JPH06312653A - Control for automatic brake device - Google Patents

Abstract

PURPOSE:To reduce oil hammering with high efficiency at the time of closing a valve in an automatic brake device which uses on-off type compressive/ decompressive solenoid valves respectively, by controlling them so as to be decompressed for a moment at every stepped compressive control, and compressed for a moment at every stepped decompression control. CONSTITUTION:An on-off type decompression solenoid valve 30 (40) is disposed between a master cylinder 14 and a wheel cylinder 17 in the brake pipe 15 of a vehicle. An accumulator 29 which always accumulates high pressure is communicated with the wheel cylinder 17 through an on-off type compressive solenoid valve 32 (42). When an automatic brake control unit foresees a possibility of collision at an automatic brake mode, it outputs a close signal to the decompressive solenoid valve 30, and a duty control signal to the compressive solenoid 32. With this constitution, for example, the control unit outputs an open signal to the decompressive solenoid valve 30 for a moment at the latter half of a period when the compressive solenoid valve 32 is made open through the duty signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of an automatic braking device which is used in a driving assistance system (ADA) of a vehicle such as an automobile and automatically brakes. Regarding measures to reduce oil hammers.

[0002]

2. Description of the Related Art In recent years, as a measure to dramatically improve the safety of a vehicle, a technique for avoiding a collision, that is, an operation system is automatically controlled to a safety side as compared with a technique for reducing a collision damage such as an airbag. A comprehensive driving support system (ADA / Active Drive Assist system) has been developed to avoid a collision. This ADA system automatically adjusts the control unit that recognizes the road condition, the external environment of other vehicles, obstacles, etc. three-dimensionally by the cameras mounted in front of and behind the vehicle, and the operation system of the brake, throttle, and steering automatically. It is configured to be capable of autonomous traveling by including various devices that are operated on. Then, as functions aimed at by the ADA system, a collision prevention function in the case of unsafe driving operation, and an automatic driving function acting on behalf of the driving operation so as to keep a safe inter-vehicle distance in the case of asleep etc. are considered.

Therefore, the automatic braking device of the ADA system is required to have a function of surely decelerating or stopping the vehicle in order to avoid a collision or the like. Here, in order to obtain the maximum deceleration of 1 G, it is necessary to quickly generate a brake pressure of, for example, 100 kg / cm ² . For this reason, the brake hydraulic control system has an accumulator in which the pressurizing source stores a high pressure of, for example, 150 to 180 kg / cm ² in consideration of pressure loss, and when the risk of collision is predicted, the accumulator pressure is immediately changed to the wheel. It is configured so that it can be introduced into a cylinder to apply pressure braking with good response. Further, as a means for electrically controlling the accumulator pressure or for electrically reducing the high brake pressure, a method of controlling by using an ON-OFF type pressure solenoid valve and pressure reduction solenoid valve has been proposed. ing.

Brake pressure control by the pressurizing and depressurizing solenoid valves will be described with reference to FIG. First, the pressurizing solenoid valve is controlled so as to be opened in a pulsed manner as indicated by symbol A in (a), so that the brake pressure is automatically increased from step 0 to step B by the accumulator pressure. The brake operates. Further, the pressure reducing solenoid valve is controlled so as to open in a pulse manner as indicated by symbol C in (b), and conversely is controlled so as to release the brake by reducing the high brake pressure stepwise like D. .

In pressurization control, a high accumulator pressure is pulse-controlled by an ON-OFF type pressurizing solenoid valve. Therefore, every time the pressurizing solenoid valve is closed, hydraulic pressure rises rapidly in the wheel cylinder as shown in the figure. Oil hammer b occurs. In the pressure reduction control, high brake pressure is similar to O
Since pulse control is performed by the N-OFF type pressure reducing solenoid valve, every time the pressure reducing solenoid valve is similarly closed, an oil hammer d in which the hydraulic pressure sharply falls as shown in the figure occurs. Therefore, at the time of automatic brake operation, these oil hammers cause vibrations and noises in the vehicle, which leads to deterioration of riding comfort and the like, and improvement of this point is required.

