JPH05319234A - Automatic brake device for vehicle - Google Patents

Abstract

PURPOSE:To prevent generation of pulsation due to repetition of switching a pressure governing valve opened/closed while sufficiently ensuring a rise up of fluid pressure at quick braking time. CONSTITUTION:A device is constituted by providing a fluid pressure generating source 33 composed of an oil pump 31 or the like for generating a specified fluid pressure independently of step-in operation of a brake pedal 22 and pressure governing valves 41, 42 provided in a hydraulic passage 34 of connecting the generating source to a brake unit of each wheel, so as to automatically apply a brake by increasing a pressure of the brake unit of each wheel under a specified condition. The device provides a chamber 44 connected to the hydraulic passage through a communication path 43 and a shutoff valve 45 for interrupting communication between the chamber and the hydraulic passage. Of the automatic braking time, the shutoff valve is controlled so as to open, when target deceleration is low, and close when the target deceleration is high. A pressure regulating valve 48, by which a fluid pressure fed from the fluid pressure generating source is decreased when the target deceleration is low of the automatic braking time, is provided between the fluid pressure generating source in the hydraulic passage and the pressure governing valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle automatic braking device for automatically applying brakes to respective wheels when avoiding contact with a front obstacle, and more particularly to a hydraulic circuit system thereof. ..

[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.

Further, in the hydraulic circuit of the automatic braking device, normally, a hydraulic pressure generating source, such as an oil pump, which generates a predetermined hydraulic pressure independent of the depression operation of the brake pedal, and the generating source and the brake of each wheel. A pressure regulating valve that is provided in a hydraulic passage communicating with the device, and that regulates the hydraulic pressure of the brake device to increase or decrease, and controls the pressure regulating valve during automatic braking to a predetermined duty ratio (time Ton of the pressure regulating valve in the ON state with respect to the control period T).
(Ton / T) ratio is used to open and close the brake system to increase the hydraulic pressure of the brake device for braking.

[0005]

By the way, in such a hydraulic circuit, there is a problem that pulsation occurs with repeated opening and closing switching of the pressure regulating valve, which adversely affects automatic braking itself.

Therefore, in order to solve such a problem, it is conceivable to provide a pulsation absorbing chamber in the hydraulic circuit. In this case, the rise of the hydraulic pressure of the brake device at the initial stage of automatic braking is gentle. Therefore, there is a drawback in that it takes a considerable time for the actual deceleration of the host vehicle to reach the target deceleration, especially during sudden braking with a high target deceleration.

The present invention has been made in view of the above points, and an object thereof is to repeatedly open and close the pressure regulating valve while sufficiently ensuring the rise of hydraulic pressure during sudden braking. It is an object of the present invention to provide an automatic braking device for a vehicle that can effectively prevent the occurrence of pulsation.

[0008]

In order to achieve the above object, the invention according to claim 1 is a hydraulic pressure generating source for generating a predetermined hydraulic pressure independently of a depression operation of a brake pedal, and the generating source. It is provided in a hydraulic passage that communicates with the brake device of each wheel, and is provided with a pressure regulating valve that increases or decreases the hydraulic pressure of the brake device, and increases the hydraulic pressure of the brake device of each wheel under a predetermined condition. In an automatic braking device for a vehicle configured to automatically apply a brake at a target deceleration, a chamber communicated with the hydraulic pressure passage via a communication passage, a chamber provided in the communication passage, and the chamber and the hydraulic pressure are provided. A configuration that includes a shutoff valve that shuts off communication with the passage, and control means that controls the shutoff valve to open when the target deceleration is low during automatic braking and to close the shutoff valve when the target deceleration is high. And

According to a second aspect of the invention, in addition to the constituent features of the first aspect of the invention, the invention is further provided between the hydraulic pressure generation source in the hydraulic pressure passage and the pressure regulating valve, and is a target during automatic braking. A configuration is provided in which a pressure adjusting valve that lowers the hydraulic pressure sent from the hydraulic pressure generation source when the deceleration is low is provided.

