JP3075065B2 - Vehicle behavior control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle behavior control device for correcting abnormal vehicle behavior such as drift-out and spin of a vehicle by applying a braking force to front wheels or rear wheels.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No.
As described in JP-A-112754, a grip limit vehicle speed at which a tire reaches a grip limit is obtained based on a detected steering angle of a steering wheel, and when the detected vehicle speed exceeds the grip limit vehicle speed, a front wheel and a rear wheel are determined. It has been conventionally known to apply a braking force to a vehicle to suppress the vehicle speed to the grip limit vehicle speed or less, thereby preventing abnormal behavior of the vehicle.

[0003]

However, in the above-mentioned conventional apparatus, the braking force is applied to all the wheels in a state where one of the front wheels or the rear wheels has already reached or is about to reach the grip limit. Is applied, the one wheel is locked or the cornering force is reduced due to the application of the braking force, and the behavior of the vehicle is not sufficiently corrected. there is a possibility. The present invention has been made to address the above-described problem, and has been made to be able to satisfactorily correct abnormal behavior of a vehicle by applying a braking force to a front wheel or a rear wheel that has not lost grip force. A vehicle behavior control device is provided.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, a structural feature of the present invention is that when one of a front wheel and a rear wheel reaches a grip limit, the grip limit is reached. The moment around the vehicle center of gravity due to the cornering force of the wheel that has reached the grip limit and the moment around the vehicle center of gravity due to the combined force of the cornering force and the braking force of the wheel that has not reached the grip limit are balanced on the other side of the wheel. The reason is that a braking force of an appropriate magnitude is applied.

[0005]

In the present invention configured as described above, focusing on the moment around the center of gravity of the vehicle, a braking force is applied to the wheel side that has not reached the grip limit to apply the braking force to the front wheel side and the rear wheel side. Since the moments around the center of gravity of the vehicle are made equal, the control by applying the braking force is effectively performed, the drift-out and the spin of the vehicle are prevented, and the behavior of the vehicle is satisfactorily corrected.

[0006]

【Example】

a. Control Method Before describing a specific device for realizing the present invention, characteristics of a control method used in the device will be described.

FIG. 5 shows a front wheel FW and a rear wheel R when the vehicle turns.
The cornering forces Ff and Fr at which W occurs are represented using a vehicle model. In FIG. 5, a is the vehicle center of gravity O.
Represents the distance from the vehicle center of gravity O to the rear wheel axle. If the vehicle is turning normally, the front wheel moments a and Ff around the vehicle center of gravity O due to the cornering force Ff and the rear wheel side moments b and Fr around the vehicle center of gravity O due to the cornering force Fr are kept equal. On the other hand, during turning of the vehicle, the tire of the front wheel FW reaches the grip limit earlier than the tire of the rear wheel RW, and the cornering force Ff by the front wheel FW becomes the maximum front wheel cornering force Ffm that the front wheel FW can generate.
When ax is reached and the cornering force Fr of the rear wheel RW further increases, the relationship between the moments on the front wheel side and the rear wheel side is a · Ff (= a · Ffmax) <b · Fr. Therefore, in this case, a yaw moment is generated in the direction to cancel the yaw rate of the vehicle, so that the vehicle passes outside the turn with respect to the target course, that is, drifts out. vice versa,
The tire of the rear wheel RW reaches the grip limit earlier than the tire of the front wheel FW, and the cornering force Fr by the rear wheel RW becomes the maximum rear wheel cornering force Frmax that can be generated by the rear wheel RW, and the cornering force of the front wheel FW. When Ff further increases, the relationship between the moments on the front wheel side and the rear wheel side is a · Ff> b · Fr (= b · Frmax). Therefore, in this case, a yaw moment is generated in the same direction as the yaw rate of the vehicle, so that the vehicle passes or spins inside the turn with respect to the target course.

A feature of the present invention is that a braking force is applied to a wheel on a side that has not reached the grip limit, so that the front wheel moment and the rear wheel moment around the center of gravity of the vehicle are balanced, and abnormal behavior of the vehicle is reduced. It is intended to be corrected or prevented. That is, when the vehicle drifts out, braking force is applied to the rear wheel RW, and when the vehicle spins, braking force is applied to the front wheel FW.

