JP3123099B2 - 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 turning performance.

[0002]

BACKGROUND ART The present applicant has previously developed the following braking force control device. This is described as an example in the specification (reference number: TSN903934) filed on the same day as the present application, and the actual slip ratio of the wheels provided on the front, rear, left, and right of the vehicle body is calculated as the target slip ratio. Controlling the braking force of each wheel by controlling
And (a) the amount of change in the target slip ratio for the left and right wheels,
Left and right wheel target slip rate change amount determining means for determining that the actual yaw rate of the vehicle body changes continuously as the yaw rate deviation from the target yaw rate changes; and (b) calculating the yaw rate change amount of the target slip rate for the front and rear wheels. A front and rear wheel target slip rate change amount determining means for determining that the change is continuously changed as the product of the deviation and the actual yaw rate changes; and (c) the left and right wheel target slip rate change amount and the front and rear wheel target slip rate change amount. And a target slip ratio determining means for determining a target slip ratio of each wheel by using a sum of the respective values. Based on the yaw rate deviation, the target slip ratio of at least one of the left wheel and the right wheel is changed to change the left / right distribution of the braking force, so that the braking force left / right distribution control that brings the actual yaw rate closer to the target yaw rate; Based on the product of the yaw rate and at least one of the front wheel and the rear wheel, the target slip ratio is changed to change the longitudinal distribution of the braking force, and the braking force longitudinal distribution control that brings the actual yaw rate close to the target yaw rate is always performed. It is something we do together. The yaw rate is a parameter having a different sign depending on the direction in which the vehicle body rotates around the vertical axis . The yaw rate deviation may be obtained by subtracting the actual yaw rate from the target yaw rate, or may be acquired by subtracting the target yaw rate from the actual yaw rate.

As described above, the braking force control device performs the braking force front-rear distribution control and the braking force left-right distribution control irrespective of the level of the friction coefficient of the road surface. However, the braking force front-rear distribution control is generally effective when the friction coefficient of the road surface is high, but is less effective when the friction coefficient is low. Therefore, when the friction coefficient of the road surface is low, useless braking force front-rear distribution control is performed.

Under such circumstances, the present applicant has improved the means for determining the target slip ratio of each wheel as follows. That is, when the absolute value of the yaw rate deviation (or the absolute value of the lateral acceleration of the vehicle body) is equal to or smaller than the set value (generally, the road surface has a low friction coefficient), The target slip ratio of each wheel is determined using the change amount of the left and right wheel target slip ratios. On the other hand, when the absolute value of the yaw rate deviation is larger than the set value (generally, the road surface has a high friction coefficient), The improvement is made to determine the target slip ratio of each wheel using the sum of the wheel target slip ratio change amount and the front and rear wheel target slip ratio change amount. In this way, the braking force left / right distribution control and the braking force front / rear distribution control are performed together when the road surface friction coefficient is high, but the braking force left / right distribution control is performed independently when the road surface friction coefficient is low. Therefore, unnecessary braking force front-rear distribution control is omitted.

[0005]

However, it has been found that this device has room for improvement. That is, in this device, when the absolute value of the yaw rate deviation increases and exceeds the set value, the change amount of the front and rear wheel target slip rates is discontinuously added to the target slip rate of each wheel. When the absolute value decreases and exceeds the set value, the amount of change in the target slip ratio between the front and rear wheels is discontinuously subtracted from the target slip ratio of each wheel, and the target slip ratio of each wheel is discontinuous in any case. It turned out that there was a problem that it could be changed. Based on the above findings, the present invention
It is an object of the present invention to perform the braking force front-rear distribution control without waste and to continuously change the target slip ratio of each wheel.

[0006]

SUMMARY OF THE INVENTION In order to solve this problem, a braking force control device according to the present invention provides a target slip of each wheel.
The amount of change from the reference value of the braking
Related to being located on at least one side of
And the amount of change between the front and rear sides of the vehicle body
The second variation associated with being located on one side
And the first amount of change is
The yaw rate deviation of the actual yaw rate from the target yaw rate
Decide to change continuously as it changes
On the other hand, the second change amount is defined as the difference between the yaw rate deviation and the actual yaw rate.
As the product and the quantity associated with the coefficient of road friction change.
Target slip rate change determined to change continuously
It is configured to include an amount determining means .

