JPH0880825A - Vehicle brake device - Google Patents

Abstract

PURPOSE: To shorten a braking distance which skidding is being prevented, by realizing the coexistence of turning and deceleration in regard to a vehicle controller. CONSTITUTION: A turning limit deciding means M1 decides from the turning behavior of a vehicle whether or not the vrhicle is at a turning limit. A deceleration acceleration detecting means M3 detects the longitudinal deceleration acceleration of the vehicle. A lateral acceleration detecting means M4 detects the lateral acceleration of the vehicle. An increase/decrease controlling means M5 conducts the increase/decrease control of braking force so that longitudinal deceleration acceleration may become equal to the absolute value of lateral acceleration at the time of automatic control decided as a turning limit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle braking system, and more particularly to a vehicle braking system for braking a vehicle.

[0002]

2. Description of the Related Art Conventionally, there is a device for controlling the behavior of a vehicle during turning by automatic braking. For example, JP-A-3
The device disclosed in Japanese Patent Publication No. 45453 automatically turns inside wheels and outside wheels in the turning direction so that the vehicle speed decreases to the limit vehicle speed in a state where the detected yaw rate approaches the target yaw rate when the detected vehicle speed reaches the tire grip limit vehicle speed. A technique for individually braking wheels is disclosed.

[0003]

In the conventional device, the braking force is controlled so that the detected yaw rate approaches the target yaw rate when automatically braking, but the magnitude of the force that can be generated between the tire and the road surface is large. Do not consider. For this reason, there is a problem that the skid becomes large and the braking distance becomes large in a situation where the tire-generating force is small such as a low μ road having a low road friction coefficient (road μ).

The present invention has been made in view of the above points,
When the vehicle reaches the turning limit, the braking force is applied so that the lateral force of the tire and the longitudinal force are balanced so that both turning and deceleration can be achieved at the same time to prevent skidding and reduce the braking distance. An object of the present invention is to provide a vehicle braking device that can be used.

[0005]

As shown in the principle diagram of FIG. 1, the present invention has a turning limit judging means M1 for judging whether or not the vehicle is at the turning limit based on the turning behavior of the vehicle. In a vehicle braking device that automatically brakes when it is determined to be a turning limit by means, a deceleration acceleration detection means M3 that detects a longitudinal deceleration acceleration of the vehicle and a lateral acceleration detection means M4 that detects a lateral acceleration of the vehicle. And an increase / decrease control means M5 for increasing / decreasing the braking force so that the longitudinal deceleration is equal to the absolute value of the lateral acceleration during automatic braking determined to be the turning limit.

[0006]

According to the present invention, since the braking force is controlled to increase or decrease so that the longitudinal deceleration of the vehicle becomes equal to the absolute value of the lateral acceleration when the turning limit is reached, the lateral force of the tire and the longitudinal direction of the tire are controlled. The braking force is applied so that the force is uniform, and both turning and deceleration are achieved, and the braking distance can be shortened while preventing skidding.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 2 is a block diagram of an embodiment of the device of the present invention. In the figure, the master cylinder 10 has two independent pressurizing chambers, and generates a brake fluid pressure proportional to the depression force of the brake pedal 11. The brake fluid pressure generated in one pressurizing chamber of the master cylinder 10 passes through the pipe 12 to
Guided to the port 2 position switching valves SAFL and SAFR,
The brake fluid pressure generated in the other pressurizing chamber is passed through the pipe 13 to the front system high pressure introducing 3-port 2-position switching valve SACC.
3-port 2-position switching valve SAC for F and rear system high pressure introduction
The CR and the proportioning valve 14 are guided to one end of each.

The pump 16 for introducing high pressure has one end connected to the reservoir 17 and the other end connected to the master cylinder 10 and the hydraulic accumulator 18. The high pressure brake is applied from the reservoir 17 to the hydraulic accumulator 18. Liquid is supplied and stored.

The hydraulic accumulator 18 is connected to each of the two-position switching valves SACCF and SACCR through a high pressure pipe 19.

The 2-position switching valve SAFL is a wheel cylinder 21 for the left front wheel and 2-port 2-position switching valves SFLH, SF.
The 2-position switching valve SAFR is connected to each of the LRs, and the 2-position switching valve SAFR is a wheel cylinder 22 for the right front wheel and a 2-port 2-position switching valve SFR.
It is connected to each of H and SFRR. Further, the two-position switching valves SFLH and SFRH are connected to the two-position switching valve SACCF, and the two-position switching valves SFLR and SFRR are connected to the reservoir 17 through the pipe 25.

