FR3057520A1 - BRAKE FORCE CONTROL SYSTEM - Google Patents

Abstract

An autonomous emergency brake control unit (AEB) (S1) autonomously actuates a vehicle braking system (3) in the event that a decision strategy generates a braking collision avoidance request ( step S2). Subsequently, a programmed electronic stability device (ESP) control unit (52) causes a change in a card used to control the electronic braking force distribution (EBD) by replacing a first braking force distribution card. (La1, Lb1) by a second braking force distribution card (La2, Lb2) (step S3). The ESP control unit (52) performs the EBD control based on the second braking force distribution board (La2, Lb2). In step S4, the ESP control unit performs control of the braking force distribution.

Description

057 520

59502 ® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number:

(to be used only for reproduction orders)

©) National registration number

COURBEVOIE © IntCI ⁸ : B 60 T 7/12 (2017.01)

PATENT INVENTION APPLICATION

A1

©) Date of filing: 11.10.17. © Applicant (s): SUZUKI MOTOR CORPORATION - © Priority: 13.10.16 JP 2016201936. JP. @ Inventor (s): NISHIZAWA HIROMITSU. ©) Date of public availability of the request: 20.04.18 Bulletin 18/16. ©) List of documents cited in the report preliminary research: The latter was not established on the date of publication of the request. (© References to other national documents ® Holder (s): SUZUKI MOTOR CORPORATION. related: ©) Extension request (s): © Agent (s): CABINET PLASSERAUD.

FR 3 057 520 - A1

104) BRAKE FORCE CONTROL SYSTEM

©) An autonomous emergency brake control unit (AEB) (S1) performs an autonomous actuation of a vehicle braking system (3) in the event that a decision strategy generates a collision avoidance request by braking (step S2). Subsequently, an electronic programmed stability device (ESP) control unit (52) causes a change in a card used for electronic brake force distribution (EBD) control by replacing a first braking force distribution card (La1, Lb1) by a second braking force distribution card (La2, Lb2) (step S3). The ESP control unit (52) performs the EBD control on the basis of the second braking force distribution card (La2, Lb2). In step S4, the control unit ESP performs a control of the braking force distribution.

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BRAKE FORCE CONTROL SYSTEM

The present invention relates to a braking force control system of a vehicle.

Vehicles like automobiles are known to be equipped with an anti-lock braking system (ABS) to prevent the wheels being braked from locking and autonomous braking to prevent a collision with an obstacle. .

Document JP H06-001229 A discloses a known braking force control system. In the known system, during autonomous braking, the brake fluid pressure on a wheel during braking is prevented from increasing further by an anti-lock braking system (ABS).

This known braking force control system can safely decelerate the vehicle without any wheel lock because the brake fluid pressure is maintained by the anti-lock brake system in the event of a wheel lock. during autonomous braking.

Patent literature 1: JP H06-001229 A

In vehicles fitted with an anti-lock braking system, a braking force control system controls the braking force distribution by electronically adjusting the braking force distribution between the front and rear wheels while maintaining the brake pressures. brake. This control, called Electronic Braking Force Distribution (EBD), aims to optimally distribute the braking forces between the wheels on the basis of wheel speeds and / or cornering. of the vehicle.

In controlling the brake force distribution, the brake fluid pressure on each of the rear wheels is kept at a low pressure level such that it prevents the rear wheels from locking up before the front wheels. The system must provide the maximum braking force during autonomous braking.

However, the system described in document JP H06-001229 A does not manage to satisfy a satisfactory level because the system does not manage to ensure the maximum braking force during autonomous braking.

An object of the present invention is to provide a braking force control system which ensures the braking force to the maximum while adjusting the braking force distribution in the case where a decision strategy generates a collision avoidance request. by braking.

According to the present implementation, a system for controlling the braking force of a vehicle is proposed, the vehicle comprising a plurality of wheels, the system being configured to: achieve autonomous actuation of a braking system of the vehicle by increasing a brake fluid pressure on each of the wheels in the case where a decision strategy generates a collision avoidance request by braking; and performing a braking force distribution, the braking force distribution performed during the autonomous actuation of the braking system being different from that during a non-autonomous actuation of the braking system in that, during the autonomous actuation of the braking system braking, the magnitude of the brake fluid pressure on at least one of the wheels may be greater than during the non-autonomous actuation of the braking system.

The implementation as described ensures the maximum braking force while adjusting the braking force distribution in the case where a decision strategy generates a collision avoidance request by braking.

Figure 1 is a block diagram of a braking force control system.

Figure 2 is a diagram of a hydraulic unit of a vehicle braking system.

Figure 3 illustrates brake force distribution maps.

Figure 4 is a flowchart.

Figure 5 is a timing diagram illustrating the behavior of brake fluid pressure on a bitter wheel immediately after a decision strategy has generated a request to avoid collision by braking.

FIG. 6 is a timing diagram illustrating the behavior of the brake fluid pressure on a rear wheel immediately after a decision strategy of a comparative example has generated a request for avoidance of collision by braking.

In the present implementation, a system for controlling the braking force of a vehicle is proposed. The vehicle has a plurality of wheels. The system is configured to: perform an autonomous actuation of a vehicle braking system in the event that a decision strategy generates a request for braking collision avoidance; and realizes a brake force distribution.

The brake force distribution achieved during the autonomous actuation of the braking system is different from that during a non-autonomous actuation of the braking system in that, during the autonomous actuation of the braking system, the magnitude of the fluid pressure brake on at least one of the wheels can increase more than during the non-autonomous actuation of the braking system.

Referring to the accompanying drawings, a braking force control system 50 is described. The system 50 controls a braking system 3 in a vehicle 1. The vehicle 1 comprises a plurality of wheels including at least one rear wheel and at least a front wheel. Figures 1 to 5 are used to describe the braking force control system 50.

