JP3030899B2 - 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 an apparatus for controlling a braking force of a vehicle, and more particularly to a technique for controlling a braking force to improve the turning performance of the vehicle.

[0002]

If braking during turning of the Related Art vehicle has been performed, cornering force is reduced slip ratio of the wheel is increased, which may oversteer or understeer occurs. A measure to suppress this tendency is a turning performance improvement measure,
JP-A-60-248466, JP-A-1-17880
It is already known from JP-A-59-59 and the like.

[0003] Japanese Patent Application Laid-Open No. 60-248466 utilizes the fact that the cornering force of a wheel changes depending on the slip ratio of the wheel, and the actual turning characteristics tend to be understeer or oversteer. If the turning characteristic value indicating both the strength of the tendency and the turning characteristic value is equal to or greater than the set value, the braking force difference that suppresses the understeer tendency or the oversteer tendency between the front wheel brake and the rear wheel brake is determined. Means for controlling the distribution of braking force before and after the braking force is provided. In the case of oversteer, the braking force of the front wheels is increased to increase the slip ratio to reduce the cornering force of the front wheels, and for the rear wheels, conversely, the cornering force is increased by decreasing the braking force. If the vehicle tends to be understeered, the braking force of the rear wheels is increased and the braking force of the front wheels is reduced, whereby the vehicle can return to neutral steering.

On the other hand, Japanese Patent Application Laid-Open No. 1-178059 discloses a vehicle in which a yaw moment is generated in a vehicle body due to a difference in braking force between a right rear wheel and a left rear wheel to suppress an understeer tendency or an oversteer tendency. A braking force left / right distribution control means for generating a braking force difference that generates the yaw moment between the right rear wheel brake and the left rear wheel brake when the lateral acceleration of the vehicle body is equal to or greater than the set lateral acceleration is provided. Can be

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The braking force control device described in Japanese Patent No. 8466 obtains a turning characteristic value by subtracting the absolute value of the target yaw rate from the absolute value of the actual yaw rate, regardless of whether the turning direction of the vehicle is left or right. If the turning characteristic value is positive, it is determined that the larger the absolute value is, the stronger the oversteering tendency is. On the other hand, if the turning characteristic value is negative, the larger the absolute value is, the stronger the understeering tendency is. That is,
Using the assumption that the sign (direction) of the actual yaw rate and the target yaw rate always coincides with each other, regardless of whether the turning direction of the vehicle is left or right, if the turning characteristic value is positive, an oversteer tendency and negative If so, it is determined that it shows an understeer tendency.

However, the signs of the actual yaw rate and the target yaw rate are not always the same. For example, in order to make a quick lane change while the vehicle is going straight, or to make a drift while the vehicle is turning, the rear wheels slip. When a so-called counter steer operation is performed to steer the front wheel, which is a steered wheel, in a direction opposite to the direction, the sign of the actual yaw rate does not match the sign of the target yaw rate. Since the braking force control device obtains the turning characteristic value by subtracting the absolute value of the target yaw rate from the absolute value of the actual yaw rate irrespective of whether or not the vehicle is in the counter steer state, the actual turning characteristic may not be correctly determined. There was a problem. Hereinafter, a specific description will be given.

[0007] In the braking force front-rear distribution control, when an understeer tendency is generated when the vehicle is turning left or right, the front wheels are set to the side where the braking force is reduced and the rear wheels are set to the side where the braking force is increased. Should occur, or when the vehicle shifts to the counter steer state, the rear wheels should be on the decreasing side and the front wheels should be on the increasing side. However, since the braking force control device obtains the turning characteristic value by subtracting the absolute value of the target yaw rate from the absolute value of the actual yaw rate, if the vehicle is not in the counter steer state, the turning characteristic value becomes negative if an understeering tendency occurs. If the oversteer tendency occurs, it becomes positive, and the direction of the actual turning characteristic can be correctly determined.
In the counter-steering state, the turning characteristic value is not always positive as in the case of the oversteer tendency, but may be positive or negative depending on the magnitude relationship between the absolute value of the actual yaw rate and the absolute value of the target yaw rate. Therefore, the direction of the actual turning characteristic cannot be correctly determined. In addition, since the braking force control device obtains the absolute value of the turning characteristic value regardless of whether the direction of the actual yaw rate and the direction of the target yaw rate are the same, the strength of the actual turning characteristic cannot be correctly determined. .

In the case where the braking force left / right distribution control is performed using the turning characteristic value obtained in this manner, the direction of the actual turning characteristic in the counter steer state is the same as in the braking force front / rear distribution control. And the strength cannot be determined correctly.

In view of these circumstances, the present invention provides a control force control device for controlling the braking force of each wheel provided at the front, rear, left and right of a vehicle body, using a parameter that accurately reflects the actual turning characteristics of the vehicle. The object of the present invention is to improve the turning performance of the vehicle.