Conventionally, regarding the above-mentioned brake pressure control,
For example, there is a prior art disclosed in Japanese Patent Laid-Open No. 4-63755. In this prior art anti-skid control device, a differential pressure control valve is provided in the pipe between the pump of the hydraulic pressure generation source and the wheel cylinder, and an electromagnetic switching valve is provided in the pipe between the wheel cylinder and the reservoir. It is shown that the differential pressure control valve increases the pressure and the electromagnetic switching valve reduces the pressure.

[0007]

By the way, in the above-mentioned prior art, since the high brake pressure is controlled to be reduced by turning on and off the electromagnetic switching valve in particular, there is a possibility that an oil hammer may occur in the wheel cylinder at this time. is there.

In view of such a point, the present invention is an ON-O.
An object of the present invention is to effectively reduce oil hammer generated in a wheel cylinder during pressurization control and depressurization control in an automatic braking device using a FF type pressurizing solenoid valve and a depressurizing solenoid valve to improve riding comfort and the like. And

[0009]

In order to achieve this object, the present invention provides an accumulator in which an ON-OFF type pressure reducing solenoid valve is provided between a master cylinder and a wheel cylinder of a brake pipe of a vehicle and constantly accumulates high pressure. ON
-If a danger of collision is predicted when the automatic brake control unit is in the automatic brake mode and communicates with the wheel cylinder via the -OFF type pressurizing solenoid valve, a close signal is output to the depressurizing solenoid valve and duty is applied to the pressurizing solenoid valve. In the automatic braking device that outputs a signal and outputs a close signal to the pressure solenoid valve and a duty signal to the pressure reduction solenoid valve when the danger of collision disappears, the latter half of the open state of the duty signal of the pressure solenoid. The momentary open signal is output to the pressure reducing solenoid valve, and the momentary open signal is output to the pressure increasing solenoid valve in the latter half of the open state of the duty signal of the pressure reducing solenoid.

[0010]

In the present invention based on the above method, when the vehicle is in the automatic brake mode, the automatic brake control unit electrically determines the relationship between the own vehicle and the preceding vehicle. When a danger of collision is predicted, the ON-OFF type pressurizing solenoid valve is opened by the duty signal, and the high accumulator pressure is introduced into the wheel cylinder to control the pressurization so that the brake pressure rises stepwise. , The vehicle is automatically braked to avoid a collision. When the danger of collision disappears, O
When the N-OFF type pressure reducing solenoid valve is opened by the duty signal, the brake pressure is controlled so that the brake pressure of the wheel cylinder is reduced stepwise, and the brake is released.

Further, in the pressurization control, the depressurization solenoid valve is momentarily opened immediately before the pressurization solenoid valve is closed, so that the oil pressure at the sudden rise of the hydraulic pressure when the pressurization solenoid valve is closed is reduced by the depressurization. , The brake pressure is corrected so that it rises smoothly. In the pressure reduction control, the pressure solenoid valve is opened for a moment immediately before the pressure reduction solenoid valve is closed, so that the oil hammer at the sharp fall of the hydraulic pressure when the pressure reduction solenoid valve is closed is reduced by pressurization, and the brake pressure is reduced. It is corrected so that it decreases smoothly. Thus ON-
When the OFF type pressurizing solenoid valve or depressurizing solenoid valve is operated to control a high accumulator pressure or a high brake pressure, the hydraulic pressure can be smoothly changed to reduce vibration and noise.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. An outline of the vehicle drive system and the brake hydraulic pressure control system will be described with reference to FIG. First, the vehicle is the left and right front wheels 1
It has L, 1R and rear wheels 2L, 2R, and the engine 3 as a drive system is connected to the left and right rear wheels 2L, 2R via the clutch 4, the transmission 5, the propeller shaft 6, the differential device 7, and the axle 8. Composed of transmission. The throttle valve 10 of the engine 3 is provided with an actuator 11 having a throttle control unit 12 so as to perform throttle control during traction control, cruise control, automatic brake control and the like.

