JP3185216B2 - Vehicle behavior control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle behavior control device, and more particularly to a device for controlling vehicle behavior using braking.

(Prior art) As a device for controlling the braking force when braking a vehicle,
As described in JP-A-59-155264. In this vehicle, a braking force difference is generated by delaying the braking timing of the outer wheels in the turning direction at the time of braking, thereby improving the turning performance of the vehicle.

(Problems to be Solved by the Invention) In the braking force control device described in the above publication, the braking force control for controlling the vehicle behavior as described above is performed only in accordance with the steering angle. I have. In the case of control in which the hydraulic pressure of the outer wheels in the turning direction at the time of control is delayed depending on only the steering angle to generate a braking force difference, the vehicle behavior is influenced by a different friction coefficient μ of the road surface.
In particular, on low μ roads, the steering force is light and the vehicle is hard to turn from a straight running state, so the rudder tends to be turned more than necessary. If the control is performed only with the information, the information may be turned too much.

An object of the present invention is to provide a vehicle capable of responding to the height of a road surface μ, improving turning performance and preventing excessive turning, and performing appropriate behavior control while ensuring vehicle stability. It is to provide a behavior control device.

(Means for Solving the Problems) According to the present invention, the following behavior control device is provided for this purpose as shown in FIG.

That is, in a vehicle equipped with control force control means capable of independently controlling the braking force of the left and right wheels, a wheel load difference detection means for determining a wheel load difference between the left and right wheels, (FIG. 1 (a)) based on a configuration having wheel braking force setting means for making a difference in braking force with (a) in FIG.
An object of the present invention is to provide a vehicle behavior control device including the following contents. That is, in a vehicle provided with braking force control means capable of independently controlling the braking force of the left and right wheels, as a first means, a wheel load difference detecting means for obtaining a wheel load difference between the left and right wheels, and as a second means A steering angle detecting means for detecting a steering angle, and a braking force difference between the braking force of the turning direction outer wheel and the braking force difference of the wheel in the turning direction inner wheel is set to be lower than a braking force of the turning direction inner wheel in accordance with outputs from both means. Wheel braking force setting means for making a difference in braking force inside and outside the turning direction so as to be set to a larger value as the load difference and the steering angle become larger, and in the braking force difference setting, as the wheel load difference becomes smaller, A braking force difference smaller than a braking force difference of a magnitude that would be set if the braking force difference was set according to only the steering angle of the second means of the first and second means. To set the braking force difference In addition, this is a vehicle behavior control device including a wheel braking force setting means for setting a larger braking force difference as the wheel load difference increases (FIG. 1B).

(Operation) Each of the above means has a means, and the wheel braking force setting means turns the braking force of the turning direction outer wheel in accordance with the output from both the wheel load difference detecting means and the steering angle detecting means. The braking force is differentiated inside and outside the turning direction so that the braking force is lower than the braking force of the inner wheel in the direction, and the braking force difference is set to a larger value as the wheel load difference and the steering angle increase. In the power difference setting, as the wheel load difference becomes smaller, the braking force difference of a magnitude that would be set if the braking force difference setting according to only the steering angle of the wheel load difference and the steering angle was used. The braking force difference is set so as to generate the braking force difference, and the larger the wheel load difference is, the larger the braking force difference is set.

Thereby, the braking force difference is set according to the level of the road surface μ, and appropriate control corresponding to the road surface μ at that time is possible,
The turning performance is not excessive in the turning control based on the braking force difference even on a low μ road, stability is secured, and in setting the braking force difference corresponding to the road surface μ, the braking force difference setting also depends on the steering angle. The braking force difference is set to a larger value as the steering angle increases, and the braking force difference decreases as the wheel load difference decreases, and the braking force difference increases as the wheel load difference increases. , Enabling fine-grained control. Therefore, it is possible to perform appropriate control corresponding to the road μ without excess or shortage, and it is possible to prevent excessive turning on a low μ road, and to improve turning while securing stability. Thus, it is possible to provide a vehicle behavior control device for achieving the above object.

Here, in the present invention, as will be described later, the wheels capable of independently controlling the left and right braking forces by the braking force control means may be targeted only to the front wheel side or only the rear wheel side, Both rear wheels can be targeted.

The present invention also preferably adjusts the generated braking force difference based on both the wheel load difference (ΔW) and the steering angle (θ) when the vehicle turns, and the wheel load difference (ΔW) and A smaller braking force difference is applied to the first region where the steering angle (θ) is smaller, and a larger braking force difference is applied to the second region where both the wheel load difference (ΔW) and the steering angle (θ) are larger. As a region between the first region and the second region, a third region in which a braking force difference that is larger than the case of the first region and smaller than that of the second region is set, In the third region, when the steering angle (θ) is the same, if the wheel load difference (ΔW) is the same, the generated braking force difference is reduced if the wheel load difference (ΔW) is small. When the steering angle (θ) is large, the braking force is generated so as to increase the braking force difference to be generated. A configuration in which differences are attached, suitably be carried out (e.g., wheel load difference later Figure 10 Δ
In the same manner, it is possible to realize the above-described operations in the areas A, B, C, D, and E according to W and the steering angle θ, and the control patterns in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows the configuration of an embodiment of the behavior control device of the present invention.