[0010]

[Means for Solving the Problems] In order to solve this problem
According to a first aspect of the present invention, there is provided a braking force control device for controlling braking forces of respective wheels provided on the front, rear, left, and right sides of a vehicle body, wherein the yaw rate of the vehicle body is such that the direction in which the vehicle body rotates about a vertical axis is rightward. The sign differs from the actual value but the sign from the target value
A braking force control means for controlling a braking force of each wheel based on a product of the deviation value and the actual value. The invention according to claim 2 is a braking force control device that controls a braking force of each wheel by controlling an actual slip ratio of each wheel provided on each of the front, rear, left, and right sides of the vehicle body to be each target slip ratio. The product of the yaw rate of the vehicle body and the difference between the actual value and the deviation value including the sign of the actual value from the target value, although the sign differs depending on whether the direction of rotation of the car body around the vertical axis is rightward or leftward. , A front and rear wheel target slip ratio changing means for changing a target slip ratio of at least one of the front wheel and the rear wheel is provided.

The "deviation" in each of the above-mentioned inventions may be a value obtained by subtracting the actual yaw rate, which is the actual value, from the target yaw rate, which is the target value of the yaw rate, or a value obtained by subtracting the target yaw rate from the actual yaw rate.

[0012]

In the braking force left / right distribution control for controlling the left / right distribution of the braking force by changing the target slip ratios of the left and right wheels, whether the vehicle has an understeer tendency when turning left or an oversteer tendency when turning right. Or when the vehicle shifts to the counter steer state during a right turn (hereinafter referred to as the preceding case), the left wheel is on the target slip rate increasing side (braking force increasing side), and the right wheel is on the target slip rate decreasing side (braking force decreasing side). On the other hand, when an oversteer tendency occurs during a left turn, an understeer tendency occurs during a right turn, or a transition is made to a counter steer state during a left turn (hereinafter, referred to as a countersteer state).
In the latter case, the right wheel is set to the target slip ratio increasing side and the left wheel is set to the decreasing side. On the other hand, the target slip ratio of the front and rear wheels
A system that controls the front and rear distribution of braking force by changing
In power front-rear distribution control, when turning left or right
The understeer tendency occurs (hereinafter referred to as
The front wheel is on the target slip rate decreasing side (corner
The rear wheel is on the side where the target slip ratio increases (corner
(On the side of reduced ring force)
To enter the counter steer state (below).
Lower, later) when the front wheels increase the target slip rate
Side and rear wheels are reduced.

On the other hand, the product of the yaw rate deviation and the actual yaw rate ( corresponding to the turning characteristic value in the conventional device) has a different sign between the former case and the latter case. Correctly reflects the direction and the strength is also correctly reflected . Therefore, in the braking force control device according to the first aspect , the braking force of each wheel is controlled based on such a product of the yaw rate deviation and the actual yaw rate, whereby the vehicle has a strong understeer tendency, a strong oversteer tendency or The occurrence of a turning abnormality such as a strong counter-steering tendency is suppressed. In the braking force control device according to the second aspect , the target slip ratio of at least one of the front wheels and the rear wheels is changed based on the product of the yaw rate deviation and the actual yaw rate.
The braking force of at least one of the wheels is changed, and as a result, abnormal turning of the vehicle is suppressed.

By the way, prior to the present invention, the present applicant has
In order to correctly determine the actual turning characteristics in the braking force front-rear distribution control, based on the product of the yaw rate deviation and the sign of the actual yaw rate, a front / rear wheel target slip ratio changing means for changing the front / rear wheel target slip ratio has been devised. . However, when the front and rear wheel target slip rate changing means is employed, the sign of the actual yaw rate changes regardless of the magnitude of the absolute value of the yaw rate deviation, so that the sign of the actual yaw rate changes from positive to negative or from negative. It has been found that there is a problem that the value of the product changes greatly when the value changes positively (the sign reverses), and the target slip ratio, that is, the braking force of the wheel may change slightly. Therefore, the braking force in the present invention
Control means and the front and rear wheel target slip rate variation means, the absolute value of the actual yaw rate before and after the sign of the actual yaw rate is changed by focusing on the fact that sufficiently close to 0, based on the product of the yaw rate deviation and the actual yaw rate, each wheel In this case, the braking force and the target slip ratio are changed.

[0015]

As is apparent from the above description, according to the present invention, the braking force of each wheel is determined by using a parameter that accurately reflects the actual turning characteristics of the vehicle, that is, the product of the yaw rate deviation and the actual yaw rate. Since the control is performed, a sufficient turning performance improvement effect can be obtained regardless of whether the vehicle is in the counter-steering state. Also, when the sign of the actual yaw rate changes,
Since the change in the target slip ratio becomes smooth,
The effect that the change in power becomes smooth can also be obtained.