[0007] One aspect of the target slip ratio change amount determining means is as follows: (a) The target slip ratio change amount for the left and right wheels is determined to change continuously as the yaw rate deviation changes. Means for determining the change amount of the target slip rate for the left and right wheels, and (b) calculating the product of the yaw rate deviation and the actual yaw rate and the road surface friction.
Front and rear wheel target slip rate change amount determining means for determining to continuously change as the friction coefficient related amount changes,
(c) configured to include a respective wheel target slip ratio determination means for determining a target slip ratio of each wheel with the sum of their left and right wheel target slip rate variation and the front and rear wheel target slip rate variation.

Further, in the above invention, "the coefficient of friction of the road surface"
For example, the "related amount" may include a lateral acceleration of the vehicle body.

[0009]

In the braking force control apparatus according to the present invention, the amount of change in the target slip ratio of the front and rear wheels , that is, each wheel is controlled so that unnecessary braking force front-rear distribution control is omitted.
Located on one or both of the front and back of the body
In particular, the change amount related to the road surface friction coefficient is continuously changed as the road surface friction coefficient related amount changes, and the target slip ratio of each wheel is also changed continuously as the road surface friction coefficient related amount changes.

[0010]

Because according to the present invention that, according to the present invention, wasteful with braking force rear distribution control is omitted, the vehicle is continuously changed target slip ratio of each wheel as a change in road surface friction coefficient related quantity The effect is obtained that the braking force of the wheels is smoothly controlled as the road surface friction coefficient-related amount changes.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment 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 passes through electromagnetic fluid pressure control valves (hereinafter simply referred to as control valves) 20.
24 is connected to the wheel cylinder 26 of the brake. The brake pressure generated in the other pressurizing chamber is transmitted to the main liquid passage 30 via the proportioning / bypass valve 16. 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, 36 via the control valves 32, respectively.

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.

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, but 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 either.

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 to allow the master cylinder 10
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, wheel speed sensors 90, 92, 94, 96, steering angle sensor 98, yaw rate sensor 100, longitudinal acceleration sensor 102, and lateral acceleration sensor 104 are connected.
The brake switch 88 detects the depression of the brake pedal 14. Wheel speed sensors 90, 92, 9
4, 96 are left and right front wheels 22, 24, left and right rear wheels 34, 36
The wheel speeds, which are the respective peripheral speeds, are detected. 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, and detects a counterclockwise yaw rate as positive and a clockwise yaw rate 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. The lateral acceleration sensor 104 is also attached to the vehicle body,
The rightward lateral acceleration is detected as positive, and the leftward lateral acceleration is detected as negative. The output port 82 has the control valve 2
0, 32 and the motor 58 are connected. ROM7
4 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 reservoirs 42 and 38 from the wheel cylinders 26 and 38. The brake fluid discharged to 46 is returned to the master cylinder 10.

The operation of the vehicle brake device will be described below. 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 the power is turned on, 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 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 rate of each wheel is 0. 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 ratios Sd-fl, Sd-fr, Sd-rl and Sd-rr of each wheel are standard values S
o, the sum of the front and rear wheel target slip ratio change amount and the left and right wheel target slip ratio change amount. 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. The change amount of the front and rear wheel target slip ratio of each wheel is a front-rear distribution coefficient Kx (a value of 0 to 1) and the basic value of the front and rear wheel target slip ratio change amount (hereinafter, simply referred to as the front and rear wheel slip ratio basic value) ΔSx-fl , ΔSx-fr, ΔSx-rl, ΔSx-rr. The left and right wheel target slip rate change amount of each wheel is a left / right distribution coefficient Ky (takes a value of 0 to 1) and a basic value of the right and left wheel target slip rate change amount (hereinafter, simply referred to as a left and right wheel slip rate basic value) ΔSy-fl , ΔSy-fr, ΔSy-rl, ΔSy-rr.

