JPH09109865A - Braking force control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely stabilize the behavior of a vehicle even when the spin trend becomes excessive, and the value of the slip angle is largely changed. SOLUTION: A final target braking force setting part 18 selects an inside rear wheel as a wheel to be braked when the sign of the actual yaw rate is different from the sign of the yaw rate deviation, and sets the target braking force of the rear wheel calculated by a target braking force calculation part 17 as the final target braking force. On the other hand, the final target braking force setting part selects an outside front wheel as a wheel to be braked when the sign of the actual yaw rate is same as the sign of the yaw rate deviation, and the slip angle is smaller than the preset angle, and the final target braking force is set based on the target braking force of the front wheel calculated by the target braking force calculation part 17. When the slip angle is not less than the preset value, the outside rear wheel is selected as the wheel to be braked, and the final target braking force is set based on the target braking force of the rear wheel calculated by the target braking force calculation part 17.

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 for improving vehicle stability by applying braking force to appropriate wheels when cornering a vehicle.

[0002]

2. Description of the Related Art In recent years, a braking force control device has been developed which applies a braking force to appropriate wheels during cornering to improve vehicle stability in view of the force acting on the vehicle during cornering of the vehicle.

For example, Japanese Patent Application Laid-Open No. 2-70561 discloses a braking force control device which controls a rotational movement about a vertical axis passing through the center of gravity of a vehicle, that is, a yaw rate which is an angular velocity of yawing. In this technology, the target yaw rate is compared with the actual yaw rate (actual yaw rate), and it is determined whether the vehicle motion state is understeer or oversteer with respect to the target yaw rate, so that the actual yaw rate and the target yaw rate match. In the case of understeer tendency, the braking force is applied to the inner wheels to correct it,
In the case of oversteer tendency, the braking force is applied to the outer wheels to correct it, so that the running stability of the vehicle is improved.

[0004]

By the way, in the above-mentioned prior art, when the braking force is applied to the outer wheels due to the oversteering tendency, the spin tendency may be increased if the braking force is applied to the outer rear wheels. It is preferable to apply braking force to the outer front wheels.

However, as the value of the angle (sideslip angle) formed by the movement direction of the vehicle body center of gravity and the longitudinal axis of the vehicle body increases, the value of the yaw moment obtained by the braking force applied to the outer front wheel decreases. Further, when the front wheels are steered in the direction opposite to the cornering direction in order to suppress the spin tendency, a yaw moment is applied in the direction of increasing the spin tendency, which causes a problem of instability.

The present invention has been made in view of the above circumstances. For example, even if a steep steering operation on a low μ road or the like causes an excessive spin tendency and a large change in the slip angle, the vehicle behavior is reliably stabilized. An object is to provide a braking force control device that can generate a yaw moment in a direction.

[0007]

In order to achieve the above object, a braking force control device according to the present invention according to claim 1 is a vehicle speed detecting means for detecting a vehicle speed, a steering angle detecting means for detecting a steering angle, and a vehicle. The actual yaw rate detecting means for detecting the actual yaw rate, the side slip angle detecting means for detecting the side slip angle, the target yaw rate calculating means for calculating the target yaw rate based on the vehicle speed and the steering angle, and the target yaw rate from the actual yaw rate The yaw rate deviation calculating means for subtracting and calculating the yaw rate deviation, the target braking force calculating means for calculating the target braking force of the front wheels and the rear wheels based on the motion state of the vehicle and the yaw rate deviation, and the signs of the actual yaw rate and the yaw rate deviation are When different, the inner rear wheel is selected as the braking wheel, and the rear wheel target braking force calculated by the target braking force calculating means is set as the final target braking force. When the signs of the actual yaw rate and the yaw rate deviation are the same, when the sideslip angle is smaller than the preset angle, the outer front wheel is selected as the braking wheel, and the front wheel target braking force calculated by the target braking force calculating means is calculated. While setting the final target braking force based on the above, when the sideslip angle is equal to or greater than the preset angle, the outer rear wheel is selected as the braking wheel and the rear wheel target braking force calculated by the target braking force calculation means is set as the base. A final target braking force setting means for setting a final target braking force, an output determining means for determining whether or not the control target area is present, and a final target braking force setting when the output determining means determines that the final target braking force is in the control area. Braking signal output means for outputting a signal to the brake drive section so as to apply the final target braking force set to the wheels selected by the means.

In the braking force control device according to the first aspect of the present invention, the vehicle speed detection means determines the vehicle speed, the steering angle detection means determines the steering angle, the actual yaw rate detection means determines the actual yaw rate of the vehicle, that is, the actual yaw rate, and the sideslip angle detection means. To detect the sideslip angle. Further, the target yaw rate calculation means calculates the target yaw rate based on the vehicle speed and the steering angle, the yaw rate deviation calculation means subtracts the target yaw rate from the actual yaw rate to calculate the yaw rate deviation, and the target braking force calculation means calculates the vehicle motion. Target braking forces of the front wheels and the rear wheels are calculated based on the state and the yaw rate deviation. Furthermore, when the signs of the actual yaw rate and the yaw rate deviation are different in the final target braking force setting means,
The inner rear wheel is selected as the braking wheel and the rear wheel target braking force calculated by the target braking force calculation means is set as the final target braking force, and when the actual yaw rate and the yaw rate deviation have the same sign, the sideslip angle is preset. When the angle is smaller than the preset angle, the outer front wheel is selected as the braking wheel, and the final target braking force is set based on the front wheel target braking force calculated by the target braking force calculation means, while the side slip angle is preset. When the angle is equal to or larger than the predetermined angle, the outer rear wheel is selected as the braking wheel, and the final target braking force is set based on the rear wheel target braking force calculated by the target braking force calculation means. Then, when the output determination means determines that the vehicle is in the control region, the braking signal output means outputs a signal to the brake drive section so as to apply the final target braking force set to the wheel selected by the final target braking force setting means. .

A braking force control device according to a second aspect of the present invention is the braking force control device according to the first aspect.
In the final target braking force setting means, when the actual yaw rate and the yaw rate deviation have the same sign, the preset angle used for comparison with the sideslip angle is a line connecting the longitudinal axis of the vehicle body and the center of gravity of the front wheel. The angle formed by and effectively prevents the yaw moment from being applied in the direction of increasing the spin tendency.

Further, the braking force control apparatus according to the present invention according to claim 3 is a vehicle speed detecting means for detecting a vehicle speed, a steering angle detecting means for detecting a steering angle, and an actual yaw rate detecting for detecting an actual yaw rate of the vehicle. Means, a side slip angle detecting means for detecting a side slip angle, a target yaw rate calculating means for calculating a target yaw rate based on the vehicle speed and the steering angle,
A yaw rate deviation calculating means for calculating the yaw rate deviation by subtracting the target yaw rate from the actual yaw rate, a target braking force calculating means for calculating the target braking force of the front wheels and the rear wheels based on the motion state of the vehicle and the yaw rate deviation, and an actual yaw rate. And the sign of the yaw rate deviation are different, the inner rear wheel is selected as the braking wheel, the rear wheel target braking force calculated by the target braking force calculating means is set as the final target braking force, and the signs of the actual yaw rate and the yaw rate deviation are set. If the same, the target braking forces of the front wheels and the rear wheels calculated by the target braking force calculation means are compared with the values corrected according to the sideslip angle, and if the front wheel correction value is smaller than the rear wheel correction value, the outer front wheels are compared. Is selected as the braking wheel and the front wheel correction value is set as the final target braking force, while if the front wheel correction value is greater than or equal to the rear wheel correction value, the outer rear wheel is selected as the braking wheel and the rear wheel correction value is set. Is set as the final target braking force, final target braking force setting means for determining whether or not it is in the control region, and final target braking force setting when the output determination device determines that it is in the control region. Braking signal output means for outputting a signal to the brake drive section so as to apply the final target braking force set to the wheels selected by the means.

