JP2017149379A - Automatic brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic brake device capable of improving a jerk in an automatic brake operation.SOLUTION: An automatic brake device 1 that actuates a brake device provided to a front wheel and a rear wheel of a vehicle respectively without depending on a brake operation by a driver includes: a primary brake control part 31 for actuating both a brake device (cylinder CF) of the front wheel WF and a brake device (cylinder CR) of the rear wheel WR for a predetermined time T1 based on relationships between the vehicle and objects around it; and a secondary brake control part 32 for actuating only the brake device of the front wheel WF after a lapse of the predetermined time T1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an automatic brake device that automatically applies a braking force to a wheel of the host vehicle when there is a possibility that the host vehicle and an object around the host vehicle collide.

  As one of the driving assistance systems, braking force is automatically applied to the wheels when there is a possibility of collision between the host vehicle and surrounding objects and the driver does not depress the brake pedal. There is an automatic emergency brake (AEB) that decelerates the vehicle. In an automobile equipped with an AEB, in general, when the distance and relative speed between the host vehicle and its surrounding objects are detected using a sensor and the electronic control unit (ECU) determines that there is a possibility of a collision, First, an alarm is issued, and a relatively small braking force is applied to the wheel as a primary brake to avoid collision. When the brake pedal is not depressed and the distance from the object is within a predetermined distance and maintained for a predetermined time, and the electronic control unit determines that the possibility of a collision is higher, the primary brake A greater braking force is applied to the wheel as a secondary brake to reduce the damage caused by the collision.

  Usually, in an automobile, brake devices are arranged on a total of four wheels, front, rear, left and right. As a brake device, a hydraulic type is widely used. In an automobile equipped with a hydraulic brake device and an AEB, the electronic control unit controls the brake fluid pressure by controlling the open / close state of a valve provided in the brake fluid passage, and ensures the predetermined braking force.

  Japanese Patent Laid-Open No. 2004-260688 applies brake hydraulic pressure based on automatic braking to brake devices provided on four wheels, respectively, when a driver depresses a brake pedal (increase operation) while the automatic brake is operating. Instead, a configuration that is applied only to some brake devices is disclosed.

JP 2000-177550 A

When the automatic brake is activated, it is desired to improve the rising acceleration (jerk, m / s ³ ) of deceleration.

  If the automatic brake jerk is large, especially if the secondary brake jerk is large, the stop distance by the automatic brake can be shortened, and the operation start timing of the secondary brake can be delayed. In this case, unnecessary operation of the automatic brake (secondary brake) can be reduced. In addition, the host vehicle can be decelerated more quickly.

  In order to increase the jerk of the automatic brake, for example, it is conceivable to increase the brake fluid pressure applied to each brake device provided on the four wheels. Typically, the magnitude of the hydraulic pressure is adjusted by a pump provided in the brake fluid path, and therefore, in order to increase the hydraulic pressure, it is necessary to increase the output of the motor that drives the pump. If a large motor is used to increase the output of the motor, the size will increase and the cost will increase.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide an automatic brake device capable of improving jerk during automatic brake operation.

The automatic brake device according to one aspect of the present invention operates a brake device provided on each of the front wheel and the rear wheel of the host vehicle regardless of the driver's brake operation,
A primary brake control unit for operating both the front wheel brake device and the rear wheel brake device for a predetermined time based on the relationship between the host vehicle and surrounding objects;
A secondary brake control unit that activates only the brake device for the front wheel after the predetermined time has elapsed.

  The automatic brake device operates both the front-wheel brake device and the rear-wheel brake device as the primary brake when there is a possibility that the host vehicle may collide with surrounding objects. In addition, since the automatic brake device operates only the brake device for the front wheel as the secondary brake, the jerk of the secondary brake can be improved as compared with the case where both the brake devices described above are operated.

1 is a schematic configuration diagram of an automatic brake device according to a first embodiment. 3 is a graph illustrating a control operation by the automatic brake device according to the first embodiment. 6 is a graph illustrating a control operation by the automatic brake device according to the second embodiment.

