JP6536972B2 - Vehicle braking system - Google Patents

Description

  The present invention relates to a braking device for a vehicle, and more particularly to a braking device for a vehicle provided with an electric brake means capable of braking a vehicle by driving a motor, and a main power supply and an auxiliary power supply capable of supplying electric power to the electric brake means.

2. Description of the Related Art Conventionally, there is known a brake system in which the braking force of each wheel is electronically controlled in order to apply an optimum braking force to a vehicle according to a traveling state. In this electronically controlled brake system, the solenoid valve is controlled so that the wheel cylinder pressure of each wheel becomes the target brake hydraulic pressure calculated based on the depression amount (for example, the stroke) of the brake pedal by the occupant.
In such an electronically controlled brake system, a pump for increasing the brake fluid pressure, a solenoid valve for adjusting the flow of the brake fluid, and the like are used, and these pumps and solenoid valves are driven using a battery as a main power source. ing. Therefore, if the power from the battery is interrupted for any reason, the necessary braking force (deceleration) can not be secured.
Therefore, in addition to the pre-equipped main power supply, a technology has been proposed in which an auxiliary power supply for backup at the time of main power supply failure is additionally provided.

A capacitor, which is a passive element, can efficiently store power and is less likely to cause deterioration of the electrode material due to charge and discharge, and thus is often used as a backup auxiliary power supply.
The vehicle braking device of Patent Document 1 switches a power supply path for switching a power supply path to a battery as a main power source, a DLC (capacitor) as an auxiliary power source, an electric brake booster, and an electric brake booster. And, when the power remaining capacity of the DLC falls below a predetermined remaining threshold, the power remaining capacity is reduced by decreasing the value of the current supplied to the electric brake booster as the power remaining capacity decreases. It is intended to reduce the discomfort caused by the change in treading force when the value of Z becomes zero.

Further, in recent years, a driving support system for avoiding a collision against an obstacle is known.
The collision avoidance support system includes a periphery detection sensor (a camera sensor, a radar sensor, etc.) capable of detecting an obstacle ahead of the vehicle, and a TTC (time until the host vehicle collides with an obstacle such as a preceding vehicle). If time collision is compared with a predetermined judgment threshold and collision avoidance is possible by normal braking operation by the occupant, alarm sound is notified to the occupant, and collision avoidance is possible by emergency braking by the occupant, or When collision avoidance is physically unavoidable, the vehicle performs automatic brake control that operates the electronically controlled brake system independently.

JP, 2010-120522, A

When a backup auxiliary power supply is added to the vehicle, it is possible to supply the power to the electronically controlled brake system by supplying power from the auxiliary power supply when the main power supply fails.
However, power supply by the auxiliary power supply is generally set to a storage capacity smaller than that of the main power supply for the purpose of emergency response, and continuous use for a long time is difficult.
In particular, a capacitor using the phenomenon of adhesion and detachment of electric charge on the electrode surface is inferior in storage capacity per mass as compared with a secondary battery because the accumulation of electric charge is limited to the surface of the electrode material.
Therefore, when the collision avoidance support system is applied to a vehicle equipped with an electronically controlled brake system, there is a concern that the expected braking effect can not be secured.

To operate the electronically controlled brake system to brake the vehicle, a minimum power (e.g., 6 V) is required to activate the motor of the electric brake booster.
That is, when the normal braking operation by the occupant is continuously performed under the situation where the power of the main power supply is reduced, the auxiliary power supply compensates for the shortage of the main power supply power, and accordingly, along with the occupant's braking operation. There is a risk that the power of the auxiliary power supply will gradually decrease.

  An object of the present invention is to provide a vehicle braking device and the like capable of securing the power necessary for executing automatic brake control according to the necessity of emergency braking.

  The braking apparatus for a vehicle according to claim 1 comprises an electric brake means capable of braking a vehicle by driving a motor, a main power supply capable of supplying electric power to the electric brake means, and an auxiliary power supply capable of supplying electric power to the electric brake means. And a control unit capable of controlling the power supplied to the electric brake unit, the braking apparatus for a vehicle comprising: a determination unit capable of determining the necessity of emergency braking of the own vehicle; An automatic brake control means for automatically operating the electric brake means based on the necessity of the emergency braking determined by the means, wherein the control means controls the electric power brake from the auxiliary power source when the automatic brake control means is inoperative. It is characterized in that available power obtained by subtracting holding power from suppliable power which can be supplied to the means is supplied.

This vehicle braking system has determination means capable of determining the necessity of emergency braking of the own vehicle, and the control means automatically makes the electric brake means based on the necessity of emergency braking determined by the determination means. Since the automatic brake control means is provided to operate the vehicle, it is possible to brake the vehicle regardless of the occupant's braking operation when emergency braking is required.
The control means is necessary to execute the automatic brake control in order to supply the usable power obtained by subtracting the storage power from the suppliable power which can be supplied from the auxiliary power supply to the electric braking means when the automatic brake control means is inoperative. Power can be secured as holding power.

