JPH11255088A - Brake assist system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a safe distance between a vehicle and another one travelling ahead even when the former decelerates rapidly to cause a pitch or nose dive in which the laser beams of its laser radar can no longer be absorbed, by boosting the braking pressure up to a value required to hold the safe inter- vehicle distance. SOLUTION: A brake assist system is provided with a brake-pedal stroke sensor 23, wheel speed sensors 28, a laser radar 31 and a longitudinal acceleration sensor, to thereby estimate future inter-vehicle distances from the previous inter-vehicle information and control the braking pressure on the basis of the estimated inter-vehicle distances so that a safe inter-vehicle distance is kept, if the inter-vehicle distance during brakeage varies discontinuously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a brake assist system.

[0002]

2. Description of the Related Art Conventional brake assist systems include, for example, the following. Tokuhei 4-2
In Japanese Patent No. 5182, a laser radar or the like is used to detect the distance to a vehicle ahead, and when the distance falls below a preset safety distance, warns the driver of danger and assists the brake pressure when the brake is depressed. Attempts have been made to do so.

[0003]

However, the laser head of the laser radar is basically installed in advance so as to detect the distance to the front by receiving the reflected wave from the reflector at the front, but the own vehicle is suddenly moved. There is a problem that the laser beam cannot be absorbed due to the rotational movement (pitching, nose dive) of the vehicle in the front-rear direction generated when the vehicle is decelerated. In this case, the inter-vehicle distance calculated by the laser radar signal changes from a continuous value to a discontinuous value, and it is not known whether it is due to a failure. As a result, there is a problem that the control of the brake assist cannot be performed sufficiently. Also, if the driver himself pitches due to the brake operation, even if the distance from the vehicle ahead (or the stopped vehicle) that suddenly stopped suddenly decreases, the brake pressure cannot be increased based on the following distance information. There is a problem that the driver who cannot fully depress the brake cannot perform the brake assist control sufficiently. The present invention has been made in view of such conventional problems, and detects a distance between a vehicle and a preceding vehicle, and increases a brake pressure to a required pressure so as to maintain a safe distance between the vehicles. When the assist system detects the inter-vehicle distance discontinuity due to braking of the own vehicle, the inter-vehicle distance is estimated from the inter-vehicle distance information up to that point, and a safe distance is calculated based on the estimated inter-vehicle distance. The above problem caused by pitching is solved by increasing the brake pressure to the required pressure so as to maintain the pressure. The discontinuity of the inter-vehicle distance can also be caused by the lane change of the preceding vehicle or the lane of the own vehicle. However, such a condition and the condition caused by the pitching are discriminated by the constraint conditions described in claims 3 to 5. can do.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 detects an inter-vehicle distance between a host vehicle and a preceding vehicle, and applies a brake so that the inter-vehicle distance maintains a safe distance. In the case of a brake assist system that increases the pressure to the required pressure, if the inter-vehicle distance is detected discontinuously due to braking of the vehicle, the inter-vehicle distance is estimated from the inter-vehicle distance information up to that point, and the estimated inter-vehicle distance is calculated. Based on the distance, the brake pressure is increased to the required pressure to maintain a safe distance. According to a second aspect of the present invention, in the brake assist system according to the first aspect, the inter-vehicle distance is estimated from the inter-vehicle distance at the time when the own vehicle brakes and the inter-vehicle distance change amount per unit time immediately before the braking. did. According to a third aspect of the invention, in the brake assist system according to the first aspect, the estimation of the inter-vehicle distance is not performed when the deceleration of the own vehicle is equal to or less than a predetermined value. According to a fourth aspect of the present invention, in the brake assist system of the first aspect, the estimation of the inter-vehicle distance is not performed when the own vehicle is not in a straight traveling state. According to a fifth aspect of the present invention, in the brake assist system according to the first aspect, the estimation of the inter-vehicle distance is not performed when the suspension deflection of the own vehicle is equal to or less than a predetermined value.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 and 2 are diagrams showing an embodiment of the present invention. 1 is an overall configuration diagram, and FIG. 2 is a configuration diagram of a negative pressure booster. First, the configuration will be described. In FIG. 1, reference numeral 21 denotes a brake pedal, and reference numeral 23 denotes a brake stroke sensor that detects an operation amount of the brake pedal.