More specifically, in S12, the front and rear wheel slip ratio basic values ΔSx-fl, ΔSx-fr, ΔSx-rl, and ΔSx-rr are stored in the ROM 74 in association with the turning characteristic value C. It is determined according to the ΔSx map. This map has the characteristics shown in the graph of FIG.
As shown by the broken line graph in FIG. 11, there is a relationship between the slip ratio and the cornering force, as the slip ratio is larger, the smaller the cornering force, the cornering of the left and right front wheels 22, 24 to suppress the understeer tendency. If it is necessary to increase the force while reducing the coaling force of the left and right rear wheels 34, 36, the left and right front wheels 22,
24, while the left and right rear wheels 34,
In order to suppress the oversteer tendency or to promote the restoration of the vehicle body posture after the countersteer operation, the left and right rear wheels 34, 34 are increased.
36, while increasing the cornering force of the left and right front wheels 22,
When it is necessary to reduce the cornering force of the left and right wheels 24, the target slip ratio of the left and right front wheels 22, 24 is increased while the target slip ratio of the left and right rear wheels 34, 36 is decreased.

In this step, the left and right wheel slip ratio basic values ΔSy-fl, ΔSy-fr, ΔSy-rl and ΔS
y-rr is determined according to the ΔSy map stored in the ROM 74 in relation to the yaw rate deviation Δγ. This map has the characteristics shown in the graph of FIG. The relationship between the slip ratio and the braking force is represented by the solid line graph in FIG. 11, and in particular, the relationship between the slip ratio utilization region and the braking force is such that the greater the slip ratio, the greater the braking force. I do. Therefore, when it is necessary to increase the braking force of the turning inner wheel and reduce the braking force of the turning outer wheel in order to suppress the understeer tendency, the target slip ratio of the turning inner wheel is increased while the target slip of the turning outer wheel is increased. In addition, it is necessary to increase the braking force of the turning outer wheel while reducing the braking force of the turning inner wheel in order to suppress the oversteering tendency or to promote the restoration of the vehicle body posture after the countersteering operation. If necessary, the target slip rate of the turning inner wheel is increased while the target slip rate of the turning inner wheel is decreased. The turning inner wheels are the left front wheel 22 and the left rear wheel 34 in the case of the left turn, while the right front wheel 24 and the right rear wheel 3 in the case of the right turn.
6. The turning outer wheels are the right front wheel 24 and the right rear wheel 36 in the case of a left turn, while the left outer wheel 22 and the left rear wheel 34 in the case of a right turn.

In this embodiment, in order to avoid excessive increase and decrease of the brake pressure, FIGS.
As shown in FIG. 2, the front and rear wheel slip ratio basic values ΔSx-fl, Δ
Upper and lower limits are provided for Sx-fr, ΔSx-rl, and ΔSx-rr, and the left and right wheel slip ratio basic values ΔSy-fl, ΔSy-fr, ΔSy-rl, and ΔSy-rr, respectively.

Thereafter, in step S13, the lateral acceleration Gy is fetched, and in step S14, the front / rear distribution coefficient Kx and the left / right distribution coefficient Ky are respectively related to the absolute value of the lateral acceleration Gy in accordance with the Kx and Ky maps stored in the ROM 74. It is determined. As shown in the graph of FIG. 13, the front-rear distribution coefficient Kx is set so as to increase as the absolute value of the lateral acceleration Gy increases, and to increase smoothly as the absolute value of the lateral acceleration Gy increases. When the absolute value of the lateral acceleration Gy is small, the effect of the braking force longitudinal distribution control is weak, so that the target slip ratio is prevented from being uselessly changed for the braking force longitudinal distribution control. On the other hand, as shown in the graph of FIG. 14, the left / right distribution coefficient Ky is maintained at 1 until the absolute value of the lateral acceleration Gy does not exceed a certain value, and gradually decreases slightly when it exceeds the absolute value. Is set. When the absolute value of the lateral acceleration Gy is large, the effect of the braking force left / right distribution control is not so necessary,
This prevents the target slip ratio from being uselessly changed for the braking force left / right distribution control.

In this step, the target slip ratios Sd-fl, Sd-fr, Sd-rl, and Sd-rr of the respective wheels are further set to a standard value So, a front-rear distribution coefficient Kx, and a front-rear wheel slip ratio basic value ΔSx-fl. , ΔSx-fr, ΔSx-rl, ΔSx-rr, the front-rear wheel target slip ratio change amount, the left-right distribution coefficient Ky, and the left-right wheel slip ratio basic values ΔSy-fl, ΔSy-fr, ΔSy-r
l, ΔSy-rr and the sum of the left and right wheel target slip ratio change amounts. However, at the time of execution of the second and subsequent times of this step, the target slip ratios Sd-fl, S
d-fr, Sd-rl, and Sd-rr are determined as the sum of the previous value thereof, the current value of the front-rear wheel target slip rate change amount, and the current value of the left-right wheel target slip rate change amount.