First, a method for calculating an appropriate value of the braking force in the case of drift out will be described. Since the maximum frictional force generated between the rear wheel RW and the road surface is equal to the maximum rear wheel cornering force Frmax, each of the rear wheels R
The ground contact loads at Wl and RWr are Wrl and Wrr, respectively.
, The maximum frictional force F of each rear wheel RWl, RWr
rlmax and Frrmax are the maximum rear wheel cornering forces Frmax
Are distributed according to the ratio of the ground loads Wrl and Wrr. In addition, Wrl in the following equations 1 and 2
0, Wrr0 are the ground contact loads (constants) of the rear wheels RWl, RWr in the stationary state or the straight traveling state of the vehicle, and the maximum rear wheel cornering force Frmax is a constant determined by the tire characteristics together with the maximum front wheel cornering force Ffmax described later.

[0010]

(Equation 1)

[0011]

(Equation 2)

First, as shown in FIG. 6, each rear wheel RWl,
Assume a friction circle representing each of the maximum frictional forces Frlmax and Frrmax of RWr. When a braking force is applied to the rear wheels RWl, RWr, the respective vectors representing the maximum frictional forces Frlmax, Frrmax rotate rearward of the vehicle. If the angle between these vectors and the vehicle lateral direction is φr, then the rear wheels RWl , RWr and the moment Mb due to braking of the rear wheels RW1, RW2 are expressed by the following equations (3) and (4), respectively.
In the following equation, Tr is a tread (constant) at the position of the rear wheel of the vehicle.

[0013]

[Equation 3] Fr = Frlmax · cosφr + Frrmax · cosφr

[0014]

Mb = (Frrmax · sinφr−Frlmax · sinφr) · Tr / 2 Here, considering that the behavior of the vehicle is stable, the front wheel F
Moment a · Ff around the center of gravity of vehicle due to cornering force Ff of W, cornering force Fr of rear wheel RW
, The moment b · Fr around the center of gravity of the vehicle and the moment Mb due to the braking force must be balanced to satisfy the following equation (5).

[0015]

A · Ff−b · Fr−Mb = 0 Here, when the cornering force Fr and the moment Mb of the above equations (3) and (4) are substituted into the equation (5), the equation (5) becomes the following equation (6).

[0016]

B · (Frlmax · cosφr + Frrmax · cosφr) + (Frrmax · sinφr−Frlmax · sinφr) · Tr / 2 = a · Ff
= A · Ffmax The variables (including Frlmax and Frrmax defined by the above equations 1 and 2) included in the above equation 6 are the rear wheels RWrl and RWrr.
Since only the ground loads Wrl and Wrr and the angle φr are detected, if the ground loads Wrl and Wrr are detected, the angle φr
Can be easily calculated. And this angle φr
By using the detected ground loads Wrl and Wrr, the target braking forces Brl * and Brr * of the rear wheels RWl and RWr are calculated by the following equation (7).
8 can be calculated.

[0017]

(Equation 7)

[0018]

(Equation 8)

By applying the target braking forces Brl * and Brr * calculated by the equations (7) and (8) to the rear wheels RWl and RWr, the moment around the vehicle center of gravity due to the cornering force Ff of the front wheels FW and the rear wheels Since the cornering force Fr of the RW balances the moment around the center of gravity of the vehicle due to the resultant force of the braking force, drift-out of the vehicle is prevented. Further, according to this, each of the rear wheels RWl, RWr exerts the maximum frictional force Frlmax, Frrmax, and the front wheel FRWmax.
Since the maximum cornering force Ffmax equal to the maximum frictional force Ffmax is exerted on W, the maximum cornering force can be used as the vehicle. Next, when the vehicle spins, the appropriate value of the braking force applied to the front wheels FW is determined. One calculation method will be described. As in the above case, assuming that the maximum cornering force Ffmax of the front wheels FW and the ground contact loads of the front wheels FWl and FWr are Wfl and Wfr, respectively, the maximum frictional forces Fflmax and Fflmax of the front wheels FWl and FWr are obtained.
Ffrmax is represented by Equations 9 and 10 below. Note that Wfl0 and Wfr0 in the following Expressions 9 and 10 are ground contact loads (constants) of the front wheels FWl and FWr in the stationary state or the straight traveling state of the vehicle.

[0020]

(Equation 9)

[0021]

(Equation 10)

Here, as described above, each front wheel FW
Assume a friction circle (see FIG. 7) representing the maximum frictional forces Fflmax, Ffrmax of l, FWr. In a state where the braking force is applied to the front wheels FWl, FWr, the respective maximum frictional forces Frlmax, Fr
Assuming that the angle between each vector representing rmax and the lateral direction of the vehicle is φf, the total cornering force Ff of the front wheels FWl and FWr and the moment Mb due to braking of the front wheels FWl and FWr.
Is expressed as in the following Expressions 11 and 12. In addition, the following number 1
Tf in 2 is the tread (constant) of the position of the front wheels of the vehicle.

