JPH05310108A - Automatic brake device for vehicle - Google Patents

Abstract

PURPOSE:To prevent vibrational deceleration in the vicinity of an objective deceleration and also increase the accuracy of feedback control with quick deceleration assured at the time of automatic braking. CONSTITUTION:A control part 50 is provided which automatically increases the brake pressure of every wheel at a specific duty ratio for evading touching a forward obstacle and so on, and also feedback-controls the brake pressure so that the actual deceleration of own vehicle becomes the objective deceleration. The control part 50 has a dead zone setting means 53, regulating the increase and decrease of brake pressure always when a difference between the actual deceleration of own vehicle and the objective deceleration is in a dead zone having a given width during feedback control; and a correcting means 56, lessening the duty ratio of both pressure increase and decrease sides, and making correction so as to narrow the width of the dead zone when the actual deceleration of the own vehicle enters the dead zone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic braking system for a vehicle which automatically applies a brake to each wheel when avoiding contact with an obstacle in front of the vehicle. The present invention relates to an improvement of feedback control of the brake pressure so that the deceleration becomes the target deceleration.

[0002]

2. Description of the Related Art Conventionally, as an automatic braking device for a vehicle of this type, as disclosed in, for example, Japanese Patent Publication No. 39-2565 and Japanese Patent Publication No. 39-5668, an optical method or ultrasonic frequency etc. Continuously detect the distance and relative speed between the host vehicle and the obstacle in front of it, judge the possibility of contact from the detection result, and activate the actuator when there is a possibility of contact. It is known to automatically apply a brake on each wheel to avoid contact with a front obstacle.

In such an automatic braking device, feedback control is introduced so that the actual deceleration of the host vehicle becomes a target deceleration set to avoid contact. For example, in Japanese Unexamined Patent Publication No. 52-1212238, deceleration detecting means for detecting the actual deceleration of the own vehicle is compared with the actual deceleration of the own vehicle detected by the detecting means and the target deceleration. However, it is disclosed that a correction circuit that corrects the control signal for the actuator according to the comparison value is provided, and the operation of the actuator is feedback-controlled by the corrected control signal. In this feedback control, the actual deceleration of the host vehicle and the target deceleration are not necessarily controlled so that they are exactly the same, but when the difference is within a predetermined value, the brake pressure of the actuator is reduced. A dead zone area is provided to regulate the increase / decrease pressure regulation. Further, the actuator has a switching valve for pressure adjustment, and the opening / closing of the switching valve is switched at a predetermined duty ratio to perform the pressure adjustment stepwise.

[0004]

The duty ratio is set to a relatively large value so that the host vehicle can be quickly decelerated to the target deceleration during automatic braking. Therefore, even when the actual deceleration of the host vehicle enters the dead zone, it is likely to be changed beyond that zone. And the overshoot of this deceleration is
There is a problem that the deceleration of the vehicle becomes oscillating in combination with the behavior delay of the vehicle from the time when the actuator is operated (that is, the switching valve is opened / closed) to the time when the vehicle actually appears as deceleration.

The present invention has been made in view of the above points, and an object of the present invention is to ensure rapid deceleration during automatic braking and prevent vibrational deceleration near a target deceleration. In addition, it is an object of the present invention to provide an automatic braking device for a vehicle that can improve the accuracy of feedback control.

[0006]

In order to achieve the above object, the invention according to claim 1 automatically increases the brake pressure of each wheel at a predetermined duty ratio under a predetermined condition, and at the same time, an actual vehicle is used. In the automatic braking device of the vehicle configured to feedback control the brake pressure so that the deceleration of becomes the target deceleration, the difference between the actual deceleration of the host vehicle and the target deceleration during the feedback control is Dead zone area setting means for regulating the increase / decrease of the brake pressure when the vehicle is in the dead zone area of a predetermined width, and the pressure increasing side and the pressure reducing side of the vehicle when the actual deceleration of the host vehicle enters the dead zone area. A correction means for reducing both the tee ratios and narrowing the width of the dead zone region is provided.

The invention according to claim 2 is based on the same premise as that of the invention according to claim 1, in which the difference between the actual deceleration of the host vehicle and the target deceleration during the feedback control is When the vehicle is in the dead zone area of a predetermined width, the dead zone area setting means for regulating the increase / decrease of the brake pressure is always provided, and when the actual deceleration of the host vehicle enters the dead zone area And a correction unit that reduces only the duty ratio on the pressure increasing side or the pressure reducing side and narrows the width of the dead zone region.