Referring to Figure 1, the vehicle 1 includes: an autonomous emergency braking control unit (AEB) 51; an Electronic Stability Program (ESP) control unit 52; an engine control module (ECM) 53; and a body control module (BCM for “Body Control Module”) 54.

The braking system 3 of the vehicle 1 includes an electronic control unit 21 in addition to other components described later, such as a master cylinder.

Each of the AEB 51 control unit, the ESP 52 control unit, the ECM 53, and the BCM 54 includes a computer unit which comprises a central processing unit (CPU). a random access memory (RAM for "Random Access Memory"), a read only memory (ROM for "Read Only Memory"), a flash memory to save emergency data, input ports, and output ports. The computer unit ROM stores programs to cause the control unit to perform its function in addition to various parameters and cards.

The control unit AEB 51 and the control unit ESP 52 can communicate with each other by a control area network (CAN) for Control Area Network 55. The ECM 53 can communicate with the control unit AEB 51 by CAN 55. The BCM 54 can communicate with control unit AEB 51 by CAN 55. The control unit AEB 51 and the control unit ESP 52 cooperate with each other. 'other to bring the hydraulic control unit 21 to regulate the braking force on each wheel of the vehicle 1.

The ESP control unit 52 is electrically connected to the hydraulic unit 21 of the braking system 3 to cause the hydraulic control unit 21 to modulate the brake fluid pressure on each of the front and rear wheels 4 and 5. A accelerometer and wheel speed sensors, which are not shown, are connected to the ESP 52 control unit. The ESP 52 control unit generates control signals to modulate the brake fluid pressures on the front wheels and rear 4 and 5 on the basis of signals detected at the accelerometer and the wheel speed sensors.

The ESP 52 control unit performs various commands, such as an Electronic Stability Control (ESC), a Traction Control System (TCS), an anti-lock braking system (ABS), and an electronic brake force distribution (EBD).

Electronic stability control is a computerized technology that keeps the vehicle from sliding sideways when cornering. The traction control system is a system that prevents the driven wheel from turning when the vehicle is started or accelerated. The anti-lock braking system is a system that prevents a wheel lock by modulating the brake fluid pressure, for example, during sudden braking.

As for the anti-lock braking system, the ESP 52 control unit estimates a vehicle speed based on the wheel speeds to determine a slip ratio threshold which is a function of the vehicle speed. If the ESP control unit 52 detects that a wheel is about to slip beyond the slip ratio threshold, it causes the hydraulic unit 21 to modulate the brake fluid pressure on the wheel concerned by using a three-stage cycle. The three-stage cycle consists of maintaining pressure, decreasing pressure, and increasing pressure. During pressure maintenance, the ESP 52 control unit interrupts the flow of fluid from the master cylinder to the wheel concerned. During the pressure decrease, the pressurized fluid moves in an accumulator to reduce the brake fluid pressure on the affected wheel, preventing a wheel lock. During the pressure increase, the pressurized fluid can flow into the affected wheel and increase the brake fluid pressure thereon.

Electronic brake force distribution is a computerized technology that optimizes the brake force distribution on the front and rear wheels 4 and 5. The ESP 52 control unit performs electronic brake force distribution based on a slip ratio of each wheel.

The slip ratio which makes the electronic brake force distribution operational is less than the slip ratio which makes the anti-lock braking system operational. In other words, the ESP 52 control unit performs the electronic braking force distribution when the slip ratio is less than the slip ratio which makes the anti-lock braking system operational.

Regarding the electronic brake force distribution, the ESP 52 control unit performs the brake force distribution by maintaining the brake fluid pressure. Maintaining the brake fluid pressure consists in interrupting the flow of fluid to one or more wheels to prevent the brake fluid pressure on the wheels from increasing further by causing the hydraulic unit 21 to operate in a maintenance mode. pressure.

The AEB control unit 51 includes a decision strategy which generates a collision avoidance request by braking on the basis of information received from various data collection devices or sensors including an onboard camera facing forward, not illustrated. . Depending on the probability of collision with an obstacle, the AEB control unit 51 uses a forward collision alert (FCA), a forward collision warning by braking (FCAbB for “Forward Collision Alert by Braking”), forward collision reduction by brake assist (FCMbBA for “Forward Collision Mitigation by Brake Assist”), and autonomous braking (AB for “Autonomous Braking”).

Forward collision alert is a technology that emits an alert in the form, for example, of the sound of a siren and the illumination of an indicator within a counter in the event that there is has probability of collision with an obstacle. In the event that the probability of collision remains or is increasing after issuing the alert, the forward collision warning by braking is initiated. Braking forward collision alert is an autonomous operation of the braking system to generate a low braking force so as to encourage the driver to resort to an operation to reduce the probability of collision. The alert is maintained during the forward collision warning by braking.

If the driver presses the brake pedal during the front collision warning by braking, the front collision warning by braking is ended and the collision reduction at the front by assistance braking is initiated. Front Collision Mitigation by Brake Assist is a technology that provides assistance to the braking force in order to increase the resulting braking force.

In the event that the probability of collision with an obstacle indicates an imminent collision, autonomous braking is initiated. Autonomous braking is a technology that increases the brake fluid pressure on each of the wheels.

In other words, autonomous braking tries to reduce the kinetic energy of the vehicle with a strong braking force so as to avoid a collision. Autonomous braking is a braking process initiated and performed independently of the driver. Thus, for example, during the event of an initiation of the braking process by the driver, an autonomous braking process can be initiated and bypass the braking process initiated by the driver. The strong braking force during autonomous braking is a braking force strong enough to effectively retard the movement of the vehicle.

The expression "there is a probability of collision with an obstacle" is used here to indicate a possibility of collision of a host vehicle with an obstacle whether the risk of collision is high or low. Thus, in the event that there is a probability of collision with an obstacle, at least one of the collision warning at the front, the collision warning at the front by braking, the attenuation of Collision at the front by braking assistance and autonomous braking can be initiated and implemented.