[0010]

With the above construction, in the invention according to claim 1,
During automatic braking, when the target deceleration is low, that is, during slow braking, the shut-off valve opens and the chamber communicates with the hydraulic passage, which causes the chamber to repeatedly open and close the pressure regulating valve in the hydraulic passage. It will absorb pulsation. On the other hand, when the target deceleration is high, that is, during sudden braking,
By closing the shutoff valve to cut off the communication between the chamber and the hydraulic passage, the rise of the hydraulic pressure of the brake device is sufficiently secured as in the case where the chamber is not provided.

Here, during the slow braking, the hydraulic pressure difference between the upstream side and the downstream side of the pressure regulating valve in the hydraulic passage becomes larger than during the rapid braking, but in the invention according to claim 2, the pressure adjustment is performed during the slow braking. Since the hydraulic pressure sent from the hydraulic pressure generation source to the pressure regulating valve is lowered by the valve, the hydraulic pressure difference between the upstream side and the downstream side of the pressure regulating valve is almost the same regardless of whether the braking is sudden braking or gentle braking. Be constant.

[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 block diagram of the automatic braking device, and FIG. 2 is a hydraulic circuit diagram of the automatic braking device. Is.

In FIG. 1, reference numeral 1 denotes an ultrasonic radar unit provided in the front part of the vehicle body. The ultrasonic radar unit 1 is not shown in detail in the drawing, but as is well known, the ultrasonic wave is transmitted from the transmitting portion to the own vehicle. Is transmitted to an obstacle such as a vehicle in front of the vehicle, and a reception section receives a reflected wave reflected by the front obstacle, and a calculation section 2 receives a signal from the radar unit 1. 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 3 and 4 denote a pair of radar head units respectively provided on the left and right of the front portion of the vehicle body. The radar head units 3 and 4 transmit pulsed laser light from an emission unit toward an obstacle ahead of the host vehicle. In addition, the reception unit receives the reflected light reflected by the front obstacle, and the calculation unit 2 receives the signals from the radar head units 3 and 4 through the signal processing unit 5. The distance and relative speed between the host vehicle and the obstacle ahead of the vehicle are calculated based on the delay time from the time when the laser received light is transmitted. Then, the calculation unit 2 prioritizes the calculation result of the distance and the relative speed by the system of the radar head units 3 and 4, and uses the calculation result of the distance and the relative speed by the system of the ultrasonic radar unit 1 as an auxiliary. Further, these constitute distance / relative speed detection means 6 for detecting the distance and relative speed between the host vehicle and the obstacle ahead.

The transmitting / receiving direction of the pulsed laser light by the radar head units 3 and 4 is provided so as to be horizontally changeable by a motor 7, and the operation of the motor 7 is controlled by the arithmetic unit 2. Reference numeral 8 denotes an angle sensor that detects the transmission / reception direction of the pulsed laser light from the rotation angle of the motor 7. The detection signal of the angle sensor 8 is input to the calculation unit 2, and the radar head unit 3, 3 in the calculation unit 2 is input. 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 No. 4.

Reference numeral 11 denotes a rudder angle sensor for detecting the rudder angle,
Reference numeral 12 is a vehicle speed sensor that detects the vehicle speed, 13 is a longitudinal G sensor that detects longitudinal acceleration (longitudinal G) of the vehicle, and 14 is a road surface μ sensor that detects a friction coefficient (μ) of the road surface. 14 detection signals and the arithmetic unit 2
The signals of the distance and the relative speed between the host vehicle and the obstacle ahead of the vehicle, which are obtained in step 1, are input to the controller 15 as the control means. The controller 15 determines the possibility of contact between the host vehicle and the front obstacle based on the distance and relative speed between the host vehicle and the front obstacle, and determines that the contact may occur. At this time, an operation signal is output to the hydraulic actuator unit 20 of the automatic braking device, and each wheel is automatically braked so as to avoid contact. Reference numeral 16 denotes an alarm display unit provided on an instrument panel in the vehicle compartment. The alarm display unit 16 is provided with an alarm buzzer 17 and a distance display unit 18 which receive signals from the controller 15, respectively.