Explaining the brake hydraulic pressure control system, a master cylinder 14 having a brake pedal 13 will be described.
As a diagonal two-system brake pipe 15, a P-system brake conduit 16 communicates with the wheel cylinders 17 of the right front wheel 1R and the left rear wheel 2L, and an S-system brake conduit 18 connects the left front wheel 1L and the right rear wheel 2R. It is communicated with the wheel cylinder 17. Therefore, the brake lines 16 and 18 for the P system and the S system
The automatic brake hydraulic unit 21 of the automatic brake device 20 is provided in the middle of the
The signal is used to automatically brake.
When the ABS device is installed, the ABS hydraulic unit is connected in series to the downstream side of the automatic brake hydraulic unit, and it is possible to prevent wheel lock during automatic brake operation.

The automatic brake hydraulic unit 21 will be described with reference to FIG. Brake piping 15 with two diagonal lines
The P-type brake pipeline 16 will be described. The P-type brake pipeline 16 is provided with a pressure reducing solenoid valve 30 and a relief valve 31. Further, as a pressurizing source 34, a pipe line 23 from the oil reservoir 22 of the master cylinder 14 communicates with an oil pump 24 so as to generate a hydraulic pressure by driving a motor 25. The discharge side conduit 26 of the oil pump 24
Communicates with the relief valve 28 via the check valve 27,
The accumulator 29 communicates with the accumulator 29 so that pressure can be accumulated, and further communicates with the P-system brake pipe 16 via a pressure solenoid valve 32. Similarly, a pressure reducing solenoid valve 40 and a relief valve 41 are also provided in the S system brake pipe 18, and a pipe line 44 branched from the pipe line 26 has a pressurizing solenoid valve 42 and communicates with the S system brake pipe line 18. .

A hydraulic pressure sensor 37 for detecting the accumulator pressure Pa is provided in the pipe line 26, and is controlled so that the motor 25 is driven at the lower limit pressure and the motor 25 is stopped at the upper limit pressure. With this motor control, the oil pump 24 is operated to constantly accumulate a high pressure in the range of the upper limit pressure and the lower limit pressure in the accumulator 29, and the accumulator pressure Pa can pressurize the brake pressure Pb with good response. A hydraulic pressure sensor 36 for detecting a pedal pressure and a hydraulic pressure sensor 33 for detecting a P system brake pressure are provided in the pipeline 16, and a hydraulic pressure sensor 43 for detecting an S system brake pressure is provided in the pipeline 18.

The depressurizing solenoid valves 30 and 40 are normally open. When the duty signal is OFF, the depressurizing solenoid valves 30 and 40 are opened to allow a normal braking action. Pressure solenoid valve 3
Reference numerals 2 and 42 are normally closed, which are closed when the duty signal is OFF, opened when ON, and pressurized when the automatic brake is activated.

The automatic brake control unit 60 will be described with reference to FIG. First, CCDs that are arranged in front of and behind the vehicle to recognize road conditions and obstacles and obtain further distance images
It has a camera 50, a vehicle speed sensor 51 for detecting a vehicle speed, an automatic brake selection switch 52, and a brake switch 53 for detecting a brake operation state. The signals of these sensors and switches and the signals of the actual brake pressure Pb of the hydraulic pressure sensors 33, 43 are input to the automatic brake control unit 60 and electrically processed.

The automatic brake control unit 60 is a CCD
It has a camera 50, an automatic brake selection switch 52, and a rear-end collision prediction unit 61 to which signals from the vehicle speed sensor 51 are input. When the vehicle travels in the automatic brake mode in which the selection switch 52 is turned on, the distance between the host vehicle and the preceding vehicle and the relative speed are calculated based on the information from the CCD camera 50 and the vehicle speed V, and the risk of a rear-end collision is calculated. Predict the presence or absence of. When the danger of a rear-end collision is predicted, an approach warning signal is output to the alarm 55. Further, the throttle opening sensor 54 and the signal for predicting a rear-end collision are input to the throttle close determination unit 62, and if the throttle opening is equal to or larger than a set value during the rear-end collision prediction, a throttle close signal is output to the throttle control unit 12.