The AEB control unit 51 sends an instruction signal according to the process of any one chosen from the front collision warning by braking, the front collision reduction by braking assistance and the autonomous braking at the ESP 52 control unit. In response to the instruction signal, the ESP 52 control unit controls the modulation of the brake fluid pressure on each of the wheels.

ECM 53 controls a motor, not shown, as the main object to be controlled. The ECM 53 provides output signals indicative of, for example, information about an accelerator pedal and information about a brake light switch, and outputs the output signals to the control unit AEB 51. The output signal indicative of information about the accelerator pedal is a signal indicative of the position of the accelerator pedal. The output signal indicative of information about the brake light switch is a signal indicating whether or not the driver is depressing the brake pedal.

The BCM 54 sends detected signals from sensors mounted on various parts of the vehicle body and controls the actuators. The BCM 54 provides output signals indicative of, for example, information about an AEB stop switch and information about an outdoor air temperature sensor, and outputs the output signals to the AEB control unit 51. The output signal indicative of information about the AEB stop switch is a signal indicating whether the driver has disabled the autonomous emergency braking to be initiated and performed by the control unit AEB 51 by performing a switching operation from a driver's seat, not shown. The outdoor air temperature information output signal is an outdoor air temperature signal detected by the outdoor air temperature sensor, not shown.

Referring to Figure 2, the braking system 3 includes a brake pedal 8 on which the driver presses to initiate and perform the braking process by the driver and a tandem master cylinder 15 which generates brake fluid pressure depending on whether the driver presses the brake pedal 8.

The master cylinder 15 is equipped with a vacuum booster in the form of a booster 14. The booster 14 uses a vacuum which is generated by a source of vacuum, such as the tubing vacuum, to amplify the force of the conductor on the pedal, giving greater brake fluid pressure.

The braking system 3 includes a hydraulic unit 21 connected to the master cylinder 15 and wheel cylinders 6 and 16 connected to the hydraulic unit 21.

The wheel cylinders 6 are respectively arranged in right and left front wheels 4 to activate the brakes on the front wheels 4. The wheel cylinders 16 are respectively arranged in right and left rear wheels 5 to activate the brakes on the rear wheels 5. In FIG. 2, the left front wheel 4 is marked LF, and the right front wheel 4 is marked RF. The left rear wheel 5 is marked LR, and the right rear wheel 5 is marked RR.

In the braking system 3, the brake fluid pressure which is generated by the master cylinder 15 acts on the wheel cylinders 6 and 16, causing the brakes on the front and rear wheels 4 and 5 to operate.

In the braking system 3, the hydraulic unit 21 modulates the brake fluid pressure which is generated by the master cylinder 15, and the hydraulic unit 21 generates a brake fluid pressure. Using the brake fluid pressure which is generated by the master cylinder 15 and modulated by the hydraulic unit 21 and the brake fluid pressure which is generated in the hydraulic unit 21, the hydraulic unit 21 pressurizes the cylinders wheel 6 and 16 to control the braking forces of the front and rear wheels 4 and 5.

The braking system 3 employs a hydraulic design known as an X-split braking system or a diagonal braking system having two independent circuits. The brake on the left front wheel 4 and the brake on the right rear wheel 5 are on one of the two independent circuits. The brake on the right front wheel 4 and the brake on the left rear wheel 5 are on the other.

The goal of having the two independent circuits is to ensure that, if a failure occurs on one circuit, then the other circuit remains capable of ensuring a certain level of functionality of the braking system.

The two independent circuits in the hydraulic unit 21 have the same configuration. For the sake of brevity, only one circuit is described.

In the following, the description focuses on the circuit on which are the brake of the left front wheel 4 (LF in Figure 2) and the brake of the right rear wheel 5 (RR in Figure 2).

The braking system 3 includes brake lines 22A, 22B and 22C. The brake line 22A connects the master cylinder 15 to the hydraulic unit 21. When the driver presses the brake pedal 8, a pressurized brake fluid is forced to go from the master cylinder 15 into the hydraulic unit 21 by passing through the brake line 22A.

The brake line 22B connects the hydraulic unit 21 to the wheel cylinder 6 of the left front wheel 4. Through this brake line 22B, a pressurized brake fluid flows to or from the wheel cylinder of the left front wheel 4.

The brake line 22C connects the hydraulic unit 21 to the wheel cylinder 16 of the right rear wheel 5. By this brake line 22C, a pressurized brake fluid flows to or from the wheel cylinder of the right rear wheel 5.

The hydraulic unit 21 includes a hydraulic pressure line 31. The hydraulic pressure line 31 is connected to the brake line 22A. The hydraulic pressure line 31 includes an SVI cut-off valve. The SVI cut-off valve includes an internal sequence valve and a normally open two-port, two-position solenoid-operated valve that has a first position or unused position and a second position or operated position. In the first position or unexploited position, the valve performs fluid communication through the hydraulic pressure line 31 and no brake fluid passes through the sequence valve. In the second position or operated position, the valve blocks the fluid communication through the hydraulic pressure line 31 and the sequence valve is made operable to effect pressure regulation of the brake fluid. Thus, the SVI cut-off valve has the first position or position not used to open the hydraulic pressure line 31 and the second position or position used to regulate the brake fluid pressure. The solenoid of the SV1 cut-off valve is electrically controlled by the ESP 52 control unit.

The hydraulic unit 21 includes hydraulic pressure lines 32 and 33. The hydraulic pressure lines 32 and 33, which branch off from the portion of the hydraulic pressure line 31 which is on the downstream side of the cut-off valve SVI, are respectively connected through the brake lines 22B and 22C mentioned above to the wheel cylinders 6 and 16.