Furthermore, the invention according to claim 3 is based on the same premise as that of the invention according to claim 1 in an automatic braking device for a vehicle,
During the feedback control, when the difference between the actual deceleration of the host vehicle and the target deceleration falls within a dead zone area of a predetermined width, dead zone area setting means for regulating the increase / decrease of the brake pressure for a predetermined time, and When the predetermined time elapses from the time when the actual deceleration of the vehicle enters the dead zone, only the duty ratio on the pressure increasing side or the pressure reducing side is reduced according to the target deceleration, and the dead zone is set. A correction unit that corrects the width of the region is provided.

[0009]

With the above construction, in the invention according to claim 1,
During automatic braking, when the host vehicle decelerates to a target deceleration with a relatively large duty ratio and enters the dead zone, the correction means changes the duty ratio to a small value on both the pressure increasing side and the pressure reducing side. As a result, the brake pressure is gradually increased or decreased. As a result, the deceleration of the vehicle does not vibrate beyond the dead zone. Further, since the width of the dead zone is narrowed by the correction means, the actual deceleration of the host vehicle is made to match the target deceleration.

Here, when the possibility of contact newly occurs and the target deceleration is set, or when the target deceleration is significantly changed during feedback control of automatic braking, the vehicle deceleration is decelerated. It is practically difficult to prevent the first overshoot at the time of first entering the dead zone region, and the invention according to claim 1 prevents the second and subsequent overshoots.

In the second and third aspects of the present invention, the second overshoot is exclusively prevented in consideration of the difficulty of preventing the first overshoot. That is, according to the second aspect of the invention, when the deceleration of the vehicle enters the dead zone, only the duty ratio on the pressure increasing side or the pressure reducing side, which is the second overshoot side, is changed to a small value, and the brake is applied. The second overshoot is prevented by gently increasing or decreasing the pressure. Further, in the invention according to claim 3, when the deceleration of the vehicle enters the dead zone, the increase and decrease of the brake pressure is restricted for a predetermined time until the first overshoot occurs, and then the second overshoot is performed. Only the duty ratio on the pressure-increasing side or the pressure-decreasing side, which is the shoot side, is changed to a small value, and the brake pressure is gradually increased or decreased to prevent the second overshoot.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an automatic braking device for a vehicle according to an embodiment of the present invention, FIG. 1 is a hydraulic circuit diagram of the automatic braking device, and FIG. 2 is a block diagram of the automatic braking device. Is.

In FIG. 1, reference numeral 1 is a master back for increasing a pedaling force of a brake pedal 2 by a driver, and 3 is a master cylinder for generating a brake pressure according to the pedaling force increased by the master back 1. The brake pressure generated in the master cylinder 3 is first sent to the hydraulic actuator unit 4 of the automatic braking device, and then passed through the hydraulic actuator unit 5 of the anti-skid brake device (ABS) to the four wheels (only one wheel is shown in the figure). It is adapted to be supplied to each brake device 6.

The hydraulic actuator section 4 of the automatic braking device has a shutter valve 11, a pressure increasing valve 12 and a pressure reducing valve 13 for cutting off the communication between the master cylinder 3 and the brake device 6 side. One valve 1
All of 1 to 13 are electromagnetic 2-port 2-position switching valves. Between the pressure increasing valve 12 and the master cylinder 3, a motor-driven oil pump 14 and the oil pump 1 are provided.
An accumulator 15 for accumulating the pressure oil discharged from No. 4 and keeping it at a constant pressure is interposed. When the shutter valve 11 is in the open position, the brake device 6 for each wheel is moved according to the depression force of the brake pedal 2.
Brakes on. On the other hand, when the shutter valve 11 is in the closed position, the pressure increasing valve 12 is in the open position and the pressure reducing valve 1 is in the open position.
3 is switched to the closed position, the pressure oil from the accumulator 15 is supplied to the brake device 6 of each wheel to increase the brake pressure, and the pressure increasing valve 12 is closed and the pressure reducing valve 13 is opened. When each of them is switched, pressure oil is returned from the brake device 6 to reduce the brake pressure.

Further, the ABS hydraulic actuator section 5 has a 3-port 2-position switching valve 21 provided for each wheel, and is applied to each braking device 6 by switching the valve 21 during ABS operation. The brake pressure is controlled to prevent each wheel from locking. Although the structure of the hydraulic actuator unit 5 is not described in detail, in addition to the switching valve 21, a motor-driven oil pump 22 and accumulators 23 and 24 are provided. The brake device 6 for each wheel includes a disk 26 that rotates integrally with the wheel, and a caliper 27 that receives the brake pressure from the master cylinder 3 side and clamps the disk 26.

