JP2884865B2 - Braking force control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force control device,
In particular, the present invention relates to a braking force control device that can control a braking force so as to generate a predetermined braking force difference between left and right 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 braking force of the left and right wheels of the vehicle so as to make a difference. Such a braking force control system can perform control using a difference in braking force, for example, to improve stability during turning braking (Japanese Patent Laid-Open No. 2-70561). An example is a yaw rate feedback type braking force control in which the left and right brake fluid pressures are controlled so as to eliminate a deviation between the actual yaw rate of the vehicle and the target yaw rate.

[0003]

However, in a braking force control system that generates a braking force difference (for example, the above-described yaw rate feedback braking force control), when a braking force difference is provided, a specific hydraulic fluid is applied to a wheel to be controlled. How to adjust and set the pressure directly affects the deceleration point and other aspects of controllability because it is during braking, and therefore more comprehensive and detailed If effective braking force difference control can be realized, the effectiveness of such control can be further enhanced. The present invention is based on the findings of the present inventor based on these viewpoints.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control system in which the difference between the left and right braking forces is controlled while suppressing the reduction of the deceleration as much as possible and improving the controllability. It is to provide an improved control force control device which can be improved.

[0005]

According to the present invention, the following control force control device is provided. Means for detecting a running state of the vehicle including at least a steering state of the vehicle; means for detecting or estimating a motion state quantity related to a plane motion of the vehicle including at least yaw motion; and control using outputs from these means. A difference is generated between the left and right braking forces of the target wheel, and a means for controlling the braking force so that the vehicle behavior becomes the target characteristic. The pressure increase and the pressure reduction of the pressure increase target side are performed in such a way that the difference between the pressure increase target and the pressure decrease target side is made different from each other, and the pressure increase reduction amount on the pressure reduction target side is increased. A brake fluid that has a function of performing a correction that adjusts the reduction of the hydraulic pressure on the target side so that it is different from the same amount instead of the same amount according to the target left-right difference or a control amount representing the same, to set the wheel brake hydraulic pressure, Braking including pressure setting means Those formed by and control means.

[0006]

The braking force control device controls the vehicle behavior by causing the braking force control means to generate a difference between the left and right braking forces of the wheel to be controlled based on the output of the traveling state detecting means and the vehicle momentum information means. In such control, the brake fluid pressure setting means for obtaining a target left-right difference value for the left and right braking force and setting the wheel brake fluid pressure is configured to set one of the left and right wheel brake fluid pressures as a pressure-increase target and the other as a pressure-decrease target to determine a difference. At the same time as increasing the pressure reduction on the pressure reduction target side, the amount of the pressure reduction on the pressure reduction target side and the reduction of the liquid pressure on the pressure reduction target side are not the same amount. The correction can be made according to the target left-right difference or the control amount representing the difference so as to make the difference.

Thus, in the pressure increasing / decreasing control, the same amount of the one-side pressure increasing and the one-side decreasing pressure is not uniformly used, but the target left-right difference or the magnitude of the control amount representing the same is used. It is possible to make adjustments to set the pressure reduction side slightly larger when the size is large while taking advantage of it, and to avoid decreasing the deceleration during braking as much as possible, and at the same time, for example, increase the inner wheel pressure in the turning direction. Therefore, the controllability can be improved as compared with the case where the outer wheel is depressurized, and the braking force difference control that balances these two can be performed.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows the configuration of an embodiment of the braking force control device of the present invention. The vehicle to be applied can independently control the left and right braking forces of the front wheels and / or the rear wheels. In this embodiment, the left and right braking forces (braking fluid pressure) of both the front and rear wheels can be controlled. I do. Further, the control method is a yaw rate feedback (F / B) method.

In the drawings, 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 (M / C). In addition, 3a is a booster as a booster of a brake, and 4a is a reservoir. Each of the wheels 1L, 1R, 2L, 2R is provided with wheel cylinders 5L, 5R, 6L, 6R for applying a braking force to each wheel by frictionally holding a brake disk by supplying hydraulic pressure. When supplied with hydraulic pressure, each wheel shall be braked individually.

