JPH0687419A - Braking hydraulic pressure control device - Google Patents

Abstract

PURPOSE:To prevent lowering braking force, by prohibiting yaw-rate F/B hydraulic control at the time of control on a split road, in a vehicle loading a yaw-rate F/B hydraulic control device through generating a braking force difference between the right and the left. CONSTITUTION:Whether a travel load is a split road or not is judged by a controller, this is made by judging a road as a split road if a DELTAVW value has a certain fixed value alpha or more by using e.g. a wheel speed difference DELTAVW between the right and the left (S101-103). When a road is not a split road, yaw- rate F/B hydraulic control (S104) is applied if a road is pertinent to the above condition, and a braking force difference is applied by reducing one side wheel pressure according to yaw-rate deviation to control vehicle behavior. When a road is judged as a split road, this control is not applied, and if an ABS vehicle, slip-ratio control is performed (S105). In the case of the ABS vehicle, a braking force lowering condition in both wheels, due to pressure-reducing in ABS in low mu road side wheels at the time of braking on the split-road, and due to that in high mu road side wheels because of yaw-rate deviation occurrence caused by vehicle deflection following the former pressure-reducing can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking hydraulic pressure control device, and more particularly to a braking hydraulic pressure control device capable of controlling a vehicle behavior by generating a braking force difference between right and left wheels of a vehicle.

[0002]

2. Description of the Related Art As a device for controlling the braking force of a vehicle, there is a control device for controlling the vehicle behavior by making a difference between the braking forces of the left and right wheels of the vehicle, which includes yaw rate feedback (F / B). ) There is a system that employs a brake fluid pressure control. With this type of system, control (active brake control) that positively utilizes the braking force difference (brake hydraulic pressure difference) during turning braking is possible, and it is possible to eliminate the deviation between the actual yaw rate of the vehicle and the target yaw rate. It is possible to control by making a difference in the brake hydraulic pressure (Japanese Patent Laid-Open No. 3-112756).

[0003]

A control device capable of controlling the yaw rate feedback hydraulic pressure as described above feeds back the deviation between the target yaw rate and the actual yaw rate to control the brake hydraulic pressure difference between the left and right wheels. Disturbances can be prevented, which can contribute to improving the maneuverability during braking. For example, if the wheels to be controlled that generate the braking force difference are on the left and right of the front wheel, when the yaw rate deviation occurs, the actual yaw rate falls below or exceeds the target value, and the actual yaw rate corresponds to the target value. The device executes the pressure reduction of the brake hydraulic pressure on one of the left and right front wheels, which corresponds to the corresponding wheel.

Although such an effect can be exhibited during turning braking, there are cases where this device acts to cause a reduction in braking force depending on the state of the traveling road during braking. For example, when the road surface condition of the road when the brake pedal is depressed is a road where the friction between the left and right wheels of the vehicle and the road surface is different (so-called split μ road), or when the vehicle is braking Focusing on the braking state when entering the road, the wheels on the low μ road side become locked, and when the vehicle is deflected at that time and the yaw rate feedback hydraulic control described above operates, the brake fluid pressure on one side is reduced. Occurs, and as a result, the braking force may decrease (decrease in deceleration).

Particularly, in a vehicle equipped with an anti-skid system (ABS), this tendency is large when the above-mentioned split road surface is suddenly braked. That is, first, the slip ratio control works on the wheel on the low μ road side, and the ABS reduces the brake fluid pressure of the wheel on the low μ road side in order to avoid the lock of the wheel. Along with that, the vehicle is swung to the high μ road side.
As a result, a yaw rate deviation occurs here, which is why
On the yaw rate feedback hydraulic pressure control side, the brake hydraulic pressure of the wheels on the high μ road side is reduced so as to suppress such disturbance of the behavior of the vehicle by providing a left-right braking force difference. That is,
In this case, the brake fluid pressure is released due to the ABS operation of the low-μ road side wheel and the brake fluid pressure is released from the high μ road-side wheel as described above. Therefore, the brake fluid pressures of the left and right wheels are both reduced, and only that. The braking force is reduced, and the degree of deceleration is greatly reduced.