In particular, according to the second aspect of the present invention, the target slip of at least one of the front wheels and the rear wheels is determined by using a parameter accurately reflecting the actual turning characteristic, that is, the product of the yaw rate deviation and the actual yaw rate. Since the rate is changed, a sufficient turning performance improvement effect can be obtained by the braking force front-rear distribution control regardless of whether the vehicle is in the counter steer state.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below in detail with reference to the drawings. In FIG. 3, reference numeral 10 denotes a master cylinder, which has two independent pressurizing chambers. The master cylinder 10 is linked to a brake pedal 14 as a brake operating member via a booster 12, and generates a brake pressure having a height proportional to the operating force of the brake pedal 14. The brake pressure generated in one pressurizing chamber is transmitted to a main liquid passage 18 via a proportioning / bypass valve (indicated by P / B in the figure) 16.
The main fluid passage 18 is bifurcated from the middle and is connected to wheel cylinders 26 of the brakes of the left and right front wheels 22 and 24 via respective electromagnetic fluid pressure control valves (hereinafter simply referred to as control valves) 20. The brake pressure generated in the other pressurizing chamber passes through the proportioning / bypass valve 16 and passes through the main liquid passage 3.
0 is transmitted. The main liquid passage 30 is also bifurcated from the middle and is connected to the wheel cylinders 38 of the brakes of the left and right rear wheels 34 and 36 via the control valves 32, respectively.

A proportioning / bypass valve 16
When the front system including the main fluid passage 18 is normal, the brake pressure in the rear system including the main fluid passage 30 is proportionally reduced, and when the front system fails, the master cylinder 1
It has a function of transmitting the brake pressure from zero to the wheel cylinders 38 of the left and right rear wheels 34, 36 as they are.

Although the control valve 20 is always in a pressure-increasing state in which the wheel cylinder 26 is communicated with the master cylinder 10 as shown in the figure, when the solenoid 40 is excited by a relatively large current, the wheel cylinder 26 When the solenoid 40 is excited by a relatively small current, the wheel cylinder 26 is disconnected from both the master cylinder 10 and the reservoir 42 when the solenoid 40 is excited by a relatively small current. It switches to the state. The control valve 32 is also a solenoid 4
4 according to the switching of the excitation state.
Is switched between a pressure-increasing state in which the pressure is communicated with the master cylinder 10, a pressure-reducing state in which the pressure is communicated with the reservoir 46, and a holding state in which the pressure is not communicated with any of them.

The brake fluid in the reservoir 42 is supplied to the pump 4
The water is pumped up by the pump 8 and returned to the main liquid passage 18 via the pump passage 50. The rear system also includes a pump 54 and a pump passage 56. These pumps 48, 54
Is driven by a motor 58.

The front system also bypasses the control valve 20 from each wheel cylinder 26 and
A return passage 60 is provided for allowing the brake fluid to flow back, and each return passage 60 is provided with a check valve 62 for preventing the brake fluid from flowing back. The rear system also includes a return passage 66 having a check valve 64.

In the figure, reference numeral 70 denotes a controller. The controller 70 is mainly composed of a computer, and includes a CPU 72, a ROM 74, a RAM 76, a timer 7
8, an input port 80, an output port 82, and a bus 84.

The input port 80 has a brake switch 8
8, a wheel speed sensor 90, 92, 94, 96, a steering angle sensor 98, a yaw rate sensor 100, and a longitudinal acceleration sensor 102 are connected. The brake switch 88 detects the depression of the brake pedal 14. Wheel speed sensors 90, 92, 94, 96
2, 24, and the wheel speeds, which are the peripheral speeds of the left and right rear wheels 34, 36, respectively. The steering angle sensor 98 is attached to the steering device, and detects an operation angle of the steering wheel as positive when the steering wheel is operated leftward from the neutral position and negative when the steering wheel is operated rightward. The yaw rate sensor 100 is attached to the vehicle body,
The left-handed yaw rate is detected as positive, and the right-handed yaw rate is detected as negative. The longitudinal acceleration sensor 102 is also attached to the vehicle body, and detects forward-facing longitudinal acceleration as positive and backward-facing longitudinal acceleration as negative. Output port 8
2, the control valves 20, 32 and the motor 58 are connected. The ROM 74 stores various programs including a braking slip control program represented by the flowcharts of FIGS. The CPU 72 controls the control valves 20 and 32 by executing the braking slip control program, and drives the motor 58 to drive the pumps 48 and 54 during the braking slip control, thereby controlling the wheel cylinders 26 and 38 to control the reservoir 4.
The brake fluid discharged to the master cylinder 10
To reflux.

Hereinafter, the operation of the vehicle brake device will be described. As described above, normally, the control valves 20 and 32 are in a state of allowing the master cylinder 10 and the wheel cylinders 26 and 38 to communicate with each other. Therefore, when the brake pedal 14 is depressed, the brake pressure of the master cylinder 10 and the wheel cylinders 26 and 38 increases, and the vehicle is braked.