In the braking force control apparatus according to the third aspect of the present invention, the vehicle speed detection means determines the vehicle speed, the steering angle detection means determines the steering angle, the actual yaw rate detection means determines the actual yaw rate of the vehicle, that is, the actual yaw rate, and the sideslip angle detection means. To detect the sideslip angle. Further, the target yaw rate calculation means calculates the target yaw rate based on the vehicle speed and the steering angle, the yaw rate deviation calculation means subtracts the target yaw rate from the actual yaw rate to calculate the yaw rate deviation, and the target braking force calculation means calculates the vehicle motion. Target braking forces of the front wheels and the rear wheels are calculated based on the state and the yaw rate deviation. Furthermore, when the signs of the actual yaw rate and the yaw rate deviation are different in the final target braking force setting means,
When the inner rear wheel is selected as the braking wheel and the rear wheel target braking force calculated by the target braking force calculating means is set as the final target braking force, and when the actual yaw rate and the yaw rate deviation have the same sign, the target braking force calculation is performed. Compare the target braking forces of the front and rear wheels calculated by the method with the values corrected according to the sideslip angle, and if the front wheel correction value is smaller than the rear wheel correction value, select the outer front wheel as the braking wheel and set the front wheel correction value. While the final target braking force is set, when the front wheel correction value is equal to or larger than the rear wheel correction value, the outer rear wheel is selected as the braking wheel and the rear wheel correction value is set as the final target braking force. Then, when the output determination means determines that the vehicle is in the control region, the braking signal output means outputs a signal to the brake drive section so as to apply the final target braking force set to the wheel selected by the final target braking force setting means. .

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 9 show Embodiment 1 of the present invention, FIG. 1 is a functional block diagram of a braking force control device, FIG. 2 is an explanatory diagram showing a schematic configuration of the braking force control device, and FIG. 4 is an explanatory view of the operation of the vehicle, FIG. 4 is an explanatory view of correction of the target braking force, FIG. 5 is a flowchart of the braking force control,
6 is a flowchart following FIG. 5, FIG. 7 is a flowchart following FIG. 6, FIG. 8 is a time chart of an example of braking force control, and FIG. 9 is an explanatory diagram of characteristics of the determination threshold value.

In FIG. 2, reference numeral 1 denotes a brake drive unit of a vehicle. The brake drive unit 1 is connected to a master cylinder 3 connected to a brake pedal 2 operated by a driver, so that the driver brakes. When the pedal 2 is operated, the master cylinder 3 causes the four wheels (left front wheel 4fl, right front wheel 4fr,
Left rear wheel 4rl, right rear wheel 4rr) wheel cylinders (left front wheel wheel cylinder 5fl, right front wheel wheel cylinder 5f)
r, the left rear wheel wheel cylinder 5rl, and the right rear wheel wheel cylinder 5rr), brake pressure is introduced to brake and brake the four wheels.

The brake drive unit 1 is a hydraulic unit equipped with a pressure source, a pressure reducing valve, a pressure increasing valve, etc., and each of the wheel cylinders 5fl, 5fr, 5 in response to an input signal.
The brake pressure can be independently introduced to rl and 5rr.

In each of the wheels 4fl, 4fr, 4rl, 4rr, the wheel speeds ω1, ω2, ω3, ω4 are wheel speed sensors (left front wheel speed sensor 6fl, right front wheel speed sensor 6fr, left rear wheel speed sensor 6rl, It is detected by the right rear wheel speed sensor 6rr). In addition, a steering wheel angle sensor 7 for detecting the steering angle θ of the steering wheel is provided on the steering wheel portion of the vehicle.
Is provided.

Reference numeral 10 indicates a control device formed by a microcomputer and its peripheral circuits. The control device 10 includes the wheel speed sensors 6fl, 6fr, 6rl,
6rr and a steering wheel angle sensor 7, a yaw rate sensor 8 as an actual yaw rate detecting means for detecting an actual yaw rate γ, and a lateral acceleration sensor 9 for detecting a lateral acceleration YG are connected, and a drive signal is output to the brake drive unit 1. To do.

The control device 10 is, as shown in FIG.
Vehicle speed calculation unit 11, steering angle calculation unit 12, sideslip angle calculation unit 13, yaw rate steady gain calculation unit 14, target yaw rate calculation unit 15, yaw rate deviation calculation unit 16, target braking force calculation unit 17, final target braking force setting unit 18 , Output determination unit 1
9 and the braking signal output unit 20 are mainly configured.

The vehicle speed calculation unit 11 uses the wheel speeds ω1, ω2, ω from the wheel speed sensors 6fl, 6fr, 6rl, 6rr.
The signals of 3, ω4 are input, and these signals are calculated by preset mathematical expressions (for example, the average value of the speed signals from the wheel speed sensors 6fl, 6fr, 6rl, 6rr is calculated. ) It is formed in a circuit as a vehicle speed detecting means for obtaining the vehicle speed V and outputting it to the side slip angle calculating section 13, the yaw rate steady gain calculating section 14, and the target braking force calculating section 17.

A signal from the steering wheel angle sensor 7 is input to the steering angle calculation unit 12, and the steering wheel angle θ is divided by the steering gear ratio N to obtain the actual steering angle δf (=
θ / N) is calculated and output to the target yaw rate calculation unit 15 and the target braking force calculation unit 17 as a steering angle detection unit.

Further, the side slip angle calculating section 13 includes the actual yaw rate γ from the yaw rate sensor 8, the lateral acceleration YG from the lateral acceleration sensor 9, and the vehicle speed calculating section 11.
Is input to the vehicle speed V from, and is formed in a circuit as a side slip angle detecting means for calculating a side slip angle β based on the following equation, and the calculated side slip angle β is input to the final target braking force setting unit 18. Is output.

Here, the integral of the function f (t) by t is
When expressed by T {f (t)} dt, β = INT {YG / V−γ} dt (1) The sideslip angle β is not limited to the one calculated based on the above formula (1). You may make it detect using the side slip angle sensor etc. which can detect the side slip angle (beta) directly.

Further, the yaw rate steady gain calculating section 14 obtains a yaw rate value (yaw rate steady gain Gγδf (0)) with respect to the actual steering angle δf when the vehicle makes a steady circle turn, based on a preset equation. The calculated yaw rate steady-state gain Gγδf (0) is output to the target yaw rate calculation unit 15 and the target braking force calculation unit 17. Here, assuming that the wheel base is L and the stability factor determined by the specifications of the vehicle is A0, the yaw rate steady-state gain Gγδf (0) is calculated by the following equation. Gγδf (0) = {1 / (1 + A0 · V 2)} · (V / L) ... (2) In addition, the stability factor A0 is a vehicle mass m, the distance between the front shaft and the center of gravity Lf, after The distance between the shaft and the center of gravity is Lr, and the equivalent cornering power of the front tire is CP
f and the equivalent cornering power of the rear tire are CPr, they are calculated by the following equation. A0 = {- m · (Lf · CPf -Lr · CPr)} / (2 · L 2 · CPf · CPr) ... (3) Further, the target yaw rate calculating section 15, the real from the steering angle calculator 12 The steering angle δf and the yaw rate steady gain Gγδf from the yaw rate steady gain calculation unit 14
Based on (0), the target yaw rate γ ′ is calculated in consideration of the response delay of the vehicle, and the target yaw rate γ ′ is output to the yaw rate deviation calculation section 16 in a circuit.
That is, the target yaw rate calculating means includes the steady yaw rate gain calculating section 14 and the target yaw rate calculating section 1.
5 are formed. The target yaw rate γ ′ can be calculated by γ ′ = {1 / (1 + T · s)} · Gγδf (0) · δf (4) where T is the time constant and s is the Laplace operator. The above equation (4) is an equation in which the response delay of the vehicle expressed by a secondary system is approximated to a primary system, and T is a time constant, which is obtained by the following equation, for example. T = (mLfV) / (2LCPr) (5) Further, in the yaw rate deviation calculation unit 16, the target yaw rate calculation unit 15 calculates the actual yaw rate γ detected by the yaw rate sensor 8. The obtained target yaw rate γ'is subtracted to obtain a yaw rate deviation Δγ (= γ-γ '), and this yaw rate deviation Δγ is supplied to the target braking force calculation unit 17, the final target braking force setting unit 18, and the output determination unit 19. It is a circuit as an output yaw rate deviation calculation means.