On the other hand, in FIG. 2, reference numeral 31 denotes an ultrasonic radar unit provided in the front part of the vehicle body. The ultrasonic radar unit 31 is not shown in detail in the drawing, but as is well known, the ultrasonic wave is emitted from the transmitting portion. It is configured to transmit toward an obstacle such as a vehicle in front of the own vehicle, and to receive a reflected wave reflected by hitting the front obstacle at the receiving unit,
Calculation unit 32 for receiving signals from this radar unit 31
Is configured to calculate the distance and relative speed between the host vehicle and a front obstacle based on the delay time from the time when the radar received wave is transmitted. Reference numerals 33 and 34 denote a pair of radar head units respectively provided on the left and right of the front part of the vehicle body, and each of the radar head units 33 and 34 transmits a pulse laser beam from an emission unit toward an obstacle in front of the vehicle. In addition, the reception unit receives the reflected light reflected by the front obstacle, and the calculation unit 32
Receives signals from these radar head units 33 and 34 through the signal processing unit 35, and calculates the distance and relative speed between the host vehicle and the obstacle ahead by the delay time from the emission point of the laser reception light. It has become. Then, the calculation unit 32 uses the radar head units 33, 3
Priority is given to the calculation results of distance and relative speed by the system of 4,
The calculation result of the distance and the relative speed by the system of the ultrasonic radar unit 31 is used as an auxiliary, and the distance and the relative speed for detecting the distance and the relative speed between the own vehicle and the obstacle ahead of the vehicle are detected. The relative speed detecting means 36 is configured.

A transmission / reception direction of the pulse laser light by the both radar head units 33, 34 is provided by a motor 37 so that it can be changed in the horizontal direction.
The operation of is controlled by the arithmetic unit 32. Reference numeral 38 denotes an angle sensor for detecting the transmission / reception direction of the pulsed laser light from the rotation angle of the motor 37. The detection signal of the angle sensor 38 is input to the arithmetic unit 32, and the radar head unit 33 in the arithmetic unit 32, The transmission / reception direction of the pulsed laser light is added to the calculation of the distance and the relative speed by the system of 34.

Reference numeral 41 denotes a rudder angle sensor for detecting the rudder angle,
42 is a vehicle speed sensor that detects the vehicle speed, 43 is a longitudinal G sensor that detects longitudinal acceleration (longitudinal G) of the vehicle, and 44 is a road surface μ sensor that detects the friction coefficient (μ) of the road surface. 44 detection signal and the arithmetic unit 3
The signals of the distance and the relative speed between the host vehicle and the front obstacle obtained in 2 are input to the contact possibility determination unit 45. The contact possibility determination unit 45 determines the possibility of contact between the host vehicle and the front obstacle based on the distance and the relative speed between the host vehicle and the front obstacle. When the section 45 determines that there is a possibility of contact, a signal is output from the determination section 45 to the control section 50 that controls the operation of the hydraulic actuator section 4 of the automatic braking device to avoid contact. The brakes are applied automatically on each wheel. Reference numeral 46 denotes an alarm display unit provided on the instrument panel in the vehicle compartment. The alarm display unit 46 is provided with an alarm buzzer 47 and a distance display unit 48 which receive signals from the contact possibility determination unit 45. There is.

The contact possibility judging section 45 first uses a threshold map stored in advance as shown in FIG. 3 in order to avoid contact with an obstacle in front of the vehicle. Calculate the threshold value L0 of the distance that must be multiplied. Next, a predetermined distance is added to each of the threshold values L0 to calculate the distance at which the slow braking is applied before the sudden braking and the distance at which the alarm buzzer 47 issues an alarm. Here, the sudden braking or the full braking means braking at the maximum deceleration (about 0.8 G), and the slow braking is the deceleration lower than the maximum deceleration (about 0.3 to 0.4).
G) means to apply a constant brake. Further, the distance for applying the slow braking is set to be several times longer than the distance for applying the sudden braking, and the distance for issuing the alarm is set longer than the distance for applying the slow braking.

In the threshold map shown in FIG. 3, a threshold line A indicates that a front vehicle as a front obstacle avoids contact with an obstacle ahead of the vehicle when the vehicle stops and stops. It indicates the vehicle-to-vehicle distance required to do so, and is the same as when the front obstacle is a stationary object (that is, when the relative speed V1 is the same as the own vehicle speed v0) regardless of the magnitude of the relative speed V1. It takes a value (numeric expression v0 ² / 2μg). The threshold line B indicates the inter-vehicle distance (numerical expression V1. (2v0-V1) / 2 .mu.g) necessary to avoid contact with the vehicle in front when the front vehicle is fully braked, and the threshold line C Indicates the inter-vehicle distance required to avoid contact with the preceding vehicle when the preceding vehicle is subjected to slow braking with a deceleration of μ / 2 g, and the threshold line D indicates this vehicle when the preceding vehicle maintains a constant vehicle speed. shows the inter-vehicle distance (numeric expression V1 ^2/2 [mu] g) required to avoid contact with. Furthermore, the threshold line E is
Although the vehicle cannot avoid contact with the vehicle in front even if self-braking is applied, it indicates the inter-vehicle distance that can reduce the impact force at the time of contact. When the threshold line is on the horizontal axis (that is, when the threshold L0 is always zero), the automatic braking is not applied and this is canceled.