The hydraulic pressure lines 32 and 33 respectively include pressure maintenance valves SV2 and SV3. The pressure maintenance valve SV2 includes a normally open two-light, two-position solenoid-operated valve which has a first position or an unexploited position in which the valve performs fluid communication through the hydraulic pressure line 32 and a second position or position operated in which the valve blocks fluid communication through the hydraulic pressure line 32. The pressure maintenance valve SV3 is a solenoid-operated valve normally open with two lights and two positions which has a first position or unused position in which the valve performs fluid communication through the hydraulic pressure line 33 and a second operated position or position in which the valve SV2 blocks fluid communication through the hydraulic pressure line 33. The solenoids of the holding valves pressure SV2 and SV3 are electrically controlled by the ESP 52 control unit.

The hydraulic unit 21 includes hydraulic pressure lines 34 and 35. The hydraulic pressure line 34 branches off from the portion of the hydraulic pressure line 32 which is on the downstream side of the pressure maintenance valve SV2. The hydraulic pressure line 35 branches off from the portion of the hydraulic pressure line 33 which is on the downstream side of the pressure maintenance valve SV3.

The hydraulic pressure lines 34 and 35 respectively include pressure reducing valves SV4 and SV5. The pressure reduction valve SV4 is a solenoid valve normally closed with two lights and two positions which has a first position or unexploited position in which the valve SV4 blocks fluid communication through the hydraulic pressure line 34 and a second position or operated position in which the valve SV4 performs fluid communication through the hydraulic pressure line 34 to allow flow to the hydraulic pressure line 36. The pressure reduction valve SV5 is a normally closed solenoid valve with two lights and two positions which has a first unused position or position in which the valve SV5 blocks the fluid communication through the hydraulic pressure line 35 and a second position or operated position in which the valve SV5 performs the fluid communication through press pipe hydraulic ion 35 to allow flow to the hydraulic pressure line 36. The solenoids of the pressure reduction valves SV4 and SV5 are electrically controlled by the ESP 52 control units.

The hydraulic unit 21 includes a reservoir 30 for brake fluid. The portion of the hydraulic pressure line 34 which is on the downstream side of the pressure reduction valve SV4 and the portion of the hydraulic pressure line 35 which is on the downstream side of the pressure reduction valve SV5 meet to join a hydraulic pressure line 36. The hydraulic pressure line 36 is connected to the reservoir 30.

The hydraulic unit 21 includes a pump 24 which is driven by an electric motor 26. The pump 24 and the reservoir 30 are connected by a hydraulic pressure line 37. The pump 24 sucks the brake fluid in the reservoir 30 through the hydraulic pressure line 37.

A hydraulic pressure line 38 is connected to the discharge side of the pump 24. The hydraulic pressure line 38 is connected to the part of the hydraulic pressure line 31 which is on the downstream side of the cut-off valve SV1. A hydraulic pressure line 39 branches off from the part of the hydraulic pressure line 31 which is on the upstream side of the cut-off valve SV1. The hydraulic pressure line 39 is connected to the hydraulic pressure line 37. The hydraulic pressure line 39 includes an accumulation control valve SV6. The SV6 accumulation control valve is a normally closed solenoid control valve which has a first position or unexploited position in which the SV6 control valve blocks fluid communication through the hydraulic pressure line 39 and a second position or operated position in which the control valve SV6 performs the fluid communication through the hydraulic pressure line 39 to allow a flow of brake fluid towards the hydraulic pressure line 37.

The ESP control unit 52 can selectively combine the positions in which the valves described in the hydraulic unit are or are offset to. Thus, with the hydraulic unit 21 operating in a mode in which, when the driver presses the brake pedal 8, the brake fluid is forced to go from the master cylinder 15 into the wheel cylinder 16 for the right rear wheel 5 without any interruption, the control unit ESP 52 can pass the hydraulic unit 21 from operation in the aforementioned mode to operation in a mode chosen from the pressure maintenance, pressure reduction and pressure increase modes.

If pressure maintenance is selected to prevent blocking of the right rear wheel 5 during braking, the ESP 52 control unit energizes the solenoid of the pressure maintenance valve SV3 to move the valve SV3 to its second position or operated position in which the valve SV3 blocks the fluid communication through the hydraulic pressure line 33 with the pressure reduction valve SV5 left in its first position or not operated position in which the valve SV3 blocks the fluid communication through the line hydraulic pressure 35. This maintains the brake fluid pressure on the right rear wheel 5 by trapping the brake fluid in the brake line 22C.

If the pressure reduction is selected to prevent blocking of the right rear wheel 5 during braking, the ESP 52 control unit energizes the solenoid of the pressure reduction valve SV5 to move the valve SV5 to its second position or operated position in which the valve SV5 performs fluid communication through the hydraulic pressure line 35 to allow the flow of brake fluid to the hydraulic pressure line 36 with the solenoid of the pressure maintenance valve SV3 kept in the excited state to keep the valve SV3 in its second position or operated position in which the valve SV3 blocks the fluid communication through the hydraulic pressure line 33. This reduces the brake fluid pressure on the right rear wheel 5 by discharging the fluid brake in the brake line 22C to the reservoir 30 through the hydraulic pressure line 36.

If the pressure increase is selected to prevent blocking of the right rear wheel 5 during braking, the ESP control unit 52 deactivates the solenoid of the pressure maintenance valve SV3 to cause the valve SV3 to operate towards its first position or unexploited position in which the valve SV3 performs the fluid communication through the hydraulic pressure line 33 and de-energizes the solenoid of the pressure reduction valve SV5 to cause the valve SV5 to operate in its first position or non-operated position in which the valve SV5 blocks fluid communication through the hydraulic pressure line 35. This increases the brake fluid pressure on the right rear wheel 5 by forcing the brake fluid to flow from the master cylinder 15 into the wheel cylinder 16 for the right rear wheel 5.