A signal for predicting a rear-end collision is input to a necessary deceleration calculating section 63, and a necessary deceleration G for keeping a safe inter-vehicle distance and avoiding a rear-end collision is calculated from the inter-vehicle distance and relative speed. The required deceleration G and the signal from the brake switch 53 are input to the target brake pressure setting unit 64 to set the target brake pressure Pt according to the required deceleration G when the brake switch is OFF. The target brake pressure Pt and the actual brake pressure Pb of the hydraulic pressure sensors 33 and 43 are input to the deviation calculating section 65 to obtain the deviation ± ΔP between them. This deviation ± ΔP is input to the dead zone determination unit 66 and compared with the dead zone ± α. If the deviation ± ΔP is within the dead zone ± α, the ON / OFF output unit 67 sends an OFF signal to the pressurizing solenoid valves 32, 42. An ON signal is output to the pressure reducing solenoid valves 30 and 40 to control the brake pressure to be maintained at a predetermined level.

If the deviation ± ΔP is outside the dead zone ± α,
The deviation ± ΔP is input to the control amount calculation unit 68, pressurization or depressurization is determined by a positive or negative sign, and the control amount C corresponding to the deviation ± ΔP is determined by PD control, for example. In the case of pressurization, the ON / OFF output unit 67 outputs an ON signal to the pressure reducing solenoid valves 30 and 40. And the controlled variable C
Is input to the duty ratio determining unit 69 to be converted into a predetermined pressurizing duty ratio Du, and this duty signal is output to the output unit 7.
0 pressurizing solenoid valves 32, 42 at predetermined time intervals
Output to. In the case of depressurization, the ON / OFF output section 67 outputs an OFF signal to the pressurizing solenoid valves 32 and 42. Then, the control amount C is input to the duty ratio determining unit 71 to be converted into a predetermined pressure reducing duty ratio Dd, and this duty signal is output to the pressure reducing solenoid valves 30 and 40 at a predetermined time interval by the output unit 72 so as to output the brake pressure. Configured to control.

Further, measures for reducing the oil hammer will be described.
First, considering the state of occurrence of the oil hammer in FIG. 6, when the pressurizing solenoid valves 32 and 42 are closed, an oil hammer b occurs in which the hydraulic pressure rises sharply, and when the pressure reducing solenoid valves 30 and 40 are closed, the oil hydraulic pressure b is generated. Generates an oil hammer d that sharply falls, and these oil hammers b and d have a relationship of antiphase. Therefore, when the pressurizing solenoid valves 32, 42 or the depressurizing solenoid valves 30, 40 are closed, the oil pressures of opposite phases are generated by the depressurizing solenoid valves 30, 40 or the pressurizing solenoid valves 32, 42, respectively. It can be reduced by offsetting the strike.

Therefore, there is provided an oil hammer reducing section 73 to which a signal for pressurizing and depressurizing is inputted, and a decompression correction amount R is set in accordance with the state of oil hammering at the time of pressurization. The amount R is input to the duty ratio determination unit 71, converted into a predetermined small pressure reduction correction duty ratio Rd, and this duty signal is output. Further, at the time of depressurization, the pressurization correction amount R is set according to the occurrence state of the oil hammer, and the OF
In the latter half of the F state, the pressurization correction amount R is set to the duty ratio determination unit 69.
To enter. In this case, too, the pressure correction duty ratio Ru is converted to a predetermined small value and the duty signal is output.