Here, the brake fluid pressure (braking fluid pressure) system of the braking device will be described. In this embodiment, the front wheel brake system 7F from the master cylinder 4 is connected to the system 7FL, which extends to the left and right front wheel cylinders 5L, 5R. 7FR, and the rear wheel brake system 7R from the master cylinder 4 is provided with cut valves 8F, 9F, 8R, 9R which normally open these systems to the systems 7RL, 7RR extending to the left and right rear wheel cylinders 6L, 6R, respectively. Insert Further, in connection with this, the accumulator 10a
And a control valve 11F, 12F, 11R, 12R as an electromagnetic proportional valve, and cylinders 13F, 14F, 13R, 14R.

The hydraulic pressure generating source here is the accumulator 1
0a, pump 10b, reservoir 10c, drive motor 10
The accumulator 10a, which includes a pressure switch d and a pressure switch 10e and can also function as a hydraulic pressure source for an automatic brake, is provided with a pump 10b which supplies the brake hydraulic pressure of a reservoir 10c to the hydraulic pressure source. Build up pressure. The drive motor 10d of the pump 10b is connected to a power supply via a pressure switch 10e. The pressure switch 10e opens when the internal pressure of the accumulator 10a reaches a specified value, and the motor 10d (the pump 10
b) shall be turned OFF. Thus, the specified pressure is always stored in the accumulator 10a.

The internal pressure of the accumulator 10a is
The cut valves 8F, 9F, 8R, and 9R are applied by a to cut off the corresponding systems 7FL to 7RR in response to the internal pressure of the accumulator 10a. The output chambers of the cylinders 13F, 14F, 13R, and 14R are connected to these systems, and the hydraulic pressure control valve 11 is connected to the input chambers of the cylinders.
Output ports of F, 12F, 11R and 12R are connected.

The hydraulic pressure control valves 11F, 12F, 11R, 12
R is a wheel cylinder 5L, 5 of the corresponding wheel, respectively.
By individually controlling the brake fluid pressure toward R, 6L, 6R,
The control of these hydraulic pressure control valves is performed by currents (control valve drive currents) I _{1 to} I ₄ from a controller (control unit) described later to the solenoids of the corresponding valves. performed, the output in accordance with the current I ₁ ~I ₄ port - the bets accumulator - motor pressure line 15a,
The hydraulic pressure which is communicated with the corresponding solenoid drive current through the drain line 15b is applied to the cylinders 13F, 14F, 13R, 1
4R.

Accumulator 10a at the hydraulic pressure source
If pressure is stored in the cut valve 8 in response to this,
F, 9F, 8R, 9R block the corresponding system 7FL-7RR
Therefore, the hydraulic pressure control valves 11F, 12F, 11F
R and 12R are drive currents I₁~ I _FourSupplied to these
When supplying proportional pressure to the corresponding cylinder, these
The cylinders are the corresponding wheel cylinders 5L, 5R, 6
L, 6R can be supplied with brake fluid pressure.
For example, the pressure in the pipeline 15a is lost due to the failure of the hydraulic pressure source.
Even then, the cut valve opens the system 7FL to 7RR at that time.
Through the brake pedal
-Master cylinder output from cylinder to system 7F, 7R
When the hydraulic pressure of the
Can be braked).

The hydraulic pressure control valves 11F, 12F, 11R, 12
R is controlled by a controller 16. The controller 16 includes a signal from a steering angle sensor 17 for detecting a steering angle of a steering wheel (handle), a signal from a brake switch 18 that is turned on when the brake pedal 3 is depressed, the wheels 1L, 1R, 2L, 2R rotation peripheral speed (wheel speed)
Signals from the wheel speed sensors 19 to 22 for detecting V _{w1 to} V _w4 , signals from a yaw rate sensor 23 for detecting a yaw rate (d / dt) φ generated in the vehicle, and the like are respectively input. The signal from the wheel speed sensor is also used for anti-skid control and traction control, if applicable.

[0016] Also, the wheel cylinders 5L of each wheel to the controller 16, 5R, 6L, fluid pressure sensor 31L for detecting the fluid pressure P ₁ to P ₄ of the 6R, 31R, 32L, with the signal from the 32R is input , signals from the hydraulic sensors 33 _1, 33 ₂ which detects the fluid pressure P _M in the master cylinder 4 (the front wheel system pressure P _M1, the rear wheels based fluid pressure P _M2) is inputted. As for the detection of the master cylinder pressure, for example, the detection may be performed by only the front wheel system and represented. The output of the hydraulic pressure sensor is controlled when the brake fluid pressure is controlled by setting the target value of the wheel cylinder fluid pressure and operating the fluid pressure control valve so that the actual wheel cylinder fluid pressure matches the target value. Used as a signal.