On the basis of the above consideration, the present invention allows the yaw rate feedback braking hydraulic pressure control, which can control the vehicle behavior by producing a difference between the left and right braking forces, while exhibiting the original function. The purpose is to reduce the above-mentioned decrease in braking force as much as possible.

[0007]

According to the present invention, the following braking hydraulic pressure control device is provided. In a vehicle in which the left and right braking forces of the front wheels and / or the rear wheels can be independently controlled, a turning state detecting means for detecting a turning state of the vehicle and a running road in which the left and right wheels have different friction states between the front wheels or the rear wheels and the road surface. The yaw rate feedback control method that causes a difference in the braking force on the left and right of the wheel to be controlled according to the output from the running state determination means and the turning state detection means so that the vehicle behavior becomes the target characteristic. Braking force control means capable of controlling the braking fluid pressure by means of a yaw rate feedback hydraulic pressure control stopping means for controlling the yaw rate feedback braking fluid pressure control to be prohibited in accordance with the output of the traveling road determination means. It is a braking fluid pressure control device provided with a control means.

[0008]

In the above braking hydraulic pressure control device, the braking force control means causes a difference between the left and right braking forces of the wheels to be controlled in accordance with the output from the turning state detection means for detecting the turning state of the vehicle, and the vehicle behavior. The braking hydraulic pressure is controlled by the yaw rate feedback control method so that the target characteristics are achieved, but the road condition determining means determines that the left and right wheels have different friction states between the front wheels or the rear wheels and the road surface. At this time, the yaw rate feedback hydraulic pressure control stopping means prohibits the yaw rate feedback braking hydraulic pressure control in accordance with the output of the traveling road determination means.

Therefore, in a state where the yaw rate feedback braking hydraulic pressure control is not prohibited, the vehicle behavior can be controlled by making a difference between the left and right braking forces, the maneuverability at the time of turning braking can be improved, and the so-called split road can be improved. Even when a yaw rate occurs during braking, the yaw rate feedback braking hydraulic pressure control is not performed. Therefore, even when a braking force difference is generated by decompressing the left and right wheels on one side, the decrease in the braking force due to that is reliably prevented.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows the configuration of an embodiment of the braking hydraulic pressure control device of the present invention. The vehicle to be applied is capable of independently controlling the left and right braking forces (braking hydraulic pressure) of the front wheels and / or the rear wheels. In the figure, 1L and 1R are front left and right wheels, 2L and 2R are left and right rear wheels, 3 is a brake pedal, and 4 is a tandem master cylinder (M / C). 3a is a booster as a brake booster, and 4a is a reservoir.
Each wheel 1L, 1R, 2L, 2R is equipped with a wheel cylinder 5L, 5R, 6L, 6R that frictionally holds a brake disc by hydraulic pressure to apply a braking force to each wheel, and these wheel cylinders (W / C) When the hydraulic pressure is supplied from the master cylinder 4, each wheel is braked individually. Here, in order to explain the brake fluid pressure (braking fluid pressure) system of the braking device, in the present embodiment, the front wheel brake system 7F from the master cylinder 4 is provided with the conduits 8F, 9F, 10.
F, hydraulic pressure control valves 11F, 12F to the left and right front wheel cylinders 5L, 5R 7, and the rear wheel brake system 7R from the master cylinder 4 includes pipe lines 8R, 9R, 10R,
The left and right rear wheel wheel cylinders 6L, 6R are brought through the hydraulic pressure control valves 11R, 12R.