In order to carry out the brake assist control, with the hydraulic circuit maintained in pressure increase, the ESP 52 control unit excites the solenoid of the SVI cut-off valve to move the SVI valve to its second position or position operated to perform pressure regulation, energizes the solenoid of the SV6 accumulation control valve to move the SV6 valve to the second position or position operated to open the hydraulic pressure line to allow the flow of brake fluid to the hydraulic pressure line 37, and activate the pump 24.

The pressurized brake fluid is forced to flow from the pump 24 into the wheel cylinder 16 for the right rear wheel 5 through the hydraulic pressure lines 38, 31 and 33 and the brake line 22C. In the event of this event, the brake fluid pressure on the wheel cylinder 16 of the right rear wheel 5 becomes higher than the brake fluid pressure forced to go from the master cylinder 15 when the driver presses the brake pedal. brake 8.

In order to carry out the control of the front collision warning by braking, the front collision reduction by braking assistance and the autonomous braking, with the hydraulic circuit maintained in pressure increase, the ESP 52 control excites the solenoid of the SVI cut-off valve to move the SVI valve to its second position or position operated to perform pressure regulation, excites the solenoid of the SV6 accumulation control valve to pass the SV6 valve in the second position or position operated to open the hydraulic pressure line to allow the flow of brake fluid to the hydraulic pressure line 37, and activate the pump 24. The pressurized brake fluid is forced to go from the pump 24 in the wheel cylinder 16 for the right rear wheel 5 through the hydraulic pressure lines 38, 31 and 33 and the brake line 22C.

During the collision reduction at the front by brake assist, the brake fluid pressure on the wheel cylinder 16 of the right rear wheel 5 becomes higher than the brake fluid pressure forced from the master cylinder 15 when the driver depresses the brake pedal 8. During control of the front collision warning by braking and autonomous braking, the brake fluid pressure on the wheel cylinder 16 of the right rear wheel 5 is determined by the ESP 52 control unit.

The foregoing description has focused on the hydraulic pressure lines in the hydraulic unit 21 which operate to transmit the pressurized brake fluid to the left front wheel 4 (LF in FIG. 2) and the right rear wheel 5 (RR in Figure 2). This description is applicable to hydraulic pressure lines 41, 42, 43, 44, 45, 46, 47, 48 and 49 which operate to transmit the brake fluid under pressure to the right front wheel 4 (RF in FIG. 2) and the left rear wheel 5 (LR in FIG. 2) because the hydraulic pressure lines 31, 32, 33, 34, 35, 36, 37, 38 and 39 and the hydraulic pressure lines 41, 42, 43, 44, 45, 46, 47, 48 and 49 are identical.

The braking system 3 includes brake lines 23 A, 23B and 23C which are identical to the brake lines 22A, 22B and 22C.

The hydraulic unit 21 includes the hydraulic pressure lines 41, 42, 43, 44, 45, 46, 47, 48 and 49 which are identical to the hydraulic pressure lines 31, 32, 33, 34, 35, 36, 37, 38 and 39.

The hydraulic unit 21 includes a cut-off valve S Vil which is identical to the cut-off valve SVI, pressure maintenance valves SVI2 and SVI3 which are identical to the pressure maintenance valves SV2 and SV3, pressure reduction valves SVI4 and SV15 which are identical to the pressure reduction valves SV4 and SV5, and an accumulation control valve SVI6 which is identical to the accumulation control valve SV6.

The hydraulic unit 21 includes a tank 40 which is identical to the tank 30, and a pump 25 which is identical to the pump 24. The pumps 24 and 25 are driven by the single electric motor 26.

In the present implementation, the braking force control system performs autonomous actuation of the braking system 3 in the event that a decision strategy of the AEB control unit 51 generates a request for avoiding collision by braking. . The ESP 52 control unit is responsible for controlling the distribution of braking force. The brake force distribution is carried out so that the brake fluid pressure on at least one of the rear wheels 5 during the autonomous actuation of the braking system 3 can be higher than during a non-autonomous actuation of the braking system braking 3. The non-autonomous actuation of the braking system 3 is here used to designate a mode in which the braking system 3 can be controlled by a command supplied as input by the driver of the vehicle.

In other words, a pressure maintenance level above which the brake fluid pressure is prevented from increasing further to achieve the brake force distribution during the autonomous actuation of the braking system 3 differs from a pressure maintenance level above which the brake fluid pressure is prevented from increasing further to achieve the distribution of braking force during the non-autonomous actuation of the braking system 3. The pressure maintenance level to achieve the distribution of braking force during the autonomous actuation of the braking system 3 is made higher than the pressure maintenance level to achieve the distribution of braking force during the non-autonomous actuation of the braking system 3.

The ESP 52 control unit includes a first braking force distribution card used to distribute the braking force during non-autonomous actuation of the braking system 3, and a second braking force distribution card used for brake force distribution during autonomous actuation of the braking system 3.

The second braking force distribution card allows the magnitude of the brake fluid pressure on the rear wheel 5 to increase more significantly than the first braking force distribution card, and sets an upper limit of the magnitude of the brake fluid pressure on the rear wheel 5 so that it is less than an upper limit of the magnitude of the brake fluid pressure on at least one of the front wheels 4. The first and second maps of Braking force distribution is further described below.

The brake fluid pressure on the rear wheel 5 is maintained in the case where a slip ratio of the rear wheel 5 increases and reaches a predetermined pressure maintenance slip ratio. The ESP 52 control unit is responsible for the above-mentioned control.

The predetermined pressure maintenance slip ratio is higher during the autonomous actuation of the braking system 3 than during the non-autonomous actuation of the braking system 3. The ESP 52 control unit is responsible for the above-mentioned control to maintain the brake fluid pressure on the rear wheel 5 to an increased level by setting the predetermined pressure maintenance slip ratio so that it is higher during the autonomous actuation of the braking system than during the non-autonomous actuation of the braking system.