After turning on the power, the controller 70 executes a braking slip control program. First, initialization is performed in step S1 of FIG. 1 (hereinafter simply referred to as S1; the same applies to other steps), and thereafter, in S2, actual wheels of the left and right front wheels 22, 24 and the left and right rear wheels 34, 36 are respectively set. The speeds Vfl, Vfr, Vrl, Vrr are captured. In S3, the actual yaw rate γa is taken in, and the actual vehicle body slip angle β is estimated. In an area of two degrees of freedom relating to the vehicle motion (a linear area of the vehicle body slip and yaw), assuming that the actual yaw rate γa is an input signal and the actual vehicle body slip angle β is an output signal, the actual yaw rate γ
A transfer function of (Gbo + Gb1 · s) / (1 + Tr · s) exists between a and the actual vehicle body slip angle β. In the above equation, s is a Laplace operator, and Gbo, Gb1, and Tr are related to an estimated vehicle speed Ve, which will be described later, and are determined according to a Gbo map, a Gb1 map, and a Tr map stored in the ROM 74. Each of these maps has the characteristics represented by the graphs of FIGS. 4, 5, and 6. That is, in this step, the actual vehicle slip angle β corresponding to the actual yaw rate γa and the estimated vehicle speed Ve is calculated using the transfer function.

Then, in S4, the actual wheel speed V of each wheel
fl, Vfr, Vrl, Vrr are converted with respect to the center position of the front wheel axle. Specifically, as shown in FIG. 7, if the tread of the vehicle is t and the wheelbase is L, the actual wheel speed V
The sum of fl and t · γa / 2 is the converted wheel speed V of the left front wheel 22
_{1. The} value obtained by subtracting t · γa / 2 from the actual wheel speed Vfr is the converted wheel speed V ₂ of the right front wheel 24 and the actual wheel speed Vrl and t ·
The sum of γa / 2 and L · β · γa is the converted rear wheel speed V ₃ of the left rear wheel 34, and the sum of L · β · γa obtained by subtracting t · γa / 2 from the actual wheel speed Vrr is the right rear. it being a translated wheel speed V ₄ of the wheel 36. The converted wheel speeds V ₁ and V
₂ , V ₃ and V ₄ are not affected by the difference in the turning trajectory of each wheel and the effect of the actual vehicle body slip angle β, and if each wheel is not slipping at all, regardless of the turning state, Matches.

Subsequently, the longitudinal acceleration Gx is fetched in S5, and the estimated vehicle speed Ve is calculated in S6. Longitudinal acceleration Gx is less than 0, and if positive is less than the upper limit value Gup is the minimum value of the converted wheel speed V _1, V _2, V ₃ and V ₄ are estimated to be the vehicle speed, longitudinal acceleration Gx less than 0, converted maximum value of the wheel speeds V _1, V _2, V ₃ and V ₄ are estimated to be the vehicle speed, longitudinal acceleration Gx is greater than the upper limit value Gup if it is negative lower limit Glo more Alternatively, if the longitudinal acceleration Gx is less than the lower limit Glo, the estimated vehicle speed Ve when the longitudinal acceleration Gx first becomes the same (the latest estimation when the longitudinal acceleration Gx is greater than or equal to the lower limit Glo and less than or equal to the upper limit Gup). Body speed Ve)
Is estimated to be the vehicle speed.

Thereafter, in S7, the reference wheel speeds Vc-fl, Vc-fr, Vc-rl, and Vc-rr of each wheel (in the current running state (straight running state or turning state), the slip ratio of each wheel is 0, and The wheel speed taken by each wheel in some cases) is determined. Specifically, the value obtained by subtracting t · γa / 2 from the estimated vehicle speed Ve is the reference wheel speed Vc-fl of the left front wheel 22, and the sum of the estimated vehicle speed Ve and t · γa / 2 is the reference value of the right front wheel 24. The value obtained by subtracting the sum of t · γa / 2 and L · β · γa from the wheel speed Vc-fr and the estimated vehicle speed Ve is the reference wheel speed Vc-rl of the left rear wheel 34, the estimated vehicle speed Ve and t · γa. The value obtained by subtracting L.beta..gamma.a from the sum of / 2 is used as the reference wheel speed Vc-rr of the right rear wheel 36. Subsequently, in S8, the actual slip ratios Sa-fl, Sa-fr, Sa-rl, and Sa-rr of each wheel are calculated. Specifically, the actual wheel speed Vc-fl, Vc-fr, Vc-rl, and Vc-rr of each wheel
The value obtained by subtracting fl, Vfr, Vrl, and Vrr is used as the reference wheel speed V
The values divided by c-fl, Vc-fr, Vc-rl, and Vc-rr are the actual slip ratios Sa-fl, Sa-fr, Sa-rl, and S, respectively.
It is a-rr.