In FIG. 2, 1L and 1R denote left and right front wheels, 2L and 2R denote left and right rear wheels, 3 denotes a brake pedal, and 4 denotes a tandem master cylinder. Each wheel 1L, 1R, 2L, 2R is wheel cylinder 5L, 5R, 6L, 6R
The wheel cylinder has a master cylinder 4
Each wheel shall be braked individually when supplied with hydraulic pressure from the vehicle.

Here, to explain the brake fluid pressure system, the front wheel brake system 7F from the master cylinder 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, the rear wheel brake system 7R from the master cylinder 4 passes through the pressure response switching valve 8R, the output chamber 9a of the pilot cylinder 9R, the lines 10R, 11R, 12R, and the left and right through the hydraulic pressure control valves 13R, 14R. Wheel wheel cylinder 6L, 6R.

In connection with the input chambers 9b of the pilot cylinders 9F and 9R, a hydraulic pressure source for automatic braking including a pump 15, a reservoir 16 and an accumulator 17 is provided, and an electromagnetic switching valve 18 is interposed between this and the pilot cylinder input chamber 9b. Insert. The valve 18 normally connects the pilot cylinder input chamber 9b to the reservoir 16 to bring the pilot cylinders 9F and 9R into the non-operating position shown in the drawing, and the ON-time pilot cylinder input chamber 9b
The piston 9c of each of the pilot cylinders 9F and 9R is stroked against the built-in spring 9d by the hydraulic pressure from now on through the accumulator 17 maintained at a constant pressure by appropriate driving of 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
Is opened as shown in the figure, and when the solenoid switching valve 18 is turned ON, the pilot cylinders 9F, 9R are switched by the pressure applied to the pilot cylinders 9F, 9R, and the system 7F, 7R is checked (liquid flow toward the master cylinder 4 is blocked). State.

Control of the electromagnetic switching valve 18, which is performed by the current i ₅ to the solenoid of the valve to be output as a control signal from a controller to be described later, when the current i ₅ is 0A (including time Fukibureki) switching valve 18 is OFF (i.e. normal), it is assumed that the ON when the current i ₅ is 2A. Further, at the time of the ON, the systems 7F and 7R are stopped as described above, and the liquid in the output chamber 9a of the pilot cylinders 9F and 9R is discharged. The hydraulic pressure is increased based on the automatic brake hydraulic pressure source regardless of the depression of the vehicle, and therefore the wheels 1L, 1R, 2L, 2R are controlled by their respective hydraulic pressure control valves 13F, 14F, 13R, 14R. The braking is automatically performed on the corresponding wheel corresponding to the target (automatic braking).

Hydraulic pressure control valves 13F, 14F, 13R, and 14R individually control the brake hydraulic pressures toward the wheel cylinders 5L, 5R, 6L, and 6R of the corresponding wheels, respectively, and provide the anti-skid and the behavior control of the present invention. In the OFF position, the brake fluid pressure is increased toward the original pressure at the OFF pressure increase pressure position shown in the figure. The first stage ON brake pressure is not increased or decreased, and the second stage ON brake fluid pressure is increased. It is assumed that a decompression position is reached in which some of the pressure is released to the reservoirs 19F and 19R and lowered.

The control of these hydraulic pressure control valves is also performed by a controller (described later) to the solenoid of the corresponding valve (control valve drive current).
made by i ₁ through i _4, the pressure increase position when the current i ₁ through i ₄ is 0A, the pressure-holding position when the current i ₁ through i ₄ is 2A, the current i ₁
Through i ₄ is at the time of 5A shall be the pressure reducing position.

The brakes in the reservoirs 19F and 19R are operated by the pumps 20F and 20R which are driven at the time of the pressure holding and the pressure reduction, respectively, by the lines 10F and 10R.
And accumulators 21F and 21R are connected to these conduits. 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 respectively turned on and off by a controller 22, and the controller 22 has a signal from a steering angle sensor 23 for detecting a steering angle θ, and a brake pedal. 3, a signal from the brake switch 24 that is turned on when the pedal is depressed, and a signal from the wheel speed sensors 25 to 28 that detect the rotational peripheral speeds V _{W1 to} V _W4 of the wheels 1L, 1R, 2L, and 2R.
A signal from a lateral acceleration sensor (lateral G sensor) 29 for detecting a lateral acceleration g of the vehicle body, a wheel load detecting means 30 for detecting a wheel load
And the like are input. The signal from the wheel speed sensor is used for anti-skid and traction control. For traction control, it is assumed that a control signal is sent from the controller 22 to the engine output regulator.