According to the invention of claim 2, in the invention of claim 1, the control means is configured to increase the holding power as the automatic brake control means is inoperable and the necessity of emergency braking determined by the determination means increases. It is characterized by increasing.
According to this configuration, it is possible to secure the power necessary for executing the automatic brake control while maintaining the braking ability of the normal braking operation by the occupant.

The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, the determination means determines the necessity of emergency braking based on the vehicle speed.
According to this configuration, the practicability of the automatic brake control can be accurately determined.

The invention according to claim 4 relates to the invention according to any one of claims 1 to 3, wherein the control means sets a target power supply amount to the electric brake means corresponding to a target deceleration of the vehicle. When the power that can be supplied from the main power supply is smaller than the target power supply amount, it is characterized in that power is supplied from the auxiliary power supply.
According to this configuration, it is possible to reduce the frequency of supplying power from the auxiliary power supply at the time of normal braking operation by the occupant, and to suppress reduction of the power that can be supplied from the auxiliary power supply.

The invention according to claim 5 is characterized in that, in the invention according to any one of claims 1 to 4, the storage power is equal to or higher than a minimum power at which the electric brake means can be operated.
According to this configuration, at the time of execution of the automatic brake control, the electric brake means can be reliably operated.

The invention of claim 6 is characterized in that, in the invention of any one of claims 1 to 5, the control means sets the reserved power higher as the vehicle speed is higher.
According to this configuration, the operation time of the electric brake means can be extended according to the necessity of the emergency braking related to the vehicle speed.

The invention according to claim 7 is characterized in that, in the invention according to any one of claims 1 to 6, the control means sets the reserved power higher as the road surface condition is worse.
According to this configuration, it is possible to prolong the operation time of the electric brake means according to the necessity of the emergency braking related to the road surface condition such as the road surface μ or the weather.

  According to the vehicle braking system of the present invention, by providing the reserved power held in the auxiliary power supply, it is possible to secure the power necessary for the execution of the automatic brake control according to the necessity of the emergency braking.

FIG. 1 is an electric circuit diagram of a vehicle brake system according to a first embodiment. It is a schematic block diagram of the brake by wire system in main power supply mode. It is a map of the treading force characteristic which shows the relationship between a stroke and treading force. It is a map of the damping | braking characteristic which shows the relationship between treading force and deceleration. 1 is a block diagram of a vehicle braking system. It is a map which shows the relationship between the number of braking operations and the correction coefficient K1. It is a map which shows the relationship between a vehicle speed and reserve electric energy. It is a flowchart which shows an automatic braking control processing procedure. It is a flow chart which shows basic braking control processing procedure. It is a flowchart which shows a target power supply correction process procedure. It is a flowchart which shows a pending power setting processing procedure.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.
The following description exemplifies the application of the present invention to a vehicle equipped with an electronically controlled brake-by-wire system, and does not limit the present invention, its application, or its application.

Hereinafter, Example 1 of the present invention will be described based on FIGS. 1 to 11.
As shown in FIG. 1, the vehicle according to this embodiment includes a vehicle power supply 1, a backup power supply unit 2, a brake-by-wire system 3, a vehicle-side load 4 including audio, an air conditioner, electronic devices, etc. Electronic Control Unit) 5 (control means) etc. are provided. This vehicle is, for example, a hybrid vehicle including an electric motor and an internal combustion engine (all not shown) as traveling drive sources, and regenerative braking that brakes the vehicle by regenerating the kinetic energy of the vehicle into electric energy. It is configured to be able to execute brake regeneration coordinated control that generates a desired braking force in combination with hydraulic pressure braking by the brake-by-wire system 3.

First, the vehicle power supply 1 will be described.
The vehicle power source 1 mainly includes a main power source 11 formed of a 12 V vehicle battery and an alternator 12 connected in series to the main power source 11 and capable of generating power by driving an internal combustion engine. The main power supply 11 is equipped with a main power supply state sensor 13 capable of detecting a functional deterioration or a function stop of the main power supply 11 through a battery power state including a state of charge (SOC) and a voltage. The detected power state of the main power supply 11 is the lighting of an indicator lamp (hereinafter referred to as an indicator) 14 (see FIG. 5) mounted on an instrument panel (not shown) disposed on the front side of the passenger compartment. The display is notified to the occupant.
The vehicle power source 1 is provided to the brake-by-wire system 3 by two lines of a first line L1 having a backup power supply unit 2 interposed in the middle and a second line L2 disposed in parallel with the first circuit L1. Are connected electrically.
The third line L <b> 3 branched from the middle of the second line L <b> 2 is connected to the vehicle-side load 4.