In addition to what is listed above, there is another approach to allow the brake fluid pressure on the rear wheel 5 to increase during the autonomous actuation of the braking system 3.

Autonomous actuation of the braking system 3 is carried out in the case where the decision strategy of the control unit AEB 51 generates a collision avoidance request by braking as a function of the probability of a collision with an obstacle. During the autonomous actuation of the braking system, the control unit ESP 52 can allow the magnitude of the brake fluid pressure on the rear wheel 5 to increase more significantly than during the non-autonomous actuation of the system braking 3 by delaying the pressure maintenance event of preventing the brake fluid pressure on the rear wheel 5 from increasing more from the start of the autonomous actuation of the braking system 3 more than by delaying the pressure maintenance event consisting in preventing the brake fluid pressure on the rear wheel 5 from increasing further from the start of the non-autonomous actuation of the braking system 3.

For example, in the event that the brake fluid pressure increases at a constant speed during autonomous braking, the magnitude of the brake fluid pressure on the rear wheel 5 may increase by delaying the timing of the hold event. pressure of a predetermined time from the timing of the pressure maintenance event which is given by the normal braking force distribution card used during the non-autonomous actuation of the braking system 3.

On the basis of the distance to an obstacle, the decision strategy of the control unit AEB 51 generates a collision avoidance request by braking according to the probability of a collision with the obstacle. The brake force distribution is carried out by the ESP control unit 52 so that the brake fluid pressure on the rear wheels 5 is inversely proportional to the distance to the obstacle.

On the basis of the speed with respect to an obstacle, the decision strategy of the control unit AEB 51 generates a collision avoidance request by braking according to the probability of a collision with the obstacle. The braking force distribution is carried out by the ESP control unit 52 so that the brake fluid pressure on the rear wheels 5 is inversely proportional to the speed relative to the obstacle.

The ESP 52 control unit controls the distribution of braking force between the front and rear wheels 4 and 5 to satisfy the distribution of braking force illustrated by one of the braking force distribution maps in the figure. 3. In FIG. 3, the vertical axis represents the braking force of the rear wheel and the horizontal axis represents the braking force of the front wheel. The brake fluid pressure is a function of the braking force.

With reference to FIG. 3, a first braking force distribution map Lal and a second braking force distribution map La2 are determined on the basis of the ideal braking force distribution curve La for the vehicle 1 in a lightly loaded condition, and a first braking force distribution map Lbl and a second braking force distribution map Lb2 are determined based on the ideal braking force distribution curve Lb for vehicle 1 in a condition heavily loaded.

The ideal braking force distribution curve La represents the ideal braking force distribution for vehicle 1 in the lightly loaded condition. The ideal braking force distribution curve Lb represents the ideal braking force distribution for vehicle 1 in the heavily loaded condition.

The ideal braking force distribution curve La for vehicle 1 in the lightly loaded condition represents the braking force distribution which can ensure the maximum braking forces of the front and rear axles for wheels 4 and 5 approaching the limits by the same time so that if the braking force distribution is not ideal, then either the front wheels or the rear wheels 4 and 5 will lock first. The ideal braking force distribution curve Lb for vehicle 1 in the heavily loaded condition represents the braking force distribution that can provide the maximum braking forces on the front and rear axles for wheels 4 and 5 approaching the limits at the same time so that if the braking force distribution is not ideal, then either the front wheels or the rear wheels 4 and 5 will lock first.

In other words, the ideal braking force distribution curve La for the vehicle 1 in the lightly loaded condition represents the braking force distribution which can provide the total braking force of the front and rear axles for the wheels 4 and 5 which is maximized. The ideal brake force distribution curve Lb for vehicle 1 in the heavily loaded condition represents the brake force distribution which can ensure the total braking force of the front and rear axles for wheels 4 and 5 which is maximized.

The magnitude of the load on the rear axle for the wheels 5 supported at the rear-ground tire contact points is greater in the case where the vehicle is in the heavily loaded condition than in the case where the vehicle is in the slightly loaded condition. The braking force which is distributed over the rear axle for the wheels 5 by the ideal braking force distribution curve Lb for the vehicle 1 which is in the heavily loaded condition is greater than the braking force which is distributed over the rear axle for the wheels 5 by the ideal braking force distribution curve La for the vehicle 1 which is in the lightly loaded condition.

Looking at FIG. 3, the braking forces distributed on the rear axle for the wheels 5 by the first braking force distribution maps Lal and Lbl are fixed below the ideal braking force distribution curves La and Lb. In other words, the first braking force distribution maps Lal and Lbl define braking forces on the rear wheels 5. The braking forces defined by the first braking force distribution maps Lal and Lbl communicate a capacity sufficient to avoid a wheel lock on the rear wheels 5.

In the case where the braking forces on the front wheels 4 and the braking forces on the rear wheels 5 are controlled by the first braking force distribution cards Lal and La2, the braking forces on the rear wheels 5 are less likely to reach the limits before the braking forces on the front wheels 4 reach the limits, but the braking forces on the wheels 5 are not used to the limits.

Each of the second brake force distribution maps La2 and Lb2 allows the magnitude of the brake fluid pressure on the rear wheel 5 to increase more than the corresponding map of the first brake force distribution maps Lal allows. and Lbl, and fixes an upper limit of the magnitude of the brake fluid pressure on the rear wheel 5 so that it is less than an upper limit of the magnitude of the brake fluid pressure on at least one of the front wheels 4.