Embodiments of the automatic brake device of the present invention will be specifically described below with reference to the drawings.
FIG. 1 shows only one front wheel WF (for example, the left front wheel fl) and one rear wheel WR (for example, the right rear wheel rr), out of a total of four wheels including the left and right front wheels and the left and right rear wheels. The other is omitted. Moreover, in FIG. 1, only cylinder CF and CR are shown among the brake devices provided in a wheel.

[Embodiment 1]
(overall structure)
The automatic brake device 1 according to the first embodiment typically includes brake devices (cylinders CF and CR) provided on each of the left and right front wheels WF and the left and right rear wheels WR, and the front wheels WF and rear wheels WR. ) And a vehicle (not shown). In this example, a hydraulic brake device is provided.
The vehicle is generally interposed between the brake pedal 4, the master cylinder 42 that generates the brake fluid pressure when the brake pedal 4 is depressed, and the brake pedal 4 and the master cylinder 42. And a booster 40 for generating power. When the driver of this vehicle depresses the brake pedal 4 in a normal state when the automatic brake device 1 is not operating, a hydraulic pressure corresponding to the pedaling force is applied to the cylinders CF and CR via the master cylinder 42, and the brake device. Can be operated. A predetermined braking force is applied to the front wheel WF and the rear wheel WR by the operation of the brake device, and the vehicle can be decelerated.
The automatic brake device 1 provided in the vehicle includes a brake device for the front wheel WF, a rear wheel, regardless of the brake operation of the driver of the host vehicle when there is a possibility of collision between the host vehicle and surrounding objects. Each of the WR brake devices is operated to decelerate the host vehicle to avoid a collision or reduce damage caused by the collision.

  The automatic brake device 1 of this example includes a brake device provided on a front wheel WF, a brake device provided on a rear wheel WR, a brake fluid path for supplying brake fluid of cylinders CF and CR provided in each brake device, A brake actuator 2 provided in the fluid path for adjusting the brake fluid pressure, detection units such as various sensors S1 and S2 for detecting the distance between the host vehicle and the surrounding object, and the relative speed between the object, and detection An electronic control unit (brake ECU) 3 that determines the possibility of collision with the object based on the detection result from the unit, and controls the brake actuator 2 and the like for collision avoidance or damage reduction based on the determination result Prepare.

  When the electronic control unit 3 determines that there is a possibility of a collision with a surrounding object based on the detection result described above, the automatic brake device 1 first operates on an alarm device, a display device (not shown) or the like. A command is issued to issue an audible and visual warning to the driver of the host vehicle, and the brake actuator 2 is controlled to operate a relatively small braking force as a primary brake. If the driver does not depress the brake pedal or operate the steering wheel during the primary brake operation and the distance from the object is within the predetermined distance, the vehicle may collide with the object. Since it is considered higher, the electronic control unit 3 operates a larger braking force as a secondary brake in order to reduce damage caused by the collision.

The automatic brake device 1 of the embodiment operates both the brake device of the front wheel WF and the brake device of the rear wheel WR as the primary brake, and operates only the brake device of the front wheel WF as the secondary brake. One of the features is that the electronic control unit 3 controls the brake actuator 2.
Hereinafter, it demonstrates in detail for every component.

(Brake device)
The brake device may be a hydraulic device such as a disc brake device or a drum brake device. In this example, the brake device for the front wheel WF is a disc brake device having a cylinder CF, and the brake device for the rear wheel WR is a drum brake device having a cylinder CR.

(Brake actuator)
The brake actuator 2 includes a pump 20 provided in a brake fluid path between the master cylinder 42 and the cylinders CF and CR, various valves MC, 22F, 22R, 24F, and 24R, and a reservoir 26.
The pump 20 pressurizes the brake fluid during automatic braking and is driven by the motor M.
In the fluid path between the pump 20 and the master cylinder 42, a pressure regulating valve MC for adjusting the pressure by the pump 20 to a predetermined brake fluid pressure is provided. Holding fluids 22F and 22R and pressure reducing valves 24F and 24R are provided in the liquid passages between the pressure regulating valve MC and the cylinders CF and CR. When the automatic brake is activated, the holding valves 22F and 22R are opened, and the pressure reducing valves 24F and 24R are closed. When stopping the automatic brake, the pressure regulating valve MC is opened to reduce the pressure.
Each valve MC, 22F, 22R, 24F, 24R is typically an electromagnetic valve, and the opening degree is adjusted by the electronic control unit 3.
In addition, a sensor S for detecting the hydraulic pressure of the master cylinder 42 is provided in the brake fluid path.