Hydraulic pressure control valves 11F, 12F, 11R, 12
R is the wheel cylinders 5L and 5L of the corresponding wheels.
By controlling the brake fluid pressure to R, 6L, 6R individually,
It is used for anti-skid and main braking hydraulic pressure control, and is a holding pressure that increases the brake hydraulic pressure toward the original pressure at the boosted position shown in the OFF state and does not increase or decrease the brake hydraulic pressure when the first stage is ON. When the second stage is turned on, the brake fluid pressure is partially released to the reservoirs 13F and 13R (reservoir tanks) to reduce the brake fluid pressure. The control of these hydraulic pressure control valves is performed by currents (control valve drive currents) I _{1 to} I ₄ from the controller (control unit) described later to the solenoids of the corresponding valves, and currents I _{1 to} I _{4 are controlled.}
Is 0 A, the pressure increasing position is set, when the currents I _{1 to} I ₄ are 2 A, the pressure maintaining position is set, and when the currents I _{1 to} I ₄ are 5 A, the pressure increasing position is set. In addition, the reservoirs 13F, 13
The brake fluid in R is returned to the pipelines 8F and 8R by the pumps 14F and 14R that are driven for pressure retention and pressure reduction, and returned to the accumulators 15F and 15R of these pipelines for reuse.

Hydraulic pressure control valves 11F, 12F, 11R, 12
R is turned on and off by a controller 16 corresponding to a braking force control means. This controller 16 has a signal from a steering angle sensor 17 for detecting a steering angle of a steering wheel (handle), and is turned on when the brake pedal 3 is stepped on. Signal from the brake switch 18 to turn the wheel 1
L, 1R, 2L, 2R rotation peripheral speed (wheel speed) V _{w1 to} V _w4
The signals from the wheel speed sensors 19 to 22 for detecting, and the signal from the yaw rate sensor 23 for detecting the yaw rate (d / dt) φ generated in the vehicle are input. In addition, the controller 16 includes wheel cylinders 5L, 5R, 6 for each wheel.
Hydraulic pressure sensor 31 for detecting the hydraulic pressures P _{1 to} P ₄ of L and 6R
Signals from L, 31R, 32L, and 32R are input, and a hydraulic pressure sensor 33 ₁ , which detects the hydraulic pressure P _M of the master cylinder 4 (front wheel hydraulic pressure P _M1 , rear wheel hydraulic pressure P _M2 ),
The signal from 33 ₂ is input. Regarding the master cylinder hydraulic pressure detection, for example, only the front wheel system may be detected and represented. The output of the hydraulic pressure sensor sets the target value of the wheel cylinder hydraulic pressure so that the actual wheel cylinder hydraulic pressure matches the target value (the difference between the set target value and the actual wheel cylinder hydraulic pressure value is It is used as a control signal when the brake fluid pressure is controlled by operating the fluid pressure control valve (so that it becomes zero or near zero). The signal from the steering angle sensor 17 is used by itself as a parameter indicating the vehicle turning state or as a part thereof. Further, the signal from the yaw rate sensor is used as a control parameter in the hydraulic pressure difference control by the yaw rate feedback method. Further, the signal from the wheel speed sensor can be used as information for estimating the vehicle speed when the vehicle speed is used as a control parameter, and is also used for the anti-skid control performed by the controller 16 in this embodiment, and It is also used to determine whether or not a traveling road surface (split road surface) where the frictional states between the left and right wheels of the vehicle and the road surface are different. In this embodiment, the turning state of the vehicle is detected based on the steering angle, the vehicle speed, and the yaw rate. Therefore, the turning state detecting means is the steering angle sensor 1
7, the yaw rate sensor 23, and a part of the controller 16 (vehicle speed estimation calculation processing part described later) correspond to this. Further, the traveling road determination means for determining the split road surface corresponds to the wheel speed sensors 19 to 22 and a part of the controller 16 (a left and right wheel speed difference ΔV _w calculation described later, and a comparison processing portion between the same and a predetermined value). .

In the anti-skid control using the 4-channel, 4-sensor system as in this example, the wheel speed detection value for each wheel, the vehicle body speed detection value, and the slip amount detection value are obtained, and the slip of the corresponding wheel is obtained. Braking force control can be performed so that the amount falls within a predetermined range, whereby wheels are individually anti-skid controlled to achieve maximum braking efficiency for each wheel, and wheel locking is avoided.