The controller 15 first applies sudden braking (also called full braking) to avoid contact with a front obstacle by using a threshold map stored in advance as shown in FIG. Calculate the distance threshold L0 that must be present. Next, a predetermined distance is added to each of the threshold values L0 to calculate the distance at which slow braking is applied before the sudden braking and the distance at which the alarm buzzer 17 issues an alarm.
Here, sudden braking or full braking means braking at the maximum deceleration (about 0.8 G), and slow braking means deceleration lower than the maximum deceleration (about 0.3 to 0.4 G). ) Means to apply constant braking. 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, the threshold line A indicates that a front vehicle as a front obstacle avoids contact with the front vehicle when the front vehicle comes in contact with the front obstacle 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 controller 15 controls the
One of the threshold lines A to E is selected according to the driving state of the vehicle, and in this threshold line, the relative position between the host vehicle and the front obstacle (front vehicle) is selected. Speed V1
The threshold value L0 corresponding to is calculated. For example, own vehicle speed v
The vehicle speed is increased by selecting the threshold line B when 0 is a high vehicle speed, the threshold value D when the host vehicle speed v0 is a medium vehicle speed, and the threshold line E when the host vehicle speed v0 is a low vehicle speed. The threshold value L0 of the possibility of contact is changed to a larger value.

When the distance between the host vehicle and the obstacle ahead reaches the distance at which an alarm is issued, an operation command signal is output from the controller 15 to the alarm buzzer 17 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, an operation signal is output from the controller 15 to the hydraulic actuator section 20 to operate the actuator section 20. Therefore, slow braking or sudden braking is applied.

On the other hand, in FIG. 2, reference numeral 21 designates a master cylinder having two hydraulic chambers 21a and 21b for respectively generating a brake pressure corresponding to the depression force of the brake pedal 22,
23FL is a brake device for the left front wheel, 23RR is a brake device for the right rear wheel, 23FR is a brake device for the right front wheel, 23
RL is a brake device for the left rear wheel, and each of these brake devices 23FL, 23RR, 23FR, 23RL is a disc 24 that rotates integrally with the wheel and a disc 24 that receives brake pressure from the master cylinder 21 side.
And a caliper 25 for sandwiching.

One hydraulic chamber 2 of the master cylinder 21
1a is a brake device 23FL, 23RR for the left front wheel and the right rear wheel via a hydraulic passage 26, and the other hydraulic chamber 21b is a brake device 23FR, 23RL for the right front wheel and the left rear wheel via a hydraulic passage 27, respectively. It is connected to form a so-called X pipe. In each of the hydraulic passages 26 and 27,
Shutter valves 28 and 29, each of which is an electromagnetic 2-port 2-position switching valve with a check valve, are provided.

Further, 31 is a motor-driven oil pump, 3
An accumulator 2 stores the pressure oil discharged from the oil pump 31 and maintains it at a constant pressure. The oil pump 31 and the accumulator 32 allow a predetermined hydraulic pressure independent of the depression operation of the brake pedal 22. A hydraulic pressure generation source 33 that generates (hydraulic pressure) is configured. The pressure oil generated in the accumulator 32 is supplied to the pressure boosting piston device 35 via the hydraulic passage 34. The boosting piston device 35 has three hydraulic chambers 35a, 35b, 35c partitioned by two pistons, and the central hydraulic chamber 35a has the hydraulic passage 34 and the drain passage 36.
The hydraulic chambers 35b, 35c on both sides are communicated with the hydraulic passages 26, 27 via the communication passages 37, 38, respectively.

A pressure increasing valve 41 is provided in the hydraulic passage 34.
A pressure reducing valve 42 is provided in the drain passage 36, and both valves 41, 42 are electromagnetic two-port two-position switching valves, and the hydraulic pressures of the brake devices 23FL, 23RR, 23FR, 23RL. It has a function as a pressure regulating valve for increasing / decreasing pressure.

In the above hydraulic circuit configuration, when the shutter valves 28 and 29 are in the open position, the brake device 23F of each wheel is in accordance with the depression force of the brake pedal 22.
Braking is applied at L, 23RR, 23FR, and 23RL. On the other hand, when the shutter valves 28 and 29 are in the closed position and the pressure increasing valve 41 is switched to the open position and the pressure reducing valve 42 is switched to the closed position, the pressure oil from the accumulator 32 is transferred to the hydraulic chamber 35a of the pressure boosting piston device 35. Is supplied to the hydraulic pressure chambers 35a to 35c of the pressure-increasing piston device 35 and the hydraulic pressures of the hydraulic chambers 35a to 35c are increased.
The brake pressure of 3RR, 23FR, 23RL is increased. In addition, the pressure increasing valve 41 is closed and the pressure reducing valve 42 is
To the open position respectively, the booster piston device 35
Of the hydraulic chambers 35a of the pressure boosting piston device 35 is reduced and the hydraulic pressures of the hydraulic chambers 35a to 35c of the pressure boosting piston device 35 are reduced.
The brake pressure of 23FR and 23RL is reduced.