Further, the target braking force calculation unit 17 considers the vehicle specifications, and based on the vehicle motion state and the yaw rate deviation, the target braking force of the front and rear wheels (the front wheel target hydraulic pressure BF1f, the rear wheel target hydraulic pressure). The target hydraulic pressures BF1f and BF1r calculated by the circuit as the target braking force calculating means for calculating the pressure BF1r) are
It is output to the final target braking force setting unit 18. The target hydraulic pressures BF1f and BF1r are calculated, for example, by the following equation. BF1f = G1 · (ΔA · 4 · L 2 · CPf · CPr · V) / {(CPf + CPr) / df} · γ ... (6) BF1r = G1 · (ΔA · 4 · L 2 · CPf · CPr · V ) / {(CPf + CPr) / dr} γ (7) where G 1 is the gain, df is the front tread, dr
Indicates a rear tread, and ΔA is ΔA = {δf / (Gγδf (0) · δf + Δγ) -1 / Gγδf (0)} / (L · V) (8). In addition, especially on low μ roads, etc. to prevent the rear wheel from slipping due to braking force on the rear wheel and losing stability, or when braking force is applied to the rear wheel, turning is against the driver's intention. In order to prevent the moment from feeling strong and unstable, the rear wheel target hydraulic pressure BF1r is reduced to a smaller value by multiplying the value obtained by the equation (7) with a gain larger than 0 and smaller than 1. Also good.

Further, the final target braking force setting unit 18 is
From the combination of the sign of the actual yaw rate γ and the sign of the yaw rate deviation Δγ, the motion state of the vehicle, that is, approximately straight traveling, left turning,
Either right turn, the target yaw rate γ'and the actual yaw rate γ substantially match, the target yaw rate γ'understeer tendency, the target yaw rate γ '
Against any of the states of oversteer tendency, and when there is an oversteer tendency, further, with respect to the slipping state of the vehicle, the sideslip angle β is compared with a preset angle to make a determination, and Depending on the state, the wheel to which the braking force is applied is selected, and the front and rear wheel target hydraulic pressures BF1f and BF1r from the target braking force calculation unit 17 are corrected as they are or based on the side slip angle β (front wheel). Correction value BF2f, rear wheel correction value BF2r), and final target braking force (right front wheel final target hydraulic pressure BFR, left front wheel final target hydraulic pressure B)
FL, right rear wheel final target hydraulic pressure BRR, left rear wheel final target hydraulic pressure BRL), which is output to the braking signal output unit 20 as a final target braking force setting means.

During an oversteer tendency, the value of the yaw moment obtained by the braking force applied to the outer front wheel decreases as the value of the sideslip angle β increases. Further, when the front wheels are steered in the direction opposite to the cornering direction in order to suppress the tendency of spin, the braking force no longer acts as a yaw moment. Therefore, in the first embodiment of the present invention, the final target braking force setting unit 1
When it is determined to be oversteer tendency in 8, the angle set in advance, that is, the angle θF formed by the longitudinal axis of the vehicle body and the line connecting the front center wheel and the center of gravity is set as the yaw moment by the braking force by one front wheel. The angle at which it does not substantially act, and this angle θF is compared with the sideslip angle β to select the braking wheel,
By setting the braking force, it is possible to always generate a yaw moment in a direction that always stabilizes the vehicle behavior even in the case of an oversteer tendency.

The setting of the final target braking forces BFR, BFL, BRR, BRL in the final target braking force setting section 18 is as follows.
The combination is as follows. The signs of the actual yaw rate γ and the target yaw rate γ ′ are both given by + for the left turning direction and − for the right turning direction of the vehicle. Further, in order to determine the straight traveling state of the vehicle, ε is set as a positive number close to 0 obtained in advance by experiments or calculations, and the state where the actual yaw rate of the vehicle substantially matches the target yaw rate γ ′ is set. In order to make a determination, εΔγ is set as a positive number close to 0, which is obtained in advance from experiments or calculations, and (Case 1). γ> ε, Δγ <-εΔγ ... When there is an understeer tendency with respect to the target yaw rate γ'in the left turning state ...
Left rear wheel braking, BRL = BF1f (Case 2a). [gamma]> [epsilon], [Delta] [gamma]> [epsilon] [Delta] [gamma], [theta] F> [beta] ... When the vehicle is in a left-turning state and there is an oversteer tendency with respect to the target yaw rate γ '. γ> ε, Δγ> εΔγ, θF ≤β ... When the vehicle is in the left-turning state and there is an oversteer tendency with respect to the target yaw rate γ '... Rear wheel braking generates a yaw moment ... Right rear wheel braking, BRR = BF2r (Case 3a). γ <ε, Δγ <−εΔγ, θF> β ...
When there is an oversteering tendency with respect to the target yaw rate γ'in the right turning state ... A yaw moment is generated by front wheel braking ... Left front wheel braking, BFL = BF2f (Case 3b). γ <ε, Δγ <−εΔγ, θF ≦ β ...
When there is an oversteer tendency with respect to the target yaw rate γ'in the right turning state ... A yaw moment is generated by rear wheel braking ... Left rear wheel braking, BRL = BF2r (Case 4). γ <ε, Δγ> εΔγ ... When the vehicle is turning right and there is an understeer tendency with respect to the target yaw rate γ '... Right rear wheel braking, BRR = BF1r (case 5). │γ│ <ε ... Almost straight ahead, or |
Δγ | ≦ εΔγ ... When the actual yaw rate γ of the vehicle substantially matches the target yaw rate γ ′, no braking wheel is selected and no braking is performed (FIG. 3).

That is, in (Case 5), when the vehicle is in a substantially straight traveling state determined by | γ | <ε, and when the actual yaw rate γ of the vehicle determined by | Δγ | ≦ εΔγ substantially matches the target yaw rate γ '. When the signs of the actual yaw rate γ and the yaw rate deviation Δγ are different in the range of the actual yaw rate γ and the yaw rate deviation Δγ other than the above, the inner rear wheel is selected as the braking wheel and the rear wheel target braking force BF1r is set as the final target control of the rear wheel. When set as power (BRR or BRL) and the signs of the actual yaw rate γ and the yaw rate deviation Δγ are the same,
When the sideslip angle β is smaller than the preset angle θ F, the outer front wheel is selected as the braking wheel and the front wheel correction value BF2
While f is set as the final target braking force (BFR or BFL) of the front wheels, the outer rear wheel is selected as the braking wheel and the rear wheel correction value BF2r is set to the rear if the sideslip angle β is equal to or greater than the preset angle θF. It is set as the final target braking force of the wheel (BRR or BRL).