Then, the contact possibility judging section 45 selects one threshold line from the above-mentioned five types of threshold lines A to E according to the driving state of the vehicle. On the line, a threshold value L0 corresponding to the relative speed V1 between the host vehicle and the front obstacle (front vehicle) is calculated. For example, when the vehicle speed v0 is high, the threshold line B is set to the vehicle speed v0
When the vehicle speed is medium, the threshold value D is selected, and when the vehicle speed v0 is low, the threshold line E is selected to change the threshold value L0 of the possibility of contact to a higher value as the vehicle speed becomes higher. ..

When the distance between the host vehicle and the obstacle ahead reaches the distance at which an alarm is issued, the contact possibility judging unit 4
An operation command signal is output from 5 to the alarm buzzer 47 and an alarm sound is emitted. Further, when the distance between the host vehicle and the front obstacle becomes further closer to reach the distance at which the slow braking or the rapid braking is applied, the contact possibility determination unit 45 outputs a deceleration command signal to the control unit 50, and the control is performed. Under the control of the section 50, the hydraulic actuator section 4 of the automatic braking device is actuated to apply slow braking or sudden braking.

As shown in FIG. 4, the control unit 50 controls the target deceleration Gr set by the contact possibility determination unit 45.
And a detection signal from the deceleration detecting means 51 for detecting the actual deceleration Ga of the host vehicle, a comparison circuit for calculating a difference e between the actual deceleration Ga of the own vehicle and the target deceleration Gr. 52 and a dead zone area for regulating the increase / decrease of the brake pressure when the difference e between the actual deceleration Ga of the host vehicle calculated by the comparison circuit 52 and the target deceleration Gr is within the dead zone area of a predetermined width. The setting means 53 and the duty ratio when the brake pressure is increased / decreased (the pressure increasing valve 12 for the control cycle T).
Alternatively, the ratio Ton / of the time Ton in the ON state of the pressure reducing valve 13
T), the duty ratio setting means 54, the dead zone area setting means 53, and the duty ratio setting means 54.
When the difference e between the actual deceleration Ga of the host vehicle and the target deceleration Gr is received outside the dead zone, the hydraulic actuator section of the automatic braking device is operated with the duty ratio set by the setting means 54. 4 is an operation command section 5 for instructing switching of the pressure increasing valve 12 and the pressure reducing valve 13 to open and close.
5, and feedback control is performed so that the actual deceleration Ga of the host vehicle becomes the target deceleration Gr.

Further, the control unit 50 receives correction signals from the contact possibility determination unit 45 (see FIG. 2), the deceleration detection unit 51, and the dead zone region setting unit 53.
Is equipped with. When the difference e between the actual deceleration Ga of the host vehicle and the target deceleration Gr falls within the dead zone, the correction means 56 reduces the duty ratios on both the pressure increasing side and the pressure reducing side. A correction signal is output to the ratio setting means 54 and a correction signal is output to the dead zone area setting means 53 so as to narrow the width of the dead zone area.

FIG. 5 shows a flow chart of the feedback control by the control unit 50. In this flow chart, after starting, first of all, step S1
After the target deceleration Gr and the actual deceleration Ga are taken in, the difference e between the target deceleration Gr and the actual deceleration Ga is calculated in step S2.

Then, in step S3, it is determined whether or not the absolute value of the difference e is larger than the half value δ0 of the width of the dead zone, that is, as shown in FIG. 6, the actual deceleration Ga rises. , It is determined whether or not the target has entered the dead zone area of the predetermined width 2δ0 centered on the target deceleration Gr. This judgment is NO
In the case of, it is determined in step S4 whether the difference e is a positive value, that is, whether the target deceleration Gr is larger than the actual deceleration Ga. And the target deceleration Gr
If YES is greater than the actual deceleration Ga, the brake pressure is increased with a relatively large duty ratio D0 in step S5, and the routine returns, while if the target deceleration Gr is NO that is less than the actual deceleration Ga. , In step S6, the brake pressure is reduced at the duty ratio D0, and the process returns.

On the other hand, when the determination in step S3 is YES, that is, when the actual deceleration Ga has entered the dead zone, the difference e between the target deceleration Gr and the actual deceleration Ga is positive in step S7. Or not. When the target deceleration Gr is larger than the actual deceleration Ga, the absolute value of the difference e is δ1 (<δ0) which is a half of the predetermined width of the dead zone in step S8.
), That is, whether or not the actual deceleration Ga is outside the dead zone region of a relatively narrow predetermined width 2δ1 centered around the target deceleration Gr. Actual deceleration G
If a is YES outside the dead zone, the brake pressure is increased with a relatively small duty ratio D1 (<D0) in step S10 and the routine returns, while if the actual deceleration Ga is NO within the dead zone, , Step S
Hold it as it is without increasing or decreasing the brake pressure at 11,
To return.