The signal from the steering angle sensor itself is used as a parameter indicating the vehicle running state or as a part thereof. Further, a signal from the yaw rate sensor is used as a control parameter in hydraulic control by a yaw rate feedback method. Further, the signal from the wheel speed sensor can be used as information for estimating the vehicle body speed when the vehicle speed is used as a control parameter.

The controller 16 includes an input detection circuit, an operation processing circuit, a storage circuit for storing various control programs executed by the operation processing circuit, operation results, and the like.
An output circuit that supplies a control signal to the hydraulic pressure control valve. In the arithmetic processing circuit, at the time of braking, when performing control by causing a difference between the left and right braking forces of the vehicle, that is, when controlling the braking force to control the turning characteristics of the vehicle, basically, Based on the predetermined input information, a deviation between a target value and an actual value for a target yaw rate, a vehicle speed, and a yaw rate, and a target wheel cylinder hydraulic pressure (a target brake hydraulic pressure) in accordance with a program for controlling a braking force by a yaw rate feedback method described later. And the like to obtain a target value as a braking force (braking force) control value for each wheel, and output a signal corresponding to the target value to the hydraulic pressure control valve.

In the present embodiment, the hydraulic pressure control valve and the controller include a hydraulic pressure control valve and a controller so that the braking hydraulic pressures on the front and / or rear wheels can be independently controlled to target values on the left and right sides of the front wheel and / or the rear wheel. Means is provided for causing a difference between the left and right brake fluid pressures of the wheels and controlling the brake fluid pressure so that the behavior of the vehicle becomes a target characteristic.

The controller 16 further controls the above-mentioned control based on the braking force difference. In generating the difference, the controller 16 increases one of the left and right braking forces and decreases the other to obtain the braking force. Wheel cylinders for the inner and outer wheels in the turning direction so that the target differential pressure can be generated by slightly increasing the pressure reduction amount on the pressure reduction side according to the magnitude of the difference between the calculated target yaw rate and the detected actual yaw rate with the aim of improving controllability. A process for correcting the hydraulic pressure value is also executed. FIG. 3 is a block diagram showing an outline of functions in the system of the embodiment shown in FIG. 2 for such control.

The control device includes a steering state detecting means 40a for detecting a steering state of the vehicle, a vehicle speed detecting means 40b for detecting a vehicle speed, and an actual yaw rate of the vehicle (generated yaw rate).
, A target yaw rate calculating means 40d for calculating a target yaw rate of the vehicle based on the detected values of the steering state detecting means 40a and the vehicle speed detecting means 40b, and a difference value between the target yaw rate and the actual yaw rate is calculated. Means 40e for calculating a yaw rate difference value, a brake force calculating means 40f for calculating a brake force control value for each wheel for correcting the yaw rate difference value in the zero direction, and a brake force operating means for operating the brake force for each wheel In addition to the braking force control value 40g, a braking force control value correcting means 40h for correcting the braking force control value according to the yaw rate difference value is included.

The braking force control value correcting means 40i is provided with a braking force calculating means 40i according to the magnitude of the yaw rate difference value.
The calculated value of f can be corrected, and the braking force operating means 40g operates the braking force based on the output signal of the braking force control value correcting means 40i.

The target yaw rate calculating means 40d, the yaw rate difference value calculating means 40e, and the braking force calculating means 40
f, the braking force control value correcting means 40i is constituted by the controller 16 of FIG. 2, and the braking force operating means 40g is constituted by including the hydraulic pressure control valves 11F, 12F, 11R, 12R. Further, the steering state detecting means, the vehicle speed detecting means, and the yaw rate detecting means are configured to include corresponding sensors and a part of the controller.

FIG. 4 shows an example of a control program executed by the controller 16 for controlling the vehicle behavior based on the brake fluid pressure difference. This processing is performed by a periodic interrupt at a fixed time interval by an operating system (not shown).