Reference numeral 25 denotes a negative pressure booster built in the solenoid valve, the details of which are shown in FIG. 26 is a master cylinder, 27 is each wheel, and its rotation speed is detected by a wheel speed sensor 28. Reference numeral 31 denotes a laser radar attached to a front grille at the front of the vehicle, and detects a distance between the vehicle and a front vehicle. Reference numeral 32 denotes a front-rear G sensor that detects the acceleration in the front-rear direction of the vehicle installed near the center of gravity of the vehicle. 29
Is a control device for performing brake assist, and a control routine thereof will be described later. The control device 29 receives information on the brake stroke, the wheel rotation speed, the inter-vehicle distance, and the longitudinal G, and outputs a control signal for driving the solenoid valve 5 described later.

FIG. 2 illustrates the structure of the negative pressure booster 25. Reference numeral 1 denotes a variable pressure chamber, which is in a negative pressure state when the brake is not operated, and a pressure with a negative pressure chamber 2 described later is balanced. When the brake is not operated, the atmosphere is introduced, a pressure difference with the negative pressure chamber 2 is generated, and the boosted load is transmitted to the master cylinder 26. Reference numeral 2 denotes a negative pressure chamber in which a predetermined negative pressure is constantly generated during engine start. Reference numeral 3 denotes a vacuum valve, which closes when the brake pedal 21 is stroked by a driver or when an electromagnetic valve described later is excited, and shuts off communication between the negative pressure chamber 2 and the variable pressure chamber 1. Reference numeral 4 denotes an atmospheric valve, which is used when the brake pedal 21 is stroked by the driver or when an electromagnetic valve 5 described later is used.
Is opened when excited, and the atmosphere is introduced into the transformation chamber 1.
5 is an electromagnetic valve, 6 is an operating rod, 7 is an electromagnetic valve interlocking member, 8 is a push rod, and when the electromagnetic valve 5 is excited, the electromagnetic valve interlocking member 7 strokes leftward in the figure, and the vacuum valve 3 and the atmosphere The opening and closing operation of the valve 4 is performed. As a result, a pressure difference is generated between the negative pressure chamber 2 and the variable pressure chamber 1, and a force is transmitted to the push rod 8 and the master cylinder via the reaction disk 9, and a braking force is generated for each wheel.

Next, the operation will be described. FIG. 3 and FIG. 4 are flowcharts showing the arithmetic processing of the control device 29. This routine is performed at a predetermined cycle (in the present embodiment, 1 in 10 msec).
This is an interrupt processing routine that is executed in a cycle that flows once.

First, in step S100, the own vehicle speed v is read from the rotational speed of the wheels.

Next, at step S101, a safe distance x1 with respect to a forward obstacle is calculated based on the vehicle speed v. In the present embodiment, the stop distance (= v ** / 2/2 g, g = 0.6 G) physically possible by v and the free running distance (= T *) from when the danger is recognized to when the brake operation is performed.
v, T = 1.0 sec).

In step S102, the laser radar 31
The actual distance x between the own vehicle and the obstacle ahead is read from.

Steps S103 to S106 are conditions for determining whether or not to estimate the inter-vehicle distance.

First, in step S103, it is determined whether or not the difference between the current distance x to the obstacle and the distance xold to the past obstacle is equal to or greater than a predetermined value α. The value of α is set to a physically impossible change amount, and a value larger than α indicates a discontinuous change in the inter-vehicle distance. In step S104, it is determined whether the vehicle is braking, in step S105, it is determined whether the vehicle is traveling straight, and in step S106, it is determined whether the front and rear G of the vehicle is large. When the occurrence of discontinuity in the inter-vehicle distance due to pitching due to sudden braking can be identified, the process proceeds to step S108, and otherwise, the process proceeds to a brake operation detection routine after step S200.

In step S107, an inter-vehicle distance is estimated. In the present embodiment, the vehicle speed VB immediately before braking is applied.
X was calculated from the time variation of the inter-vehicle distance x before that. In step S108, it is determined whether or not the detected (or calculated) x is greater than the safe distance target value x1, that is, whether or not the vehicle is approaching too much. Control is performed.