Next, the operation of this embodiment will be described. First, when the engine is operating, the pressure reducing solenoid valves 30 and 40 are turned off and open in the brake control system, and the master cylinder 14 communicates with the wheel cylinders 17 of the front and rear wheels 1L, 2L, .... Therefore, when the vehicle is stopped or running,
By operating the brake pedal 13 normally, it is possible to generate the brake pressure Pb in the wheel cylinder 17 and perform braking. The pressurizing solenoid valves 32 and 42 are OF
Closed at F, the pressure source 34 is disconnected from the wheel cylinder 17. In the pressure source 34, the pump 24 is operated by the motor control by the hydraulic pressure sensor 37, and the accumulator 29 is operated.
A high accumulator pressure Pa is constantly accumulated in the.

When the driver turns on the automatic brake selection switch 52 while the vehicle is traveling, the automatic brake mode is set. Therefore, in the automatic brake control unit 60, the CCD
When the distance between the host vehicle and the preceding vehicle or the obstacle and the relative speed are detected based on the information of the camera 50 and the vehicle speed and these values are equal to or less than the set values and the danger of a rear-end collision is predicted, an approach warning is given by an alarm 55. At this time, when the driver normally operates the brake and the brake switch 53 is turned on, the automatic brake mode is released.

On the other hand, when the brake is not operated, the target brake pressure Pt is set high in accordance with the required deceleration G based on the inter-vehicle distance to the preceding vehicle and the relative speed, and the target brake pressure Pt and the actual braking of the brake system. The deviation ΔP from the pressure Pb is calculated, and the pressurization is determined. Therefore, the pressure reducing solenoid valves 30 and 40 are immediately closed by turning on as shown in FIG.
Shut off from 4. At this time, the control amount C corresponding to the deviation ΔP
The pressurizing duty ratio Du is set by, and this duty signal is output to the pressurizing solenoid valves 32 and 42 to turn on and open in a pulse manner as shown in FIG. Therefore, the accumulator pressure Pa of the pressurizing source 34 is introduced into the wheel cylinder 17 and is rapidly pressurized, so that the brake pressure Pb follows the target brake pressure Pt with good response and rises with a stepwise characteristic. Feedback controlled.

In this pressurization control, the pressure reduction correction duty ratio Rd is further set by the pressure reduction correction amount R, and the pressure reduction solenoid valve 30 is immediately before the pressure solenoid valves 32 and 42 are closed as shown in FIG. , 40 are momentarily turned off and opened, and the wheel cylinder 17 is controlled so as to communicate with the oil reservoir 22 side. Therefore, the pressure solenoid valves 32, 42
The hydraulic pressure that rapidly rises in the wheel cylinder 17 when the valve is closed is reduced by the pressure reducing solenoid valves 30 and 40, thereby reducing the occurrence of oil hammer. Therefore, the brake pressure Pb has a characteristic that it smoothly rises in the absence of oil hammer as shown in FIG.

Then, the target brake pressure Pt and the brake pressure P
When b becomes substantially equal and the deviation ΔP between them enters the dead zone ± α, the pressurizing solenoid valves 32 and 42 are turned off and the depressurizing solenoid valves 30 and 40 are turned on and similarly closed. Therefore, the brake pressure Pb of the wheel cylinders 17 is kept constant by the containment, and even if the brake pressure Pb fluctuates to some extent, the dead zone ± α limits the brake pressure feedback control to maintain a comfortable ride. The front and rear wheels 1L, 2L, ... Are automatically braked by the pressurization control and the holding control described above, whereby the vehicle is decelerated or stopped at a speed equal to the required deceleration G, and a rear-end collision with the preceding vehicle is avoided.

When the relative distance and relative speed with respect to the preceding vehicle increase due to the automatic brake control and the risk of a rear-end collision disappears, the target brake pressure Pt is set low. Therefore, in this case, the pressure reduction is judged and the pressurizing solenoid valves 32 and 42 are immediately turned off and closed as shown in FIG. At this time, the deviation between the target brake pressure Pt and the actual brake pressure Pb-
The decompression duty ratio Dd is set by the control amount C according to ΔP, and this duty signal is used as the decompression solenoid valves 30, 40.
Then, it is turned off in a pulse manner and opened as shown in FIG. Therefore, the brake pressure Pb of the wheel cylinder 17 gradually escapes to the oil reservoir 22 and is reduced with a stepwise characteristic to release the brake.