[0023]

[Equation 11] Ff = Fflmax · cosφf + Ffrmax · cosφf

[0024]

Mb = (Fflmax · sinφf−Ffrmax · sinφf) · Tf / 2 Also in this case, the moments a · Ff around the vehicle center of gravity due to the cornering force Ff of the front wheels FW1 and FWr, and the front wheel F
The moment Mb due to the braking force of Wl, FWr and the rear wheel RW
Considering the balance between the momentum b and Fr around the center of gravity of the vehicle by the cornering force Fr of l, RWr, the following expression 13 is satisfied, so the following expression 14 is established.

[0025]

## EQU13 ## a.Ff + Mb-b.Fr = 0

[0026]

## EQU14 ## a · (Fflmax · cosφf + Ffrmax · cosφf) + (F
flmax ・ sinφf-Ffrmax ・ sinφf) ・ Tf / 2 = b ・ Fr = b ・
Frmax The variables (including Fflmax and Ffrmax defined in Equations 9 and 10) included in Equation 14 are the front wheels FWl and F
Since only the ground contact loads Wfl and Wfr of Wr and the angle φf are given,
If the ground loads Wfl and Wfr are detected, the angle φf can be easily calculated. Then, using this angle φf and the detected ground loads Wfl and Wfr,
The target braking forces Bfl * and Bfr * of the front wheels FWl and FWr can be calculated by the following equations (15) and (16).

[0027]

(Equation 15)

[0028]

(Equation 16)

When the target braking forces Bfl * and Bfr * calculated by the above equations (15) and (16) are applied to the front wheels FWl and FWr, the cornering force Ff of the front wheels FWl and FWr is obtained.
Thus, the moment around the center of gravity of the vehicle due to the resultant force of the braking force and the moment around the center of gravity of the vehicle due to the cornering force Fr of the rear wheels RWl and RWr are balanced, so that the vehicle is prevented from spinning. Also in this case, each front wheel FWl, FWr
The maximum cornering force Frmax, which is equal to the maximum frictional force Frmax, is exerted on the rear wheels RWl, RWr while the maximum frictional force Fflmax, Ffrmax is exerted on the rear wheels RWl, RWr.

In the above control method, the rear wheel RW
l, RWr, even when braking force is applied to the front wheels FWl, FRW
Even when a braking force is applied to Wr, angles φr and φf formed by the combined force of the braking force and the cornering force and the lateral direction of the vehicle.
Are the same on the left and right, but these angles φr and φf may be left and right separately. In this case, the angles φr with respect to the rear wheels RWl and RWr are denoted by φrl and φrr, respectively, and the angles φf with respect to the front wheels FWl and FWr are denoted by φfl and φfr, respectively.
[Mathematical formula-see original document] Equations (6) and (14) are expressed by the following equations (17) and (18), respectively.
become that way.

[0031]

## EQU17 ## b · (Frlmax · cosφrl + Frrmax · cosφrr) +
(Frrmax · sinφrr−Frlmax · sinφrl) · Tr / 2 = a · Ff
= A · Ffmax

[0032]

[Equation 18] a · (Fflmax · cosφfl + Ffrmax · cosφfr) +
(Fflmax · sinφfl−Ffrmax · sinφfr) · Tf / 2 = b · Fr
= B · Frmax In these equations 17 and 18, the ground contact loads Wrl and Wrr
Is detected, equation 17 includes two angles φrl and φrr as variables, and equation 18 includes two angles φfl and φfr as variables. Therefore, in these cases,
The conditions for maximizing the total braking force Br, Bf on the left and right shown in Fig. 3 are added to each angle φrl, φr by applying the nonlinear programming method.
Calculate r, φfl, and φfr.

[0033]

[Equation 19] Br = Frlmax · sinφrl + Frrmax · sinφrr

[0034]

Bf = Fflmax · sinφfl + Ffrmax · sinφfr In the case of drift-out, each rear wheel RWl, RWr
The target braking forces Brl * and Brr * of the front wheels FWl and FWr are calculated by the following equations 21 and 22, respectively.
The target braking forces Bfl * and Bfr * are calculated by the following equations 23 and 24, respectively.