On the other hand, the other end of the proportioning valve 14 and the 2-position switching valve SACCR are connected to the 3-port 2-position switching valve SARR. 2 position switching valve SARR is 2
The port 2 position switching valves SRLH and SRRH are connected to each other, and the two position switching valve SRLH is a wheel cylinder 2 for the left rear wheel.
The 3-position and 2-port 2-position switching valve SRLR is connected, and the 2-position switching valve SRRH is connected to the wheel cylinder 24 of the right rear wheel and the 2-port 2-position switching valve SRRR. Each of the two-position switching valves SRRH and SRRR is connected to the reserve 17 through a pipe 25.

The electronic control unit (ECU) 30 has a steering angle signal for detecting the steering angle δ of the steering wheel, a vehicle speed signal for detecting the vehicle speed V of the vehicle, a lateral acceleration signal for detecting the lateral acceleration GY of the vehicle, and a vehicle. Longitudinal acceleration GX
The front-rear direction acceleration signals that have detected are respectively supplied.
The ECU 30 generates a drive signal on the basis of the above signal to generate two-position switching valves SAFL, SFLH, SFLR, S which are electromagnetic valves.
AFR, SFRH, SFRR, SACCF, SACC
R, SARR, SRLH, SRLR, SRRH, SRR
It is supplied to each R to switch the position of each 2-position switching valve.

In FIG. 2, the two-position switching valve SAF is shown.
L, SFLH, SFLR, SAFR, SFRH, SFR
R, SACCF, SACCR, SARR, SRLH, S
Each of RLR, SRRH, and SRRR indicates the off position.

FIG. 3 shows a flowchart of the braking control process executed by the ECU 30. This processing is, for example, 5 msec
Etc. is a time interrupt routine interrupted every predetermined time such as.

In the figure, in step S10 corresponding to the deceleration acceleration detecting means M3 and the lateral acceleration detecting means M4, the steering angle δ, the vehicle speed V, the lateral acceleration GY and the longitudinal acceleration GX are read and inputted. Next, in step S20, the target lateral acceleration GY ^* is calculated using the equation (1).

[0016]

[Equation 1]

However, A is a stability factor (constant), L is a wheel base (constant), and g is a gravitational acceleration (constant).

The target lateral acceleration GY ^* is the lateral acceleration expected based on the steering angle δ and the vehicle speed V.

Thereafter, in step S30 corresponding to the turning limit determination means M1, the absolute value | G of the target lateral acceleration GY ^*
Absolute value | GY | of lateral acceleration GY detected as Y ^* |
Compare with. The absolute values are compared because the lateral acceleration GY and the target lateral acceleration GY ^* are positive in the right direction and negative in the left direction, for example. Similarly, the longitudinal acceleration GX is positive in the acceleration direction and negative in the deceleration direction.

Here, if | GY ^* | ≦ | GY |, the detected actual lateral acceleration is equal to or greater than the target lateral acceleration, and the vehicle has not reached the turning limit, so the routine proceeds to step S40. In step S40, the two-position switching valves SAFL, SF
LH, SFLR, SAFR, SFRH, SFRR, SA
CCF, SACCR, SARR, SRLH, SRLR,
All of SRRH and SRRR are set to the off position, that is, the state of FIG. As a result, the brake fluid pressure of the master cylinder 10 is applied to all of the wheel cylinders 21 to 24 and the normal brake control is performed. After the execution of step S40, this process ends.

On the other hand, in the case of | GY ^* |> | GY |, the target lateral acceleration GY ^* exceeds the actual lateral acceleration GY, and the actual lateral acceleration GY has not been obtained due to tire slip. Instead, it is determined that the vehicle is at the turning limit, and the process proceeds to step S50. In step S50, the two-position switching valve SA
CCF, SAFL, SAFR, SACCR, and SARR are set to ON positions, and the brake hydraulic pressure (power pressure) of the accumulator 18 higher than the brake hydraulic pressure of the master cylinder 10 is supplied to each of the wheel cylinders 21 to 24.

Next, in step S60, it is determined whether or not the sum of the actual absolute value of the lateral acceleration GY and the longitudinal acceleration GX exceeds 0. When | GY | + GX> 0, the leftward or rightward lateral acceleration GY generated by the tires of the entire vehicle is deceleration (negative longitudinal acceleration −G
X), that is, when the deceleration (-GX) is insufficient, the process proceeds to step S70. Step S70
2 position switching valves SFLH, SFRH, SRLH, SR
The brake fluid pressure supplied to each of the wheel cylinders 21 to 24 is increased by opening each of the RHs in the off position and opening the two-position switching valves SFLR, SFRR, SRLR, and SRRR in the off position. The pressure is controlled, and then the process is terminated.