The front wheel correction value BF2f and the rear wheel correction value BF2r are calculated, for example, based on the following equations. The angle between the line connecting the vehicle longitudinal axis and after one wheel and the center of gravity as θR, BF2f = (df / 2 ) / {sin (θF -β) · (df 2/4 + Lf 2) 1/2} · BF1f (9) However, θF> β.

[0029] BF2r = (dr / 2) / {sin (θR + β) · (dr 2/4 + Lr 2) 1/2} · BF1r ... (10) Further, the above (9), (10) is, P = When the df / 2 Q = sin (θF -β) · (df 2/4 + Lf 2) 1/2 R = dr / 2 S = sin (θR + β) · (dr 2/4 + Lr 2) 1/2 to, BF2f = P / Q · BF1f (11) BF2r = R / S · BF1r (12) and the front wheel correction value BF2f and the rear wheel correction value BF2r are
As shown in FIGS. 4 (a) and 4 (b), the target is set so that the yaw moment that is supposed to be originally generated by braking of one side wheel is set with reference to the actual moving direction of the vehicle (including the side slip angle β). The braking forces BF1f and BF1r are corrected. By adding the correction in this way, for example, low μ
Even if a vehicle body slips due to steering on a road or the like, an optimum yaw moment can always be applied to the vehicle.

The output determination unit 19 determines the yaw rate deviation Δ
A determination threshold εΔ for determining whether γ is in the control region is set as described below, and the determination threshold εΔ and the yaw rate deviation Δ are set.
It is formed in a circuit as an output judging means for comparing with γ and judging whether or not it is in the control region and outputting it to the braking signal output section 20.

A first threshold value εΔM is usually set as the judgment threshold value εΔ, and a set time (preliminarily set in a timer in advance after the vehicle behavior shifts from the understeer tendency to the oversteer tendency). Time), or even if within this time, after the tendency to oversteer,
Until the value of either the yaw rate deviation or the actual yaw rate becomes approximately zero, the second threshold value εΔS is set to the above determination threshold value εΔ
Is set as. Here, the first threshold ε
Both ΔM and the second threshold εΔS are positive numbers previously obtained from experiments or calculations, and the yaw rate deviation Δγ
The magnitude of each threshold for determining is εΔM> εΔS ≧ εΔγ
It is.

As shown in FIG. 9, the first threshold value εΔM and the second threshold value εΔS can be set at a variable value in a memory table or the like according to the vehicle speed. Accordingly, a more appropriate value can be set as the determination threshold value εΔ. In other words, when the vehicle speed is low, compared to when it is high, even if the vehicle behavior becomes unstable, the driver can easily correct it and control is not required, so the non-control area is set to a large range. it can.
Therefore, as shown in FIG. 9A, the first threshold value ε
Both ΔM and the second threshold εΔS may be set smaller as the speed increases, and as shown in FIG. 9B, the second threshold εΔS may be set to be constant and the first threshold The threshold εΔM may be set smaller as the speed increases, and as shown in FIG. 9 (c), the first threshold εΔM is kept constant and the second threshold εΔS is increased in speed. Therefore, it may be set to a smaller value.

The braking signal output unit 20 sets the braking wheel selected by the braking wheel discrimination unit 18 to the brake driving unit 1 based on the determination signal of the control region by the output determination unit 19. Final target braking force (BFR, BFL, BR
It is a circuit as a braking signal output means for outputting a signal so as to add either R or BRL).

Next, the braking force control according to the first embodiment of the present invention will be described with reference to the flow charts of FIGS. This braking force control program is executed, for example, every predetermined time (for example, 10 ms) while the vehicle is running, and when the program starts, at step (hereinafter abbreviated as S) 101, the steering wheel steering angle θ from the steering wheel angle sensor 7, Wheel speeds ω1, ω2, ω3, ω4 from each wheel speed sensor 6fl, 6fr, 6rl, 6rr
, The actual yaw rate γ is read from the yaw rate sensor 8 and the lateral acceleration YG is read from the lateral acceleration sensor 9, and the process proceeds to S102.

In step S102, the steering angle calculator 12 calculates the actual steering angle δf (= θ / N) from the steering wheel angle θ, and the vehicle speed detector 11 calculates the wheel speeds ω1, ω2, ω3, ω.
4, the vehicle speed V is calculated, the yaw rate steady-state gain calculating unit 14 further calculates the yaw rate steady-state gain Gγδf (0) by the equation (2), and further the side slip angle β by the equation (1).

Next, in S103, the target yaw rate calculating unit 15 calculates the target yaw rate γ'from the equation (4), and in S104, the yaw rate deviation calculating unit 16
The yaw rate deviation Δγ (= γ−γ ′) is calculated at S1, and S1
In 05, the target braking force calculation unit 17 performs the above (6),
Based on the equation (7), the front wheel target hydraulic pressure BF1f and the rear wheel target hydraulic pressure BF1r are calculated, and the routine proceeds to S106.

In the following, steps S106 to S128 are procedures performed by the final target braking force setting section 18. First, in step S106, it is determined whether or not the actual yaw rate γ is larger than ε, that is, whether or not the vehicle is in a leftward turning state to some extent. If the actual yaw rate γ is equal to or less than ε, the process proceeds to S107, and it is determined whether the actual yaw rate γ is smaller than −ε, that is, whether or not the state is a right turning state that is somewhat large. . In this S107, the range of the actual yaw rate γ (ε ≧ γ ≧ −ε) which is determined not to be a large right turn state
Then, since the motion state is a substantially straight-ahead motion state, the process proceeds to S128, and the braking wheel is not selected and the braking is not performed. If it is determined in step S106 that γ> ε and the vehicle is in a left-turning state that is relatively large, the process proceeds to step S108, in which the yaw rate deviation Δγ is |
It is close to 0 when Δγ | ≦ εΔγ, and it is determined whether or not the actual yaw rate γ substantially matches the target yaw rate γ ′.

Then, in step S108, | Δγ | ≦ εΔ
γ, and if it is determined that the actual yaw rate γ substantially matches the target yaw rate γ ′, the process proceeds to S128, and in other cases (understeer tendency or oversteer tendency), the process proceeds to S109.

This step S109 is a step of determining whether there is an understeer tendency or an oversteer tendency.
<-ΕΔγ or Δγ> εΔγ is determined, and Δγ <
-ΕΔγ and the sign of the yaw rate deviation Δγ is negative and different from the sign of the actual yaw rate γ, the target yaw rate γ ′
Is determined to be understeer, the process proceeds to S110, the left rear wheel 4rl is selected as a braking wheel, and the rear wheel target hydraulic pressure BF1r obtained in S105 is set to the left rear wheel final target hydraulic pressure BR.
Set as L (BRL = BF1r). On the other hand, Δγ>
If εΔγ and the sign of the yaw rate deviation Δγ is the same positive as the sign of the actual yaw rate γ, it is determined that the target yaw rate γ ′ is oversteer, and the process proceeds to S113.

Then, in S113, the preset angle θF is compared with the side slip angle β, and when the side slip angle β is smaller than the angle θF (θF> β).
Advances to S114, the front wheel correction value BF2f is calculated based on the equation (9), the right front wheel 4fr is selected as the braking wheel in S115, and the front wheel correction value BF2f is set as the right front wheel final target hydraulic pressure BFR. (BFR = BF2f).

As a result of the comparison in S113, if the sideslip angle β is equal to or more than the angle θF (θF ≦ β), S1
16, the rear wheel correction value BF is calculated based on the equation (10).
2r is calculated, the right rear wheel 4rr is selected as a braking wheel in S117, and the rear wheel correction value BF2r is set to the right rear wheel final target hydraulic pressure B.
Set as RR (BRR = BF2r).