Next, the backup power supply unit 2 will be described.
When there is a possibility that the operation of the brake-by-wire system 3 may cause trouble in the operation of the brake-by-wire system 3 such as when the vehicle power supply 1 is abnormal or the power of the main power supply 11 is reduced, the backup power supply unit 2 Is an auxiliary power supply unit dedicated to the brake-by-wire system 3 capable of supplying
As shown in FIG. 1, the backup power supply unit 2 includes a capacitor 21 as an auxiliary power, a charging circuit unit 22, and an auxiliary power state sensor 23 capable of detecting a power state including the voltage of the capacitor 21.

The capacitor 21 is formed of, for example, a capacitor cell group in which cells of an electric double layer capacitor are connected in series and parallel, and is configured to be able to generate a voltage of 12V.
The discharge side end of the capacitor 21 is electrically connected to the first circuit L1 via the first contact 24 which can switch the on / off state electrically. A second contact 25 which can electrically switch the on / off state is disposed in the middle of the first circuit L1 corresponding to the first contact 24 and the vehicle power source 1.
The charging circuit unit 22 is configured to be able to charge the capacitor 21 by the vehicle power supply 1.
The downstream end of the charging circuit portion 22 is connected to the charging end of the capacitor 21, and the upstream end is connected to the upstream portion of the second contact 25 of the first circuit L1.
When discharging power from the capacitor 21, the ECU 5 turns on the first contact 24 and turns off the second contact 25. When charging the capacitor 21, the ECU 5 turns off the first contact 24 and turns on the second contact 25, and when charging and discharging, both the first and second contacts 24 and 25 turn off. Ru.

Next, the brake by wire system 3 will be described.
As shown in FIG. 1, the by-wire system 3 electrically opens / closes the power supply control circuit unit 31 to which power is supplied from each of the first and second circuits L1 and L2, the motor 32, and the brake fluid passage. Possible solenoid valves 33 to 36 and a control unit 37 etc. are mainly configured.
The power supply control circuit unit 31 distributes the supplied power to the motor driver 32a, the solenoid valve drivers 33a to 36a and the control unit 37 based on predetermined control conditions.
Specifically, the power from the vehicle power supply 1 is distributed to the motor 32, the solenoid valves 33 to 36, and the control unit 37, and the power from the backup power supply unit 2 is distributed to the motor 32.

Here, a schematic configuration relating to an operation system of the brake-by-wire system 3 will be described.
As shown in FIG. 2, the brake-by-wire system 3 is an electric motor consisting of a master cylinder 42 capable of generating a brake fluid pressure corresponding to the stroke St of the brake pedal 41, a motor 32 and a pump unit driven by the motor 32. The brake hydraulic pressure generated by the brake booster 43 (electric brake means), the reaction force generation mechanism 44, the master cylinder 42 or the electric brake booster 43, or the brake fluid generated by the master cylinder 42 and the electric brake booster 43 The control unit 37 is provided with wheel cylinders 45a to 45d for braking the rotation of the front and rear left and right wheels FL, FR, RL, and RR by pressure.

The master cylinder 42 includes a first pressure generating chamber 42a and a second pressure generating chamber 42b. The first and second pressure generating chambers 42a and 42b are respectively connected to the reservoir tank 46, and each have a compression spring therein. The first and second pressure generating chambers 42 a and 42 b are configured to be capable of pressure-feeding substantially the same brake hydraulic pressure according to the stepping-on operation of the brake pedal 41.
The first pressure generating chamber 42a is in communication with the wheel cylinders 45a, 45b via the openable / closable solenoid valve 33, and the second pressure generation chamber 42b is in communication with the wheel cylinders 45c, 45d via the openable solenoid valve 36. It is done.

As shown in FIG. 2, the pump portion of the electric brake booster 43 is in communication with the wheel cylinders 45a and 45b through the openable and closable solenoid valves 34, and is connected to the wheel cylinders 45c and 45d through the openable and closable solenoid valves 35. It is done. The minimum amount of electric power E0 which can start the motor 32 of the electric brake booster 43 is 6 V, for example.
The reaction force generation mechanism 44 is connected to a flow path that connects the first pressure generation chamber 42a and the solenoid valve 33, and for example, a cylinder, a piston slidable in the cylinder, and a bias that biases the piston. It is formed by means or the like. Thus, when the occupant steps on or depresses the brake pedal 41, a reaction force (depression force) having a preset characteristic can be applied to the occupant via the brake pedal 41.

The control unit 37 closes the solenoid valves 33 and 36 and opens the solenoid valves 34 and 35 when the main power supply 11 is normal according to a control signal input from the ECU 5, and the main power supply 11 loses its function or is lost At the time of depression, all the solenoid valves 33 to 36 are opened.
Further, the control unit 37 is configured to be able to execute the deceleration control process and the depression force control process by controlling the electric brake booster 43, the reaction force generation mechanism 44, the stroke sensor 47, and the solenoid valves 33 to 36. It is done.