[0035]

(Equation 21)

[0036]

(Equation 22)

[0037]

(Equation 23)

[0038]

(Equation 24)

In the case of drift-out, the target braking forces Brl * and Brr * are applied to the rear wheels RWl and RWr, respectively, and in the case of spin, the target braking forces Bfl * and Bfr * are applied to the front wheels FWl and FWr. Respectively, the braking force of the vehicle is more accurately controlled, and the behavior of the vehicle is better corrected.

B. Next, an embodiment of an apparatus according to the present invention using the above-described method will be described with reference to the drawings. FIG. 1 schematically shows a vehicular brake device to which a vehicle behavior control device according to the present invention is applied, and a block diagram of an electric control device for controlling the device.

The brake device is provided with a master cylinder 12 for pumping brake oil from the first and second ports in response to a depression operation of a brake pedal 11. The first port of the master cylinder 12 is provided with electromagnetic valves 21 and 31
Are in communication with the wheel cylinders 22 and 32 for the left and right front wheels via the two valves 21 and 31 respectively. The second port of the master cylinder 12 communicates with the left and right rear wheel cylinders 42 and 52 via the proportional valve 13 and the electromagnetic valves 41 and 51 when the electromagnetic valves 41 and 51 are in the illustrated state.

The vehicle brake device includes a hydraulic pump 14, which supplies the oil pumped from the reservoir 15 to the high-pressure oil passage L1. An accumulator 16 for storing high-pressure oil is connected to the high-pressure oil passage L1. Between the high-pressure oil passage L1 and the low-pressure oil passage L2 connected to the reservoir 15, brake hydraulic control units 20, 30, 40, and 50 for left and right front wheels and left and right rear wheels are connected. The brake hydraulic pressure control device 20 for the left front wheel includes the electromagnetic valve 21 described above.
In addition to the wheel cylinder 22 and a wheel cylinder 22, an electromagnetic valve 23 for increasing pressure and an electromagnetic valve 24 for reducing pressure are provided. The electromagnetic valve 23 connects the high-pressure oil passage L1 to the wheel cylinder 22 in the illustrated state when the electromagnetic valve 21 is switched from the illustrated state, and prohibits the communication in the state switched from the illustrated state. When the electromagnetic valve 24 is switched from the illustrated state, the electromagnetic valve 24 switches the wheel cylinder 2 in the switched state from the illustrated state.
2 is communicated with the low-pressure oil passage L2, and the communication is prohibited in the illustrated state.

The brake hydraulic control device 30 for the right front wheel is also
In addition to the electromagnetic valve 31 and the wheel cylinder 32 described above, there are provided electromagnetic valves 33 and 34 which function in the same manner as the brake hydraulic control device 20 for the front left wheel. The brake hydraulic control device 40 for the left rear wheel also includes electromagnetic valves 43 and 44 that function in the same manner as the brake hydraulic control device 20 for the left front wheel, in addition to the electromagnetic valve 41 and the wheel cylinder 42 described above. . The brake hydraulic control device 50 for the right rear wheel also includes the brake hydraulic control device 2 for the left front wheel in addition to the electromagnetic valve 51 and the wheel cylinder 52 described above.
Electromagnetic valves 53 and 54 functioning in the same manner as in the case of 0 are provided. Each of the above-described electromagnetic valves is kept in the illustrated state when not energized, and is switched from the illustrated state when energized.

Next, an electric control device for controlling these electromagnetic valves will be described. The electric control device includes a vehicle speed sensor 61, a steering angle sensor 62, a lateral acceleration sensor 63, a yaw rate sensor 64, load sensors 65a to 65d, and hydraulic sensors 66a to 66d. Each of these sensors 6
1 to 64 are vehicle speed V, front wheel steering angle (steering wheel steering angle) θ
f, lateral acceleration Gy and yaw rate γ, respectively,
Each detection signal representing these physical quantities is output. The front wheel steering angle (steering wheel steering angle) θf, the lateral acceleration Gy, and the yaw rate γ are each positive in the left direction and negative in the right direction. Each of the load sensors 65a to 65d can be replaced by a stroke sensor provided in the suspension device at each wheel position, and measures each vertical displacement of the sprung member (vehicle body) with respect to the wheel (road surface). The product of each measured displacement and the spring coefficient of the suspension device is calculated, and the sum of the value obtained by removing the vibration component of the vehicle body from the calculated product and a predetermined standard load value (initial load value) is calculated. Each load Wfl, Wfr, Wrl, Wrr of each front wheel and rear wheel
Detected as The hydraulic pressure sensors 66a to 66d detect the braking forces Ba to Bd applied to the respective wheels by measuring the brake oil pressures applied to the wheel cylinders 22, 32, 42, 52, respectively. Bd
Is output.

