JPH09249102A - Automatic brake device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve riding comfortableness by providing an automatic brake device which obtains the time until a vehicle is stopped by the brake pressure determined according to the distance to an obstacle and the relative speed, and performs the brake control for reducing the pressure of brake at the time of detecting that the obtained time becomes a preliminarily set time or below. SOLUTION: An electronic control unit(ECU) 7 calculates the time until a vehicle is stopped from the running speed and acceleration speed thereof detected by a speed sensor 2 and an acceleration sensor 3 at the time of a first brake control according to the pressure of brake determined in response to the distance to an obstacle and a relative speed thereto. The ECU determines whether the calculated time becomes a preliminarily set time or below or not, and performs changeover to a second brake control for reducing the pressure of brake to a target value from the first brake control. Accordingly it is possible to give occupants in the vehicle a soft stop feeling without the feeling of shock at the stoppage thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle automatic brake device for automatically driving a vehicle brake.

[0002]

2. Description of the Related Art Conventionally, as an automatic brake device for a vehicle of this type, for example, a vehicle-mounted radar determines a distance and a relative speed with respect to an obstacle (including a vehicle traveling in front), and the calculated distance and relative speed. There is a method in which the risk of collision is determined and the control target amount of the brake drive is determined according to the risk to perform the drive control of the brake of the vehicle (see Japanese Patent Publication No. 6-14400).

[0003]

The problem to be solved is that in the conventional vehicle automatic brake device, the control target amount for stopping the vehicle is uniformly set to drive the brake. Therefore, when the vehicle is stopped, a shock is generated due to the deceleration G until then, and the riding comfort is deteriorated.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a brake is released immediately before a vehicle is stopped so as to mitigate deceleration G and suppress a shock at the time of stopping, in accordance with a distance to an obstacle and a relative speed. At the time of the first brake control according to the determined brake pressure, the time until the vehicle stops is calculated, and when the calculated time becomes equal to or less than the preset time, the brake pressure is reduced to the target value. It is arranged to switch to the second brake control for lowering.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, an automatic brake device for a vehicle according to the present invention has a vehicle-mounted device which detects an obstacle in the traveling direction of the vehicle and measures a distance and a relative speed with respect to the obstacle. The radar 1, the speed detector 2 for detecting the traveling speed of the own vehicle, and the acceleration detector 3 for detecting the acceleration of the own vehicle
, A brake pressure detector 4 for detecting the operating pressure of the brake 6 of the own vehicle, an actuator 5 for driving the brake 6 of the own vehicle, measurement data of distance and relative speed with respect to an obstacle by the radar 1, each detector 2 , 3 and 4 are read, and the ECU 7 controls the brake drive according to a predetermined algorithm on the basis of the obtained data.

As the actuator 5, for example, an EC
Under the control of U7, the brake pressure can be changed by adjusting the opening degree of the electromagnetic valve provided between the high pressure chamber that is constantly pressurized by the pump and the booster that raises and lowers the brake pressure. However, the brake 6 that can be appropriately driven is used. Alternatively, it may be electrically driven.

The acceleration may be obtained by differentiating the traveling speed of the vehicle detected by the speed detector 2 without providing the acceleration detector 3 in particular.

According to the present invention having such a configuration, the ECU 7 is made to perform the following brake control.

First, under the control of the ECU 7, the radar 1 finds the distance D and the relative speed Vr with respect to the obstacle in the traveling direction of the vehicle in every fixed cycle, and according to the found distance D and the relative speed Vr. So that the brake pressure Bp is determined by the following equation (1) so that the brake pressure detected by the brake pressure detector 4 becomes Bp.
The brake 6 is appropriately driven through the actuator 5.

Bp (t) = Bp (t−1) + Kv × Vr + Kd × (D-Do) (1)

Here, Bp (t) is the brake pressure determined in the current control cycle, and Bp (t-1) is the brake pressure determined in the previous control cycle. Further, Do is a target stop distance when the vehicle stops before an obstacle, Kv is a constant proportional coefficient corresponding to the relative speed Vr,
Kd is a constant proportional coefficient according to the distance (D-Do).

