then, as the rotation of the wheel is restored, the controller 22 turns off the hydraulic pressure control valve of the corresponding wheel to the pressure increasing position, thereby increasing the brake hydraulic pressure toward the master cylinder hydraulic pressure. By repeating the above skid cycle, the brake fluid pressure of each wheel is controlled to a value that achieves the maximum braking efficiency, and normal anti-skid control is performed.

FIG. 3 shows a control program for main turning behavior control executed by the controller 22. This process is performed by an operating system (not shown) for a certain period of time (for example, 5m).
5) is performed at every scheduled interrupt.

First, in steps 101 and 102, the steering angle θ of the steering wheel, the vehicle speed V, the rear wheel steering angle δ, and the wheel cylinder hydraulic pressures P1 to P4 are read, respectively. Next step 103
Then, the vehicle speed V is a predetermined value ■. Determine whether or not the above is true. As a result, if No (V<V.), the process proceeds to step 104 and rear wheel reverse phase steering control is executed, and if Yes, (■≧■).

) Proceed to step 112 to execute wheel braking force control.

First, when proceeding from step 103 to step 104, here, the rear wheel target steering angle δ, (S
) to determine. FIG. 4 shows an example of characteristics for determining the rear wheel target steering angle δ7(S) with respect to the steering angle θ. In the case shown, the rear wheel target steering angle δ, (S) is the steering angle θ. is less than a predetermined value of 61, the rear wheels are fixed (i.e., δ, (S) = O
), and the characteristics as shown in the figure are set corresponding to the steering angle θ so that the rear wheels are steered in a direction opposite to that of the front wheels in the range of a predetermined value 08 or more. It should be noted that the turning angle of the rear wheels during rear wheel reverse phase steering is suppressed to a constant value in a region of a predetermined value of 62 or more. In step 104, a target value of the rear wheel steering angle is calculated from the above-mentioned relationship based on the steering angle θ at the time of execution of the step.

Next, in step 105, the difference between the rear wheel target steering angle δ, (S) obtained in step 104 and the actual rear wheel steering angle δ, that is, the deviation er, is calculated, and in the next step 106, the deviation er is calculated. Accordingly, the current (current command value) required to control the rear wheels to steer to the target steering angle δ, (S) is calculated as the current 10 to be output to the rear wheel steering motor 43. In this embodiment, this is calculated according to the following equation.

io = K c X e r ”・
(1) Here, Kc is a proportionality constant.

The motor current 10 is thus determined and output in step 107.

Rear wheel steering control is executed by the above process, and during low-speed turns, the steering angle θ increases, and in the region where θ≧θ holds, the rear wheels are in opposite phase to the front wheels, resulting in improved turning performance. The so-called understeer tendency is reduced.

At low speeds, such reverse-phase rear wheel steering enables brisk driving even in FF or 4WD vehicles.

In the following step 108, in this embodiment, the next step 1
Set the e value applied to the process in 09 to the value 0. Here, the eP value is the inner wheel IL in the turning direction (when turning left) in braking force control to create a difference in braking force between the inner and outer wheels in the turning direction, which is performed when turning in a high speed range, which will be described later.
Or, it represents the difference (deviation) between the target wheel cylinder hydraulic pressure at IR (when turning right) and the actual hydraulic pressure of the relevant wheel cylinder, but the value e is set so that such a braking force difference does not occur in the low speed range. , is set to 0.

Steps 108 to 10 above in the low vehicle speed range
When proceeding to Step 9, in Step 109, the control valve drive current L (when turning left) or i2 corresponding to the inner Bizen wheel in the turning direction is determined.
(when turning right) remains at 0, and in the next step 110, the outside front axle in the turning direction IR (
(when turning left) or LL (when turning right), rear wheels 2L, 2
Control valve drive current 12 or 11+1ff+ corresponding to R
14 is set. The solenoid switching valve 18 is normally 0FF (i
s=o), and therefore, in this case, the control valve drive current 12 or il+ 13+ 14 is set to 0 according to 15=0. Thus, the control valve drive current amounts 1 to i4 and the switching valve drive current i are output in step 111. In this case, hydraulic control valves 13F and 14F.

13R and 14R are at the pressure increasing positions shown in the figure, and the switching valve 18 also maintains the position shown in the figure, so there is no difference in braking force between the inner and outer wheels in the turning direction, and as mentioned above, the brake pedal 3, the switching valve current i, is i,
- As a result, the state of the multi-valve is still maintained at the illustrated position. Therefore, the brake fluid pressure of each wheel (wheel cylinder fluid pressure) can be made to depend on the fluid pressure from the master cylinder 4 when the brake pedal 3 is depressed, and normal braking is possible, and the braking force is the same as above. No difference (one-sided brake effect) will occur.