Each of these sensors 61-64, 65a-6
A microcomputer 70 is connected to 5d.
The microcomputer 70 executes a program corresponding to the flowchart of FIG. 2 to control the brake device to automatically correct the drift-out state or the spin state when the vehicle enters the drift-out state or the spin state. Is output to the brake control circuit 80. The brake control circuit 80 includes oil pressure sensors 66a to 66d.
, And each of the electromagnetic valves 21, 23, 24,
31, 33, 34, 41, 43, 44, 51, 53, 5
By controlling the energization and non-energization of 4, the supply / discharge of brake oil to / from the wheel cylinders 22, 32, 42, 52 is controlled.

Next, the operation of the embodiment configured as described above will be described. The microcomputer 70 starts the execution of the program in step 100 of FIG. 2 by starting the vehicle, and repeatedly executes a circulation process including steps 102 to 130. In step 102, each sensor 61-6
The vehicle speed V and the front wheel steering angle θ from 4, 65a to 65d, respectively.
f, lateral acceleration Gy, yaw rate γ, and loads Wfl, Wfr, W
The detection signals representing rl and Wrr are input, and step 104
The slip angle β of the vehicle is calculated by executing the calculation of the following equation 25 using the input vehicle speed V, lateral acceleration Gy and yaw rate γ (see FIG. 3).

[0047]

Equation 25] _{β = ∫ (G Y / V} -γ) dt Note that in this embodiment the slip angle beta of the vehicle as calculated by the integral calculation of the number 25 as described above, in the integration operation Alternatively, the slip angle β may be calculated by a first-order lag pseudo-integral operation. Alternatively, the slip angle β of the vehicle may be measured.

Next, at step 106, the calculated vehicle slip angle β, the input yaw rate γ, and the vehicle speed V
And the front wheel steering angle θf and the slip angles αf and the rear wheels RWl, RWr of the front wheels FWl, FWr by the following equations (26) and (27).
Is calculated (see FIG. 3). In the following Expressions 26 and 27, a is a predetermined fixed value indicating the distance between the vehicle center of gravity O and the front wheel axle, and b is a predetermined fixed value indicating the distance between the vehicle center of gravity O and the rear wheel axle. is there.

[0049]

[Formula 26] αf = θf−β + a · γ / V

[0050]

Αr = β−b · γ / V Next, in step 108, the time differential value dγ / dt of the input yaw rate γ is calculated, and this time differential value is calculated.
The cornering force Ff and the rear wheel R of FWl and FWr are calculated by the following equations (28) and (29) using dγ / dt and the lateral acceleration Gy.
The cornering force Fr of Wl, RWr is calculated. In the following Expressions 28 and 29, M is a predetermined fixed value representing the vehicle weight, and I is a predetermined fixed value representing the yaw moment of inertia of the vehicle.

[0051]

[Equation 28]

[0052]

(Equation 29)

In the processing of steps 106 and 108, the microcomputer calculates the slip angles αf and αr and the cornering forces Ff and Fr calculated last time.
The slip angle αf (n−1), α calculated at the previous time in the next step 110 is
r (n-1) and cornering forces Ff (n-1), Fr (n-1)
Using the slip angles αf (n) and αr (n) and the cornering forces Ff (n) and Fr (n) calculated this time,
31 is a partial differential value H obtained by partially differentiating the cornering forces Ff, Fr with the slip angles αf, αr by the differential operation of
Calculate f and Hr.

[0054]

[Equation 30]

[0055]

(Equation 31)

Next, at step 112, the partial differential value H
It is determined whether one of f and Hr is negative. Here, the physical meaning of these partial differential values Hf and Hr will be described. When the slip angles αf, αr are equal to or smaller than a predetermined angle α0 determined by the characteristics of the tire, etc., as shown in FIG. 4, the cornering forces Ff, Fr increase as the slip angles αf, αr increase, and the maximum cornering force Ffma
x, Frmax are reached. However, when the slip angles αf, αr exceed the predetermined angle α0, the cornering forces Ff, Fr begin to decrease. The point at which the slip angles αf, αr reach the predetermined angle α0 is the grip limit of the front wheels FWl, FWr and the rear wheels RWl, RWr, and the slip angles αf, αr are the predetermined angles α
Beyond zero, the vehicle will drift out or spin. Therefore, by determining whether the partial differential values Hf and Hr are positive or negative, the front wheels FWl and FWr and the rear wheels RWl and RWr are determined.
Has reached the slip limit.