(Electronic control unit)
The electronic control unit 3 uses the detection results from the various sensors S1, S2, etc. to calculate the distance and relative speed between the host vehicle and the surrounding objects, and compares the calculated value with a threshold value to perform a collision. A collision possibility determination unit for determining the possibility of a collision, a warning command unit for issuing an operation command to an alarm device or the like when it is determined that there is a possibility of a collision, a primary brake control unit 31 and a secondary brake control unit 32 to be described later And a storage unit for storing various setting values and calculation values (details of each unit are not shown). An appropriate microcomputer can be used for the electronic control unit 3. As the sensors S1, S2, etc., a radar sensor such as a laser radar or a millimeter wave radar, an image sensor equipped with a stereo camera, or the like can be used. In the laser sensor, the distance and relative speed between the host vehicle and the surrounding objects can be obtained by transmitting and receiving pulse waves. In addition, the electronic control unit 3 is attached with a sensor S3 such as an acceleration sensor for grasping the deceleration state of the vehicle.

The electronic control unit 3 receives detection results (measurement information) from the sensors S1, S2, etc. at predetermined intervals (for example, 2 ms), and the own vehicle and surrounding objects collide based on the received information. Calculate the collision prediction time indicating the possibility of the The collision prediction time is obtained, for example, by dividing the distance between the host vehicle and the object by the relative speed. The electronic control unit 3 determines the start time t1 of the primary brake control and the start time t2 of the secondary brake control based on the predicted collision time. For example, the time when the calculated predicted collision time is shorter than a preset threshold is determined as the start time t1 of the primary brake control. The electronic control unit 3 issues a control command to the primary brake control unit 31 at the start time t1.
Further, for example, based on the calculated collision prediction time, a time when the host vehicle can be stopped in a state where the host vehicle is separated from the object by a predetermined distance is determined as the start time t2 of the secondary brake control. The electronic control unit 3 issues a control command to the secondary brake control unit 32 at the start time t2.

Primary brake control unit The primary brake control unit 31 determines both the brake device for the front wheel WF and the brake device for the rear wheel WR based on the relationship between the host vehicle and the surrounding objects determined by the electronic control unit 3. Is operated for a predetermined time T1 (= t2-t1). In the primary brake control unit 31 of this example, the hydraulic pressure at which a predetermined deceleration g1 is obtained is applied to both the cylinder CF provided in the brake device for the front wheel WF and the cylinder CR provided in the brake device for the rear wheel WR. As described above, a command to open the holding valves 22F and 22R and a command to adjust the opening of the pressure regulating valve MC are issued to the valves 22F, 22R and MC. The hydraulic pressure is maintained until the secondary brake control start time t2, and the primary brake is operated for a predetermined time T1. When the primary brake is activated or a warning is generated, the driver of the vehicle can depress the brake pedal 4 or operate the steering (not shown) while the primary brake is activated. This makes it easier to avoid collisions. The predetermined time T1 is obtained and set by the arithmetic unit based on the start time t1 of the primary brake and the start time t2 of the secondary brake.

Secondary brake control unit The secondary brake control unit 32 operates only the brake device for the front wheel WF after the elapse of a predetermined time T1 for performing the primary brake control. The secondary brake control unit 32 of this example obtains a predetermined deceleration g2 in the command for closing the holding valve 22R of the cylinder CR provided in the brake device for the rear wheel WR and the cylinder CF provided in the brake device for the front wheel WF. A command to keep the holding valve 22F open and a command to adjust the opening of the pressure regulating valve MC are issued to the valves 22F, 22R, and MC so that the hydraulic pressure is added. The braking force based on the deceleration g2 is set sufficiently larger than the braking force based on the deceleration g1 of the primary brake. With this braking force, the vehicle can be decelerated to prevent a collision or damage caused by the collision. It can be reduced. And this braking force is generated only by the brake device of the front wheel WF. For example, a case where a certain amount of brake fluid is distributed from the master cylinder 42 to both the brake device for the front wheel WF and the brake device for the rear wheel WR is compared with the case where the brake fluid is supplied only to the brake device for the front wheel WF. When the amount of fluid from the master cylinder 42 is kept constant, the brake fluid pressure can be increased more when the brake fluid is supplied only to the brake device of the front wheel WF than when the fluid is distributed to both. Alternatively, if the brake fluid is supplied only to the brake device of the front wheel WF, even if the amount of brake fluid is reduced, the same brake fluid pressure as that obtained when distributing to both of the brake devices can be obtained. Therefore, when the brake fluid is supplied only to the brake device of the front wheel WF, the time for reaching the predetermined deceleration g2 can be made shorter than when the brake fluid is supplied to both the brake devices.