The control unit 37 has a pedal effort characteristic map M1 and a braking characteristic map M2.
As shown in FIG. 3, the map M1 is defined by a predetermined function, for example, logarithm.
The control unit 37 sets the depression force F corresponding to the target operation reaction force based on the stroke St by the stroke sensor 47 and the depression force characteristic map M1, and the operation command signal corresponding thereto is generated by the reaction force generation mechanism 44. Output to
As shown in FIG. 4, the control unit 37 sets the target deceleration D of the vehicle using the pedaling force F set via the detected stroke St and the braking characteristic map M2, and corresponds to the target deceleration D. The operation command signal is output to the motor 32 (motor driver 32a).
Thus, the wheel cylinders 45a to 45d are driven via the brake fluid pressure, and the braking operation of the deceleration D based on the braking characteristic map M2 is performed.
Further, at the same time, the control unit 37 outputs control signals regarding the stroke St and the target deceleration D to the ECU 5.

Next, the ECU 5 will be described.
The ECU 5 supplies the electric power to the electric brake booster 43 from the main power supply 11 only, and the first and second electric power supplies to the electric brake booster 43 from both the main power supply 11 and the capacitor 21. The auxiliary power supply combined mode is configured to be executable. Specifically, in the main power supply mode, the target power supply amount E required for the operation of the electric brake booster 43 to be the main power supplyable power E1 that can be supplied by the main power supply 11 (hereinafter abbreviated as the suppliable power E1). In the above case, power corresponding to the target power supply amount E is supplied only from the main power supply 11. In the first auxiliary power supply combined mode, when the sum of the suppliable electric power E1 and the usable electric power ΔE2 of the capacitor 21 is the target electric power supply amount E or more, the target electric power supply amount E equivalent from both the main power supply 11 and the capacitor 21 The second auxiliary power supply combined mode can be supplied from both the main power supply 11 and the capacitor 21 when the sum of the suppliable power E1 and the usable power ΔE2 of the capacitor 21 is less than the target power supply amount E. Supply power less than the target power supply amount E.
The usable power ΔE2 of the capacitor 21 means the auxiliary power available power E2 that can be supplied by the capacitor 21 (hereinafter, abbreviated as the available power E2). Withhold of the capacitor 21 basically not used except during emergency braking. It is a difference of the power E2a.

As shown in FIG. 5, the ECU 5 is electrically connected to the main power state sensor 13, the auxiliary power state sensor 23, the control unit 37, the wheel speed sensor 61, the periphery detection sensor 62, and the wiper sensor 63, The detection signal and control signal output from these sensors etc. are input.
The wheel speed sensor 61 is configured to be able to detect the wheel speeds of the respective wheels FL, FR, RL, and RR. The periphery detection sensor 62 is, for example, a radar sensor such as a millimeter wave radar or a laser radar disposed on the front side of the vehicle, or a camera sensor such as a CCD or a CMOS. It is possible to detect the relative position (separation distance) of the object and the relative velocity. The wiper sensor 63 is configured to be able to detect whether or not the wiper device is operating via a driving current of a wiper device (not shown) that wipes raindrops attached to the windshield glass.

The ECU 5 is configured of a central processing unit (CPU), a ROM, a RAM, an in-side interface, an out-side interface, and the like. The ROM stores various programs and data, and the RAM is provided with a processing area used when the CPU performs a series of processing.
As shown in FIG. 5, the ECU 5 sets a determination unit 51 (determination means), an automatic brake control unit 52 (automatic brake control means), a power state detection unit 53 (power state detection means), and a target power supply amount setting. A unit 54, a target power supply correction unit 55, and a reserve power setting unit 56 are provided.

First, the determination unit 51 will be described.
The determination unit 51 determines the necessity of emergency braking of the host vehicle.
The necessity of emergency braking is the degree of risk of collision between the vehicle and an object (obstacle).
Therefore, the determination unit 51 calculates TTC (Time To Collision) corresponding to the time until the host vehicle collides with an obstacle such as the preceding vehicle. Among the obstacles detected by the surrounding area detection sensor 62, the obstacle closest to the vehicle is determined, and the TTC for the obstacle is calculated.

In addition to the TTC determination, the determination unit 51 also determines the degree of risk associated with an erroneous operation by the occupant. Specifically, it is determined that the higher the vehicle speed V, the higher the degree of danger, and the higher the degree of danger if the road surface μ of the traveling road is lower μ lower than a predetermined determination value. Further, even when the wiper device is in operation, the visibility of the occupant is deteriorated, so it is determined that the degree of danger is high.
The vehicle speed V is determined by the slower wheel speed of the left and right driven wheels, and the road surface μ is calculated using a separately obtained driving force of the vehicle and a ground load.