Now, the front wheels FWl, FWr are also rear wheels RWl, R
Wr also does not reach the slip limit and the partial differential values Hf and Hr
Are both positive, the determination in step 112 is “NO” and the program proceeds to step 118. Step 1
At 18, a control signal indicating that the braking force control is not performed is output to the brake control circuit 80. The brake control circuit 80 responds to the same control signal to all the electromagnetic valves 2.
1,23,24,31,33,34,41,43,4
4, 51, 53 and 54 are de-energized and the valve 2
1,23,24,31,33,34,41,43,4
4, 51, 53 and 54 are kept in the illustrated state. In such a state, when the driver depresses the brake pedal 11 while the vehicle is running, the first and second brakes of the master cylinder 12 are moved.
Brake oil is discharged from the port. The brake oil discharged from the first port is supplied to the wheel cylinders 22 and 32 via the electromagnetic valves 21 and 31,
The brake oil discharged from the port is supplied to the wheel cylinders 42, 52 via the proportional valve 13 and the electromagnetic valves 41, 51. Accordingly, in this case, a braking force corresponding to the depression operation of the brake pedal 11 is applied to each wheel, and the vehicle is braked.

On the other hand, the front wheels FWl, FWr or the rear wheels RWl,
When one of the RWr reaches the slip limit, the two partial differential values Hf and H
If any one of r becomes negative, “YES” is determined in step 112 and the program is executed in steps 114 and 1.
Proceed to 16. In steps 114 and 116, the moment a · Ff around the vehicle center of gravity due to the cornering force Ff of the front wheels FWl and FWr is compared with the moment b · Fr around the vehicle center of gravity due to the cornering force Fr of the rear wheels RWl and RWr.

If the front wheel side moment a · Ff is smaller than the rear wheel side moment b · Fr, that is, if the front wheels FWl and FWr have reached the slip limit and the vehicle is in a drift-out state, “YES” is determined in step 114. If it is determined, the program proceeds to steps 120 to 124. Step 1
In step 20, the angle φr is calculated by solving the above equations 1, 2 and 6 using the input loads Wrl and Wrr on the left and right rear wheels RWl and RWr. In step 122, the target braking forces Brl * and Brr * of the left and right rear wheels RWl and RWr are calculated by the calculation of the equations (7) and (8) using the solved angle φr and the loads Wrl and Wrr. In step 124, a control signal indicating that braking force control of the left and right rear wheels RWl, RWr is to be performed and a control signal indicating respective target braking forces Brl *, Brr * of the rear wheels RWl, RWr are output to the brake control circuit 80. I do.

The brake control circuit 80 starts with the electromagnetic valve 2
1, 31, 41, and 51 are energized. As a result, the electromagnetic valves 21, 31, 41, and 51 are switched from the illustrated state.
The supply path of the brake oil to the cylinders 22, 32, 42, and 52 is closed, and the supply and discharge of the brake oil to and from the cylinders 22, 32, 42, and 52 are performed by electromagnetic valves 23, 24, 33, 34, and 4, respectively.
3,44,53,54. In this state, the brake control circuit 80 controls the electromagnetic valves 2 in the brake hydraulic pressure control devices 20 and 30 for the left and right front wheels FWl and FWr.
3, 24, 33 and 34 are energized. As a result, the wheel cylinder 22 is connected to the low-pressure oil passage L2 via the electromagnetic valves 21 and 24, and the wheel cylinder 32 is also connected to the low-pressure oil passage L2 via the electromagnetic valves 31 and 34. , FWr is not provided with a braking force.

The brake control circuit 80 compares the calculated target braking forces Brl *, Brr * of the left and right rear wheels RWl, RWr with the detected braking forces Bc, Bd detected by the hydraulic sensors 66c, 66d, respectively. Meanwhile, each electromagnetic valve 43, 44, 53,
Control the energization / de-energization of the left and right rear wheels RWl, RW
Target braking forces Brl * and Brr * are given to r. That is, each target braking force Brl *, Brr * is changed to each detected braking force Bc,
If it is larger than Bd, the electromagnetic valves 43, 44, 53, 5
4 is de-energized and the high-pressure oil passage L1 is
The brake hydraulic pressure in the cylinders 42, 52 is increased by connecting them to the wheel cylinders 42, 52 via 1, 53, 51. Each target braking force Brl *, Brr * is equal to each detected braking force B
If it is smaller than c and Bd, the electromagnetic valves 43, 44, 53,
By energizing 54, the wheel cylinders 42, 52 are connected to the low-pressure oil passage L2 via the electromagnetic valves 41, 44, 51, 54 to reduce the brake hydraulic pressure in the cylinders 42, 52. If the target braking forces Brl * and Brr * are equal to the detected braking forces Bc and Bd, the electromagnetic valves 43 and 53 are energized and the electromagnetic valves 44 and 54 are deenergized. The hydraulic pressure is disconnected from the oil passage L1 and the low-pressure oil passage L2, and the brake oil pressure in the cylinders 42 and 52 is maintained as it is.