The controller 16 includes an input detection circuit, an arithmetic processing circuit, and a storage circuit for storing various control programs executed by the arithmetic processing circuit and arithmetic results.
And an output circuit for supplying a control signal to the hydraulic pressure control valve. In the arithmetic processing circuit, when performing control by causing a difference between the left and right braking forces of the vehicle during braking, that is, when controlling the braking force to control the behavior of the vehicle, the yaw rate feedback method described later is used. A target yaw rate, vehicle speed, target wheel cylinder hydraulic pressure (target brake hydraulic pressure), etc. are calculated according to a program for controlling the braking hydraulic pressure to obtain a target value as a braking hydraulic pressure (braking force) control value for each wheel. Then, the corresponding signal is output to the hydraulic pressure control valve.
Regarding the control based on the braking force difference, the controller 16 also executes a process of prohibiting the braking hydraulic pressure control by the yaw rate feedback when it determines that the traveling road is a split road surface. Therefore, in this embodiment, the yaw rate feedback hydraulic pressure control stop means corresponds to a part of the controller 16.

FIG. 3 is an example of a braking force control program including the yaw rate feedback braking hydraulic pressure control prohibiting process executed by the controller 16. In the figure, step S101 is a calculation process for obtaining the difference ΔV _w between the wheel speeds of the left and right wheels, step S102 is a process for setting a split road judgment value (discrimination value) α that serves as a reference for comparison of the ΔV _w values, and step S103 is a process for checking whether or not the left / right wheel speed difference ΔV _w is larger than the split road judgment value α, and in this program example, it is judged whether or not the road is a left / right split road.

Specifically, it can be performed as follows.
Wear. Figure 4 shows the difference between left and right road friction.
Chiskid control (ABS control) Left and right wheel speed at the time of entry
Of the change of t₀Is the ABS control start time, V ₀
Is a rapid deceleration start speed immediately before starting the ABS control.
Start time t₀From time t after Δt₁At that time,
If there is a difference in road surface friction (μ) between the left and right wheels,
Wheel speed V on the wheel side_WFL1And the wheel speed V on the right wheel side_WFR1Of both
Difference ΔV_W(V_WFR1-V_WFL1) Occurs.

Thus, the difference between the left and right wheel speeds means that there is a difference in the road surface friction between the left and right wheels, and the degree of the difference in the road surface friction is reflected in the difference ΔV _W. It is possible to determine whether the road is a left-right split road by looking at the wheel speed difference ΔV _W and determining whether it exceeds a predetermined value set in advance. In the present embodiment, the determination is performed by the method as described above, and the wheel speed difference ΔV _W is obtained as ΔV _W = | V _WFR1 −V _WFL1 |, and the α value is used as the split road determination value. Used, ΔV
_{When W} > α holds, it is regarded as a left and right split road. Therefore, during braking, based on the output values from the wheel speed sensors for the left and right wheels (for example, the left and right front wheels here), the difference ΔV in the wheel speeds between them is detected in order to detect the difference in road surface friction between the left and right wheels.
_W is calculated and compared with a split road judgment value α which is a judgment value. As a result, the ΔV _W value is a value α.
If it is larger than the above, it is determined that the frictional state between the left and right wheels with respect to the road surface is a traveling road (split road) different from each other with a difference equal to or greater than the value α, and in steps S101 to S103, The split road discrimination using the left and right wheel speed difference is executed.

The judgment value α may be a fixed value, but may be a variable judgment value which is changed according to a turning condition such as a vehicle speed or a steering condition, and other parameters applicable to road surface μ detection. In step S102, the split road judgment value α is calculated according to the turning state and the like, and is applied to step S103. On the other hand, if a fixed value is adopted, the above-described calculation of the α value is unnecessary, and in that case, step S101 is followed by step 10
The preset fixed value α in 3 may be applied to the comparison judgment.