On the other hand, if it is determined in step S107 that γ <-ε and the vehicle is in the right turning state to some extent, the process proceeds to step S118.
It is determined whether the yaw rate deviation Δγ is close to 0 when | Δγ | ≦ εΔγ and the actual yaw rate γ substantially matches the target yaw rate γ ′.

Then, in step S118, | Δγ | ≦ εΔ
γ, and if it is determined that the actual yaw rate γ substantially matches the target yaw rate γ ′, the process proceeds to S128, and in other cases (understeer tendency or oversteer tendency), the process proceeds to S119.

This S119 is a step of determining whether the tendency is understeer or oversteer.
> ΕΔγ or Δγ <−εΔγ is determined, and Δγ>
If εΔγ and the sign of the yaw rate deviation Δγ is positive and different from the sign of the actual yaw rate γ, it is determined that there is an understeer tendency with respect to the target yaw rate γ ′, and the process proceeds to S120.
The right rear wheel 4rr is selected as a braking wheel, and the rear wheel target hydraulic pressure BF1r obtained in S105 is set as the right rear wheel final target hydraulic pressure BRR (BRR = BF1r). On the other hand, Δγ <−ε
If Δγ and the sign of the yaw rate deviation Δγ are the same negative as the sign of the actual yaw rate γ, it is determined that the target yaw rate γ ′ is oversteer and the process proceeds to S123.

Then, the flow proceeds to S123, where the angle θF
Is compared with the sideslip angle β. If the sideslip angle β is smaller than the angle θF (θF> β), the process proceeds to S124, where the front wheel correction value BF2f is calculated based on the equation (9), and in S125. The left front wheel 4fl is selected as a braking wheel, and the front wheel correction value BF2f is set as the left front wheel final target hydraulic pressure BFL (BFL = BF2f).

As a result of the comparison in S123, if the sideslip angle β is equal to or more than the angle θF (θF ≦ β), S1
26, the rear wheel correction value BF is calculated based on the equation (10).
2r is calculated, the left rear wheel 4rl is selected as the braking wheel in S127, and the rear wheel correction value BF2r is set to the left rear wheel final target hydraulic pressure B.
Set as RL (BRL = BF2r).

Further, when the process proceeds from S107, S108 or S118 to S128, no braking wheel is selected and no braking is performed.

Then, the above S110 or S120
If the processing with the understeer tendency (selection of braking wheel and setting of hydraulic pressure) is performed, the procedure proceeds to S129, and the above S1 is performed.
When the processing in the oversteering tendency (selection of braking wheel and setting of hydraulic pressure) is performed in 15, S117, S125 or S127, the process proceeds to S130, and the process proceeds from S128 to S131.

In step S110 or S120, understeer tendency processing (selection of braking wheel and setting of hydraulic pressure) is performed, and when the processing proceeds to step S129, an understeer state passage flag FUS is set (FUS ← 1) and step S132. And the first threshold value εΔM is set as the determination threshold value εΔ, and S1 is set.
Proceed to 36. This understeer state passing flag FUS
Is a flag that indicates that the vehicle is operating in the understeer tendency, and is a flag that is cleared (FUS ← 0) when a predetermined time has elapsed after shifting to the oversteer tendency or when the oversteer tendency changes to the neutral steer tendency. Is.

Further, the above S115, S117, S125
Alternatively, in S127, processing for oversteering tendency (selection of braking wheel and setting of hydraulic pressure) is performed, and when proceeding to S130, it is determined whether or not the understeer state passage flag FUS is set (FUS = 1). If the understeer state passage flag FUS is set and it is determined that the understeer tendency operation was performed before, the process proceeds to S133, and if the understeer state passage flag FUS is cleared, the process jumps to S136. Generally, when the road surface friction coefficient is low, the vehicle is in an understeer tendency state. However, when the understeer tendency is changed to the oversteer tendency by the main braking force control, the understeer state passage flag FUS is set. Cage,
With S130, the process proceeds to S133. But,
If the understeer tendency is not obtained and the oversteer tendency is obtained for some reason, the procedure jumps to S136 without performing the steps S133 to S135.

In the above S130, it is determined that FUS = 1, and S1
At step 33, the timer start flag FTR is cleared (F
It is determined whether or not TR = 0). The timer start flag FTR is a flag that is set (FTR ← 1) when the threshold setting timer is started and cleared (FTR ← 0) when the threshold setting timer is stopped.

S133, timer start flag FTR
Is cleared (FTR = 0) and it is determined that the threshold setting timer is stopped, the process proceeds to S134 to start the threshold setting timer, starts the threshold setting timer, and starts the timer start flag FTR.
Is set, the process proceeds to S135, the second threshold εΔS is set as the determination threshold εΔ, and the process proceeds to S136.

If it is determined in step S133 that the timer start flag FTR is set (FTR = 1) and the threshold value setting timer is operating, the process jumps to step S136.

FUS is determined in the above S132 and S130.
= 0, FTR = 1 in the determination of S133, and if any of the above S135 proceeds to S136, the yaw rate deviation Δγ is compared with the determination threshold εΔ (comparison of absolute values), and the yaw rate deviation Δγ is set in the control region. If there is (| Δγ |> ε
In step S137, the braking signal output unit 20 outputs a signal to the brake driving unit 1.

That is, when it is determined in S136 that it is in the control region, and when S110 through S129, the brake drive unit 1 causes the wheel cylinder 5rl to generate a braking force corresponding to the hydraulic pressure BRL = BF1r. When the process from S120 to S129 is performed, the brake drive unit 1 causes the wheel cylinder 5rr to generate a braking force corresponding to the hydraulic pressure BRR = BF1r.
When 115 is passed through S130, the brake drive unit 1 applies hydraulic pressure BFR = B to the wheel cylinder 5fr.
When the braking force corresponding to F2f is generated and the process from S117 to S130 is performed, the brake driving unit 1 causes the wheel cylinder 5rr to generate a braking force corresponding to the hydraulic pressure BRR = BF2r, and from S125 described above. S13
If 0, the brake drive unit 1 causes the wheel cylinder 5fl to generate a braking force corresponding to the hydraulic pressure BFL = BF2f, and if S127 to S130, the brake drive unit 1 outputs the brake force. For 5 rl, a braking force corresponding to the hydraulic pressure BRL = BF2r is generated.

On the other hand, in S136, the yaw rate deviation Δγ
Is in the non-control area (| Δγ | ≦ εΔ), S13
Proceed to 8.

Further, when the routine proceeds from S128 to S131, the straight traveling / steady traveling state flag FNS indicating that the vehicle is in a substantially straight traveling state or the actual yaw rate γ substantially matches the target yaw rate γ'is set (FNS ← 1). And S138
Proceed to.

Then, the above S131 or S13 is performed.
When the routine proceeds from S6 to S138, the braking signal is not output and the set hydraulic pressure is cleared. That is, the above S13
7 or S138 is a process performed by the braking signal output unit 20.

After that, proceeding to S139, it is determined whether or not the timer start flag FTR is set (whether or not the threshold setting timer is operating).

In step S139, the timer start flag FTR is cleared, and if the threshold value setting timer is not operating, the process proceeds to step S145 to clear the straight / steady running state flag FNS and exit the program to start the timer. When the flag FTR is set and the threshold setting timer is operating, the process proceeds to S140, and it is determined whether or not a fixed time has elapsed.

If it is determined in S140 that the fixed time has elapsed, the process proceeds to S142, the understeer state passage flag FUS is cleared, the first threshold εΔM is set as the determination threshold εΔ in S143, and the threshold setting timer is set in S144. Stop, the timer start flag FTR is cleared, the straight / steady running state flag FNS is cleared in S145, and the program exits.