Here, FIG. 3 shows an example of the wheel load detecting means. In the illustrated example, the strain gauge type load sensor 302 is used as a wheel load sensor, and the wheel load (wheel load on the left front wheel side in the figure) is detected by disposing the strain gauge type sensor between the strut 320 and the vehicle body. And

In the drawing, reference numeral 330 denotes a spring, and in this embodiment, a wheel load sensor is attached to each wheel, and a sensor for the left front wheel is provided.
Similar to 301, the sensor for the right front wheel (302), a sensor for the left rear wheel (303), and the wheel load W ₁ of the respective wheels detected by the sensor (304) for the right rear wheel, W _2, W ₃ and it provides a signal indicative of W ₄ to the controller 22 of FIG. 2. These pieces of information are applied in a control program to be described later as control parameters in a case where control is performed so as to make a difference between left and right braking forces according to wheel loads.

Moreover, the wheel cylinders 5L of each wheel to the controller 22 as shown in FIG. 2, 5R, 6L, fluid pressure sensor 31R for detecting the fluid pressure P ₁ to P ₄ of the 6R, 31L, 32L, the signal from the 32R Is entered. The output of the hydraulic pressure sensor for each wheel is set so that the deviation between the target value and the actual wheel cylinder hydraulic pressure is set to zero (that is, the wheel cylinder hydraulic pressure is set to the target value). This value is used as a control signal when the brake fluid pressure is feedback-controlled (to match the value).

In the system of the above embodiment, during normal braking,
Braking is performed as follows.

When the brake pedal 3 is normally depressed, the controller 22 receives the signal from the brake switch 24 which closes in response to the brake, and keeps the electromagnetic switching valve 18 OFF (i ₅ = 0). As a result, the pilot cylinders 9F and 9R
b is connected to the reservoir 16 to maintain the illustrated position, the pressure response switching valves 8F, 8R also maintain the illustrated position, and the front and rear wheel brake systems 7F, 7R
Is open. Further, the controller 22 includes the wheels 1L, 1R, 2
Hydraulic pressure control valves 13F, 14F, 13
R and 14R are turned off (i _{1 to} i ₄ = 0) to keep the state shown in the figure.

Therefore, the same hydraulic pressure (master cylinder hydraulic pressure) simultaneously output to the front and rear wheel brake systems 7F and 7R from the master cylinder 4 when the brake pedal 3 is depressed is applied to the pressure response switching valves 8F and 8R and the pilot cylinders 9F and 9R, respectively. Output room 9a,
After passing through the pipelines 10F, 10R and the hydraulic pressure control valves 13F, 14F, 13R, 14R, the brake hydraulic pressure reaches the wheel cylinders 5L, 5R, 6L, 6R, and individually brakes the wheels 1L, 1R, 2L, 2R. .

During this time the controller 22, the wheels 1L detected by the sensor 25 to 28, 1R, 2L, obtains a pseudo vehicle speed by a known computation from the circumferential speed of rotation (wheel speed) V _W1 ~V _W4 of 2R, this and the individual wheel speed Then, the braking slip ratio of each wheel is calculated. Then, the controller 22 determines the braking lock of each wheel from this slip ratio, and when it is about to be locked, the hydraulic pressure control valve 13F,
By turning on the 14F, 13R or 14R by one step to set the pressure holding position, further increase in brake fluid pressure of the corresponding wheel is prevented. If the brake lock occurs despite this, the controller 22 lowers the brake hydraulic pressure of the corresponding wheel by preventing the brake lock by setting the hydraulic pressure control valve of the corresponding wheel to the two-stage ON position to set the pressure reduction position. As a result, when the corresponding wheel starts to rotate (spin-up), the controller 22 sets the hydraulic pressure control valve of the corresponding wheel to the pressure holding position and stops the brake fluid pressure from further decreasing. Then, as the rotation of the wheel is recovered, the controller 22 turns off the hydraulic pressure control valve of the corresponding wheel to set 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 at which the maximum braking efficiency is achieved, and normal anti-skid control is performed.

FIG. 4 is a control program showing an example (behavior control during foot braking) for the present behavior control including a braking force difference setting process according to the wheel load executed by the controller 22. This processing is performed by a periodic interrupt at a fixed time interval by an operating system (not shown).

First, in step 101, in this example program writes the wheel load W ₁ to _W-4 of the respective wheels each loaded based on the signals from the respective wheel load sensor. In the next step 102, the brake switch 24 is
It is determined whether or not the driver has depressed the brake pedal 3 based on whether or not N. As a result, if NO, that is, if the brake pedal 3 has not been depressed, in this example of the program, this behavior control is unnecessary,
Then, proceed to 6 to set ΔP as the brake fluid pressure difference command value described later.
Is set to the value 0. In this case, the program is terminated through steps 104 and 105.
i ₁ through i ₄ is remains 0A, the hydraulic pressure control valve maintains the OFF position of Figure 2 the normal.