As described above, as described in the above control method, the cornering force Ff of the front wheels FWl, FWr (=
Ffmax) and the moment around the center of gravity of the vehicle and the rear wheel RW
l, RWr cornering force Fr and braking force Brl *, B
Since the moment around the center of gravity of the vehicle due to the resultant force of rr * is balanced, drift-out of the vehicle is prevented. Also, according to this, each of the rear wheels RWl, RWr has its own maximum frictional force Frlma.
x, Frrmax, and the maximum cornering force Ffmax equal to the maximum frictional force Ffmax on the front wheel FW.
In contrast to the case where the maximum cornering force can be used as a vehicle, if the front wheel side moment a · Ff is larger than the rear wheel side moment b · Fr,
That is, if the rear wheels RWl and RWr have reached the slip limit and the vehicle is in a spinning state, then at step 116, "YE
S "and the program proceeds to steps 126-130. In step 126, the angle φf is calculated by solving the above equations (9), (10) and (14) using the input loads Wfl and Wfr for the left and right front wheels FWl and FWr. In step 128, the equations (15) and (16) are calculated using the solved angle φf and the loads Wfl and Wfr.
The respective target braking forces Bfl *, Bfr * of the left and right front wheels FWl, FWr are calculated. In step 130, the left and right front wheels FWl,
A control signal indicating that the braking force of the FWr is to be controlled and a control signal indicating the target braking forces Bfl * and Bfr * of the front wheels FWl and FWr are output to the brake control circuit 80.

The brake control circuit 80 first supplies power to the electromagnetic valves 21, 31, 41, and 51, and controls the electromagnetic valves in the brake hydraulic pressure control devices 40 and 50 for the left and right rear wheels RWl and RWr. 43,44,53,5
4 so that no braking force is applied to the left and right rear wheels RWl, RWr. Further, as described above, the brake control circuit 80 determines the calculated target braking forces Bfl * and Bfr * of the left and right front wheels FWl and FWr and the hydraulic sensors 66a and 66b.
, Control the energization / de-energization of the electromagnetic valves 23, 24, 33, 34 in the brake hydraulic pressure control devices 20, 30, respectively, while comparing the detected braking forces Ba, Bb detected by , FWr to each target braking force Bfl *, Bf
r * is assigned.

As described above, the moment around the center of gravity of the vehicle due to the combined force of the cornering force Ff of the front wheels FWl, FWr and the braking forces Bfl *, Bfr *, and the cornering force Fr of the rear wheels RWl, RWr
(= Frmax) and the moment around the center of gravity of the vehicle are balanced, so that spinning of the vehicle is prevented. Also in this case, the maximum frictional force Fflmax, Ffrm is applied to each front wheel FWl, FWr.
ax, and the maximum cornering force Frmax equal to the maximum frictional force Frmax applied to the rear wheels RWl, RWr.
The maximum cornering force can be used as a vehicle.

As described above, according to the above embodiment, the microcomputer 70 executes steps 112 to 1
The processing (detection means) of step 16 detects that the front wheels FWl, FWr and the rear wheels RWl, RWr are at the grip limit. If the front wheels FWl, FWr are at the grip limit, the processing of steps 120 and 122 (first calculation). Means), the target braking forces Brl *, Brr * of the rear wheels RWl, RWr are calculated. If the rear wheels RWl and RWr are at the grip limit, the target braking forces Bfl * and Bfr * of the front wheels FWl and FWr are calculated by the processing of steps 126 and 128 (second calculating means). Each of these target braking forces Brl *, Brr *, Bfl
*, Bfr * are the moment around the vehicle center of gravity due to the cornering force of the wheel that has reached the grip limit, the braking force applied to the wheel that has not reached the grip limit, and the resultant force of the cornering force of the same wheel. Step 12 is determined so that the moment is balanced.
4 and 130 (control means), in cooperation with the brake control circuit 80 (control means), the respective target braking forces Brl
*, Brr *, Bfl *, Bfr * to rear wheel RWl, RWr or front wheel F
It is characterized in that it is added to Wl, FWr. Thus, according to the above embodiment, focusing on the moment around the vehicle center of gravity, the braking force is applied to the wheel side that has not reached the grip limit, and the moments around the vehicle center of gravity on the front wheel side and the rear wheel side are equal. As a result, the braking force is effectively applied and the vehicle is prevented from drifting out and spinning.