Next, the automatic brake control unit 52 will be described.
The automatic brake control unit 52 outputs an operation command signal to the motor 32 (motor driver 32a) based on the TTC determined by the determination unit 51 regardless of the operation of the brake pedal 41 by the occupant. Specifically, when the TTC is equal to or more than the first threshold (for example, 4 seconds), a collision can be avoided by a normal braking operation by the occupant, so the flag f is set to zero and no control from the vehicle side is executed. When the TTC is less than the first threshold, the flag f is set to 1.
If the TTC is less than the first threshold and greater than or equal to the second threshold (for example, 2.3 sec), a collision can be avoided by the emergency braking operation performed by the occupant. If TTC is less than the second threshold, collision avoidance is inevitable even in the case of emergency braking operation by the occupant, so the motor 32 is operated to perform automatic braking which is emergency braking.

Next, the power supply state detection unit 53 and the target power supply amount setting unit 54 will be described.
Based on the detection result of main power supply state sensor 13, power supply state detection unit 53 is based on the detection results of suppliable power E1 which can be supplied to electric brake booster 43 (motor 32) by main power supply 11 and auxiliary power supply state sensor 23. The capacitors 21 are configured to respectively detect the suppliable electric power E2 that can be supplied to the electric brake booster 43.
Further, the power state detection unit 53 compares the judgment threshold L set in advance with the suppliable electric power E1, and when the suppliable electric power E1 is less than the judgment threshold L, the main power supply 11 is deteriorated in function or stopped. It is detected that it is a failure condition).

The target power supply amount setting unit 54 is a requested deceleration that requires the electric brake booster 43 to operate based on the target deceleration D input from the control unit 37 and the deceleration D0 that the occupant can generate with their own stepping force. D1 is calculated using the following equation (1).
D1 = D−D0 (1)
The deceleration D0 is obtained in advance by experiment or the like based on the maximum pedaling force that the occupant can exert.
The calculated required deceleration D1 is converted into a braking target torque, and a target power supply amount E necessary for the operation of the electric brake booster 43 is calculated based on the braking target torque.

Next, the target power supply correction unit 55 will be described.
The target power supply correction unit 55 reduces and corrects the target power supply amount E when the power state detection unit 53 detects a functional decrease or a functional stop of the main power supply 11.
By reducing the amount of power supplied from the capacitor 21, when the functional deterioration or the functional stop of the main power supply 11 is detected, the period in which power can be supplied by the capacitor 21 can be extended, and the automatic brake control unit 52 It is possible to secure the power necessary for the execution of the automatic braking.

The target power supply correction unit 55 corrects the target power supply E using the correction coefficients K1 and K2.
As shown in FIG. 6, the target power supply correction unit 55 has in advance a map M3 showing a linear function relationship between the number of braking operations N (times) and the correction coefficient K1 (0 <K1 <1). There is.
When the automatic brake is in the inoperative state and the collision can not be avoided by the normal braking operation by the occupant (in the case of f = 1), the depression operation of the brake pedal 41 from the time when the function decrease or the function stop of the main power supply 11 is detected K1 is set based on the number of times N, and the target power supply amount E is corrected using the set K1 and the following equation (2).
(1-K1) × E (2)
In the present embodiment, the initial value of the correction coefficient K1 is defined as 0.1, and the maximum value is defined as 0.3.
N is reset to zero when the main power supply 11 has been de-functioned or stopped.

In addition, when the collision can be avoided by the normal braking operation by the occupant (in the case of f = 0), the target power supply correction unit 55 corrects the target power supply E with the correction coefficient K1 as in the following equation (3) The correction is made using the coefficient K2 (0 <K2 <1).
{1- (K1 + K2)} × E (3)
In the present embodiment, the correction coefficient K2 is defined as a constant (for example, 0.1).
When the automatic brake control unit 52 is executing automatic braking, correction of the target power supply amount E is prohibited.

Next, the hold power setting unit 56 will be described.
The storage power setting unit 56 sets the storage power E2a which is the minimum remaining power of the capacitor 21 as the automatic brake by the automatic brake control unit 52 is in the inoperative state and the necessity of the emergency braking determined by the determination unit 51 becomes higher. It is configured to do more.
This is for securing the power necessary for the execution of the automatic braking by the automatic brake control unit 52.

The holding power setting unit 56 sets the holding power E2a using the correction coefficients K3, K4, and K5 reflecting the necessity of the emergency braking and the vehicle speed V.
As indicated by the solid line in FIG. 7, when the road surface μ is larger than the determination threshold, the storage power setting unit 56 sets the storage power E2a to be proportional to the vehicle speed V based on the correction coefficient K3 (0 <K3). ing. Specifically, the reserved power E2a is calculated using the following equation (4) so as to be larger than the minimum power amount E0 for activating the motor 32 of the electric brake booster 43.
E2a = E0 + K3 × V (4)