If it is determined that the road is not a split road as a result of the determination in step S103, the process proceeds to step S104, and the yaw rate feedback hydraulic pressure control permits this. FIG. 5 shows an example of such a yaw rate F / B hydraulic pressure control routine for vehicle behavior control based on the braking hydraulic pressure difference. In the figure, first, in step S110, a steering angle sensor,
Based on the outputs of the wheel speed sensor, the yaw rate sensor, the wheel cylinder, and the master cylinder hydraulic pressure sensor, the steering angle δ and the wheel speed V _{w1 of} each wheel 1L, 1R, 2L, 2R.
V _w4 , yaw rate (d / dt) φ, master cylinder hydraulic pressure P _M
And the wheel cylinder hydraulic pressures P _{1 to} P ₄ of the respective wheels are read. In the following step S111, the speed of the vehicle body is estimated. In this embodiment, wheel speeds of all wheels (wheel rotation speed)
Is used to calculate the vehicle speed (pseudo vehicle speed) by a method that is usually used in anti-skid control.
And

Next, because of the yaw rate feedback type braking force control (active braking) at the time of braking, the target yaw rate (d / dt) φ _ref is calculated in step S112 from the vehicle speed V and the steering angle δ. . In this embodiment, the target yaw rate is calculated according to the following equation.

## EQU1 ## (d / dt) φ _ref = δ × V / A (1 + KV ² ) --- 1 where A is a constant determined by the vehicle wheel base and steering gear ratio, and K is the vehicle's It is a constant representing the steer characteristic. In the next step S113, the yaw rate difference value Δ (d / dt) φ which is the difference between the target yaw rate (d / dt) φ _ref obtained in step S112 and the actual yaw rate (d / dt) φ (actual yaw rate). Is

## EQU00002 ## Δ (d / dt) φ = (d / dt) φ _ref − (d / dt) φ ---- 2 is calculated, and in the subsequent step S114, the Δ (d / dt) φ is calculated.
Based on, the target differential pressure ΔP (S) to be generated in the wheel cylinders on the left and right of the controlled wheel is calculated according to the following equation.

## EQU00003 ## .DELTA.P (S) = H.times..DELTA. (D / dt) .phi .--- 3 where H is a constant determined by vehicle specifications. 1 above
The ΔP (S) value obtained by the equations (3) can be determined and calculated in accordance with the turning direction, the state at the time of turning, etc., including its size and polarity. In the case of the above three equations, a so-called proportional control method is used as a feedback control method for the yaw rate difference value Δ (d / dt) φ, but the feedback control method is not limited to this, and either a differential operation or an integral operation is performed. A control method in which one or both are added may be used. In this way, the actual yaw rate response and stability of the vehicle with respect to the target yaw rate can be improved.

Therefore, in the following step S115, the target wheel cylinder hydraulic pressure P _j (S) (j) of each wheel is used by using the target differential pressure ΔP (S) and the master cylinder hydraulic pressure P _M.
= 1 to 4) is performed as follows, for example. That is, for example, when ΔP (S)> 0 so that a differential pressure is generated on the front wheel side,

[Equation 4] P ₁ (S) = P _M −ΔP (S) ---- 4a P ₂ (S) = P _M ---- 4b P ₃ (S) = P _M ---- 4c P ₄ (S) = P _M ---- 4d When ΔP (S) <0

[Formula 5] P ₁ (S) = P _M ---- 5a P ₂ (S) = P _M + ΔP (S) ---- 5b P ₃ (S) = P _M ---- 5c P ₄ ( S) = P _M ---- 5d and the target wheel cylinder hydraulic pressure P _j (S) (j = 1 to 1
4) is calculated. As described above, in step S115, with respect to the target wheel cylinder hydraulic pressure P _j (S) of each wheel, in the present embodiment, the target value is set so that one of the corresponding wheel pressures is reduced as described above. The Rukoto(
That is, in order to generate the required hydraulic pressure difference ΔP (S) between the left and right, one-side pressure reduction control is performed).

After the target wheel cylinder hydraulic pressure P _j (S) value is obtained in step S115, next, step S1
16, in S117, the target wheel cylinder hydraulic pressure value P
_Since it may occur that _j (S) becomes a negative value, in that case, the processing for setting the target wheel cylinder hydraulic pressure P _j (S) to the value 0 is executed. Then, as described above, after the target wheel cylinder hydraulic pressure of each wheel is determined, step S12
At 0, the brake fluid pressure control is executed so that the wheel cylinder fluid pressures (brake fluid pressures) of the respective wheels actually become the target fluid pressures, and this routine ends.