Subsequently, the actual steering angle θ is fetched in S9, and the target yaw rate γd is calculated in S10. Assuming that the actual steering angle θ is an input signal and the target yaw rate γd is an output signal, and that they are on a first-order lag system, γo / (1 + τ · s) is calculated between the actual steering angle θ and the target yaw rate γd. Transfer function exists. Where s is the Laplace operator, and γo and τ are related to the estimated vehicle speed Ve and are determined according to the γo map and τ map stored in the ROM 74. Each of these maps has the characteristics represented by the graphs of FIGS. That is, in this step, the target yaw rate γd corresponding to the actual steering angle θ and the estimated vehicle speed Ve is calculated using the transfer function.

Thereafter, in S11, the yaw rate deviation Δγ is calculated by subtracting the actual yaw rate γa from the target yaw rate γd, and the turning characteristic value C is calculated by multiplying the yaw rate deviation Δγ by the actual yaw rate γa. The sign of the turning characteristic value C does not change depending on whether the turning direction is left or right. If the turning characteristic value C is positive, the larger the absolute value is, the stronger the understeering tendency is. The larger the value, the stronger the oversteer tendency. Then, S12
-14, the target slip ratio Sd-fl, Sd-f of each wheel
r, Sd-rl and Sd-rr are determined. The target slip rates Sd-fl, Sd-fr, Sd-rl, and Sd-rr of each wheel are the standard value So and the target slip rate change amounts ΔSx-fl, ΔSx-f of the front and rear wheels of each wheel.
r, ΔSx-rl, and ΔSx-rr (hereinafter, collectively referred to as ΔSx). In this embodiment, the standard value So is the same for all four wheels, but can be different from each other depending on, for example, the vehicle motion characteristics.

More specifically, in S12, the front and rear wheel target slip ratio change amounts ΔSx-fl, ΔSx-fr,
ΔSx-rl and ΔSx-rr are related to the turning characteristic value C,
It is determined according to the ΔSx map stored in OM74. This map has the characteristics shown in the graph of FIG. Fig. 1 shows the relationship between slip ratio and cornering force.
As indicated by the broken line graph in FIG. 1, since the cornering force is smaller as the slip ratio is larger, the cornering force of the left and right front wheels 22, 24 is increased to suppress the understeer tendency, while the left and right rear wheels 34, 36 are increased. If it is necessary to reduce the coiling force of the vehicle, the target slip ratio of the left and right front wheels 22 and 24 is reduced, while the target slip ratio of the left and right rear wheels 34 and 36 is increased, and the tendency of oversteering is suppressed. Or when it is necessary to increase the cornering force of the left and right rear wheels 34, 36 while decreasing the cornering force of the left and right front wheels 22, 24 in order to promote the restoration of the vehicle body posture after the countersteering operation. And reducing the target slip ratio of the left and right front wheels 22, 24 while decreasing the target slip ratio of the left and right rear wheels 34, 36. A.

In short, the target slip ratio is set to the front wheels 22 and 2
In the braking force front-rear distribution control that is changed between the rear wheel 4 and the rear wheels 34 and 36, the rear wheel 3 is used when an understeer tendency occurs (hereinafter referred to as the first case) regardless of whether the vehicle is turning left or right.
4 and 36 are on the increasing side of the target slip ratio, and the front wheels 22 and 24 are on the decreasing side. On the other hand, when the oversteering tendency occurs or the countersteering operation is performed (hereinafter, referred to as the later case), the front wheels 22 and 24 are increased. Numeral 24 denotes a side where the target slip ratio increases, and rear wheels 34 and 36 denote a side where the target slip ratio decreases. The sign of the turning characteristic value C is positive in the former case, negative in the latter case, and Since the absolute value of the turning characteristic value C relatively accurately reflects the difference between the actual yaw rate γa and the target yaw rate γd, the turning characteristic can be determined without determining whether the actual turning direction of the vehicle is left or right. Immediately from the value C, the front and rear wheel target slip rate change amounts ΔSx-fl, ΔSx-fr,
ΔSx-rl and ΔSx-rr can be correctly determined.

In this embodiment, in order to avoid excessive increase and decrease of the brake pressure, as shown in FIG. 10, the front and rear wheel target slip ratio change amounts ΔSx-fl, ΔSx-fr,
An upper limit and a lower limit are provided for ΔSx-rl and ΔSx-rr.

Thereafter, in S14, the target slip rates Sd-fl, Sd-fr, Sd-rl and Sd-rr of each wheel are set to a standard value S.
o and the target wheel slip ratio change ΔSx-fl, ΔS for each wheel
x-fr, ΔSx-rl, ΔSx-rr. However, in the second and subsequent executions of this step, the target slip ratios Sd-fl, Sd-fr, Sd-rl, and Sd-rr of each wheel.
Is the previous value and the target wheel slip ratio change Δ
It is determined to be the sum of Sx-fl, ΔSx-fr, ΔSx-rl, and ΔSx-rr with the current value.