Applying braking force to the inner wheel to create a difference in braking force between the inner and outer wheels in the turning direction at low speeds (or when lateral acceleration is small) improves turning performance, but on the other hand, the braking is applied too frequently. In contrast, in this embodiment, the braking force control described above is not performed at low speeds, and the brakes tend to fade.
As mentioned above, during a turn, the rear wheels can be reversed to reduce the understeer tendency and improve turning performance.
The frequency of braking is not excessive and the brakes do not tend to fade.

On the other hand, braking force control is used to improve turning performance at high speeds. The difference in braking force is used to ensure stability by leaving the rear wheels as normal without performing reverse phase control.

That is, if the result of the determination in step 103 is that the vehicle speed V is equal to or higher than the predetermined value 70, the process proceeds to step 112;
In this embodiment, from step 112 onwards, automatic brakes are activated, and the wheel braking force is varied between the inner and outer front wheels in the turning direction, thereby controlling the vehicle to generate a yaw rate. First, in step 112, the target brake fluid pressure of the inner wheel in the turning direction of the front wheels IL and IR, that is, the wheel cylinder 5L is determined.
Target value P of hydraulic pressure (when turning left) or SR (when turning right)
Determine (S). FIG. 5 shows an example of the characteristics for determining the target value P(S) with respect to the steering angle θ. is set to 0, and if the predetermined value is 01 or more, θ
The characteristics shown in the figure are set in response to the steering angle so that the steering angle increases up to a predetermined upper limit in proportion to the steering angle.

Here, the predetermined value θ, which is set as the discrimination value for the steering angle θ, is specifically set as the following value. In other words, in a high vehicle speed range where the vehicle speed V is above the predetermined value 70, the steering angle θ will generally not exceed this value (in normal driving, the driver does not adjust the steering angle to such a state at high speeds). The value of θ1 is determined based on the viewpoint that the wheel will not be cut often). In step 112, the target value P(S) is calculated from the above-mentioned relationship based on the steering angle θ at the time of execution of the step.

In the next step 113, the switching valve drive current i is set in accordance with the steering angle θ. That is, when the steering angle θ is less than the predetermined value 01, the switching valve 18 is kept in the normal OFF state:
s=0, but if the steering angle θ is greater than or equal to the predetermined value 09, the automatic braking hydraulic pressure source will brake for 1 s.
= 2A, that is, the current is switched and set to turn on the switching valve 18.

In the next step 114, the deviation ea between the target value P (S) calculated in step 112 and the actual hydraulic pressure Pi, (P or Pz) of the wheel cylinder to be controlled is calculated, and the step Proceed to 109 and below.

In the high speed range, when the process proceeds to step 109 after passing through the processes of steps 112 to 114, in step 109, the hydraulic control valve driving current i+ is determined according to the current pressure deviation e.
(when turning left) or pattern 12 (when turning right) is determined. That is, in order to perform feedback control, here, the hydraulic pressure control valve 13F (
The ON-OFF pattern of the control valve is set to operate 14F (when turning left) or 14F (when turning right). Specifically, when performing feedback control, a pattern is set so that the wheel cylinder hydraulic pressure appropriately converges to the target value P(S) according to the magnitude of the deviation e2.

In addition, ■≧■. Even in this state, when the steering angle θ is in the range of θ to θ1, the target value is P(S)=0 as described above, and the switching valve 18 remains OFF, so the braking force by the automatic brake is Differential braking will not be performed. That is, in such a case, eP=0 and step 1
Even if 09 to 111 are executed, the control valve 13F or 14F
The ON-OFF pattern is not output.

In step 110, the hydraulic control valve drive currents for other wheels, that is, wheels other than the front axle on the inside in the turning direction, are set according to the switching valve drive current i, but in this case, i remains at 0. When ■≧■, the same setting process as described above is performed. When both of and θ≧θ1 are established and the switching valve drive current i is switched to 2A, the hydraulic control valve drive current iZ (when turning left) or i
, (when turning right), ! Set 3+14 to 28, and switch the corresponding hydraulic pressure control valve to the 1-stage ON L pressure holding position so that it is held at that position.

At high speed, set each current 11 to i5 in this way,
In step 111, these are output to control the electromagnetic switching valve 18 and hydraulic pressure control valves 13F, 14F, 13R, and 14R, respectively.