In particular, the second braking force distribution maps La2 and Lb2 more closely approximate the ideal braking force distribution maps La and Lb than the first braking force distribution maps Lal and Lbl. This results in an increase in the total braking force of the front and rear wheels 4 and 5 because the braking forces of the rear wheels 5 can increase to the limit by adjusting the distribution of braking force between the front and rear axles for the wheels 4 and 5 on the basis of the second braking force distribution maps La2 and Lb2. Even in the case of braking where the braking forces on the rear wheels 5 have reached the limits before the braking forces on the front wheels 4, the rear wheels 5 are prevented from locking by the ABS control. This prevents loss of directional control.

In the case where the decision strategy of the control unit AEB 51 fails to generate a collision avoidance request by braking, for example, in the case where there is no probability that a vehicle host can collide with an obstacle, the ESP 52 control unit performs electronic brake force distribution (EBD) control on the basis of the first brake force distribution cards Lal and Lbl.

In the case where the decision strategy of the control unit AEB 51 generates a collision avoidance request by braking, for example, in the case where there is a probability that a host vehicle can collide with an obstacle , the ESP 52 control unit performs the electronic brake force distribution (EBD) control on the basis of the second brake force distribution cards La2 and Lb2.

In the present implementation, the ESP 52 control unit includes the first brake force distribution boards Lal and Lbl for use in the event that the decision strategy of the AEB control unit 51 fails to generate a collision avoidance request by braking, for example, in the event that there is no probability that a host vehicle could collide with an obstacle, and the second braking force distribution maps La2 and Lb2 for use in the case where the decision strategy of the control unit AEB 51 generates a collision avoidance request by braking, for example, in the case where it is probable that a host vehicle can enter colliding with an obstacle. In the present implementation, these braking force distribution maps Lal, Lbl, La2 and Lb2 are not directly designated as targets to be reached, but the distribution of braking force between the front and rear axles for the wheels 4 and 5 which is represented by one of the braking force distribution maps is carried out by monitoring the slip ratio and by carrying out a control of the slip ratio on the basis of the braking force distribution map.

Referring now to the flow diagram of Figure 4, braking force control steps to be performed by the braking force control system 50 are described.

In step SI, it is determined whether there is a collision avoidance request by braking or not. In this implementation, this determination is made by the control unit AEB 51.

In step S2, if it is determined in step SI that there is a request for collision avoidance by braking, the autonomous actuation command of the braking system 3 is carried out. In the present implementation, the control unit AEB 51 sends the request to the control unit ESP 52. The control unit ESP 52 performs the autonomous actuation of the braking system 3 according to the request for collision avoidance by braking. In other words, the control unit AEB 51 performs the control of brake fluid pressures on the front and rear wheels 4 and 5 during braking by controlling the hydraulic unit 21 via the control unit ESP 52 .

In step S3, the first braking force distribution cards Lal and Lbl are replaced by the second braking force distribution cards Lb2 and Lb2. In this implementation, the ESP 52 control unit performs this card replacement.

In step S4, the control of the electronic braking force distribution (EBD) is carried out on the basis of the second braking force distribution maps La2 and Lb2. In this implementation, the ESP 52 control unit performs this distribution of braking force. Since, in this step S4, the braking force distribution is carried out on the basis of the second braking force distribution maps La2 and Lb2, during the autonomous actuation of the braking system 3, the magnitude of the fluid pressure of brake on each of the rear wheels 5 can increase more significantly than during the non-autonomous actuation of the braking system 3. Thus, the ESP 52 control unit performs the control of the braking force distribution so that the pressure brake fluid on each of the rear brakes 5 is maintained at a higher level in the case where there is a request for collision avoidance by braking than in the case where there is no request for the avoidance of braking collision.

For example, in the case of a braking process initiated by the driver by depressing the brake pedal 8 in response to a request for collision avoidance by braking, an autonomous braking process can be initiated, which then exceeds the braking process by the driver. Thus, it is preferred that if initially, an amount of brake fluid pressure which is generated by the braking process by the driver is high enough for braking, the control of the braking force distribution in step S4 is achieved by maintaining the brake fluid pressure generated by the braking process by the driver.

In the present implementation, the control of the braking force distribution based on the second braking force distribution cards La2 and Lb2 is carried out during the autonomous actuation of the braking system 3. It is preferable that the control of the braking force distribution based on the second braking force distribution maps La2 and Lb2 is performed as long as there is a probability that the host vehicle can collide with an obstacle.

Referring to Figure 5, the chronological variation of the brake fluid pressure on the rear wheels 5 during the realization of the electronic brake force distribution (EBD) control based on the second force distribution maps braking La2 and Lb2 in response to the autonomous actuation of the braking system 3 is described in comparison with the comparative example shown in FIG. 6 in which the control of the electronic braking force distribution (EBD) is carried out on the basis of the first Lal and Lbl braking force distribution maps.

FIG. 5 is a timing diagram illustrating the chronological variation of the brake fluid pressure on the rear wheels 5 during the realization of the electronic brake force distribution (EBD) control on the basis of the second force distribution maps of braking La2 and Lb2. FIG. 6 is a timing diagram illustrating the chronological variation of the brake fluid pressure on the rear wheel 5 during the realization of the electronic brake force distribution (EBD) control on the basis of the first force distribution maps of braking Lal and Lbl. In each of Figures 5 and 6, the brake fluid pressure on the rear wheel 5 is indicated by a thick line; the wheel speed of the rear wheel 5 is indicated by a thick dashed line; the acceleration of vehicle 1 is indicated by a thin line; and an autonomous emergency braking request (AEB) is indicated by a broken dash.

During or immediately after the autonomous actuation of the braking system 3 in order to achieve, for example, the autonomous braking in response to a request for autonomous braking, the brake fluid pressure on the rear wheel 5 increases and is maintained at a brake fluid pressure P2 which is higher than normal by preventing the brake fluid pressure from increasing further. Thus, the brake fluid pressure on the rear wheel 5 is maintained at the brake fluid pressure P2.