Thereafter, in S15 of FIG. 2, it is determined whether or not the brake switch 88 detects that the brake pedal 14 is depressed, that is, whether or not the brake pedal is in the ON state. Valve 20,
After the demagnetization signal is output to the solenoids 40 and 44 of 32, the process returns to S2 of FIG. 1. If so, the steps after S17 are executed, and the control valves 20 and 32 should be realized this time. The brake pressure control mode is
The mode is selected from the holding mode and the pressure increasing mode. S1
Step groups 7 to 21 are sequentially executed for each of the four wheels. In S17, it is determined whether or not the actual slip ratio Sa of one wheel is equal to or more than the target slip ratio Sd. If so, the depressurization mode is selected in S18, otherwise, in S19, the actual wheel speed of the wheel is determined. It is determined whether the wheel acceleration Gw, which is the time differential value of Vw, is equal to or less than the set wheel acceleration Gwo. If so, the holding mode is selected in S20, and if not, the pressure increase mode is selected in S21. Thereafter, in S22, it is determined whether or not the selection of the control mode has been completed for all four wheels. If so, in S23, a signal for realizing the selected control mode is given to each of the four-wheel control valves 20, 32. Is issued. Thereafter, the process returns to S2 of FIG.

Therefore, in this embodiment, the target slip ratio of the front and rear wheels is changed by using the product of the yaw rate deviation and the actual yaw rate, which is a parameter that accurately reflects the actual turning characteristics, so that the vehicle is in the counter steer state. Irrespective of whether or not it is possible to obtain a sufficient turning performance improvement effect by the braking force front-rear distribution control.

Further, in this embodiment, the absolute value of the actual yaw rate is 0 before and after the sign of the actual yaw rate changes.
Focusing on the fact that the yaw rate deviation is multiplied by the actual yaw rate, the target slip ratio of the front and rear wheels is changed based on the product of the yaw rate deviation and the actual yaw rate. And the sign of the actual yaw rate, the smoothing is smoother than when the target slip ratio of the front and rear wheels is changed, and thus the effect of smoothing the change in the braking force of the front and rear wheels is also obtained. You.

As is clear from the above description, in the present embodiment, the computers of S2 to S6 and S9 of FIG.
Steps 14 to 14 constitute the braking force control means according to the first aspect of the invention and also constitute the front and rear wheel target slip ratio changing means according to the second aspect of the invention.

As described above, the braking force control device capable of performing the braking force longitudinal distribution control has been described as one embodiment of the present invention. However, the present invention can be implemented as a braking force control device capable of performing the braking force lateral distribution control. der Ru.

The present invention can also be embodied as a braking force control device that constantly performs the braking force longitudinal distribution control and the braking force left / right distribution control. Hereinafter, an embodiment thereof will be described with reference to the drawings.

The RO of the controller 70 in the present embodiment
M74 stores a braking slip control program in which the flowchart of FIG . 1 is changed to the flowchart of FIG . In this program, S201 to S21
1 is performed in the same manner as S1 to S11 in FIG.
At 212, the target slip ratios Sd-fl, Sd-f of each wheel
r, Sd-rl and Sd-rr are determined. The target slip ratios Sd-fl, Sd-fr, Sd-rl, and Sd-rr of each wheel are standard values So.
And the target wheel slip ratio change ΔSx-fl, ΔSx-
This is the sum of fr, ΔSx-rl, ΔSx-rr and the left and right target slip ratio changes ΔSy-fl, ΔSy-fr, ΔSy-rl, ΔSy-rr of each wheel. More specifically, in S212, the change amounts ΔSx-fl, ΔSx-fr, ΔSx-fl,
Sx-rl and ΔSx-rr are related to the turning characteristic value C and are shown in FIG.
In addition, the left and right wheel target slip rate change amounts ΔSy-fl, ΔSy-fr, ΔSy-rl, and ΔSy-rr are determined in accordance with the yaw rate deviation Δγ in FIG.
Determined according to the Sy map. Then, in S214, the target slip rates Sd-fl, Sd-fr, Sd-rl, and Sd-rr of each wheel are set to the standard value So and the target slip rate change amounts ΔSx-fl, ΔSx-fr, ΔSx-rl, and the front and rear wheel target slip rates. It is determined as the sum of ΔSx-rr and the left and right wheel target slip rate change amounts ΔSy-fl, ΔSy-fr, ΔSy-rl, and ΔSy-rr. However, at the time of the second and subsequent executions of this step, the target slip rates Sd-fl, Sd-fr, Sd-rl, and Sd-rr of each wheel are set to the previous value and the front-rear wheel target slip rate change ΔSx− fl, ΔSx-fr, Δ
It is determined as the sum of the current values of Sx-rl and ΔSx-rr and the current values of the left and right wheel target slip rate change amounts ΔSy-fl, ΔSy-fr, ΔSy-rl, and ΔSy-rr. Thereafter, the steps after S15 in FIG. 2 are executed.