On the other hand, if the answer to step 102 is Yes and it is determined that the brake pedal 3 is depressed, the process proceeds to step 103 and the subsequent steps to perform the behavior control targeted by the present invention. That is, a difference is generated between the left and right braking forces on the front wheel side and / or the rear wheel side according to the wheel load,
A process is executed for controlling the braking force of the wheel with a large wheel load to be lower than the braking force of the wheel with a small wheel load.

In step 103, a ΔP value is calculated as a brake fluid pressure difference command value for generating a braking force difference based on the wheel load W _j (j = 1 to 4) (ΔP = f (W _j )).

Specifically, the wheel load difference ΔW is calculated using the wheel loads W _{1 to} W ₄ detected in step 101 by the following equation: ΔW = | (W ₁ + W ₃ ) − (W ₂ + W ₄ ) | (1) And the ΔP value is determined accordingly.
FIG. 5 shows an example of a characteristic for calculating a hydraulic pressure difference ΔP to be set according to the wheel load difference ΔW.

As shown in the drawing, the hydraulic pressure difference ΔP is set so that ΔP = 0 when the wheel load difference ΔW is equal to or less than a predetermined value ΔW ₀ , and the wheel pressure difference is set when the wheel load difference ΔW exceeds the predetermined value ΔW ₀ and is smaller than the predetermined value ΔW _1. The wheel load difference ΔW is set such that the larger the ΔW is, the larger the value (in other words, the smaller the ΔW is, the smaller the value is) and within a range of a predetermined value ΔW ₁ or more, it is suppressed to a constant value. Correspondingly, the characteristics are set as shown in the figure.

Here, the difference between the left and right wheel loads appearing when turning the vehicle, as will be described later, is different in size according to the height of the road surface μ, for example, even when running through a corner with the same steering amount, The wheel load difference is small on a low μ road where the road surface μ is low, while the wheel load difference is large on a high μ road. Therefore, the above characteristics correspond to what the state of μ of the road surface is at the time of performing the vehicle behavior control for improving the turning performance using the braking force at the time of control by the braking force distribution control. And the function of automatically correcting the set brake fluid pressure difference ΔP, and therefore the generated braking force difference, and the brake fluid pressure difference (accordingly, the braking force difference) becomes smaller on a low μ road where the yaw moment described later may become excessively large. Will be done.

Thus, at step 103, the brake fluid pressure difference ΔP is calculated and determined from the above relationship.

Next, in steps 104 and 105, the hydraulic pressure difference Δ
Using P, brake fluid pressures _Pj (j = 1 to 4) are set such that the difference in brake fluid pressure between a wheel having a large wheel load and a wheel having a small wheel load becomes a value ΔP. Look up and output the hydraulic pressure control valve drive current i. In order to achieve the determined hydraulic pressure difference, for example, wheels 1R, 2R (when turning left) or 1L, 2L (when turning left) or wheels with large wheel loads (left turning) so that a hydraulic pressure difference ΔP is generated between the left and right wheels. Hydraulic pressure during turning)
Lower P ₂ , P ₄ (when turning left) or P ₁ , P ₃ (when turning right). In this case, in this embodiment, the hydraulic pressure sensors 31
L, 31R, 32L, since 32R is provided, it compares the magnitude of the wheel load W _j, if the determined result, for example, the right wheel side wheel load than the left wheel side is determined to be larger (left turn) if, obtains the set brake fluid pressure P ₄ for setting the brake fluid pressure P ₂ and / or the right rear wheel 2R of the right front wheel 1R as follows, it can be feedback controlled so as to coincide with the target value .

P ₂ = P ₁ −ΔP (2) P ₄ = P ₃ −ΔP (3) Here, the first term on the right side in each of the above equations is the left front wheel, respectively.
Actual hydraulic pressure of the wheel cylinders 5L and 6L due to the depression force of the brake pedal of 1L and the rear wheel 2L, that is, the brake hydraulic pressure detected by the hydraulic pressure sensors 31L and 32L (master cylinder hydraulic pressure)
It is. In the present example, the hydraulic pressure on the wheel side having a large wheel load is set to be lower by ΔP based on this. Thus, wheels 1L and 2L with small wheel loads
The driving force i ₁ , i ₃ of the hydraulic pressure control valves 13F, 13R is set to 0 A while the braking force of the brake pedal is caused by the brake pedal depressing force, while the wheel 1R having a large wheel load , 2R, so as to actuate the hydraulic pressure control valves 14F, 14R so as to limit (depressurize) the braking force, that is, so that the brake hydraulic pressure is in accordance with the equations (2) and (3). The pattern of the currents i ₂ and i ₄ (control pattern of the control valve) may be determined and output.