As a result of the above, rear wheel reverse phase steering and braking force control can be controlled individually.
It can be used appropriately in the II area, and can be used in FF cars and 4W
Even in D cars, it is possible to cope with the increase in understeer caused by pressing the accelerator pedal while turning by improving turning performance. In other words, in braking force control in a high-speed range, the brake fluid pressure of the wheel on the inside in the turning direction is controlled to the target value, while the brake fluid pressure of the other wheels is prevented from increasing. As a result, a braking force difference is automatically generated between the inner and outer wheels in the turning direction. Through such braking, the vehicle receives a yaw moment in the turning direction, which helps the vehicle turn, thereby increasing the turning performance of the vehicle.Furthermore, since the rear wheels 2L and 2R remain normal, the lateral force on the rear wheels is reduced even at high speeds. In this embodiment, such wheel braking control is performed so that ■≧■.and θ≧θ
Although the execution is performed targeting one region, as described above, the predetermined value θ regarding the steering angle θ is ■≧■. In the region of , the value generally does not satisfy θ≧θ1. Therefore, ■≧■. If the driver steers the steering angle θ beyond θ1 in this state, it means that a considerable degree of urgency (avoidance action) is required. In this example, even in such a case, the braking force of the inner wheel in the turning direction is increased as θ becomes larger (that is, the greater the turning ability is required). In addition, it is possible to improve retrospective performance while ensuring stability.

In this embodiment, wheel braking force control is performed so that a difference in braking force is generated between the inner and outer wheels in the turning direction of the front wheels, but the control may be applied to both the front wheels and the rear wheels. It is also possible to target only

Further, although the rear wheel reverse phase steering and wheel braking force control are applied to different application areas using the vehicle speed (2), it is also possible to use the vehicle lateral acceleration g instead of or in addition to the vehicle speed V. When the lateral acceleration g is used instead of the vehicle speed ■, the lateral acceleration g is set to the predetermined value g instead of the determination regarding the vehicle speed ■ in step 103 in FIG. What is necessary is to make a judgment as to whether or not the above is true, that is, whether or not g≧g0, and in this case as well, the same effects as in the embodiment described above can be obtained.

(Effects of the Invention) Thus, as described above, when the detected value of the vehicle speed or lateral acceleration at the time of vehicle turning is less than a predetermined value, the understeer tendency is reduced by the reverse phase steering control of the rear wheels, so that the turning behavior control device of the present invention When the turning performance is exceeded, the turning performance can be improved by braking force control that differs the wheel braking forces on the inside and outside of the turning direction so that a yaw moment that promotes turning is generated, so these anti-phase steering control and braking force By applying control to each control target area, turning behavior can be appropriately controlled, and even when turning at high speed or with large lateral acceleration, reducing the lateral force on the rear wheels can prevent this, thus improving stability. It is possible to obtain the necessary turning performance while ensuring the following. Moreover, the frequency of braking to improve turning performance is not excessive, and performance deterioration due to brake fade is also prevented.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the turning behavior control device of the present invention, and Figure 2 (a
) and (b) are system diagrams of a braking control system and a four-wheel steering control system respectively 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 on the same side; Figure 4 is a diagram showing an example of the characteristics for setting the rear wheel target steering angle applied in the same program, and Figure 5 is a diagram showing an example of the characteristics for setting the front axle target hydraulic pressure on the inner side of the turning direction. It is a diagram. LL, IR...Front wheel 2L, 2R...
Rear wheel 3... Brake pedal 4... Tandem master cylinder 5L, 5R, 6L, 6R... Wheel cylinder 7
F...Front wheel brake system 7R...Rear wheel brake system 8F, 8R...Pressure response switching valve 9F, 9R...Pilot cylinder 10F, IO
R, IIF, IIR, 12F, 12R, 34L,
34R, 37° 38... Pipe line 13F, 13R, 14F, 14R... Hydraulic pressure control valve 15, 20F, 2OR, 35... Pump 16, 19
F, 19R, 36...Reservoir 17, 21F, 2
1R...Accumulator 1st...Solenoid switching valve
22... Controller 23... Steering angle sensor
24... Brake switch 25, 26.27.28
... Wheel speed sensor 29 ... Lateral acceleration sensor 31L, 31R, 32L, 32R, 33 ... Hydraulic pressure sensor 34 ... Rear wheel steering angle sensor 35 ... Vehicle speed sensor 36 ... Steering wheel 37 ... Axis 38.42 ... Gear box 39, 46 ... Rack shaft 40.47 ... Tie rod 4L 48 ... Knuckle arm 43 ... Motor 44 ... Worm gear 45 ... Worm wheel Figure 2 (Figure 4 Figure 5)

Claims (1)

[Claims] 1. In a vehicle equipped with rear wheel steering means for steering the rear wheels to a predetermined steering angle in response to the front wheel steering angle during front wheel steering, a steering state detection means for detecting a steering state; and a vehicle speed. Or, based on signals from a running state detecting means for detecting lateral acceleration applied to the vehicle, the steering state detecting means, and the running state detecting means, when the detected value of the running state detecting means is less than a predetermined value during a turn, the rear wheels The rear wheels are steered in opposite phases by the steering means, and when the detected value is equal to or greater than a predetermined value, the braking force of the wheels is varied between the inner and outer sides of the turning direction so as to generate a yaw moment that promotes turning in the vehicle according to the turning state. 1. A turning behavior control device for a vehicle, comprising: wheel control means.