If it is determined in S140 that the fixed time has not elapsed, the process proceeds to S141, in which it is determined whether the straight traveling / steady running state flag FNS is set (FNS = 1).

Then, the straight traveling / steady running state flag F is set.
If NS is cleared (FNS = 0), exit the program. If set, proceed to S142, clear the understeer state passage flag FUS, and set the first threshold εΔM as the determination threshold εΔ in S143. And then S14
In step 4, the threshold setting timer is stopped, the timer start flag FTR is cleared, and in step S145, the straight / steady running state flag FNS is cleared and the program exits.

That is, even before the time for the threshold value setting timer expires, if the vehicle is in the straight traveling / steady running state, the first threshold value εΔM is set as the determination threshold value εΔ.

Next, FIG. 8 shows an example of the control performed in the flow charts of FIGS. This figure shows an example of the case where a vehicle that has been traveling straight from t0 turns left at t1. Fig. 8 (a) shows changes in the target yaw rate γ'and the actual yaw rate γ, and Fig. 8 (b) shows The change in the yaw rate deviation Δγ is shown in FIG.
8 (d) shows the setting of the timer start flag FTR in the control, FIG. 8 (e) shows the setting of the understeer state passing flag FUS in the control, and FIG. 8 (f) shows the braking signal output section. 20 shows ON-OFF of the braking signal output from 20 respectively.

After t1, the actual yaw rate γ also increases following the gradually increasing target yaw rate γ ′, but the difference between the actual yaw rate γ and the target yaw rate γ ′ gradually increases, and the target yaw rate γ ′ from the actual yaw rate γ is increased. The difference between
That is, the yaw rate deviation Δγ is an absolute value | Δ in the negative direction.
γ | increases.

The absolute value | Δγ | of the yaw rate deviation Δγ is
From t2, the actual yaw rate γ becomes larger than the threshold value εΔγ for discriminating when the actual yaw rate γ'is substantially in agreement with the target yaw rate γ '. Further, the straight traveling / steady running state flag FNS which has been set up to t2 is cleared from t2. further,
Determination threshold εΔ in the non-control area (hatched range in FIG. 8B)
The first threshold value εΔM is set as, and the braking signal is not output until the absolute value | Δγ | of the yaw rate deviation Δγ becomes t3 which is larger than the determination threshold value εΔ.

Then, after t3, the yaw rate deviation Δ
The braking signal is output until the absolute value .vertline..DELTA..gamma. of .gamma. becomes t4 which is smaller than the determination threshold value .epsilon..DELTA .. The output of this braking signal is γ> ε (positive sign, left turn), Δ
γ <−εΔγ (negative sign, understeer tendency), which is the case of (Case 1) in FIG. 3, and in this case 1, the braking force is applied to the left rear wheel 4rl to correct it by adding the moment of the arrow, and drift. Eliminate out. In this state, for example, even when the left rear wheel 4rl is excessively braked and the left rear wheel 4rl shows a locking tendency, and the lateral force is lost, the vehicle is in the oversteer direction and the original control is performed. A yaw rate in the same direction as the law (arrow direction) can be generated.

Since the actual yaw rate γ approaches the target yaw rate γ'and there is an understeer tendency between t4 and t5, the absolute value | Δγ | of the yaw rate deviation Δγ is smaller than the judgment threshold value εΔ and is in the non-control area. , The braking signal is not output. Further, between t5 and t6, the absolute value | Δγ | of the yaw rate deviation Δγ becomes smaller than the threshold value εΔγ, the actual yaw rate γ substantially matches the target yaw rate γ ', and the straight traveling / steady running state flag FNS is set. To be done.

Then, when the absolute value | Δγ | of the yaw rate deviation Δγ increases in the positive direction and t6 elapses and the yaw rate deviation Δγ becomes oversteer with respect to the target yaw rate γ ', the vehicle goes straight ahead.
The steady running state flag FNS is not set, the timer start flag FTR is set, the threshold setting timer is operated, and the second threshold εΔS whose absolute value is smaller than the first threshold εΔM is set as the determination threshold εΔ. It

Thereafter, until t7, the yaw rate deviation Δγ
Since the absolute value | Δγ | of is a value equal to or smaller than the determination threshold value εΔ, the braking signal is not output, and the braking signal is output after t7. The output of this braking signal is γ> ε
(Positive sign, left turn), Δγ> εΔγ (positive sign, oversteer tendency), and when the sideslip angle β is smaller than a preset angle θ F, (case 2 in FIG.
a), and in this case 2a, the right front wheel 4
The braking force is added to fr and the moment of the arrow is added to correct it, and the spin is eliminated. In this state, even if the right front wheel 4fr is excessively braked and the right front wheel 4fr shows a locking tendency, and the lateral force is lost, the vehicle is in the understeer direction and the same direction as the original control law (arrow Direction) yaw rate can be generated. In addition, when the sideslip angle β becomes equal to or more than the angle θF, (case 2 in FIG.
In the case 2b, in the case 2b, the right rear wheel 4 capable of effectively generating a yaw moment from the right front wheel 4fr.
The braking force is added to rr and the moment of the arrow is added to correct it, and the spin is eliminated.

From t8, the absolute value | Δγ | of the yaw rate deviation Δγ is smaller than the judgment threshold value εΔ and is in the non-control region, and before the threshold setting timer expires, t9.
Therefore, the actual yaw rate γ substantially matches the target yaw rate γ '.

Therefore, at time t9, the straight / steady running state flag FNS is set, the understeer state passing flag FUS is cleared, the threshold setting timer is stopped, and the timer start flag FTR is cleared. Also,
A first threshold εΔM is set as the determination threshold εΔ.

Thereafter, between t10 and t11, the absolute value | Δγ | of the yaw rate deviation Δγ is again the threshold value ε from t10.
It becomes larger than Δγ, the straight traveling / steady running state flag FNS is cleared, the steering becomes understeer with respect to the target yaw rate γ ', and the understeer state passing flag FUS is set.

Then, from t11, the yaw rate deviation Δγ
Absolute value | Δγ | becomes smaller than the threshold value εΔγ, and the actual yaw rate γ substantially matches the target yaw rate γ ′ (the straight traveling / steady running state flag FNS is also set).
Here, the understeer state passage flag FUS remains set, but in general, before the vehicle becomes oversteer, there is no problem because it goes through an understeer tendency.

After t8, the absolute value | Δγ | of the yaw rate deviation Δγ is smaller than the judgment threshold value εΔ and is in the non-control region, so that the braking signal is not output.

That is, in the output determination section 19, from the time when the oversteer tendency is generated after the understeer tendency to the set time, or until the control in the oversteer tendency is completed even if the set time has not elapsed. ,
Since the second threshold εΔS, whose absolute value is smaller than the first threshold εΔM, is set as the determination threshold εΔ, the control starts faster when the oversteer tendency occurs after the understeer tendency (Fig. As indicated by the chain double-dashed line in Fig. 8, in the conventional control, the control starts at the time of the oversteer tendency after the understeer tendency is t7 '). Therefore, the actual yaw rate γ and the target yaw rate γ '
Does not increase after the tendency to oversteer, the actual yaw rate can be quickly converged to the target yaw rate γ ', the driver does not feel discomfort, and smooth control can be performed. It is possible.
Further, when shifting from an understeer tendency to an oversteer tendency, a large non-control area is set for an understeer tendency in which braking force control by the rear wheels is performed, and a small non-control area is set for an oversteer tendency in which braking force control by the front wheels is performed. Therefore, the braking force control by the rear wheels is suppressed. Furthermore, as the determination threshold value εΔ, the return from the second threshold value εΔS to the first threshold value εΔM is surely performed by the timer and the detection of the control end due to the oversteer tendency. In addition, the actual yaw rate γ is used to determine the turning direction of the vehicle, and the actual yaw rate γ and the yaw rate deviation Δγ are used to reliably determine whether the running state is understeer or oversteer with respect to the target yaw rate γ '. In the case of a tendency, drift-out and spin can be reliably prevented by selecting the most appropriate wheel to be braked among the four wheels in consideration of the sideslip angle β of the vehicle. That is, during a spin tendency, the yaw moment can be generated in a direction that reliably stabilizes the vehicle behavior even if the spin tendency becomes excessive due to sudden steering on a low μ road or the like, and the value of the slip angle changes significantly. Further, when the vehicle tends to drift out, braking force is applied to the front wheels to prevent the drift out from increasing.