With the above control, the braking force of the wheel having a large wheel load (the braking force of the outer wheel in the turning direction) is made smaller than the value corresponding to the pedaling force of the brake pedal 3 based on the wheel load during braking by depressing the brake pedal 3. Therefore, the vehicle receives the yaw moment in the turning direction and is encouraged to turn.Moreover, in this case, as a result of making a difference by the wheel load, it can automatically respond to the height of the road μ, and when turning on a low μ road, Automatic hydraulic correction by the road surface is also performed so that the differential pressure becomes small, that is, the braking force difference becomes small and the yaw moment becomes small.

FIG. 6 is an example of a time chart for understanding the control contents when the braking force control is executed according to the control program of FIG. 4, and specifically, the steering wheel is turned to the left during braking. (in this example the right front wheel 1R in cases as allowed to generate the braking force difference in the front-wheel side) large right wheel of the wheel load in the case of cut indicating the change of the brake fluid pressure P ₂ other various quantities. 6A shows the steering angle θ, FIG. 6B shows the yaw rate, and FIG. 6C shows the wheel load difference Δ.
W, the (d) of FIG is each change of the right front wheel brake fluid pressure P _2.

Further, among the yaw rate characteristics shown in FIG. 3B, l (D) b is the characteristic in the case of the braking force control according to the present invention on a dry road having a high μ, and l (I) b is on ice having a low μ. The characteristic l (D) c of the wheel load difference ΔW shown in FIG. 10C shows the change in the difference between the left and right wheel loads occurring on a dry road, and l (D). I) c represents a change in wheel load difference occurring on an icy road, respectively. Furthermore, among those showing the change in the brake fluid pressure (wheel cylinder pressure) P ₂ of the right wheel, characteristic l (D) d is the fluid pressure change in the case of the control in the dry road, also characteristic l
(I) d shows the hydraulic pressure change in the case of the main control on the icy road, respectively.

In the figure, the brake pedal is depressed at time t _0, the driver is turned to the steering wheel to the left in the subsequent time t _1. During from time t ₀ to time t _1, the wheel load difference as shown in FIG. 5 (c) is not caused, thus the liquid pressure difference command value ΔP even during braking is the value 0. Therefore, as shown in FIG. 2 (d), the brake fluid pressure of each wheel, including the brake fluid pressure P ₂ of the right front wheel are both equal to the master cylinder pressure P _M, the braking with no attached a difference in right and left braking force Has been done.

Thus, when the left steering is started at time t _1, along with this, cause wheel load difference, wheels on the left and right relates wheel load becomes small wheel of larger wheels and wheel load of the wheel load, thus Δ
The W value changes according to the change as shown in FIG. 3C, and its size varies depending on the road surface μ.
In contrast to (D) c, the difference between the left and right wheel loads is small on a low μ road on an icy road as indicated by a characteristic l (I) c. This control focuses on such a change in wheel load.

In the case of a dry road that is a high μ road, the wheel load difference is a characteristic l
(D) left and right wheels load as represented by c is changed, as a result, the brake fluid pressure P ₂ of the right front wheel 1R are large wheels wheel load, as shown in FIG. 2 (d), the wheel load small pressure reduction control for the braking force difference allowed is (time t ₂ decreases relative to the brake fluid pressure of the left front wheel is a wheel (P ₁ = P _M) is started, so if [Delta] W value exceeds the [Delta] W ₁ of, vacuum is suppressed to a predetermined amount (time t ₄ after)), thereby a difference is given to the braking force, whereas, when was the ice passage of low μ road, the wheel load difference characteristic l (I) c As shown in the above, the left and right wheel loads change, and as a result, the braking force is different so that the braking force of the wheel 1R having a large wheel load is lower than the braking force of the wheel having a small wheel load. the case, the degree of the difference after the pressure reduction control is started in this case (time t ₃₎ is smaller than that of the state in the case of high μ road It is made of.

The braking force control according to the level of the road surface μ as described above is performed, and in this control, the hydraulic pressure changes in this way depending on the road surface. That is, characteristics l (D) d, as shown in l (I) d, in accordance with the state of the road surface mu at that time, mu is the brake fluid pressure P ₂ is higher is lowered significantly, down small when low mu is Can be As a result, as shown in FIG. 3B, the yaw rate has characteristics l (D) d and l (I) b on a dry road and on an icy road, respectively. In FIG. (B), as a comparative example, the case of normal braking (without the control by the braking force difference, as indicated by a one-dot chain line in FIG. 2 (d), when the hydraulic pressure of each wheel is P _M ) Shows the characteristics (a) and (b) on dry roads and icy roads,
In contrast to these (a) and (b), this control can improve the turning performance, and further, as a comparative example, the characteristics (c)
However, even on an icy road, the yaw rate does not have such a characteristic (c) (when the wheel load is not considered).