FIG. 6 shows an example of such a brake fluid pressure control routine. The subroutine determines the pressure increase, pressure retention, and pressure reduction of each wheel cylinder hydraulic pressure, and according to the determination, the drive currents I ₁ , I ₂ , I ₃ , I required for the hydraulic pressure control valves 11F, 12F, 11R, 12R. _It consists of the process of outputting ₄ . That is, in the figure, in step S121, the target wheel cylinder hydraulic pressure P _j (S) and the actual wheel cylinder hydraulic pressure P
_j (j = 1 to 4) (P ₁ to read in step S110)
P ₄ value) and the absolute value of the difference | P _j (S) −P _j |
Is below a predetermined value Δβ set in advance. As a result of the determination, when the absolute value is equal to or less than the value Δβ (when the answer is Yes), it means that the actual wheel cylinder hydraulic pressure P _j is almost controlled to the target wheel cylinder hydraulic pressure P _j (S). If so, at that time, the process proceeds to the pressure maintaining process of step S122, and the hydraulic pressure control valve is controlled to maintain the hydraulic pressure state. On the other hand, as a result of the above determination, the absolute value is the value Δβ.
If it is larger (the answer is No), further step S1
At 23, the target wheel cylinder hydraulic pressure P _j (S) is compared with the actual wheel cylinder hydraulic pressure P _j , and if the target wheel cylinder hydraulic pressure P _j (S) is larger, step S1.
24, the hydraulic pressure control valve is controlled so as to increase the wheel cylinder hydraulic pressure. On the contrary, if the actual wheel cylinder hydraulic pressure P _j is higher, step S12
5, the hydraulic pressure control valve is controlled so as to reduce the wheel cylinder hydraulic pressure. In this way, the holding pressure, increasing pressure, and reducing pressure of the wheel cylinder hydraulic pressure are determined, and the current value to be output to the hydraulic pressure control valve is set according to the determination,
It is output by this routine.

Returning to FIG. 3, after step S104, the routine proceeds to a slip ratio control routine for anti-skid control (step S105), and this program ends. The content of the slip ratio control routine may be that performed by normal anti-skid control. On the other hand, in contrast to the above, when ΔV _W > α is satisfied as a result of the determination in step S103 and the traveling road is determined to be a split road, the processing in step S104 is skipped, and the yaw rate feedback hydraulic pressure control is interrupted (prohibited). To be done. Therefore, in this case, the yaw rate feedback hydraulic pressure control is not performed even if the yaw rate occurs, and the slip ratio control is executed in step S105.

In this way, when braking on the left and right split roads, the braking hydraulic pressure control (active braking) by the yaw rate feedback is stopped.
Even in vehicles equipped with ABS, brake fluid pressure on high μ road wheels due to yaw rate generation due to vehicle deflection as described above after brake fluid pressure loss (reduction) due to anti-skid operation of low μ road wheels Can be prevented from falling out,
Therefore, the situation in which both the brake fluid pressures of the left and right wheels are released does not occur, and it is possible to prevent both wheels from being in a braking force reduction state.

FIG. 7 shows another example for determining the split road. In the above embodiment, the judgment is made based on the left and right wheel speed difference as described with reference to FIG. 4, but in the present embodiment, the judgment is made based on the recovery time difference between the left and right wheel speeds during the ABS pressure reducing control. ABS
In the skid cycle, the brake fluid pressure is reduced when the wheels are about to lock, and the brake fluid pressure is controlled to increase when the wheel rotation speed (wheel speed V _W ) is restored, and this is repeated. The recovery time of the wheel speed in this case reflects the condition of the road surface μ. Therefore, when the road surface μ of the left and right wheels are different, the transition as shown in FIG. 7 is made, which is used in this embodiment.