As shown by the dotted line in FIG. 7, when the road surface μ is equal to or less than the determination threshold and the wiper is in the inoperative state, the storage power E2a uses the following equation (5) based on the correction coefficient K3 and the correction coefficient K4 (1 <K4). It is set to be proportional to the vehicle speed V. This is because the road surface μ is low and the degree of danger is high.
K4 × (E0 + K3 × V) (5)
As shown by the one-dot chain line in FIG. 7, when the road surface μ is equal to or less than the determination threshold and the wiper is in operation, the storage power E2a is based on the correction coefficients K3 and K4 and the correction coefficient K5 (1 <K5). Are set to be proportional to the vehicle speed V. This is because the visibility of the occupant is reduced, the road surface condition is deteriorated, and the degree of danger is high.
K4 × K5 × (E0 + K3 × V) (6)
As described above, the higher the degree of danger, that is, the higher the possibility that the automatic braking is performed, the higher the holding power E2a, which is the power for performing the automatic braking.
When the automatic brake control unit 52 is executing the automatic braking, the holding power E2a is set to the minimum power amount E0.

The ECU 5 determines the usable electric power ΔE2 of the capacitor 21 supplied to the electric brake booster 43 based on the normal braking operation by the occupant. The ECU 5 calculates the suppliable electric power E2 based on the detection result of the auxiliary power state sensor 23, and subtracts the holding electric power E2a set by the holding electric power setting unit 56 from the suppliable electric power E2 to perform the normal braking operation by the occupant. The usable power ΔE2 of the capacitor 21 at the time is calculated.
Thereby, the power necessary for the execution of the automatic braking by the automatic brake control unit 52 is secured in the capacitor 21.

Next, an automatic braking control processing procedure will be described based on the flowchart of FIG.
Note that Si (i = 1, 2...) Indicates steps for each process.

As shown in FIG. 8, first, various information is read (S1), and the process proceeds to S2.
In S2, a time TTC until the own vehicle collides with an obstacle is calculated, and the process shifts to S3.
In S3, it is determined whether TTC is less than a first determination threshold.
As a result of the determination in S3, if TTC is less than the first determination threshold, there is a need for emergency braking, so 1 is substituted for the flag f (S4), and the process proceeds to S5.
If it is determined in S3 that TTC is equal to or greater than the first determination threshold, the necessity of emergency braking is extremely low, so zero is substituted for the flag f (S8), and the process returns.

At S5, it is determined whether TTC is less than a second determination threshold.
As a result of the determination in S5, when TTC is less than the second determination threshold, collision avoidance is inevitable even in the emergency braking operation by the occupant, so that automatic braking by the vehicle is executed (S6), and the process returns.
At this time, the electric brake booster 43 is supplied with electric power that can be supplied from the capacitor 21 including the holding electric power E2a for automatic braking.
As a result of the determination in S5, when TTC is equal to or greater than the second determination threshold, the collision can be avoided by the emergency braking operation by the occupant, so the alarm means 64 is activated (S7), and the process returns.

  Next, a basic braking control processing procedure will be described based on the flowcharts of FIGS. The basic braking control process is performed in parallel with the automatic braking control process.

As shown in FIG. 9, first, various information such as each sensor output, correction coefficients K1 to K5, and maps M1 to M3 are read (S11), and the process proceeds to S12.
In S12, it is determined whether the occupant has depressed the brake pedal 41 or not.
When the occupant depresses the brake pedal 41 as a result of the determination in S12, the target deceleration D is calculated based on the stroke St of the brake pedal 41 and the maps M1 and M2 (S13).
If the occupant does not depress the brake pedal 41 as a result of the determination in S12, the process proceeds to S29.

In S14, the required deceleration D1 required of the vehicle is calculated using the calculated target deceleration D and the deceleration D0 that can be generated by the occupant with his own pedaling force.
In S15, the target power supply amount E necessary for the operation of the electric brake booster 43 is calculated using the calculated required deceleration D1.
In S16, the suppliable electric power E1 that can be supplied from the main power supply 11 to the electric brake booster 43 is calculated based on the detected power supply state of the main power supply 11.
In S17, the suppliable electric power E2 that can be supplied from the capacitor 21 to the electric brake booster 43 is calculated based on the detected power state of the capacitor 21.

In S18, it is determined whether the suppliable power E1 is less than the determination threshold L.
As a result of the determination in S18, if the suppliable power E1 is less than the determination threshold L, there is a possibility that the function of the main power supply 11 may be deteriorated or stopped, so N + 1 is substituted for the number N of depression operations of the brake pedal 41 (S19 ), The target power supply correction process (S20) is executed to correct the target power supply E, and the process proceeds to S21.
As a result of the determination in S18, when the suppliable power E1 is equal to or greater than the determination threshold L, the possibility of functional deterioration or functional stop of the main power supply 11 is extremely low. S27) The process proceeds to S21 while maintaining the target power supply amount E without correction (S28).