As a feature of the present invention, a variable volume chamber 44 is provided between the pressure increasing valve 41 and the pressure increasing piston device 35 in the hydraulic pressure passage 34 via a communication passage 43.
And the communication passage 43 is provided with a shut-off valve 45 formed of an electromagnetic 2-port two-position switching valve that shuts off the communication between the chamber 44 and the hydraulic passage 34. During automatic braking, the target position is switched to the open position during slow braking with low target deceleration, and to the closed position during rapid braking with high target deceleration.

Further, between the accumulator 32 of the hydraulic passage 34 and the pressure increasing valve 41, the electromagnetic 2-port 2 is provided.
The position switching valve 46 and the pressure reducing valve 47 are provided in parallel with each other. The switching valve 46 is switched to the closed position during gentle braking with a low target deceleration during automatic braking, and at this time, the pressure reducing valve 47 reduces the hydraulic pressure sent from the accumulator 32 to a predetermined pressure. It has become. Therefore, the switching valve 46 and the pressure reducing valve 47 constitute a pressure adjusting valve 48 that lowers the hydraulic pressure sent from the accumulator 32 at the time of gentle braking.

The various electromagnetic valves used in the hydraulic circuit as described above, that is, the shutter valves 28 and 29, the pressure increasing valve 41, the pressure reducing valve 42, the shutoff valve 45, and the switching valve 46 are all in the controller 15 (see FIG. 1). The position switching is controlled by receiving a signal from the control device (see), and these electromagnetic valves automatically control the operation of the brake devices 23FL, 23RR, 23FR, 23RL of each wheel. A hydraulic actuator section 20 of the device is configured. In FIG. 2, 51 is a rear wheel side brake device 23RR, 23RL for each hydraulic passage 26, 27.
Is a pressure regulating valve provided in a branch portion communicating with the.

Next, the automatic braking device of the above embodiment, in particular,
The operation of the hydraulic actuator section 20 will be described.

The controller 15 determines the possibility of contact with the front obstacle on the basis of the distance and relative speed between the host vehicle and the front obstacle, and when it is determined that there is the possibility of contact, The shutter valves 28 and 29 are closed, the pressure increasing valve 41 is switched to the open position, and the pressure reducing valve 42 is switched to the closed position. As a result, the pressure oil from the accumulator 32 is supplied to the hydraulic chamber 35a of the pressure boosting piston device 35, and the pressure boosting piston device 3
The hydraulic pressures in the hydraulic chambers 35a to 35c of No. 5 are increased, and the brake devices 23FL, 23RR, and 23F of the wheels are accordingly increased.
The brake pressure of R and 23RL is increased and automatic braking is applied. When increasing the brake pressure, the pressure increasing valve 41 is not maintained in the open position and is opened at a predetermined ratio (duty ratio) so that the brake pressure is increased at a predetermined rising edge. It can be switched between the position and the closed position.

Of the automatic braking, particularly during slow braking with a low target deceleration, the shut-off valve 45 is opened and the chamber 44 communicates with the hydraulic passage 34 under the control of the controller 15, so that the chamber is closed. 44 can effectively absorb the pulsation caused by the repeated switching of the position of the pressure increasing valve 41 in the hydraulic passage 34.

Further, during the slow braking, the hydraulic pressure difference between the upstream side and the downstream side of the pressure increasing valve 41 in the hydraulic passage 34 becomes larger than that during the rapid braking, but in the present embodiment, the switching valve 46 is closed, The pressure oil from the actuator 32 is reduced to a predetermined oil pressure by the pressure reducing valve 47, and the pressure increasing valve 41
Is fed to the upstream side of the pressure increasing valve 41, the hydraulic pressure difference between the upstream side and the downstream side of the pressure increasing valve 41 can be made substantially constant regardless of whether the braking is sudden braking or gentle braking. Braking can be controlled easily and accurately.