Generally, at a certain vehicle speed V ₀ , the front wheel slip angle β _f (or the steering angle (steering angle) θ) of the steering wheel.
And the lateral force Y (or lateral acceleration) generated by the tire differs depending on the state of the road surface μ. FIG. 7 shows the steering angle θ on the horizontal axis.
, The relationship between the lateral force Y and θ is shown, and the relationship between the high μ road (dry road) and the low μ road (on ice) is as shown in the figure.

Above, to generate a predetermined lateral force Y _0, the high μ road, while the theta steering angle is theta _D, the low μ road theta
_I (θ _I > θ _D ). That is, low μ
In the case of the road, there is so hard the driver does not bend easily to have turned the steering wheel, and therefore, in order to generate a lateral force Y ₀ necessary to run through a certain corner in the car speed V _0, low Larger steering angle θ for μ road
_I is required. Therefore, in the case where the yaw moment is generated by the braking force difference to improve the turning performance,
In the characteristic shown in FIG. 8 which depends only on the steering angle θ, the low μ
On the road, the braking force difference (ΔB) becomes too large, and the generated yaw rate is too large, which leads to a loss of stability.

However, according to the method of making a difference between the left and right braking forces according to the wheel load, the characteristics l (D) d, l in FIG.
(I) As shown in d, the hydraulic pressure changes depending on the road surface (in the case of the conventional control, the hydraulic pressure does not change depending on the road surface), and the braking force difference is made appropriate according to the road surface μ at that time. Therefore, it is possible to automatically respond to the height of the road surface μ, to improve the turning performance, and to prevent excessive turning. Since there is a relationship of Y∽ΔW between the ΔW value and the Y value focused on in this control, the necessary lateral force Y
ΔW is suitable for checking (adjusting). Rather than the method of uniformly determining the difference only with θ, the fifth embodiment
The control using only the wheel load as the control parameter as shown in the figure is effective, exhibits a high effect, and can realize behavior control excellent in responsiveness.

Thus, in the case of this control, it is possible to avoid an excessive yaw moment on a low μ road, such as when the braking force difference is determined only by the steering angle, and the braking force difference is determined according to the magnitude of the wheel load. As a result, the braking force of the wheel with a large load (the outer wheel in the turning direction) can be generated by making the braking force smaller than the braking force of the wheel with a smaller wheel load (the inner wheel). It is possible to prevent the vehicle from becoming unstable due to excessive turning while improving. As a result, the poor turning performance and the poor rudder effect, which generally occur during braking, do not cause the short turning performance (the vehicle may not be able to expand its running trajectory outward in the turning direction while the steering wheel is turned off). Tendency to be eliminated) and low μ
A situation in which the driver turns more than the driver's steering amount on a road or the like can be avoided, and control without excess or deficiency is realized.

In the above description, the brake fluid pressure difference ΔP is obtained by the wheel load difference ΔW, but in addition to this, the fluid pressure difference may be changed according to the vehicle speed.

By obtaining the vehicle speed by vehicle speed detecting means such as estimating the vehicle speed from the rotation speed of the driven wheels, and by determining the brake fluid pressure difference ΔP based on the vehicle speed at that time, finer control is possible. .

FIG. 9 shows another example of the program for behavior control of the present invention.

This program uses the wheel load and the information indicating the turning state, so that both can adjust the generated braking force difference,
This shows an example in which finer control is possible. Specifically, the braking force of the outer wheel in the turning direction is controlled to a value lower than the braking force of the inner wheel in the turning direction according to the output from the wheel load detecting means 30 and the turning state detecting means, for example, the steering angle sensor 23. I will do it.

Note that both this program and the program shown in FIG. 12 to be described later are executed by a periodic interruption at regular time intervals.

In FIG. 9, the reading of the steering angle θ is added in step 101, and the brake fluid pressure difference between the inner and outer wheels in the turning direction according to the wheel load difference ΔW and the steering angle θ is replaced with the processing in step 103 in FIG. The ΔP setting process (step 103a) is executed. The processing in step 103a includes an area search based on an area diagram (map) set in advance corresponding to the wheel load difference ΔW value and the steering angle θ value.
When the area is determined, a control pattern of the hydraulic pressure control valve driving current for the outside wheel in the turning direction set in advance for each corresponding area is determined, and the braking force is controlled.

FIG. 10 is an example of the above-mentioned region diagram. As shown in FIG. 10, the wheel load difference ΔW is divided into three parts, and the steering angle θ is also divided into three parts. In the area search, the current wheel load difference ΔW and the steering angle θ among the A, B, C, D, and E areas as shown in the figure defined by the combination of the divided wheel load difference area and the steering angle area. Is determined by determining which region corresponds to. Here, each area setting is ΔW and θ
Is set to be the area A when both are small, and to be the area E when both ΔW and θ are large.