In S21, it is determined whether the suppliable power E1 is less than the target power supply amount E.
As a result of the determination in S21, if the suppliable power E1 is less than the target power supply amount E, power supply from the capacitor 21 is necessary, and the suppliable power E2 is reduced, so the holding power setting process (S22) is executed. The reserved power E2a is set, and the process proceeds to S23.
As a result of the determination in S21, when the suppliable power E1 is equal to or more than the target power supply amount E, the power supply from the capacitor 21 is not necessary and the suppliable power E2 does not decrease, so the main power feeding mode is executed (S26), Return

In S23, it is determined whether the total power of the suppliable power E1 and the usable power ΔE2 is equal to or more than the target power supply amount E.
As a result of the determination in S23, when the total power of the suppliable power E1 and the usable power ΔE2 is equal to or more than the target power supply amount E, the target power supply amount E can be supplied with the reserve power E2a remaining in the capacitor 21. The first auxiliary power supply combined mode for supplying power equivalent to the power supply amount E is executed (S24), and the process returns.
As a result of the determination in S23, if the total power of the suppliable power E1 and the usable power ΔE2 is less than the target power supply amount E, the target power supply amount E can not be supplied with the reserve power E2a remaining in the capacitor 21. The second auxiliary power supply combination mode for supplying power less than the target power supply amount E is executed with the reserve power E2a remaining at 21 (S25), and the process returns.
In the second auxiliary power supply combined mode, the amount of electric power supplied to the electric brake booster 43 becomes lower than the target electric power supply amount E because the reserved electric power E2a for emergency braking is left in the capacitor 21. The braking performance of the electric brake booster 43 Is less than the required deceleration D1.
However, since the solenoid valves 33 and 36 are opened, the braking performance is artificially compensated for by the braking operation (stepping on / backing back) by the subsequent occupant.

In S29, it is determined whether the flag f is zero.
When the flag f is zero as a result of the determination in S29, the collision can be avoided by the normal braking operation by the occupant, and thus the process proceeds to S30.
In S30, it is determined whether the suppliable power E2 of the capacitor 21 is equal to or higher than the charge threshold (for example, full charge).
As a result of the determination in S30, if the suppliable power E2 of the capacitor 21 is equal to or higher than the charging threshold, the process returns. If the suppliable electric power E2 of the capacitor 21 is less than the charging threshold, the capacitor 21 is charged (S31). Do.
As a result of the determination in S29, if the flag f is not zero, it is determined that the automatic braking is being performed or the necessity of the emergency braking exists, so the processing returns.

Next, the target power supply correction process procedure in S20 will be described.
As shown in the flowchart of FIG. 10, in the target power supply correction process, first, at S41, it is determined whether the flag f is zero.
As a result of the determination in S41, when the flag f is zero, the braking force can be secured by the occupant's own braking operation (stepping-in), and the braking force by the electric brake booster 43 can be reduced. Then, the target power supply amount E is reduced and corrected (S42), and the process ends.
If it is determined in step S41 that the flag f is not zero, the process proceeds to step S43.

In S43, it is determined whether automatic braking is in progress.
As a result of the determination in S43, when the automatic braking is being performed, since the degree of danger is high, the target power supply amount E is not corrected (S44), and the process is ended.
As a result of the determination in S43, if the automatic braking is not being performed, the target power supply amount E is decreased and corrected using Formula (2) (S45), and the process is ended.

Next, the power saving setting procedure in S22 will be described.
As shown in the flowchart of FIG. 11, in the on-hold power setting process, first, at S51, it is determined whether or not the automatic brake is inoperative.
As a result of the determination in S51, if the automatic brake is not activated, the process proceeds to S52, and it is determined whether the road surface μ is low. As a result of the determination in S51, when the automatic braking is in progress, the reserve power E2a is set to the minimum power amount E0 (S57), and the process proceeds to S58.

As a result of the determination in S52, when the road surface μ is low, the process proceeds to S53, and it is determined whether the wiper is in operation. If the road surface μ is not low as a result of the determination in S52, the possibility of the automatic braking being performed is not so high, so the reserve power E2a is set using the equation (4) (S56), and the process proceeds to S58. .
As a result of the determination in S53, when the wiper is in operation, the field of view is lowered, and there is a high possibility that the automatic braking is performed, so the reserve power E2a is set using the equation (6) (S54), Transfer to S58. As a result of the determination in S53, when the wiper is not in operation, there is a high possibility that the automatic braking is performed, so the reserve power E2a is set using the equation (5) (S55), and the process shifts to S58.
In S58, after the reserve power E2a is subtracted from the suppliable power E2 to calculate the usable power ΔE2, the process ends.