In the figure, first, in step S110,
Based on the outputs of the steering angle sensor, the wheel speed sensor, the yaw rate sensor, the wheel cylinder and the master cylinder hydraulic pressure sensor, the steering angle δ, the wheel speeds V _{w1 to} V _{w4 of} the wheels 1L, 1R, 2L, 2R, and the yaw rate (d / dt) φ, the master cylinder pressure P _M and the wheel cylinder liquid pressure P ₁ to P ₄ respectively read.

In the following step S111, the speed of the vehicle body is estimated. In this embodiment, the vehicle speed (pseudo-vehicle speed) is calculated using the wheel speeds (wheel rotation speeds) of all the wheels by a method normally performed in anti-skid control, and this is set as a vehicle speed value V. Next, in order to control the yaw rate feedback braking force at the time of braking, the target yaw rate (d / dt) φ _{ref is} calculated from the vehicle speed V and the steering angle δ in step S112.
Is calculated. In the present embodiment, the target yaw rate is calculated according to the following equation.

[0027]

(D / dt) φ _ref = δ × V / A (1 + KV ² ) (1) where A is a constant determined by the wheelbase and the steering gear ratio of the vehicle, and K is the vehicle Is a constant representing the steer characteristic of. In the next step S113, a yaw rate difference value Δ (d / dt) φ which is a 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

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

ΔP (S) = H × Δ (d / dt) φ (3) where H is a constant determined by vehicle specifications.

ΔP (S) obtained by the above equations (1) to (3)
The value, including its magnitude and polarity, can be determined and calculated according to the turning direction, the state at the time of turning, and the like. In addition,
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. However, the present invention is not limited to this, and one of a differential operation and an integral operation or It is good also as a control method which added both. In this manner, the responsiveness and stability of the actual yaw rate of the vehicle with respect to the target yaw rate can be improved.
Then, in the subsequent step S115, the target differential pressure Δ
It calculates the P (S) and the master cylinder pressure P _M from the target wheel cylinder pressure _{P j (S) (j =} 1~4).

In the present embodiment, the difference in the brake fluid pressure between the left and right wheels for controlling the vehicle behavior to the target characteristics is given on the front wheel side, and the target value is calculated according to the following equation.

P ₁ (S) = P _M −ΔP (S) / 2 (4)

P ₂ (S) = P _M + ΔP (S) / 2 (5)

P ₃ (S) = P _M ---- (6)

P ₄ (S) = P _M ---- (7)

Therefore, in this example, when the required hydraulic pressure difference ΔP (S) is generated between the left and right front wheels as in the above formulas (4) and (5), the difference is basically reduced to 1/2 by each of the left and right wheels. It is possible to generate a differential pressure by increasing and decreasing the wheel cylinder hydraulic pressure at each rate (FIGS. 5 and 6).
reference). In step S115, the target wheel cylinder fluid pressure P _j (S) value of each wheel is calculated in this manner. For the left and right front wheels, one of them is reduced on the basis of _PM and, if applicable, one is on the pressure reducing side and the other is on the other side. Is set as the pressure increasing side, and the target value is set.

Next, in step S116, the yaw rate difference value Δ (d / dt) φ is used in the present example program as the target left / right difference or a corresponding amount representing the target left / right difference (the value Δ (d / dt)
φ, between the calculated target differential pressure ΔP (S) values, ΔP (S)
= H × Δ (d / dt) φ, the ΔP
The (S) value may be used), whereby the calculated target wheel cylinder hydraulic pressure P _j (S) is corrected. Here, the processing in this step is not the same amount of one-side pressure increase and one-side pressure decrease even in the pressure increase / decrease control, but the yaw rate difference value Δ (d / dt) φ
Of the yaw rate difference value Δ
When (d / dt) φ is large, the pressure reduction side should be adjusted slightly larger to set the target wheel cylinder fluid pressure. The target wheel cylinder hydraulic pressure value of the front wheel is corrected so that the hydraulic pressure for increasing or decreasing the pressure is deviated.

In the present embodiment, more specifically, although the correction is made according to the yaw rate difference value Δ (d / dt) φ, the target differential pressure Δ
P (S) also secures this, and when the yaw rate difference value Δ (d / dt) φ is large according to the magnitude of the yaw rate difference value Δ (d / dt) φ, On the pressure increase side, the pressure increase is limited to a certain set value, and the pressure decrease side is increased to generate the target differential pressure. Therefore, the pressure increase side limit value determined by the following equation is obtained. _The target pressure difference ΔP (S) is generated by increasing the pressure to _L, and reducing the pressure on the decompression side to a large extent (FIG. 6).