Next, FIGS. 10 and 11 show the second embodiment of the present invention, FIG. 10 is an explanatory view of the operation of the vehicle by the braking force control, and FIG. 11 is a flowchart of the braking force control. In the second embodiment of the present invention, in the final target braking force setting unit 18 described in the first embodiment of the present invention, the actual yaw rate γ and the yaw rate deviation Δγ have the same sign, and the side slip angle β is preset. When the angle is smaller than the preset angle θ F, first, the front wheel correction value BF2f and the rear wheel correction value BF2r
Then, the front wheel correction value BF2f is compared with the rear wheel correction value B
When it is smaller than F2r, the outer front wheel is selected as the braking wheel and the front wheel correction value BF2f is set as the final target braking force. On the other hand, when the front wheel correction value BF2f is the rear wheel correction value BF2r or more, the outer rear wheel is selected as the braking wheel. Rear wheel correction value BF2r
Is set as the final target braking force.

When the side slip angle β is larger than the angle θF, the outer rear wheel is selected as the braking wheel, and the rear wheel correction value BF2r is calculated and set as the final target braking force.

Therefore, the final target braking force setting unit 18 determines, based on the combination of the signs of the actual yaw rate γ and the yaw rate deviation Δγ, the motion state of the vehicle, that is, one of substantially straight, left turn, and right turn, and the target. Determine whether the yaw rate γ'and the actual yaw rate γ substantially match, the state of understeer tendency to the target yaw rate γ ', or the state of oversteer tendency to the target yaw rate γ',
Further, when there is an oversteer tendency and the sideslip angle β is smaller than the preset angle θF, based on the front wheel target braking force BF1f and the rear wheel target braking force BF1r calculated by the target braking force calculation unit 17. , The front wheel correction value BF2f and the rear wheel correction value BF2r corrected according to the side slip angle β are calculated, and the front wheel correction value BF2f and the rear wheel correction value BF2r are compared and determined, and the braking force is changed according to each state. To which the final target braking force (the right front wheel final target hydraulic pressure BF is set) is selected.
R, left front wheel final target hydraulic pressure BFL, right rear wheel final target hydraulic pressure B
RR, left rear wheel final target hydraulic pressure BRL), and when the sideslip angle β is larger than the above angle θF, the outer rear wheel is selected as the wheel to apply the braking force, and the rear wheel target braking force BF1r is used as the basis. The rear wheel correction value BF2r corrected according to the side slip angle β is calculated, set as the final target braking force, and output to the braking signal output unit 20.

The front wheel correction value BF2f and the rear wheel correction value BF
2r is obtained by the equations (9) and (10).

During oversteering, as the value of the sideslip angle β increases, the value of the yaw moment obtained by the braking force applied to the outer front wheels decreases, so the braking force to be applied to the front wheels must be set large. I will have to do it. Therefore, in the second embodiment of the present invention, when the final target braking force setting unit 18 determines that there is an oversteer tendency, the outside front wheel and the outside wheel are arranged so that the yaw moment can be efficiently and reliably generated with a small braking force. The rear wheels are compared by the braking force, and the outer wheel having the smaller braking force is selected as the braking wheel to set the braking force.

Each final target braking force BFR, BFL, B in the final target braking force setting section 18 of the second embodiment of the present invention.
The RR and BRL are set by the following combinations. (Case 1). γ> ε, Δγ <-εΔγ ... When there is an understeer tendency with respect to the target yaw rate γ'in the left turning state ...
Left rear wheel braking, BRL = BF1f (Case 2a). γ> ε, Δγ> εΔγ, BF2f <B
F2r, θF> β ... When the vehicle is overturned to the target yaw rate γ'in the left turning state ... A yaw moment is generated by front wheel braking ... Right front wheel braking, BFR = BF2f (case 2b). γ> ε, Δγ> εΔγ, BF2f ≧ B
F2r, or θF ≤ β ... When the vehicle is overturned to the target yaw rate γ'in the left turning state ... A yaw moment is generated by rear wheel braking ... Right rear wheel braking, BRR = BF2r (case 3a). γ <ε, Δγ <−εΔγ, BF2f <
BF2r, θF> β ... Target yaw rate γ'when turning right
On the other hand, when there is an oversteer tendency ... A yaw moment is generated by front wheel braking ... Left front wheel braking, BFL = BF2f (Case 3b). γ <ε, Δγ <−εΔγ, BF2f ≧
BF2r, or θF ≤ β ... When the vehicle is turning right and oversteer tends to the target yaw rate γ '... Yaw moment is generated by rear wheel braking ... Left rear wheel braking, BRL = BF2r (Case 4). γ <ε, Δγ> εΔγ ... When the vehicle is turning right and there is an understeer tendency with respect to the target yaw rate γ '... Right rear wheel braking, BRR = BF1r (case 5). │γ│ <ε ... Almost straight ahead, or |
Δγ | ≦ εΔγ ... When the actual yaw rate γ of the vehicle substantially matches the target yaw rate γ ′, no braking wheel is selected and no braking is performed (FIG. 10).

Next, the braking force control according to the second embodiment of the present invention will be described with reference to the flowchart of FIG. The flowchart of FIG. 11 corresponds to the flowchart of FIG. 6, and the flowchart of FIG. 11 continues from FIG.
The flowchart of FIG. 7 is continued after the flowchart of FIG. Then, in S109, it is determined that there is an oversteer tendency with respect to the target yaw rate γ ', and S
At 121, the sideslip angle β and the preset angle θF
If the sideslip angle β is smaller than the angle θF, the process proceeds to S201, the front wheel correction value BF2f and the rear wheel correction value BF2r are calculated based on the equations (9) and (10), and the process proceeds to S202. .

In S202, the front wheel correction value BF2f and the rear wheel correction value BF2r are compared, and as a result of the comparison, the front wheel correction value BF2f is smaller than the rear wheel correction value BF2r (BF2
If it is determined that f <BF2r), the process proceeds to S115, the right front wheel 4fr is selected as the braking wheel, and the front wheel correction value BF2f is selected.
Is set as the final target hydraulic pressure BFR for the right front wheel (BFR =
BF2f).

As a result of the comparison in S202, the front wheel correction value BF2f is not less than the rear wheel correction value BF2r (BF2f ≧ B
If it is determined to be (F2r), the process proceeds to S117, and the right rear wheel 4rr
Is selected as the braking wheel, and the rear wheel correction value BF2r is set as the right rear wheel final target hydraulic pressure BRR (BRR = BF2).
r).

On the other hand, as a result of the comparison in S121, if it is determined that the sideslip angle β is larger than or equal to the angle θF, the process proceeds to S122, and the rear wheel correction value BF2r is calculated based on the equation (10), The right rear wheel 4rr is selected as the braking wheel, and the rear wheel correction value BF2r is set as the right rear wheel final target hydraulic pressure BRR.