When the determination in step S7 is NO, that is, when the target deceleration Gr is smaller than the actual deceleration Ga, the target deceleration Gr is further calculated in step S9.
Whether the absolute value of the difference e between the actual deceleration Ga and the actual deceleration Ga is larger than a value δ1 which is one half of the predetermined width of the dead zone, that is, the actual deceleration Ga is centered on the target deceleration Gr. It is determined whether or not it is outside the dead zone area of width 2δ1. If the actual deceleration Ga is outside the dead zone region, YES, in step S12, the brake pressure is reduced at a relatively small predetermined duty ratio D1, and the routine returns, while the actual deceleration Ga is within the dead zone region NO. In case of, in step S13, the brake pressure is not increased or decreased but is maintained as it is, and the process returns.

Therefore, according to the feedback control according to such a flow chart, the contact possibility judging section 4
When it is determined in 5 that there is a possibility of contact between the host vehicle and the front obstacle, and the determination unit 45 outputs a signal of the target deceleration Gr for avoiding the contact to the control unit 50, By increasing the brake pressure with a relatively large duty ratio D0 (step S5), the actual deceleration Ga of the host vehicle rapidly increases and quickly reaches the target deceleration Gr. Therefore, contact avoidance can be surely performed.

When the actual deceleration Ga of the host vehicle approaches the target deceleration Gr and enters the dead zone of the predetermined width 2δ0, the duty ratio D0 is smaller than that on both the pressure increasing side and the pressure reducing side. The value is changed to D1 (<D0), and the brake pressure is gently increased / decreased by this small duty ratio D1 (steps S10 and S12). As a result, it is possible to prevent the deceleration of the vehicle from vibrating beyond the dead zone, and it is possible to ensure smooth automatic braking. Moreover, the width of the dead zone is 2
Since δ0 is changed to a smaller value 2δ1 (<2δ0) and narrowed, the actual deceleration Ga of the host vehicle can be more accurately matched with the target deceleration Gr, and the accuracy of feedback control is improved. You can

7 and 8 are flow charts showing a modification of the feedback control. In this flowchart, after starting, first, in step S
At 21, the current target deceleration Gr1 and the previous target deceleration Gr0
Then, after taking in the actual deceleration Ga, it is judged in step S22 whether or not a new target deceleration Gr2 is given,
If the determination is YES, in step S23, the new target deceleration Gr2 and the current target deceleration Gr1 are replaced with the current target deceleration Gr1 and the previous target deceleration Gr0, respectively, and then the process returns.

When the determination in step S22 is NO, the difference e between the current target deceleration Gr1 and the actual deceleration Ga of the host vehicle is calculated in step S24, and then the current target deceleration Gr1 is calculated in step 25. The magnitude relation with the target deceleration Gr0 is judged. Here, when the target deceleration Gr1 at the present time is larger than the previous target deceleration Gr0, when slow braking or sudden braking is automatically applied while the vehicle is traveling, or when shifting from slow braking to sudden braking When the current target deceleration Gr1 becomes smaller than the previous target deceleration Gr0, it is the case where the sudden braking is changed to the slow braking (see FIG. 9).

When the current target deceleration Gr1 is greater than the previous target deceleration Gr0, the absolute value of the difference e between the current target deceleration Gr1 and the actual deceleration Ga of the host vehicle is the dead zone in step S26. Whether the actual deceleration Ga rises toward the target deceleration GrH for sudden braking, as shown in FIG. 9, for example, as shown in FIG. = GrH) centered width 2
It is determined whether or not the dead zone area of δ0 is entered.

When the determination in step S26 is NO, it is determined in step S27 whether the difference e between the current target deceleration Gr1 and the actual deceleration Ga of the vehicle is a positive value.
That is, it is determined whether the current target deceleration Gr1 is greater than the actual deceleration Ga. When the target deceleration Gr1 at the present time is YES, which is larger than the actual deceleration Ga, the brake pressure is increased with a relatively large duty ratio D0 in step S28, and the routine returns while the target deceleration Gr is actually reduced. When NO is smaller than the speed Ga,
In step S29, the brake pressure is reduced at the duty ratio D0, and the process returns.