[0033]

ΔP _L = k × Δ (d / dt) φ (8) (k is a proportional constant) Therefore, in this case, the amount of pressure reduction on the pressure reduction side is ΔP (S) −Δ
P _L. Here, k is a proportional constant, but this may be a function of, for example, vehicle speed, steering, and yaw rate. When this is the degree of biased from the increase and decrease of the target wheel cylinder pressure P _M (reference pressure) changes the pressure reduction amount of the size of the left vacuum side to maintain the target pressure difference [Delta] P (S) by these As described above,
It can contribute to improvement of late controllability. Thus, the corrected target wheel cylinder hydraulic pressure is set as follows in view of the above equations 4 to 7.

[0034]

P ₁ (S) = P _M − (ΔP (S) −ΔP _L ) --- (9)

P ₂ (S) = P _M + ΔP _L ---- (10)

P ₃ (S) = P _M ---- (11)

P ₄ (S) = P _M ---- (12)

The target wheel cylinder hydraulic pressure P based on the yaw rate difference value Δ (d / dt) φ in step S116
After executing the correction processing of the _j (S) value, next, in step S11
7. At S118, the corrected target wheel cylinder hydraulic pressure value P _j (S) may become a negative value. In this case, the target wheel cylinder hydraulic pressure P _j (S) is set to 0. Execute the process.

After the target wheel cylinder hydraulic pressures of the respective wheels are determined as described above, in step S120, the brakes are set so that the wheel cylinder hydraulic pressures (brake hydraulic pressures) of the respective wheels actually become the target hydraulic pressures. Execute the hydraulic pressure control and end the program. The brake fluid pressure control routine is performed in accordance with the target wheel cylinder fluid pressure P _j (S)
The drive currents I ₁ , I ₂ , I ₃ , I ₄ are looked up from preset table data (relational characteristics between the solenoid proportional valve drive current and the target wheel cylinder fluid pressure) so that These are connected to the hydraulic pressure control valves 11F, 12F, 11R, 12
R, whereby each wheel is braked with the corresponding target wheel cylinder hydraulic pressure P _j (S) (the sensor detection hydraulic pressure P _j is more accurate in this case). Can be used for braking).

In the control of this embodiment, the correction of the target value at the time of increasing and decreasing the pressure is performed in this way. FIG. 5 and FIG. 6 show the control without correction (that is, the control when the P _j (S) value is uniformly set as the target value in the state where the above equations 4 to 7 are kept) and the step S116. 6 is a time chart for comparing and comparing with the control of the present embodiment when the correction of FIG.
Here, FIG. 6 showing the case where the correction process is performed is shown in the case where the target wheel cylinder pressure of the pressure increasing / decreasing side wheel is corrected in accordance with the yaw rate difference value Δ (d / dt) φ (the case according to the equations 9 to 12). Control) is shown.

When comparing with and without correction, FIGS.
Therefore, in the present embodiment, the target cylinder pressure difference ΔP (S) is not only increased or decreased by ± 1/2 (ΔP (S)) wheel cylinder pressure, but also increased by the yaw rate difference value Δ (d / dt) φ. The wheel cylinder pressure on the pressure side is regulated (the pressure increase amount is ΔP
(S) / 2 is limited to ΔP ₁ ), and it can be seen that the wheel cylinder pressure on the pressure reduction side is corrected accordingly. Therefore, by this, the possibility of locking on the pressure increasing side can be reduced, the yaw rate controllability is improved, and in that case, the decrease in deceleration can be avoided as much as possible, and the necessary target differential pressure ΔP (S) can be reduced. It can also be generated with no added or missing.

The present control skillfully balances both the improvement of the yaw rate controllability and the prevention of the reduction of the deceleration. This point will be further described with reference to FIGS.
This can be explained as follows. First, this control is based on a combination of a one-pressure increase and a one-pressure reduction in the braking force difference braking, which is performed from the following viewpoint.