Thereafter, in S15 of FIG. 2, it is determined whether or not the brake switch 88 has detected that the brake pedal 14 has been depressed, that is, whether or not the brake pedal 14 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 absolute value of the lateral acceleration Gy (this is the coefficient of the road surface friction coefficient in the present invention)
The front / rear distribution coefficient Kx is continuously changed as the change in the front / rear wheel slip rate basic value ΔSx is obtained as the front / rear wheel slip rate change amount. Therefore, the target slip ratio of each wheel using the sum of the change amount of the front and rear wheel target slip ratio and the change amount of the left and right wheel target slip ratio can be continuously changed as the absolute value of the lateral acceleration Gy changes. The effect that the braking force of each wheel can be smoothly changed in the braking slip control is obtained.

As is apparent from the above description, in the present embodiment, the computers S2 to S6 and S9 in FIG.
Steps 14 through 14 are executed by the " target slip rate change amount determining means.
It constitutes a "stage." In addition, the first actual
At the time of execution, the standard value So functions as the "reference value"
At the time of each execution after the first time, the target slip ratio Sd-
The previous values of fl, Sd-fr, Sd-rl and Sd-rr are "reference values"
It functions as Also, the left and right wheel target slip rates
The change amount is the “first change amount”, the front and rear wheel target slip ratio change amount
Correspond to the “second amount of change”. Ma
The target slip rate change for the left and right wheels is
The target slip ratio change amount for the front and rear wheels is determined.
Because both are determined, both the left and right sides of the vehicle
Is "at least one of the left side and the right side of the vehicle body"
And both the front and rear sides of the
Left side and / or right side "
Because Note that the change amount of the left and right wheel target slip rates is shown in FIG.
The size is the same for both the left and right wheels as shown in
Are determined to be different, and the target slip ratio of the front and rear wheels is also determined.
The amount of change is large for both front and rear wheels as shown in FIG.
Are the same and the signs are different.

In the embodiment described in detail above, 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 an angle 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 are related to the estimated vehicle speed Ve and are values obtained according to the maps of FIGS. 15 and 16. 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 in detail above, the braking force is varied between the left wheels 22, 34 and the right wheels 24, 36, and the cornering between the front wheels 22, 24 and the rear wheels 34, 36 is performed. Although the target slip ratio Sd of each wheel is made variable and the set wheel acceleration Gwo is not changed in order to make the force different, the set wheel acceleration Gwo can also be made variable.

In the embodiment described in detail above, the target slip ratio Sd of each wheel is realized by controlling the braking force by the brake at the time of vehicle braking. Even if the target slip ratio Sd of each wheel is realized by controlling the driving force, the target slip ratio Sd of each wheel is realized by the control of the braking force by the brake and the control of the driving force by the engine or the like. Good. 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 the embodiment of the present invention has been described in detail with reference to the drawings, this is merely an example, and the present invention may be implemented in various modified and improved forms based on the knowledge of those skilled in the art. Of course you can.

[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 in FIG. 3;

FIG. 13 is a graph showing a map stored in a ROM in FIG. 3;

FIG. 14 is a graph showing a map stored in a ROM in FIG. 3;

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 an actual 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 an actual 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 104 Lateral acceleration sensor

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60T 8/32-8/66

Claims (2)

(57) [Claims] An actual slip ratio of wheels provided on the front, rear, left and right sides of a vehicle body is controlled so as to become each target slip ratio .
In the braking force control device that controls the braking force of each wheel, the amount of change from the reference value of the target slip ratio of each wheel is calculated for each vehicle.
The wheel is positioned on at least one of the left and right sides of the vehicle
The first variation associated with placing
Located on at least one of the side and the rear
Determined as the sum with the related second change amount,
One change amount is the target yaw rate of the actual yaw rate of the vehicle body.
Continuously changes as the yaw rate deviation from
And the second variation is determined by the yaw rate
And the actual yaw rate and the friction coefficient of the road surface
Changes continuously as the quantity associated with
A braking force control device characterized in that a target slip ratio change amount determining means for determining the slip rate is provided. 2. The method according to claim 1, wherein the road surface friction coefficient-related amount is a lateral acceleration of the vehicle body.
The braking force control device according to claim 1, further comprising a degree.