In the above embodiment, step 1
In steps 20 and 126, the angles φr and φf are calculated using the above equations 1, 2, 6, 9, 10, and 14, and at step 12
At 2,128, the target braking forces Brl *, Brr *, Bfl *, Bfr * are calculated using the above formulas 7, 8, 15, and 16. However, as described in the above control method, 1
The above equations 1, 2, 9, 10, 17 to 20 at 20, 126
Are used to calculate the angles φrl, φrr, φfl, and φfr, and in steps 122 and 128, the target braking forces Brl *, Brr *, Bfl *, and Bfr * are calculated using the equations 21 to 24. Is also good. As a result, as described above, the braking force of the vehicle is accurately controlled as described in the above-described control method, and the drift-out and the spin of the vehicle are more appropriately corrected.

Also, in the above embodiment, step 1
The front wheels FWl and FWr and the rear wheel R
Wl and RWr are each detected to be at the grip limit. However, the fact that the front wheels FWl, FWr are at the grip limit corresponds to the negative partial differential value Hf, and the fact that the rear wheels RWl, RWr are at the grip limit corresponds to the partial differential value Hr. , 11
6 is omitted, and in the determination process of step 112,
If the partial differential value Hf is negative, the program proceeds to step 120.
If the partial differential value Hr is positive, the program may proceed to step 126.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a vehicle brake device and an electric control device for the brake device according to an embodiment of the present invention.

FIG. 2 is a flowchart of a program executed by the microcomputer of FIG. 1;

FIG. 3 is a two-wheel model diagram of a vehicle for describing respective slip angles of the vehicle, front wheels, and rear wheels.

FIG. 4 is a graph showing a change characteristic of a cornering force with respect to a slip angle of a front wheel and a rear wheel.

FIG. 5 is a two-wheel model of a vehicle for explaining moments around the center of gravity of the vehicle due to the cornering forces of the front wheels and the rear wheels according to the features of the present invention.

FIG. 6 is a vehicle model diagram for explaining a change state of the moment when a braking force is applied to a rear wheel.

FIG. 7 is a vehicle model diagram for explaining a change state of the moment when a braking force is applied to a front wheel.

[Explanation of symbols]

11: brake pedal, 12: master cylinder, 20,
30, 40, 50 ... brake hydraulic pressure control device for each wheel, 2
2, 32, 42, 52: wheel cylinder, 61: vehicle speed sensor, 62: steering angle sensor, 63: lateral acceleration sensor, 6
4: Yaw rate sensor, 65a to 65d: Load sensor,
66a to 66d: oil pressure sensor, 70: microcomputer, 80: brake control circuit.

Continuation of the front page (56) References JP-A-4-362474 (JP, A) JP-A-4-197858 (JP, A) JP-A-3-112754 (JP, A) JP-A-4-185560 (JP) JP-A-4-146819 (JP, A) JP-A-6-16117 (JP, A) JP-A-6-99796 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B60T 8/58 B60T 8/24

Claims (1)

(57) [Claims] 1. A detecting means for detecting that a front wheel and a rear wheel have reached a grip limit, respectively, and, when the detecting means detects that a front wheel has reached a grip limit, a center of gravity of a vehicle by a cornering force of the front wheel. First calculating means for calculating a first target braking force for the rear wheels such that a peripheral front wheel side moment and a rear wheel side moment around the vehicle center of gravity due to a resultant force of a cornering force of the rear wheel and a braking force are balanced; When the detecting means detects that the rear wheel has reached the grip limit, the rear wheel side moment around the vehicle center of gravity due to the cornering force of the rear wheel, and the front wheel side around the vehicle center of gravity due to the combined force of the cornering force of the front wheel and the braking force. A second calculating means for calculating a second target braking force for the front wheels so that the moment is balanced; When it is detected that has reached the grip limit, a control signal based on the calculated first target braking force is output to the brake device for the rear wheels to apply the first target braking force to the rear wheels, and When the detecting means detects that the rear wheel has reached the grip limit, a control signal based on the calculated second target braking force is output to the front wheel brake device, and the first target braking force is applied to the front wheels. A vehicle behavior control device comprising: control means for imparting a vehicle.