That is, referring to FIGS. 8 and 9, for example, in the yaw rate feedback braking force control as described above,
Simply determining the differential pressure ΔP (target differential pressure) to be generated on the left and right wheels according to the difference value between the target yaw rate and the actual yaw rate, and generating the braking force difference by one-side pressure reduction control as shown in FIG. The deceleration decreases. In this case, in order to obtain the required determined differential pressure ΔP, this is performed by reducing the wheel cylinder pressure of only one side wheel ΔP (the other wheel is the same as the master cylinder pressure). With control, the deceleration decreases. Therefore, ΔP during the control period
Accordingly, the braking force decreases accordingly, and the braking distance also increases. On the other hand, FIG.
The use of the pressure increase / decrease control as described in (1) is advantageous in preventing the decrease in the deceleration as described above. That is, in this case, the determined differential pressure ΔP is obtained by simultaneously controlling the wheel cylinder pressures of the left and right wheels and increasing the other and decreasing the other, so that the determined differential pressure ΔP is exactly the same. Reduce the wheel cylinder pressure on the pressure reduction side to 1/2
The pressure is reduced by P, and at the same time, the other wheel cylinder pressure is reduced by 1 /
By increasing the pressure by 2.multidot..DELTA.P, the change in deceleration can be offset as a whole and the required differential pressure .DELTA.P can be generated during the control period regardless of the magnitude of .DELTA.P. First, we focus on this.

However, such an advantage is merely a factor of 1/2
In the case of control by each method, when considering the controllability aspect, there are points that can be devised, for example, the same amount of turning inner wheel increase and turning outer wheel reduction control by yaw rate feedback control Instead, the present inventors have found that a slightly larger pressure reduction side provides better results for the yaw rate controllability. The second of the basics of this control lies in this idea.

This is based on the following. The one shown in FIG. 7 is provided to explain the consideration of the effect of the braking force of each wheel on the operability of the vehicle in the braking force control. FIG.
The upper part of the figure shows the state of tire generation force during decompression and the state of yawing moment generation by decompression, focusing on the outer wheel before turning, including the friction circle of the tire for each wheel, and the lower part, The frictional circle of the tire assuming that the product μW of the road surface μ and the wheel load W is assumed to be constant, and the components of the braking force and the lateral force are under the condition that the radius of the circle is determined by μW as shown in the figure.
For example, if the braking force decreases, the lateral force increases accordingly. Now, regarding the influence (yawing moment) on the vehicle behavior when the braking force of each wheel is controlled, using the above-described concept of the friction circle of the tire, the contents up to the wheel lock area are as follows. Become like

(A) Depressing the inner wheel before turning → Lateral force: increasing → small moment change Braking force: decreasing Similarly to increasing pressure, the moment change is also small (b) Depressing the outer wheel before turning → lateral force: increasing → turning Moment generation Braking force: Decrease Pressure increase, conversely, turning moment suppression

Therefore, as mentioned above, when controlling the yawing moment of the vehicle, it can be seen that "increase / decrease of the front outer wheel" is effective in (b), and particularly, the turning performance is improved. `` It can be said that it is preferable to perform the pressure reduction control of the front outer wheel.However, when the control mode is combined with the point of preventing the deceleration reduction due to the one-side pressure increase and the one-side pressure reduction, the overall It is better to slightly increase the depressurization side (decrease the braking force of the wheel) in the range that does not cause extreme deceleration than to increase the turning inner wheel pressure and turn the wheel pressure reduction control by the amount. If the braking force is small and the μW is constant from the relationship of the friction circle in FIG.
The component of the lateral force increases accordingly (see the upper part of the figure), and the turning force is further increased by the increase in the lateral force.

From the above viewpoints, when the yaw rate difference value Δ (d / dt) φ is large, the pressure reduction amount on the pressure reduction side is increased to meet this requirement (ie, the turning performance due to the increase in the lateral force). It can be said that the above-mentioned correction, which can meet the requirements (with a larger contribution), can be effective.

Thus, in this embodiment, it is possible to improve the yaw rate controllability while suppressing the decrease in the deceleration as much as possible, and the pressure increasing side has a small degree of the pressure increasing, so that the pressure increasing side can be locked. At the same time, the possibility of wheel lock is reduced (ie, the control area is expanded), and the instability of control that would otherwise occur if the wheel is locked can be avoided. In addition, such an improvement in controllability can be achieved by reducing the pressure difference to be generated as compared with the case where the main correction is not performed by the amount corresponding to the above-described lateral force. If the required control can be achieved with a small differential pressure, the control amount can be reduced accordingly, which also helps to improve the responsiveness.