  By maintaining this hydraulic pressure until the predetermined time T2 has elapsed after reaching the predetermined deceleration g2, the vehicle can be decelerated by sufficiently applying the braking force to the front wheels WF.

(Operating state of automatic brake device)
With reference to FIG. 2, the operation state of the automatic brake device 1 of the first embodiment and the operation of the conventional control for operating both the front wheel brake device and the rear wheel brake device in both the primary brake and the secondary brake. A description will be given in comparison with the state.

  FIG. 2 is a graph schematically showing the relationship between the elapsed time (s) when the automatic brake is operated and the deceleration (G), where the horizontal axis indicates the elapsed time and the vertical axis indicates the deceleration. The solid line graph shows the operating state of the first embodiment, and the broken line graph shows the operating state of the conventional control. In the conventional control, the period between the times t1 to t200 when the primary brake control is performed overlaps with a solid line graph indicating the operating state of the automatic brake device 1 of the first embodiment.

  As shown in the broken line graph, in the conventional control, when it is determined that the operation of the automatic brake is necessary, when the primary brake control is started at time t1, a predetermined brake is applied to both the front wheel brake device and the rear wheel brake device. The hydraulic pressure is applied to reach a predetermined deceleration g1 (G). Thereafter, as indicated by a straight line parallel to the horizontal axis, a constant braking force is maintained by maintaining a predetermined brake fluid pressure. When the secondary brake control is started at time t200, a predetermined brake fluid pressure is applied to both the brake devices, and a predetermined deceleration g2 (G) is reached at time tg. The slope of the broken line graph indicates jerk based on the sum of the brake fluid pressure by the front wheel brake device and the brake fluid pressure by the rear wheel brake device. In the conventional control, the inclination in the primary brake control and the inclination in the secondary brake control are substantially the same.

  On the other hand, in the control by the automatic brake device 1 according to the first embodiment as shown in the solid line graph, when it is determined that the operation of the automatic brake is necessary, when the primary brake control is started at the time t1, the same as the above-described conventional control In addition, a predetermined brake fluid pressure is applied to both the brake devices to reach a predetermined deceleration g1 (G). Therefore, in the control by the automatic brake device 1 of the first embodiment, the inclination in the primary brake control is the same as the conventional control described above between the brake fluid pressure by the front wheel brake device and the brake fluid pressure by the rear wheel brake device. Indicates a jerk based on the sum.

  When the secondary brake control is started at time t2 after the predetermined brake fluid pressure is held for a predetermined time, the predetermined brake fluid pressure is applied only to the brake device for the front wheel WF. As described above, the brake fluid pressure applied to the brake device for the front wheel WF can be made larger than that in the conventional control as described above, assuming that the amount of brake fluid is the same as that in the conventional control. As a result, in the control by the automatic brake device 1 of the first embodiment, the inclination in the secondary brake control, that is, the jerk based on the brake fluid pressure by the brake device for the front wheels can be made larger than the inclination in the primary brake control. Moreover, it can be larger than the inclination (jerk) in the conventional brake control. Therefore, when the time tg at which the deceleration g2 is reached is the same as in the conventional control, the start time t2 of the secondary brake control can be made later than the start time t200 in the conventional control.