In the figure, V _I is an estimated vehicle speed, λ ₁ is a predetermined reference value (wheel speed comparison value) represented by, for example, λ ₁ = V _I × k (k is a λ ₁ coefficient, k <1) And the λ
_The left and right wheel speed recovery times T ₁ and T ₂ are as shown in the figure based on the ₁ value. The right and left wheel speed recovery time T
₁ , the absolute value of the difference between T ₂ and their recovery time difference Δt = | T
_1- T ₂ |, and a determination value α _t for split road determination is set for the recovery time difference, and Δt
When the value is larger than the α _t value, that is, Δt> α _t
If the condition is satisfied, it is determined that the road is a left / right split road. The split road determination may be performed by such a method. Also in this case, the α _t value may be a fixed value, or may be variable according to the vehicle speed, the steering state, and the turning state, as in the above embodiment.

The present invention is not limited to the above embodiments and modifications. For example, the split road determination as the traveling road determination is made based on whether the frictional state between the front left and right wheels and the road surface is different, but the left and right rear wheels may be determined. In addition to the above-described split road determination, the accumulation of the difference between the wheel rotational speeds of the left and right wheels becomes a certain value or more (also in this case, a variable determination value may be used), or the left and right wheels during braking. The determination may be made based on the difference in deceleration of the rotation speed.

Further, the present control can be applied regardless of the presence or absence of the anti-skid control, that is, whether or not the vehicle has the ABS. That is, when it is determined that the vehicle is on the split road, the hydraulic pressure control by the yaw rate feedback can be stopped and the normal brake can be restored. Even in this case, if the yaw rate feedback hydraulic pressure control is performed on the split road, it will not occur. It is possible to prevent a reduction in braking force. Furthermore, like that
Even in the case of a system that does not have the BS control itself, for example, the determination method as shown in FIG. 4 can be used for the split road determination if the wheel speeds on the left and right front wheels are detected.

[0030]

According to the present invention, the yaw rate feedback braking hydraulic pressure control for the vehicle behavior control by the left and right braking force difference is performed depending on whether the road is a road having different frictional states between the left and right wheels. It is possible to control non-operation and operation, and therefore, when turning braking on a road where the yaw rate feedback braking hydraulic pressure control is not prohibited, the original function can be fully exerted to improve maneuverability, and so-called split When braking on the road, it is possible to prevent the loss of braking fluid pressure that would occur if the yaw rate feedback braking fluid pressure control were not prohibited, and it is possible to avoid that the braking force is reduced by that amount. The braking force can be secured.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a braking hydraulic pressure control device of the present invention.

FIG. 2 is a system diagram showing an embodiment of a braking hydraulic pressure control device of the present invention.

FIG. 3 is a flowchart showing an example of a control program of a controller in the same example.

FIG. 4 is a diagram illustrating an example of a split road determination method.

5 is a program flow chart showing an example of a yaw rate feedback hydraulic pressure control routine of FIG.

FIG. 6 is a program flow chart showing an example of a subroutine of brake fluid pressure control applied in FIG.

FIG. 7 is a diagram showing another example of split road determination.

[Explanation of symbols]

 1L, 1R Left and right front wheels 2L, 2R Left and right rear wheels 3 Brake pedal 4 Master cylinder 5L, 5R, 6L, 6R Wheel cylinder 11F, 12F, 11R, 12R Hydraulic control valve 16 Controller 17 Steering angle sensor 19-22 Wheel speed sensor 23 Yaw rate sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinji Matsumoto 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. In a vehicle capable of independently controlling left and right braking forces of front wheels and / or rear wheels, a turning state detecting means for detecting a turning state of the vehicle, and a friction state between a front wheel or a rear wheel and a road surface are left and right. The vehicle behavior becomes a target characteristic by causing a difference between the left and right braking forces of the wheels to be controlled according to the output from the traveling road determination means that determines that the traveling roads are different from each other and the turning state detection means. Braking force control means capable of controlling the braking fluid pressure by the yaw rate feedback control method, and controlling the yaw rate feedback fluid pressure control to prohibit the yaw rate feedback braking fluid pressure control in accordance with the output of the traveling road determination means. And a braking force control means including a braking fluid pressure control device.