Then, in the ECU 7, during the first brake control according to the brake pressure Bp determined according to the distance D to the obstacle and the relative speed Vr described above,
From the traveling speed Vi and the acceleration Ai of the own vehicle detected by the speed detector 2 and the acceleration detector 3, the time Tstop until the vehicle stops is calculated according to the following equation (2).

Vi + Ai × Tstop = 0 ∴Tstop = -Vi / Ai (2)

Since Ai is during deceleration, it has a minus sign.

Next, in the ECU 7, the calculated time Tstop is set to a preset time to (for example, 0.
(5 seconds) It is determined whether or not it has become less than or equal to Tstop
When ≦ to, the first brake control is switched to the second brake control for reducing the brake pressure to the target value.

Specifically, when Tstop≤to, the brake pressure is switched from the brake pressure Bp determined by the equation (1) to the brake pressure Bp determined by the following equation (3). Is done.

Bp (t) = Bp (t−1) + Tcycle × {Bpr−Bp (t−1)} / T stop (t−1) (3)

Here, Bpr is a target value, and is set to a brake pressure low enough to stop the creep running by the automatic transmission of the own vehicle. Tcycle is
The time of the control cycle.

That is, by controlling the brake pressure according to the equation (3), the brake pressure Bp is obtained within the time Tstop until the vehicle is stopped, which is obtained during the first brake control.
So that the final target value Bpr is reached, the brake pressure Bp is relaxed by the second brake control immediately before the vehicle stops according to the to time.

Therefore, the deceleration G is moderated by releasing the brake immediately before the vehicle is stopped, and the occurrence of shock when the vehicle is stopped is suppressed, so that the occupant can be given a soft feeling of stopping the vehicle.

FIG. 2 shows the relative characteristics of the brake pressure Bp controlled by the present invention and the traveling speed Vi of the vehicle at that time.

FIG. 3 shows the relative characteristics of the brake pressure Bp and the traveling speed Vi of the host vehicle at that time when the vehicle is stopped only by the first brake control.

[0023]

As described above, in the automatic brake device for a vehicle according to the present invention, from the first brake control according to the brake pressure determined according to the distance to the obstacle and the relative speed, it is just before the vehicle stops. By switching to the second brake control that sometimes loosens the brake pressure to the target value, the deceleration G is effectively alleviated just before the vehicle stops, and a soft vehicle stop feeling that does not make the occupant feel a shock at the time of stopping is provided. It has the advantage that it can be given.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a vehicle automatic brake device according to the present invention.

FIG. 2 is a diagram showing a relative characteristic between a brake pressure Bp controlled by the present invention and a traveling speed Vi of a vehicle.

FIG. 3 shows a brake pressure Bp and a traveling speed Vi of the host vehicle when the vehicle is stopped only by the first brake control.
It is a figure which shows the relative characteristic with.

[Explanation of symbols]

 1 radar 2 speed detector 3 acceleration detector 4 brake pressure detector 5 actuator 6 brake 7 ECU

Claims (3)

[Claims] 1. An automatic brake device for a vehicle, wherein a distance and a relative speed of an obstacle in a traveling direction of a vehicle are obtained, and a brake pressure is determined according to the distance and the relative speed to control driving of a brake of the vehicle. A means for obtaining the time until the vehicle stops during the first brake control according to the brake pressure determined according to the distance and the relative speed with respect to the obstacle, and the obtained time is equal to or less than a preset time. And a means for switching to a second brake control for reducing the brake pressure to a target value. 2. The first vehicle speed and acceleration are detected, and the time until the vehicle stops is calculated from the detected vehicle speed and acceleration.
An automatic brake device for a vehicle according to the item. 3. The brake pressure is reduced by the second brake control so that the brake pressure reaches a target value within the time required for the vehicle to stop, which is obtained during the first brake control. The automatic brake device for a vehicle according to the above item 1.