On the other hand, during sudden braking with a high target deceleration,
The shutoff valve 45 is closed and the communication between the chamber 44 and the hydraulic passage 34 is shut off. As a result, the hydraulic pressure in the hydraulic chambers 35a to 35c of the booster piston device 35, and thus the rise of the brake pressure in the brake devices 23FL, 23RR, 23FR, 23RL of the respective wheels is not affected by the chamber 44. It is possible to sufficiently secure a predetermined amount, and it is possible to speed up braking during sudden braking.

The present invention is not limited to the above embodiment, but includes various other modifications.
For example, in the above embodiment, the automatic braking device that applies automatic braking to avoid contact with an obstacle is described, but the present invention is not limited to this, the vehicle may be stopped at a predetermined stop line, or the vehicle speed may be reduced. The present invention 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 it exceeds.

Further, in the above embodiment, the hydraulic pressure (hydraulic pressure) from the accumulator 32 constituting the hydraulic pressure generation source 33 is introduced into the pressure boosting piston device 35, and the brake of each wheel is passed through the pressure boosting piston device 35. Device 23FL, 23RR, 23
The case where the invention is applied to the automatic braking device configured to indirectly increase the brake pressure of FR and 23RL has been described, but the present invention does not use the pressure boosting piston device 35, but the accumulator 3
Of course, the hydraulic pressure from 2 can be similarly applied to the automatic braking device configured to directly introduce the hydraulic pressure to the braking device of each wheel.

[0036]

As described above, according to the vehicle automatic braking apparatus of the present invention, the shut-off valve is opened to activate the chamber during the slow braking, and the shut-off valve is closed to prevent the chamber from operating during the sudden braking. As a result, it is possible to effectively achieve both a sufficient rise of the brake pressure depending on the braking state and the prevention of pulsation due to repeated opening / closing switching of the pressure regulating valve.

In particular, according to the second aspect of the present invention, during the slow braking, the hydraulic pressure sent from the hydraulic pressure generation source to the pressure regulating valve is lowered by the pressure adjusting valve, so that it is possible to distinguish between the rapid braking and the slow braking. Regardless, the hydraulic pressure difference between the upstream side and the downstream side of the pressure regulating valve can be made substantially constant, and the accuracy of braking control can be improved.

[Brief description of drawings]

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

FIG. 2 is a hydraulic circuit diagram of the automatic braking device.

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

[Explanation of symbols]

15 controller (control means) 22 brake pedal 23FL, 23RR, 23FR, 23RL brake device 31 oil pump 32 accumulator 33 hydraulic pressure source 34 hydraulic passage (hydraulic passage) 41 pressure increasing valve (pressure regulating valve) 42 pressure reducing valve (pressure regulating valve) ) 43 communication passage 44 chamber 45 shutoff valve 46 switching valve 47 pressure reducing valve 48 pressure adjusting valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoyuki Hikita 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (2)

[Claims] 1. A brake fluid pressure source that generates a predetermined fluid pressure independently of the operation of depressing a brake pedal, and a fluid pressure passage that connects the brake fluid source and the brake device of each wheel. A pressure regulating valve for increasing or decreasing the hydraulic pressure of the vehicle, and automatically braking the vehicle configured to increase the hydraulic pressure of the brake device of each wheel under a predetermined condition to automatically brake at a predetermined target deceleration. In the apparatus, a chamber that communicates with the fluid pressure passage through a communication passage, a shutoff valve that is provided in the communication passage and that shuts off communication between the chamber and the fluid passage, and a target reduction during automatic braking. An automatic braking device for a vehicle, comprising: a control unit that controls to open the shutoff valve when the speed is low and to close the shutoff valve when the target deceleration is high. 2. The hydraulic pressure is provided between the hydraulic pressure generation source of the hydraulic pressure passage and the pressure regulating valve, and lowers the hydraulic pressure fed from the hydraulic pressure generation source when the target deceleration is low during automatic braking. The automatic braking device for a vehicle according to claim 1, further comprising a pressure regulating valve.