On the other hand, in S119, it is also determined that there is an oversteer tendency, and in S121, the sideslip angle β and the angle θ are determined.
When F is compared and the sideslip angle β is smaller than the angle θ F, the process proceeds to S203, where the front wheel correction value BF2f and the rear wheel correction value BF2r are calculated based on the equations (9) and (10), and the procedure proceeds to S204. move on.

In S204, the front wheel correction value BF2f and the rear wheel correction value BF2r are compared, and as a result of the comparison, the front wheel correction value BF2f is smaller than the rear wheel correction value BF2r (BF2
If it is determined that f <BF2r), the process proceeds to S125, the left front wheel 4fl is selected as a braking wheel, and the front wheel correction value BF2f is selected.
Is set as the final target hydraulic pressure BFL for the left front wheel (BFL =
BF2f).

As a result of the comparison in S204, the front wheel correction value BF2f is not less than the rear wheel correction value BF2r (BF2f ≧
BF2r), the process proceeds to S127, where the left rear wheel 4
rl is selected as the braking wheel, and the rear wheel correction value BF2r is set as the left rear wheel final target hydraulic pressure BRL (BRL = BF
2r). On the other hand, as a result of the comparison in S121, if it is determined that the sideslip angle β is greater than or equal to the angle θF, the process proceeds to S122, the rear wheel correction value BF2r is calculated based on the equation (10), and the left rear wheel is calculated. 4rl is selected as the braking wheel, and the rear wheel correction value BF2r is set to the left rear wheel final target hydraulic pressure B.
Set as RL. The subsequent steps are the same as in the first embodiment of the invention.

As described above, in the second embodiment of the present invention,
In the case of oversteer tendency, the outer wheel with the smaller braking force is selected as the braking wheel and the braking force is set, so before the yaw moment generation by the outer front wheel becomes difficult, Stable yaw moment can be generated by the rear wheels.

[0092]

As described above, according to the present invention,
For example, a yaw moment can be reliably generated in a direction that stabilizes the vehicle behavior even if the spin tendency becomes excessive due to sudden steering on a low μ road or the like and the value of the slip angle changes significantly.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a braking force control device according to a first embodiment of the present invention.

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

FIG. 3 is an explanatory diagram of the operation of the vehicle by the braking force control according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of correction of a target braking force according to the first embodiment of the present invention.

FIG. 5 is a flowchart of braking force control according to the first embodiment of the present invention.

FIG. 6 is a flowchart continued from FIG. 5;

FIG. 7 is a flowchart following FIG. 6;

FIG. 8 is a time chart of an example of braking force control according to the first embodiment of the present invention.

FIG. 9 is an explanatory diagram of characteristics of a determination threshold value according to the first embodiment of the present invention.

FIG. 10 is an explanatory diagram of the operation of the vehicle by the braking force control according to the second embodiment of the present invention.

FIG. 11 is a flowchart of braking force control according to the second embodiment of the present invention.

[Explanation of symbols]

 1 Brake drive unit 4fl, 4fr, 4rl, 4rr Wheels 5fl, 5fr, 5rl, 5rr Wheel cylinders 6fl, 6fr, 6rl, 6rr Wheel speed sensor 7 Handle angle sensor 8 Yaw rate sensor 9 Lateral acceleration sensor 10 Control device 11 Vehicle speed calculation unit 12 Steering angle calculation unit 13 Side slip angle calculation unit 14 Yaw rate steady gain calculation unit 15 Target yaw rate calculation unit 16 Yaw rate deviation calculation unit 17 Target braking force calculation unit 18 Final target braking force setting unit 19 Output determination unit 20 Braking signal output unit δf Actual steering Angle V Vehicle speed YG Lateral acceleration Gγδf (0) Yaw rate steady gain β Sideslip angle θF Preset angle εΔ Judgment threshold γ Actual yaw rate γ'Target yaw rate Δγ Yaw rate deviation BF1f, BF1r Target braking force BF2f, BF2r Correction value BFR, BFL, BRR, BRL Final target braking force

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Munenori Matsuura 3-9-6 Osawa, Mitaka City, Tokyo Subaru Research Institute, Inc.

Claims (3)

[Claims] 1. A vehicle speed detecting means for detecting a vehicle speed, a steering angle detecting means for detecting a steering angle, an actual yaw rate detecting means for detecting an actual yaw rate of a vehicle, and a side slip angle detecting means for detecting a side slip angle. A target yaw rate calculating means for calculating a target yaw rate based on the vehicle speed and the steering angle,
A yaw rate deviation calculating means for calculating the yaw rate deviation by subtracting the target yaw rate from the actual yaw rate, a target braking force calculating means for calculating the target braking force of the front wheels and the rear wheels based on the motion state of the vehicle and the yaw rate deviation, and an actual yaw rate. And the sign of the yaw rate deviation are different, the inner rear wheel is selected as the braking wheel, the rear wheel target braking force calculated by the target braking force calculating means is set as the final target braking force, and the signs of the actual yaw rate and the yaw rate deviation are set. When the sideslip angle is smaller than the preset angle, the outer front wheel is selected as the braking wheel, and the final target braking force is set based on the front wheel target braking force calculated by the target braking force calculation means. On the other hand, when the sideslip angle is equal to or greater than a preset angle, the outer rear wheel is selected as the braking wheel, and the rear wheel target braking calculated by the target braking force calculating means is performed. Final target braking force setting means for setting a final target braking force based on the above, output determining means for determining whether or not the final target braking force is in the control area, and the final target braking force when the output determining means determines that it is in the control area. A braking force control device comprising: a braking signal output unit that outputs a signal to a brake drive unit so as to apply a final target braking force set to a wheel selected by the power setting unit. 2. The final target braking force setting means, when the actual yaw rate and the yaw rate deviation have the same sign, is used as a preset angle for comparison with the sideslip angle. The braking force control device according to claim 1, wherein the angle is an angle formed by a line connecting the center of gravity and the center of gravity. 3. A vehicle speed detecting means for detecting a vehicle speed, a steering angle detecting means for detecting a steering angle, an actual yaw rate detecting means for detecting an actual yaw rate of the vehicle, and a side slip angle detecting means for detecting a side slip angle. A target yaw rate calculating means for calculating a target yaw rate based on the vehicle speed and the steering angle,
A yaw rate deviation calculating means for calculating the yaw rate deviation by subtracting the target yaw rate from the actual yaw rate, a target braking force calculating means for calculating the target braking force of the front wheels and the rear wheels based on the motion state of the vehicle and the yaw rate deviation, and the actual yaw rate. And the sign of the yaw rate deviation are different, the inner rear wheel is selected as the braking wheel, the rear wheel target braking force calculated by the target braking force calculating means is set as the final target braking force, and the signs of the actual yaw rate and the yaw rate deviation are set. If the same, the target braking forces of the front wheels and the rear wheels calculated by the target braking force calculation means are compared with the values corrected according to the sideslip angle, and if the front wheel correction value is smaller than the rear wheel correction value, the outer front wheels are compared. Is set as the braking wheel and the front wheel correction value is set as the final target braking force, while if the front wheel correction value is greater than or equal to the rear wheel correction value, the outer rear wheel is selected as the braking wheel and the rear wheel correction value is set. Is set as the final target braking force, a final target braking force setting means for determining whether or not it is in the control area, and a final target braking force setting when the output determination means determines that it is in the control area. And a braking signal output means for outputting a signal to the brake driving section so as to apply the final target braking force set to the wheels selected by the braking force control device.