Next, the operation and effects of the vehicle braking system will be described.
The vehicle braking apparatus according to the first embodiment has the determination unit 51 capable of determining the necessity of the emergency braking of the own vehicle, and the ECU 5 is automatically based on the necessity of the emergency braking determined by the determination unit 51. In addition, since the automatic brake control unit 52 for operating the electric brake booster 43 is provided, the vehicle can be braked regardless of the braking operation of the occupant when the emergency braking is necessary.
Since the ECU 5 supplies the usable power ΔE2 obtained by subtracting the reserve power E2a from the suppliable power E2 which can be supplied from the capacitor 21 to the electric brake booster 43 when the automatic brake control unit 52 is inoperative, Necessary power can be secured as hold power E2a.

  The ECU 5 maintains the braking ability of the normal braking operation by the occupant in order to increase the reserved power E2a as the automatic brake control unit 52 is inoperable and the necessity of the emergency braking determined by the determination unit 51 becomes higher. At the same time, it is possible to secure the power necessary for the execution of the automatic brake control.

  Since the determination unit 51 determines the necessity of emergency braking based on the vehicle speed V, it can accurately determine the feasibility of the automatic brake control.

  The ECU 5 sets the target power supply amount E to the electric brake booster 43 corresponding to the target deceleration D of the vehicle, and when the available power E1 that can be supplied from the main power supply 11 is smaller than the target power supply amount E, Since power is supplied from the capacitor 21, the frequency of supplying power from the capacitor 21 can be reduced at the time of normal braking operation by the occupant, and reduction of the available power E2 of the capacitor 21 can be suppressed.

  Since the storage power E2a is equal to or higher than the minimum power E0 capable of operating the electric brake booster 43 (motor 32), the electric brake booster 43 can be reliably operated when executing the automatic brake control.

  Since the ECU 5 sets the reserve power E2a higher as the vehicle speed V is higher, the operation time of the electric brake booster 43 can be extended according to the necessity of the emergency braking related to the vehicle speed V.

  Since the ECU 5 sets the storage power E2a higher as the road surface condition is worse, the operation time of the electric brake booster 43 can be extended according to the necessity of emergency braking relating to the road surface condition such as the road surface μ or weather. .

Next, a modification in which the embodiment is partially changed will be described.
1) In the above embodiment, an example using a capacitor which is a passive element as an auxiliary power supply has been described, but a lithium ion battery which is a secondary battery may be used. Moreover, it is also possible to use a normal battery (lead storage battery).

2) In the above embodiment, the correction factor K3, K4 and K5 have been described as constant, but the correction factor K3 is an acceleration, the correction factor K4 is a road surface μ, and the correction factor K5 is a variable proportional to the illuminance of view. Alternatively, any one or two correction coefficients may be used as variables.

3) In the above embodiment, an example in which one auxiliary power supply is provided has been described, but a plurality of auxiliary power supplies may be provided. In this case, the suppliable power is detected for each of the auxiliary power supplies, and the total power thereof is treated as the auxiliary power supplyable power.

4) In addition, those skilled in the art can carry out the embodiments in which various modifications are added to the embodiments or a combination of the embodiments without departing from the spirit of the present invention, and the present invention can be implemented as such It also includes various modifications.

3 Brake by Wire System 5 ECU
11 Main Power Supply 21 Capacitor 32 Motor 41 Brake Pedal 45a to 45d Wheel Cylinder 53 Power Condition Detection Unit 54 Target Power Supply Setting Unit 55 Target Power Supply Correction Unit FL, FR, RL, RR Wheel

Claims (7)

Electric brake means capable of braking a vehicle by driving a motor, a main power supply capable of supplying electric power to the electric brake means, an auxiliary power supply capable of supplying electric power to the electric brake means, and electric power supplied to the electric brake means And a control means capable of controlling
It has determination means capable of determining the necessity of emergency braking of the own vehicle,
The control means is provided with automatic brake control means for automatically operating the electric brake means based on the necessity of emergency braking determined by the determination means.
The braking device for a vehicle according to the present invention, wherein said control means supplies usable power obtained by subtracting holding power from suppliable power which can be supplied from said auxiliary power supply to said electric brake means when said automatic brake control means is inoperative. .   The vehicle according to claim 1, wherein the control means increases the reserved power as the automatic brake control means is inoperable and the necessity of emergency braking determined by the determination means becomes higher. Braking device.   The vehicle braking system according to claim 1 or 2, wherein the determination means determines the necessity of emergency braking based on the vehicle speed.   The control means sets a target power supply amount to the electric brake means corresponding to a target deceleration of the vehicle, and when the power which can be supplied from the main power supply is smaller than the target power supply amount, the auxiliary power supply The vehicle braking device according to any one of claims 1 to 3, wherein power is supplied from   5. The vehicle brake system according to claim 1, wherein the storage power is equal to or higher than a minimum power at which the electric brake means can be operated.   The vehicle control system according to any one of claims 1 to 5, wherein the control means sets the reserved power higher as the vehicle speed is higher. The vehicle braking apparatus according to any one of claims 1 to 6, wherein the control unit sets the storage power higher as the road surface condition is worse.

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