On the other hand, when the determination in step S26 is YES, that is, when the actual deceleration Ga has entered the dead zone, the difference e between the current target deceleration Gr1 and the actual deceleration Ga is determined in step S30. It is determined whether it is a positive value. The current target deceleration Gr is the actual deceleration G.
If YES is larger than a, it is further determined in step S31 whether the absolute value of the difference e is larger than the half value δ1 (<δ0) of the predetermined width of the dead zone, that is, the actual deceleration Ga is present. It is determined whether or not it is outside the dead zone area of the relatively narrow predetermined width 2δ1 centered on the target deceleration Gr1 of. Actual deceleration Ga is outside the dead zone YES
If NO, the brake pressure is increased with a relatively large duty ratio D0 in step S33, and the routine returns. On the other hand, if the actual deceleration Ga is NO in the dead zone, the brake pressure is maintained as it is without increasing or decreasing in step S34. And then return.

When the determination in step S30 is NO, that is, the target deceleration Gr1 at the present time is the actual deceleration Ga.
If the absolute value of the difference e between the current target deceleration Gr1 and the actual deceleration Ga is larger than the half value δ1 of the predetermined width of the dead zone, that is, the actual The deceleration Ga of is the target deceleration Gr1 at the present time.
It is determined whether or not it is outside the dead zone region having a relatively narrow predetermined width 2δ1 centered at. If the actual deceleration Ga is outside the dead zone, YES, in step S35, the brake pressure is reduced with a relatively small duty ratio D1, and the routine returns, while if the actual deceleration Ga is within the dead zone, NO. In step S34, the brake pressure is maintained as it is without increasing or decreasing, and the process returns.

When the determination in step S25 is NO, that is, when the current target deceleration Gr1 is smaller than the previous target deceleration Gr0, the current target deceleration Gr1 and the actual deceleration Ga of the host vehicle are determined in step S36. Whether or not the absolute value of the difference e is smaller than the half value δ0 of the width of the dead zone region,
For example, as shown in FIG. 9, the actual deceleration Ga decreases from the rapid deceleration target deceleration GrH toward the slow braking target deceleration GrL, and is centered around the current target deceleration Gr1 (= GrL). It is determined whether or not it has entered the dead zone area of width 2δ0.

When the determination in step S36 is NO, the process proceeds to steps S27 to S29, in which the brake pressure is increased with a relatively large duty ratio D0 according to the magnitude relationship between the target deceleration Gr and the actual deceleration Ga. If the determination is YES while the pressure or the pressure is reduced, it is determined in step S37 whether the difference e between the current target deceleration Gr1 and the actual deceleration Ga is a positive value. And the current target deceleration G
When r is YES that is greater than the actual deceleration Ga,
In step S38, it is further determined whether or not the absolute value of the difference e is larger than the half value δ1 (<δ0) of the predetermined width of the dead zone, that is, the actual deceleration Ga is the current target deceleration Gr1.
It is determined whether or not it is outside the dead zone region having a relatively narrow predetermined width 2δ1 centered at. When the actual deceleration Ga is outside the dead zone, YES, the brake pressure is increased with a relatively small duty ratio D1 in step S40, and the routine returns, while when the actual deceleration Ga is within the dead zone, NO. In step S41, the brake pressure is maintained as it is without increasing or decreasing, and the process returns.

When the determination in step S37 is NO, that is, the target deceleration Gr1 at the present time is the actual deceleration Ga.
If the absolute value of the difference e between the current target deceleration Gr1 and the actual deceleration Ga is larger than the half value δ1 of the predetermined width of the dead zone, that is, the actual The deceleration Ga of is the target deceleration Gr1 at the present time.
It is determined whether or not it is outside the dead zone area having a relatively narrow predetermined width Δ1 centered at. If the actual deceleration Ga is outside the dead zone, YES, in step S42, the brake pressure is reduced with a relatively large duty ratio D0 and the routine returns, while the actual deceleration Ga is within the dead zone N.
When it is O, the brake pressure is maintained as it is without increasing or decreasing in step S41, and the process returns.

According to the feedback control according to such a flow chart, when the current target deceleration Gr1 becomes larger than the previous target deceleration Gr0, for example, when slow braking or sudden braking is automatically applied while the vehicle is traveling. First, the brake pressure is increased at a relatively large duty ratio D0 (step S28), and the actual deceleration Ga of the host vehicle quickly approaches the target deceleration Gr1 at the present time. Then, when the actual deceleration Ga enters the dead zone region of the predetermined width 2δ0 centered on the current target deceleration Gr1, the duty ratio D0 is the same value on the pressure increasing side, but is on the depressurizing side. It is changed to a smaller value D1 (<D0) (step S35). Therefore, as shown in FIG. 9, when the actual deceleration Ga exceeds the target deceleration GrH for sudden braking, overshoots once outside the dead zone, and then decreases again toward the target deceleration GrH, the brake is applied. The pressure is gradually reduced and gradually approaches the target deceleration GrH, and it is possible to prevent the deceleration of the vehicle from vibrating beyond the dead zone.