Therefore, in this embodiment, the left and right wheel target slip rate change amounts and the front and rear wheel target slip rate change amounts are determined based on the yaw rate deviation and the product of the actual yaw rate, respectively. A sufficient turning performance improvement effect can be obtained by the left-right distribution control and the front-rear distribution control.

As is clear from the above description, in this embodiment, S202 to S206 and S209 to S21 in FIG.
A portion for executing the 1 and 214 part and is claimed to determine the front and rear wheel target slip rate variation ΔSx of S212
The present invention according to claim 1 constitutes the braking force control means and also constitutes the front and rear wheel target slip ratio changing means according to the invention according to claim 2 .

The present invention can also be implemented as a braking force control device that always performs the braking force left / right distribution control, but performs the braking force front / rear distribution control as needed. Hereinafter, an embodiment thereof will be described in detail with reference to the drawings.

RO of controller 70 in this embodiment
M74 stores a braking slip control program in which the flowchart of FIG . 1 is changed to the flowchart of FIG . In this program, S301 to S31
1 is performed in the same manner as S1 to S11 in FIG.
At 312, the target slip ratio change Δ
Sx-fl, ΔSx-fr, ΔSx-rl, and ΔSx-rr are the turning characteristic values C
Is determined according to the ΔSx map of FIG.
Also, the left and right wheel target slip rate change amounts ΔSy-fl, ΔSy-f
r, ΔSy-rl, and ΔSy-rr are determined according to the ΔSy map of FIG. 12 in relation to the yaw rate deviation Δγ. Thereafter, in S313, it is determined whether or not the absolute value of the yaw rate deviation is equal to or smaller than the set yaw rate deviation γmax. If so, in S314a, the target slip rates Sd-fl, Sd-fr, Sd-rl of each wheel are determined. , Sd-rr are the standard value So and the left and right wheel target slip rate change amounts ΔSy-fl, ΔSy-fr, ΔSy-r
l, ΔSy-rr, otherwise, S3
At 14b, the standard value So, the front and rear wheel target slip rate change amounts ΔSx-fl, ΔSx-fr, ΔSx-rl, ΔSx-rr and the left and right wheel target slip rate change amounts ΔSy-fl, ΔSy-fr, ΔSy-rl,
It is determined as the sum with ΔSy-rr. However, 2 of S314a
At the time of each execution after the first execution, the target slip ratio S of each wheel
The previous values of d-fl, Sd-fr, Sd-rl, and Sd-rr and the left and right wheel target slip rate change amounts ΔSx-fl, ΔSx-fr, ΔSx-rl, ΔSx-
rr is determined to be the sum of the current value and the current value, and at the time of execution of each of the second and subsequent steps of S314b, the target slip ratio Sd−
The previous values of fl, Sd-fr, Sd-rl, and Sd-rr and the change amounts of the front and rear wheel target slip rates ΔSy-fl, ΔSy-fr, ΔSy-rl, and ΔSy-rr
And the target slip rate change ΔSy-fl, ΔS of the left and right wheels
It is determined as the sum of y-fr, ΔSy-rl, and ΔSy-rr with the current value. Thereafter, the steps after S15 in FIG. 2 are executed.

In general, a turning performance improvement measure by the braking force front-rear distribution control is effective when the friction coefficient of the road surface is high, but the effect is weak when the friction coefficient is low. Therefore, when the braking force front-rear distribution control is always performed regardless of the level of the friction coefficient of the road surface, the target slip ratio may be changed unnecessarily. Therefore, in the present embodiment, when the absolute value of the yaw rate deviation is equal to or less than the set yaw rate deviation, it is determined that the friction coefficient of the road surface is low, and the braking force front-rear distribution control is omitted, thereby reducing waste of the target slip ratio. To prevent significant changes.

As is clear from the above description, in the present embodiment, the computer performs steps S302 to S30 in FIG.
6, 309 to 311, 313 and 314b, and the front and rear wheel target slip rate change Δ in S312.
A portion for determining the Sx is to constitute the wheel target slip ratio changing means before and after the invention according to claim 2 as well as constitutes a braking force control means in the invention according to claim 1.

It should be noted that, in each of the embodiments described above, the target slip ratio Sd of each wheel is continuously changed according to the yaw rate deviation Δγ or the turning characteristic value C, which are both continuous values. In addition, it is possible to prevent the braking force of each wheel from being changed discontinuously, and to obtain an effect that the behavior change of the vehicle body becomes smooth. However, such a continuous change of the target slip ratio Sd is not indispensable for practicing the present invention. For example, the target slip ratio Sd can be changed stepwise according to the yaw rate deviation Δγ or the turning characteristic value C. is there.