Thus, in this way according to the search area, the braking force control about pivot outward wheel for obtaining the yaw moment, i.e. for the wheel hydraulic pressure control valve drive current i ₂ and / or i ₄ (left turn Hour) or i ₁ and / or i ₃ (right turn)
Is set using the table data shown in FIG. The table data indicates how many milliseconds the drive current is
The pattern (depressurization) is to repeat the cycle of setting the pressure control valve on the outer wheel to the pressure holding position with 2A (one stage ON) for 5 seconds (2 stages ON) and setting the control valve to the decompression position for several milliseconds. Control pattern), and the time of the pressure reduction position (t _ON2 )
As the ratio is higher than the time (t _ON1 ) ratio of the _pressure- holding position, the braking force of the outer wheel is greatly reduced, that is, a large braking force difference is applied to generate a large turning direction yaw moment. Specifically, here, the area A
_Are set to t _ON1A = 0 msec and t _ON2A = 0 m sec (accordingly, the non-control region where the pressure increasing position is maintained), and the other regions B to
For E, t _ON1B = 80> t _ON1C = 60> t _ON1D = 40> t
_ON1E = 20 (both _msec ), and _tON2B = 20 < _tON2C = 4
0 <t _ON2D = 60 <t _ON2E = 80 (m sec).

Accordingly, assuming the same condition (left turn during braking) as in the case of FIG. 6, it is determined that the region is a region C because θ is a medium region and ΔW is a medium region. In this case, the hydraulic pressure control valve drive current i ₂ for the front wheel outside the turning direction is selected as a control pattern that repeats a cycle of 2 A for 60 msec at a cycle of 100 msec and 5 A for 40 msec. Is determined not to be in the C region but in the B region (when θ is a medium region but ΔW is a small region), the driving current i ₂ becomes 80 m
A control pattern of 2 A during sec and 5 A during 20 m sec will be selected.In this case, too, the turning force will not be excessive due to a small braking force difference when turning on a low μ road. Automatic hydraulic correction by road surface is performed.

As described above, even in this control, the braking force difference can be made appropriate according to the road surface μ at that time, and in addition, the braking force difference can be set also by the steering angle θ. , And can be controlled more finely.

Although the steering angle θ is used for detecting the turning state in the above example, a lateral acceleration, a yaw rate, or the like may be used for detecting the turning state instead of the steering angle. Also, as in the previous example,
Further, the hydraulic pressure difference may be changed according to the vehicle speed.

FIG. 12 is a control program showing still another example of the present invention. In the control program, each of the programs is controlled only when the brake pedal is depressed, but the turning behavior control during non-foot braking is also performed. It is like that.

The processing in steps 101 to 105b is performed in steps 101 to 10 in FIG.
Although it is similar to the case of 5, if it is determined in step 102 that the brake pedal 3 has not been depressed, it is determined in step 106a whether or not it is the automatic brake pedal ON timing. This can be determined, for example, by checking whether or not the vehicle is in a predetermined turning state.

If the answer in step 106a is Yes, the then switched set in order to perform the braking by the automatic brake pressure source in step 106b i ₅ = 2A states, the switching valve 18 to the current to the ON, the following In step 106c, a hydraulic pressure difference ΔP calculation process is executed based on FIG. 5, similarly to step 103. Thus, in step 106d, the brake fluid pressure P _WL of the wheel with a small wheel load (the inner wheel in the turning direction) (P ₁ and / or P ₃ in the case of a left turn,
If during a right turn sets the P ₂ and / or P ₄₎ in the ΔP value, this for the brake fluid pressure P _WH large wheels wheel load (outer wheel) is set to 0, step 105a ,
Execute 105b to end this program. In this case, (when turning right) control valve drive current i ₁ and / or i ₃ (during a left turn) or i ₂ and / or i ₄ corresponds to a small wheel of wheel load, the corresponding wheel wheel When the cylinder fluid pressure rises toward the original pressure by the automatic braking system, the ΔP
The pattern (ON-OFF pattern of the control valve) is set to operate the corresponding control valve so as to obtain a value. On the other hand, for a wheel having a large wheel load, the drive current of the hydraulic control valve for the wheel is set to 2A. The pressure is switched to the pressure holding position so as to be held. In this way, by setting and outputting the respective currents i _{1 to} i ₄ and i ₅ to control the electromagnetic switching valve 18 and the hydraulic pressure control valves 13F, 14F, 13R and 14R, the automatic brake system operates and the turning The brake fluid pressure of the inner wheel in the direction is controlled to the ΔP value, while the brake fluid pressure of the outer wheel is prevented from increasing, and a braking force difference is automatically generated between the two to generate a yaw moment. And the braking force difference can be made appropriate according to the road surface μ at that time.

If the answer to step 106a is NO, step 10
At 6e, ΔP is set to a value of 0, and the automatic brake system is also kept inactive.