As a specific example of performing the automatic brake braking in step S109, the electromagnetic valve 5 is driven so that the vacuum valve 3 of the negative pressure booster 25 is at the closed position and the atmospheric valve 4 is at the open position, and the variable pressure chamber 1 is operated. , A pressure difference between the negative pressure chamber 2 and the master cylinder 26 to the wheel cylinder is generated.

In step S200, the brake pedal 21
Is detected.

In step S201, the brake stroke speed is calculated from the past history of the detected brake stroke amount.

In step S202, the brake pedal 21
It is determined whether is depressed. If not, the process proceeds to step S205, and if depressed, the BA flag is determined in step S203.

The BA flag is set to 1 when the stroke speed of the driver is high and it is estimated that the driver is in an emergency condition, and when the brake pedal 21 is returned (step S20).
This flag is reset to 0 in 5).

If the BA flag is set in step S203, the process proceeds to step S206 to continue the assist control. If not, in step S204, whether the brake stroke speed is greater than the BA threshold value is determined.
That is, it is determined whether it is an emergency state.

If it is determined in step S204 that the brake stroke speed is higher than the BA threshold value, the process proceeds to step S206 to perform assist control. If not, the assist control is canceled (or not performed) in step S207.

As a specific example of performing the assist control in step S206, the electromagnetic valve 5 is driven so that the vacuum valve 3 of the negative pressure booster 25 is in the closed position and the atmospheric valve 4 is in the open position.
By introducing the atmosphere into the variable pressure chamber 1, a pressure difference from the negative pressure chamber 2 is generated, and a hydraulic pressure is generated in the master cylinder 26 to the wheel cylinder.

On the other hand, as a specific example of releasing the assist control in step S207, the electromagnetic valve 5 is set so that the vacuum valve 3 of the negative pressure booster 25 is in the open position and the atmospheric valve 4 is in the closed position.
Is driven to end the control. It should be noted that the vacuum valve 3 is brought to the open position and the atmospheric valve 4 is brought to the closed position by the urging force of the spring just by interrupting the energization of the solenoid valve 5, so that the purpose of terminating the braking is achieved.

[0024]

As described above, according to the brake assist system of the present invention, when the inter-vehicle distance is discontinuously detected during braking, the inter-vehicle distance is calculated based on the inter-vehicle distance information up to that point. Is estimated, and the brake pressure is increased to a required pressure so as to maintain a safe distance based on the estimated inter-vehicle distance, so that a safe distance from the preceding vehicle can be maintained.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a negative pressure booster according to the embodiment.

FIG. 3 is a flowchart illustrating a calculation process of a control device.

FIG. 4 is a flowchart illustrating a calculation process of the control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable pressure chamber 2 Negative pressure chamber 3 Vacuum valve 4 Atmospheric valve 5 Solenoid valve 6 Operating rod 7 Solenoid valve interlocking member 8 Push rod 9 Reaction disc 21 Brake pedal 23 Brake stroke sensor 25 Negative pressure booster 26 Master cylinder 27 Wheel 28 Wheel speed sensor 29 control device 31 laser radar 32 front and rear G sensor

Claims (5)

[Claims] 1. An inter-vehicle distance between a host vehicle and a preceding vehicle is detected,
A brake assist system that increases the brake pressure to the required pressure to maintain a safe distance between vehicles. If the vehicle's braking causes discontinuous detection of the distance between vehicles, the information on the distance between vehicles up to that point will be used after that. A brake assist system that estimates the distance between vehicles and increases the brake pressure to the required pressure to maintain a safe distance based on the estimated distance between vehicles. 2. The brake assist system according to claim 1, wherein the inter-vehicle distance is estimated from the inter-vehicle distance at the time when the vehicle is braked and the inter-vehicle distance change amount per unit time immediately before the braking. Brake assist system. 3. The brake assist system according to claim 1, wherein the estimation of the inter-vehicle distance is not performed when the deceleration of the own vehicle is equal to or less than a predetermined value. 4. The brake assist system according to claim 1, wherein the estimation of the inter-vehicle distance is not performed when the own vehicle is not in a straight traveling state. 5. The brake assist system according to claim 1, wherein the estimation of the inter-vehicle distance is not performed when the suspension deflection of the own vehicle is equal to or less than a predetermined value.