(Function and effect)
In the automatic brake device 1 of the first embodiment, when there is a possibility of collision between the host vehicle and the surrounding objects, both the brake device for the front wheel WF and the brake device for the rear wheel WR are operated as the primary brake. The possibility of a collision can be alerted to the driver with a weak brake. And in the automatic brake device 1, only the brake device of the front wheel WF is operated as a secondary brake. Therefore, it is easy to increase the brake fluid pressure of the cylinder CF provided in the brake device for the front wheel WF, compared to the conventional control that operates both the brake device for the front wheel WF and the brake device for the rear wheel WR. That is, it is easy to increase the rising acceleration of deceleration. Therefore, the automatic brake device 1 of Embodiment 1 can improve the jerk of the secondary brake without increasing the output of the motor M of the pump 20. As a result, unnecessary operation of the secondary brake can be reduced. In addition, the host vehicle can be decelerated more quickly.

[Embodiment 2]
The basic configuration of the automatic brake device of the second embodiment is the same as that of the first embodiment. In the automatic brake device according to the second embodiment, the secondary brake control unit 32 operates both the brake device for the front wheel WF and the brake device for the rear wheel WR after operating only the brake device for the front wheel WF. The difference from 1. Hereinafter, this difference will be described in detail, and the detailed description of the same configuration and effects as those of the first embodiment will be omitted.

  When only the brake device of the front wheel WF is used as the secondary brake, for example, if the road surface friction coefficient μ is low, the tire of the front wheel WF reaches the lock limit and does not reach the predetermined deceleration g2 (FIG. 3). The tire of the front wheel WF tends to slip. In this case, since the deceleration g2 cannot be reached by the operation of only the brake device for the front wheel WF, the brake device for the front wheel WF and the brake device for the rear wheel WR at time t3 as shown by the solid line in FIG. Operate both. The secondary brake control unit 32 in this example includes a command to turn the holding valve 22R of the cylinder CR provided in the brake device for the rear wheel WR from a closed state to an open state, a command to keep the holding valve 22F open, and a pressure regulating valve A command for adjusting the opening of the MC is issued to the valves 22F, 22R, and MC.

  In the automatic brake device of the second embodiment, during the operation of the secondary brake control, by switching from the operation of only the brake device of the front wheel WF to the operation of both of the brake devices, the predetermined deceleration g2 or the road surface limit The deceleration can be reached reliably. Further, the brake device for the rear wheel WR is closed while the brake fluid pressure during the primary brake control is maintained. Therefore, at time t3, the brake fluid pressure of the brake device for the rear wheel WR is high to some extent. Since this state is changed to the open state, the time lag until the predetermined brake fluid pressure is reached can be shortened. Here, the drum type brake device used as the brake device for the rear wheel WR in this example generally has a higher brake hydraulic pressure at which a predetermined braking force acts than the disc type brake device. However, in the automatic brake device of the second embodiment, as described above, the brake device for the rear wheel WR is also used during the primary brake control, so that when the secondary brake control is used during the operation, the predetermined brake is used. The time required to reach the hydraulic pressure at which the power acts can be shortened.

[Modification]
At least one of the following modifications can be made to the first and second embodiments.
(1) Both the brake device for the front wheel WF and the brake device for the rear wheel WR are disc brake devices or drum brake devices.
(2) The brake device for the front wheel WF is a drum brake device, and the brake device for the rear wheel WR is a disk brake device.

  The automatic brake device of the present invention is provided in an automobile and can be used as one of driving support systems.

DESCRIPTION OF SYMBOLS 1 Automatic brake device 2 Brake actuator 20 Pump 22F, 22R Holding valve 24F, 24R Pressure reducing valve 26 Reservoir 3 Electronic control unit 31 Primary brake control unit 32 Secondary brake control unit 4 Brake pedal 40 Booster device 42 Master cylinder CF, CR Cylinders provided in the brake device S1, S2, S3, S Sensor MC Pressure regulating valve M Motor WF Front wheel WR Rear wheel

Claims (1)

An automatic brake device that operates a brake device provided on each of the front wheel and the rear wheel of the host vehicle regardless of a driver's brake operation,
A primary brake control unit for operating both the front wheel brake device and the rear wheel brake device for a predetermined time based on the relationship between the host vehicle and surrounding objects;
An automatic brake device comprising: a secondary brake control unit that activates only the brake device for the front wheel after the predetermined time has elapsed.

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