In step S60, | GY | + GX≤0,
When the leftward or rightward lateral acceleration GY generated by the tires of the entire vehicle is smaller than the deceleration acceleration, that is, the lateral acceleration GY is insufficient, the process proceeds to step S80. In step S80, the two-position switching valves SFLH, SFRH, S
Each of the RLH and SRRH is in the ON position to be in the closed state, and the two-position switching valves SFLR, SFRR, SRLR, SR
By opening each of the RRs in the ON position to open the brake cylinders, the brake hydraulic pressure supplied to each of the wheel cylinders 21 to 24 is controlled to be reduced, and thereafter, the processing ends. The above steps S60, S70 and S80 correspond to the increase / decrease control means M5.

Here, the absolute value of the lateral acceleration | GY | increases as shown by the solid line in FIG. 4, and | GY ^* at time t ₀ ^.
When |> | GY |, the control of the automatic braking operation starts, and the pressure increase control is performed during the period T1 of | GY |> -GX, and the deceleration-GX increases as indicated by the broken line. Thereafter, the pressure reduction control is performed in the period T2 where | GY | ≦ −GX, and similarly, the pressure increase control is performed alternately in the periods T3 and T5, and the pressure reduction control is performed alternately in the period T4 so that | GY | and −GX become equal. Controlled as. After that, at time t ₁ , | GY ^* | ≦ |
When it becomes GY |, the control of the automatic braking operation ends.

In the present invention, when the turning limit of the vehicle is reached, the braking force is controlled so that the deceleration (negative longitudinal acceleration-GX) and the lateral acceleration absolute value | GY | become equal. As shown in FIG. 5, the tire friction circle of the entire vehicle is evenly divided into a lateral force (cornering force) and a longitudinal force (braking force).

From the viewpoint of lateral slippage, when lateral slip occurs at the turning limit, the braking force is increased to give a deceleration acceleration -GX. Force) is getting smaller,
Moreover, skidding becomes greater. However, the absolute amount of skidding decreases as the vehicle speed decreases. That is, the inertial energy of the vehicle body is absorbed by the forward and backward deceleration in addition to the skid. This makes it possible to achieve both turning and braking during automatic braking operation when the turning limit is reached, and to prevent skidding while reducing the braking distance.

Further, this braking force control is performed by the lateral acceleration GY.
Can be executed simply by comparing the longitudinal acceleration GX with
The configuration of control can be simplified.

[0028]

As described above, according to the present invention, when the turning limit is reached, the braking force is increased or decreased so that the longitudinal deceleration of the vehicle becomes equal to the absolute value of the lateral acceleration. The braking force is applied so that the lateral force and the front-rear direction force of the vehicle are even, and both turning and deceleration can be achieved to prevent skidding and the braking distance can be shortened. Automatic braking control can be performed by detecting two accelerations, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of the device of the present invention.

FIG. 3 is a flowchart of a braking control process.

FIG. 4 is a diagram for explaining braking control of the present invention.

FIG. 5 is a diagram showing a friction circle for braking control according to the present invention.

[Explanation of symbols]

10 Master Cylinder 11 Brake Pedal 12, 13, 19, 25 Piping 14 Proportioning Valve 16 Pump 17 Reservoir 18 Accumulator 21-24 Wheel Cylinder 30 ECU SAFL, SAFR, SACCF, SACCR, SAR
R 3 port 2 position switching valve SFLH, SFLR, SFRH, SFRR, SRLH,
SRLR, SRRH, SRRR 2 port 2 position switching valve M1 turning limit determination means M3 deceleration acceleration detection means M4 lateral acceleration detection means M5 increase / decrease control means

Claims (1)

[Claims] 1. A vehicle braking device having turning limit determination means for determining whether or not a vehicle is at a turning limit based on the turning behavior of the vehicle, and automatically braking when the turning limit determination means determines a turning limit. In the above, the deceleration acceleration detecting means for detecting the longitudinal deceleration of the vehicle, the lateral acceleration detecting means for detecting the lateral acceleration of the vehicle, and the longitudinal deceleration acceleration during the automatic braking determined as the turning limit are An increasing / decreasing control means for increasing / decreasing a braking force so as to be equal to an absolute value of a directional acceleration.