In the above-described embodiment, the actual yaw rate γa is obtained by using the yaw rate sensor 100 and the actual vehicle body slip angle β is estimated by using the actual yaw rate γa. The actual vehicle body slip angle β may be obtained using a sensor. By the way, in the region of linear two degrees of freedom relating to the vehicle body motion, if the actual steering angle θ is an input signal and the actual yaw rate γa is an output signal, then (Tr · s + 1) · between the actual steering angle θ and the actual yaw rate γa. γo / (a · s ² + b · s + 1) exists, while the actual steering angle θ is defined as an input signal,
Assuming that the actual vehicle body slip angle β is an output signal, a transfer function of (Gbo + Gb1 · s) · γo / (as · ² + bs · s + 1) exists between the actual steering angle θ and the actual yaw rate γa. Here, Tr, γo, Gbo and Gb1 are values obtained according to the maps of FIGS. 6, 8, 4 and 5, respectively, as described above.
a and b relate to the estimated vehicle speed Ve, respectively .
15 and values obtained according to the map of FIG. Therefore, the actual yaw rate γa and the actual vehicle body slip angle β can be estimated from the actual steering angle θ only with the steering angle sensor 98 without the yaw rate sensor 100 and the vehicle body slip angle sensor.

In the embodiment described above, the braking force is made different between the left wheels 22, 34 and the right wheels 24, 36, and the cornering force is made between the front wheels 22, 24 and the rear wheels 34, 36. Although the target slip ratio Sd of each wheel is variable and the set wheel acceleration Gwo is invariable in order to make the wheel speed Gwo different, the set wheel acceleration Gwo can also be variable.

In the embodiment described above, the target slip ratio Sd of each wheel is realized by controlling the braking force by the brake during vehicle braking. Even if the target slip ratio Sd of each wheel is realized by controlling the force, the target slip ratio Sd of each wheel may be realized by the control of the braking force by the brake and the control of the driving force by the engine or the like. . Further, the target slip ratio Sd may be realized not only at the time of vehicle braking but also at the time of non-braking of the vehicle by these methods. That is, the braking force of each wheel in the present invention means a force of each wheel for suppressing the advance of the vehicle body.

While some embodiments of the present invention have been described in detail with reference to the drawings, these are merely examples, and various modifications and improvements are made based on the knowledge of those skilled in the art. Can of course be implemented.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the first half of a braking slip control program in a braking force control device according to one embodiment of the present invention.

FIG. 2 is a flowchart showing a latter half of the braking slip control program.

FIG. 3 is a system diagram of a vehicle brake device including the braking force control device.

FIG. 4 is a graph showing a map stored in a ROM in FIG. 3;

FIG. 5 is a graph showing a map stored in a ROM in FIG. 3;

FIG. 6 is a graph showing a map stored in a ROM in FIG. 3;

FIG. 7 is a diagram for explaining a relationship between an actual wheel speed and a converted wheel speed.

FIG. 8 is a graph showing a map stored in a ROM in FIG. 3;

FIG. 9 is a graph showing a map stored in a ROM in FIG. 3;

FIG. 10 is a graph showing a map stored in a ROM in FIG. 3;

FIG. 11 is a diagram for explaining a relationship among a slip ratio, a braking force, and a cornering force.

FIG. 12 is a graph showing a map stored in a ROM of a braking force control device according to another embodiment of the present invention .

FIG. 13 is a flowchart showing a first half of a braking slip control program in the braking force control device according to the another embodiment.

FIG. 14 is a flowchart showing the first half of a braking slip control program in a braking force control device according to still another embodiment.

FIG. 15 is a graph for explaining a variable a used for estimating an actual yaw rate and an actual vehicle body slip angle from a steering angle.

FIG. 16 is a graph for explaining a variable b used for estimating an actual yaw rate and an actual vehicle body slip angle from a steering angle.

[Explanation of symbols]

 Reference Signs List 10 master cylinder 20 electromagnetic hydraulic pressure control valve 22 left front wheel 24 right front wheel 26 wheel cylinder 32 electromagnetic hydraulic pressure control valve 34 left rear wheel 36 right rear wheel 38 wheel cylinder 70 controller 88 brake switch 98 steering angle sensor 100 yaw rate sensor 102 longitudinal acceleration Sensor

Claims (2)

(57) [Claims] 1. A braking force control device for controlling braking forces of wheels provided on the front, rear, left and right sides of a vehicle body, wherein a yaw rate of the vehicle body and a direction in which the vehicle body rotates around a vertical axis are rightward or leftward. polarized code depending on whether it is including the sign of the target value of the actual value but different
A braking force control device comprising: braking force control means for controlling a braking force of each wheel based on a product of a difference value and the actual value. 2. A braking force control device for controlling a braking force of each wheel by controlling an actual slip ratio of each wheel provided on the front, rear, left and right sides of the vehicle body so as to become each target slip ratio. Although the sign differs depending on whether the yaw rate and the direction in which the vehicle body rotates about the vertical axis is rightward or leftward, the deviation including the sign of the actual value from the target value is included.
A braking force control device comprising: front and rear wheel target slip ratio changing means for changing a target slip ratio of at least one of a front wheel and a rear wheel based on a product of a difference value and the actual value.