When the target deceleration Gr1 at the present time is smaller than the previous target deceleration Gr0, such as when shifting from sudden braking to gentle braking, the brake pressure is first reduced at a relatively large duty ratio D0 (step S29), the actual deceleration Ga of the host vehicle quickly approaches the current target deceleration Gr1. Then, when the actual deceleration Ga enters the dead zone region of the predetermined width 2δ0 centered on the current target deceleration Gr1, the duty ratio D0 is the same value on the pressure reducing side, but is on the pressure increasing side. Less than D1 (<
It is changed to D0) (step S40). Therefore, in FIG.
As shown in, when the actual deceleration Ga exceeds the target deceleration GrL of the slow braking and overshoots to outside the dead zone once, and then increases again toward the target deceleration GrL, the braking pressure gradually increases. It becomes possible to prevent the deceleration of the vehicle from vibrating beyond the dead zone by being pressed and gradually approaching the target deceleration GrL.

Further, in any of the cases where the above-mentioned current target deceleration Gr1 becomes larger than the previous target deceleration Gr0 and when the current target deceleration Gr1 becomes smaller than the previous target deceleration Gr0. , When the actual deceleration Ga enters the dead zone area, the width 2δ0 of the dead zone area is changed to a smaller value 2δ1 (<2δ0) and narrowed, so that the actual deceleration Ga of the host vehicle is set as the target. Deceleration G
The r value can be matched more accurately, and the accuracy of feedback control can be improved.

FIG. 10 is a flow chart showing another modification of the feedback control. In this flowchart, after the start, first of all, step S51
It is determined whether or not the automatic braking is being controlled. If the determination is YES, the process proceeds to step S52, while if the determination is NO, the counter c and the holding confirmation flag f are both cleared to zero in step S67, and then the process returns.

In step S52, the target deceleration Gr and the actual deceleration Ga are fetched, and thereafter, step S52.
At 53, it is determined whether the holding confirmation flag f is "1",
When this determination is NO, the difference e between the target deceleration Gr and the actual deceleration Ga is calculated in step S54. Then, in step S55, it is determined whether or not the difference e is larger than the width δu of the pressure-increasing side portion of the dead zone (that is, the portion between the target deceleration and the lower limit of the dead zone), that is, the actual deceleration Ga increases. It is determined whether the pressure is within the dead zone area. When the determination is not within the dead zone area of YES, the brake pressure is increased at a relatively large duty ratio Du in step S56 and the routine returns, while when the determination is within the dead zone area of NO In step S57, the brake pressure is held without being increased or decreased, and the holding confirmation flag f is set to "1",
To return.

If the determination in step S53 is YES, that is, after the actual deceleration Ga enters the dead zone, is the counter c at a predetermined number n (about 3 times) in step S58? Determine whether or not. When this determination is NO, after the counter c is incremented in step S65, the process returns with the brake pressure held in step S66. On the other hand, if the determination is YES, the difference e between the target deceleration Gr and the actual deceleration Ga is calculated in step S59, and then the absolute value of the difference e is calculated in step S60 so that the depressurization side portion of the dead zone (that is, the target). It is determined whether or not it is larger than a width Δd1 of a portion between the deceleration and the dead zone region upper limit value).

When the determination in step S60 is YES, the brake pressure is reduced with a relatively large duty ratio Dd1 in step S64, and the process returns. When the determination in step S60 is NO, it is further determined in step S61 whether or not the absolute value of the difference e is larger than the width δd2 (<δd1) of the pressure reducing side portion of the dead zone region. If this determination is YES, the duty ratio Dd2 is relatively small in step S63.
(<Dd1) reduces brake pressure and returns,
When the determination is NO, the brake pressure is maintained without being increased or decreased in step S62, and the process returns.

According to the feedback control according to the flow chart as described above, when the slow braking or the sudden braking is automatically applied while the vehicle is running, the brake pressure is increased with a relatively large duty ratio Du (step S56), The actual deceleration Ga of the vehicle quickly approaches the target deceleration Gr. When the actual deceleration Ga enters the pressure-increasing side portion within the dead zone slightly lower than the target deceleration Gr, the brake pressure is not increased or decreased for a predetermined time (until the counter c reaches the predetermined number of times n). During the period), it is held constant (steps S57 and S66). During this period, the actual deceleration Ga is based on the vehicle behavior delay from the time when the pressure increase at the actuator section is stopped until the deceleration of the vehicle actually becomes constant.
It may exceed the target deceleration Gr and may overshoot to outside the dead zone.