In the above embodiment, Δ
Although the correction is performed using P _L , the braking force control is executed by the same amount of pressure increase / decrease control without correction when the difference is small to some extent even in the case of the yaw rate difference value. You may do so. This control is intended to prevent the pressure-increase side wheel from being locked (for example, control such as cutting the pressure-increase side braking force at a specified value according to the detected wheel load or the like).
The present control can be executed in a control area expanded to a lock area, and control for preventing lock can be performed when the control is exceeded.

In the embodiment, the yaw rate feedback (F / B) braking force control is performed. However, the present invention is not limited to this. For example, a feedforward (F / F) control method may be used instead of or together with this. In the case of feedforward control, the motion state amount related to yaw motion can be estimated by a vehicle model, and can be used to calculate the target left-right differential pressure for generating the braking force difference. Even in this case, the same effect of correction as described in the embodiment can be obtained by the F / F control. Furthermore, although the control target wheel is the front wheel, this may be the rear wheel or both the front and rear wheels. In that case, the front wheel side may be selectively used as in the F / F control, and the rear wheel side may be selectively used as in the F / B control.

[0049]

According to the present invention, when the vehicle behavior is controlled by generating a braking force difference between the left and right wheels, the braking force difference is controlled by increasing the pressure on one of the left and right wheels and reducing the pressure on the other. Even in control, it is possible to make adjustments to set the pressure reduction side somewhat larger while taking advantage of the prevention of deceleration reduction as much as possible instead of the same amount of one side pressure increase and one side pressure reduction, deceleration during braking , And controllability can be improved as compared with, for example, increasing the inner wheel pressure in the turning direction and reducing the outer wheel pressure in the same direction, and performing a braking force difference control that balances these two. .

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a braking force control device according to the present invention.

FIG. 2 is a system diagram showing a configuration according to an embodiment of a braking force control device of the present invention.

FIG. 3 is a functional block diagram illustrating an example of control contents in the same example.

FIG. 4 is a flowchart showing an example of a control program of a controller in the same example.

FIG. 5 is a time chart of an example of an operation in control without correction;

FIG. 6 is a time chart showing an example of an operation at the time of correction shown in comparison with FIG. 5;

FIG. 7 is a diagram provided for explaining an effect of a braking force on a vehicle operability;

FIG. 8 is a time chart showing a control example in the case of one-side pressure reduction control.

FIG. 9 is a time chart showing a control example in the case of one-side pressure increase and one-side pressure reduction.

[Explanation of symbols]

1L, 1R Front left and right wheels 2L, 2R Rear left and right wheels 3 Brake pedal 4 Master cylinder 5L, 5R, 6L, 6R Wheel cylinder 11F, 12F, 11R, 12R Hydraulic pressure control valve 16 Controller (braking force control means, brake hydraulic pressure setting means) 17) Steering angle sensor 19-22 Wheel speed sensor 23 Yaw rate sensor

──────────────────────────────────────────────────続 き Continuation of the front page (72) Atsushi Nano, Inventor Nissan Motor Co., Ltd. 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-2-70561 (JP, A) JP-A-4- 197858 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60T 8/58

Claims (1)

(57) [Claims] 1. A means for detecting a running state of a vehicle including at least a steering state of a vehicle; a means for detecting or estimating a motion state quantity related to a plane motion of a vehicle including at least a yaw motion; A difference is generated between the left and right braking forces of the wheels to be controlled using the output, and a means for controlling the braking force so that the vehicle behavior becomes the target characteristic. wheel braking liquid while the pressure increase target pressure, together with the other forms so as to differentiate a vacuum object relates the pressure increasing vacuum, in a direction to increase the amount of decompression of the decompression target side, the liquid of the pressure increase side of the object Increasing pressure and reducing pressure
The brake fluid pressure has a function to adjust the reduction of the fluid pressure on the side so that it is different from the same amount instead of the same amount , according to the target left-right difference or the control amount representing this. A braking force control device comprising: braking force control means including setting means.