In this depressurization control, the pressurization correction duty ratio Ru is further set by the pressurization correction amount R and the pressurization solenoid valve 30 or 40 is closed immediately before the pressurization solenoid valve 30 or 40 is closed as shown in FIG. The valves 32 and 42 are momentarily turned on and opened, and the pressure source 34 is controlled so as to communicate with the wheel cylinder 17. Therefore, contrary to the case of the above-described pressurization control, the rapid fall of the hydraulic pressure of the wheel cylinder 17 when the pressure reducing solenoid valves 30 and 40 are closed is replenished by the pressurization of the pressurizing solenoid valves 32 and 42, and the oil pressure is similarly changed. The occurrence of strikes is reduced. Therefore, the brake pressure Pb has a characteristic of smoothly decreasing in the absence of oil hammer as shown in FIG.

The embodiment of the present invention has been described above, but the present invention is not limited to this.

[0031]

As described above, according to the present invention,
In an automatic brake device using an ON-OFF type pressurizing solenoid valve and a depressurizing solenoid valve, the solenoid is controlled so that the pressure is reduced momentarily for each stepwise pressure control and the pressure is increased momentarily for each stepwise pressure control. Oil hammer when the valve is closed can be effectively reduced. Therefore, vehicle vibration,
Noise is reduced, riding comfort is improved, and durability of the brake hydraulic control system is also improved. Since the pressure control and the pressure reduction control are used together, the structure of the hydraulic system is not changed and the control is easy. Further, since the amount of pressurization and the amount of pressure reduction can be changed by adjusting the degree of pressurization and pressure reduction, the pressurization and pressure reduction can be controlled more finely and smoothly.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an electric control system suitable for a control method for an automatic braking device according to the present invention.

FIG. 2 is a hydraulic circuit diagram showing a hydraulic unit of the automatic brake device.

FIG. 3 is a diagram schematically showing a vehicle drive system and a brake hydraulic pressure control system.

FIG. 4 is a diagram showing a duty signal and a brake pressure characteristic of pressurization control.

FIG. 5 is a diagram showing duty signals and brake pressure characteristics of pressure reduction control.

FIG. 6 is a diagram showing a state of occurrence of an oil hammer in conventional pressurization / depressurization control.

[Explanation of symbols]

 14 master cylinder 15 brake pipe 17 wheel cylinder 20 automatic brake device 21 automatic brake hydraulic unit 29 accumulator 30, 40 pressure reducing solenoid valve 32, 42 pressurizing solenoid valve 60 automatic brake control unit, 65 deviation calculator 68 control amount calculator 69, 71 Duty ratio determination unit 73 Oil hammer reduction unit

Claims (2)

[Claims] 1. An ON-OFF type pressure reducing solenoid valve is provided between a master cylinder and a wheel cylinder of a brake pipe of a vehicle, and an accumulator for constantly accumulating high pressure is applied to a wheel cylinder via an ON-OFF type pressure solenoid valve. When it is in communication and the collision risk is predicted when the automatic brake control unit is in the automatic braking mode, the closing signal is output to the pressure reducing solenoid valve and the duty signal is output to the pressurizing solenoid valve. In an automatic braking device that outputs a close signal to the pressure solenoid valve and a duty signal to the pressure reducing solenoid valve, outputs a momentary open signal to the pressure reducing solenoid valve at the latter half of the open state of the duty solenoid solenoid valve to reduce the pressure. When the duty signal of the solenoid is open, the pressure solenoid valve is reset at the latter half of the time. A method for controlling an automatic braking device, which is characterized by outputting an instantaneous opening signal. 2. The method for controlling an automatic brake device according to claim 1, wherein the open signals output to the pressure reducing solenoid valve and the pressure increasing solenoid valve respectively reduce the occurrence of oil hammer.