As described above, during non-braking (when non-foot braking)
This control also applies automatic braking during turning,
In such a case, control may be performed to increase the brake fluid pressure of the inner wheels so that a braking force difference is generated according to the size of the road surface μ.

This embodiment is also applicable to the system shown in FIG.

In the present invention, the control may be performed for both the front wheels and the rear wheels, or the braking force difference may be generated only for the front wheels or only for the rear wheels. The hydraulic pressure difference ΔP may be a function of time. For example, once determined, the hydraulic pressure difference ΔP may be gradually reduced as time elapses and ΔP = 0 after a predetermined time. Further, the detected value was used using a hydraulic pressure sensor to control the brake hydraulic pressure of the wheels in order to have a braking force difference, but the hydraulic pressure value is previously made to correspond to the ON-OFF operation of the hydraulic pressure control valve. If this is done, a hydraulic pressure sensor is not required, and if a proportional valve is used instead of an ON-OFF type control valve, the hydraulic pressure is determined by the current command. Yes, such a configuration may be used.

(Effect of the Invention) Thus, the behavior control apparatus of the present invention is as described above.
Since it is configured as described, it is possible to control properly without excess or deficiency corresponding to the road surface μ, and it is possible to prevent excessive turning on low μ roads and improve turning while securing stability. Therefore, it is possible to cope with the height of the road surface μ, improve turning performance, prevent excessive turning, and perform appropriate behavior control while ensuring vehicle stability. A vehicle behavior control device can be provided. In the case of claim 2, as a configuration as described in the claim,
Can be controlled more finely,
The above can be realized.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the behavior control device of the present invention, FIG. 2 is a system diagram showing one embodiment of the behavior control device of the present invention, FIG. 3 is a diagram showing an example of means for detecting wheel load, FIG. FIG. 5 is a flowchart showing an example of a control program of the controller in the same example. FIG. 5 is a view showing an example of a characteristic for setting a brake fluid pressure difference ΔP ₁ according to a wheel load difference applied in the program. Fig. 7 is a time chart for explaining an example of the control content in the case of the same program. Fig. 7 is a diagram showing an example of the relationship between the steering angle and the lateral force. Fig. 8 is a diagram showing the braking force difference depending only on the steering angle. FIG. 9 is a diagram showing characteristics when setting, FIG. 9 is a flowchart showing another example of a control program of the controller, FIG. 10 is a diagram showing an example of a region diagram applied by the program, and FIG. Hydraulic control valve drive for outer wheel in each turning direction FIG. 12 is a flow chart showing still 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 …… Pipe line 13F, 13R, 14F, 14R …… Hydraulic pressure control valve 15,20F, 20R… … Pumps 16,19F, 19R… Reservoirs 17,21F, 21R …… Accumulators 18 …… Solenoid switching valves, 22 …… Controllers 23 …… Steering angle sensors, 24 …… Brake switches 25,26,27,28 …… Wheel speed sensor 29: lateral acceleration sensor, 30: wheel load detecting means 31L, 31R, 32L, 32R: hydraulic pressure sensor 301-304: strain gauge type load sensor

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinji Matsumoto 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Inside Nissan Motor Co., Ltd. (72) Hideto Murakami 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Shunichi Inoue Nissan Motor Co., Ltd., 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-49-103325 (JP, A) JP-A-1-180661 (JP, A) JP-A-2-70561 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60T 8/24 B60T 8/58

Claims (2)

(57) [Claims] 1. A vehicle provided with braking force control means capable of independently controlling the braking force of the left and right wheels, wherein a first means includes a wheel load difference detecting means for obtaining a wheel load difference between the left and right wheels; Means for detecting a steering angle, and a braking force applied to the outer wheels in the turning direction to a value lower than a braking force applied to the inner wheels in the turning direction in accordance with outputs from the two means. The difference is wheel braking force setting means for making a difference in the braking force inside and outside the turning direction so that the wheel load difference and the steering angle are set to larger values as the steering angle becomes larger. The smaller, the first and second
The braking force difference is set so as to generate a braking force difference smaller than the braking force difference of a magnitude that would be set if the braking force difference was set only in accordance with the steering angle by the second means. And a wheel braking force setting means for setting a larger braking force difference as the wheel load difference increases. 2. The method according to claim 1, wherein when the vehicle is turning, the generated braking force difference is adjusted based on both the wheel load difference and the steering angle. A power difference is provided, and a larger braking force difference is provided in a second region where both the wheel load difference and the steering angle are larger. The first region is defined as a region between the first region and the second region. A third region where a braking force difference larger than the case of the second region and smaller than the case of the second region is set, and the third region is set.
When the steering angle is the same, the braking force difference generated when the wheel load difference is small is reduced when the steering angle is the same, and when the steering angle is large, the braking force difference is generated when the wheel load difference is the same. The behavior control device for a vehicle according to claim 1, wherein a braking force difference is provided so as to increase the braking force.