When the actual deceleration Ga overshoots beyond the dead zone at the time when the predetermined time has elapsed, the brake pressure is reduced with a relatively large duty ratio Dd1 (step S64). When the actual deceleration Ga is on the pressure reducing side of the predetermined width δd1 within the dead zone after the elapse of a predetermined time, or the actual deceleration Ga is on the pressure reducing side within the dead zone due to the reduction of the brake pressure. If the brake pressure is reduced to, the brake pressure is gently reduced with a relatively small duty ratio Dd2 (step S63). For this reason, the actual deceleration Ga becomes asymptotic to the target deceleration Gr1, and it is possible to prevent the deceleration of the vehicle from vibrating beyond the dead zone. Moreover, at this time, since the width δd1 of the pressure reducing side portion of the dead zone is changed to a smaller value δd2 (<δd1) and narrowed, the actual deceleration Ga of the host vehicle is reduced to the target deceleration G.
The r can be matched more accurately, and the accuracy of feedback control can be improved.

In this feedback control,
Although only the case where the target deceleration at the present time is larger than the previous target deceleration, such as when the vehicle is automatically driven by slow braking or sudden braking, the feedback control shown in FIGS. Similarly, it is needless to say that the present invention may be applied to the case where the deceleration is feedback-controlled when the current target deceleration is smaller than the previous target deceleration.

Further, in the above embodiment, the automatic braking device for applying the automatic brake for avoiding contact with the obstacle is described, but the present invention is not limited to this, and the own vehicle may be stopped at a predetermined stop line. Further, it can be similarly applied to an automatic braking device or the like that automatically decelerates to a predetermined legal speed or a safe speed when the vehicle speed is over.

[0052]

As described above, according to the automatic vehicle braking system of the present invention, when the actual deceleration of the host vehicle enters the dead zone during automatic braking, the duty ratio is reduced and the width of the dead zone is reduced. By making the change so as to narrow it, it is possible to prevent the deceleration of the vehicle from vibrating beyond the dead zone area while shortening the time to reach the target deceleration, and The actual deceleration can be more accurately matched with the target deceleration to improve the accuracy of feedback control.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of an automatic braking device for a vehicle according to an embodiment of the present invention.

FIG. 2 is a block diagram of an automatic braking device.

FIG. 3 is a diagram showing a map for calculating a contact avoidance threshold value.

FIG. 4 is a block configuration diagram of a control unit.

FIG. 5 is a flowchart of feedback control by a control unit.

FIG. 6 is a diagram showing a change state of an actual deceleration with respect to a target deceleration.

FIG. 7 is a flowchart showing a modified example of feedback control.

FIG. 8 is a flowchart of the same.

9 is a view corresponding to FIG.

FIG. 10 is a flowchart showing another modified example of feedback control.

[Explanation of symbols]

 36 Distance / Relative Velocity Detection Means 45 Contact Possibility Judgment Unit 50 Control Unit 51 Deceleration Detection Means 52 Comparison Circuit 53 Dead Zone Area Setting Means 54 Duty Ratio Setting Means 55 Operation Command Unit 56 Correction Means

Claims (3)

[Claims] 1. The brake pressure of each wheel is automatically increased under a predetermined condition at a predetermined duty ratio, and the brake pressure is feedback-controlled so that the actual deceleration of the vehicle becomes a target deceleration. In the automatic braking device for a vehicle configured as described above, when the difference between the actual deceleration of the host vehicle and the target deceleration during the feedback control is within a dead zone region of a predetermined width, the increase / decrease of the brake pressure is regulated. The dead zone region setting means and the duty ratio on the pressure increasing side and the pressure reducing side when the actual deceleration of the host vehicle enters the dead zone region are both reduced, and the width of the dead zone region is narrowed. An automatic braking device for a vehicle, comprising: a correction unit. 2. The brake pressure of each wheel is automatically increased under a predetermined condition at a predetermined duty ratio, and the brake pressure is feedback-controlled so that the actual deceleration of the vehicle becomes a target deceleration. In the automatic braking device for a vehicle configured as described above, when the difference between the actual deceleration of the host vehicle and the target deceleration during the feedback control is within a dead zone region of a predetermined width, the increase / decrease of the brake pressure is regulated. Dead zone region setting means for reducing the duty ratio on the pressure increasing side or the pressure reducing side according to the target deceleration when the actual deceleration of the host vehicle enters the dead zone region. The automatic braking device for a vehicle, comprising: a correcting unit that corrects the width of the vehicle. 3. The brake pressure of each wheel is automatically increased under a predetermined condition at a predetermined duty ratio, and the brake pressure is feedback-controlled so that the actual deceleration of the vehicle becomes a target deceleration. In the automatic braking device for a vehicle configured as described above, during the feedback control, when the difference between the actual deceleration of the host vehicle and the target deceleration falls within the dead zone of a predetermined width, the braking pressure is increased or decreased. Dead zone area setting means for regulating for a predetermined time, and when the predetermined time elapses from the time when the actual deceleration of the host vehicle enters the dead zone, the pressure increasing side or the pressure reducing side depending on the target deceleration. An automatic braking device for a vehicle, comprising: a correction unit that reduces only the duty ratio and corrects the width of the dead zone region.