The brake fluid pressure as high as the brake fluid pressure P2 is applied to the rear wheel 5 during the initial stage of braking at high vehicle speed. As shown in Figure 5, this results in a considerable increase in vehicle deceleration, often referred to as "initial deceleration".

In the case of initiating autonomous braking in an intermediate speed range of approximately 50 km / h, a loss of directional control is less likely compared to the case of initiating autonomous braking in a range of high speeds exceeding 100 km / h, in the present implementation, the braking distance of the vehicle is shortened as much as possible by braking with the brake fluid pressure as high as the brake fluid pressure P2 which gives priority to an increase of initial deceleration without significant loss of directional control.

Since the high brake fluid pressure P2 shown in Figure 5 is on one of the second braking force distribution maps La2 and Lb2 which closely approximate the ideal braking force distribution curves La and Lb, the speed of wheel of the rear wheel 5 during braking with the brake fluid pressure P2 decreases without any noticeable slippage. Even if a slip occurs, a loss of directional control is prevented by the anti-lock braking system (ABS) control. This creates a deceleration of the vehicle without any noticeable loss of directional control.

Turning to the comparative example shown in FIG. 6, the brake fluid pressure on the rear wheel 5 is controlled on the basis of the first braking force distribution maps Lal and Lbl in the case of the occurrence d '' an autonomous emergency braking request (AEB). Thus, the brake fluid pressure on the rear wheel 5 is maintained at a brake fluid pressure P1 which is lower than the brake fluid pressure P2. In the comparative example, the initial deceleration cannot be increased due to braking with the brake fluid pressure as high as the low brake fluid pressure P1 which gives priority to directional control rather than the efficiency of the braking.

In the present implementation, the ESP control unit 52 performs a control of the brake force distribution by maintaining the brake fluid pressure on the rear wheel 5, but it can perform a control of the force distribution of braking by maintaining the brake fluid pressure on the front wheel 4 only or by maintaining the brake fluid pressure on the front and rear wheels 4 and 5 depending on the type of vehicle. Even in this case, the brake force distribution is carried out by maintaining the brake fluid pressure on the front wheel 4 or the brake fluid pressures on the front and rear wheels 4 and 5.

As described, in the present implementation, the ESP control unit 52 performs the autonomous actuation of the braking system 3 in the case where the decision strategy of the AEB control unit 51 generates a request to avoid collision by braking, and, during the autonomous actuation of the braking system 3, the magnitude of the brake fluid pressure can increase more significantly than during the non-autonomous actuation of the braking system 3.

This configuration increases the total braking force. This ensures maximum braking force while adjusting the braking force distribution between the front and rear wheels 4 and 5 during the autonomous actuation of the braking system 3.

In the present implementation, the ESP control unit 52 performs an autonomous actuation of the braking system 3 in the case where the decision strategy of the AEB control unit 51 generates a request for collision avoidance by braking, and, during the autonomous actuation of the braking system 3, the magnitude of the brake fluid pressure on the rear wheel 5 can increase more significantly than during the non-autonomous actuation of the braking system 3.

This configuration increases the total braking force. This ensures maximum braking force while adjusting the braking force distribution between the front and rear wheels 4 and 5 during the autonomous actuation of the braking system 3.

In the present implementation, the braking force control system includes a first braking force distribution card Lal or Lbl used to effect the braking force distribution during the non-autonomous actuation of the braking system 3, and a second braking force distribution card La2 or Lb2 used to distribute the braking force during the autonomous actuation of the braking system. The second braking force distribution card allows the magnitude of the brake fluid pressure on the rear wheel 5 to increase more than the first braking force distribution card allows, and sets an upper limit of the magnitude of the brake fluid pressure on the rear wheel 5 so that it is less than an upper limit of the magnitude of the brake fluid pressure on the front wheel 4.

This configuration ensures maximum braking force while adjusting the distribution of braking force between the front and rear wheels 4 and 5 during the autonomous actuation of the braking system 3.

In the present implementation, the pressure maintenance event of preventing the brake fluid pressure on the rear wheel 5 from increasing further is delayed from the start of the autonomous actuation of the braking system more than the pressure maintenance event of preventing the brake fluid pressure on the rear wheel 5 from increasing further is delayed from the start of non-autonomous actuation of the brake system to allow the magnitude of the brake fluid pressure on the rear wheel 5 to increase during the autonomous actuation of the braking system 3 more than during the non-autonomous actuation of the braking system 3.

This configuration ensures maximum braking force while adjusting the distribution of braking force between the front and rear wheels 4 and 5 during the autonomous actuation of the braking system 3.

In the present implementation, the brake fluid pressure on the rear wheel 5 is maintained in the case where a slip ratio of the rear wheel 5 increases and reaches a predetermined pressure maintenance slip ratio.

In the present implementation, the predetermined pressure maintenance slip ratio is made higher during the autonomous actuation of the braking system 3 than during the non-autonomous actuation of the braking system 3.

Since the slip ratio can be higher during the autonomous actuation of the braking system 3 than during the non-autonomous actuation of the braking system 3, the brake fluid pressure on the rear wheel 5 is maintained at the higher pressure . This ensures maximum braking force while adjusting the braking force distribution between the front and rear wheels 4 and 5 during the autonomous actuation of the braking system 3.

In the present implementation, on the basis of the distance to an obstacle, the decision strategy of the control unit AEB 51 generates the collision avoidance request by braking. The brake force distribution is carried out so that the brake fluid pressure on the rear wheel 5 is inversely proportional to the distance to the obstacle.

This configuration ensures maximum braking force while adjusting the distribution of braking force between the front and rear wheels 4 and 5 during the autonomous actuation of the braking system 3.

In the present implementation, on the basis of the speed relative to an obstacle, the decision strategy of the control unit AEB 51 generates the collision avoidance request by braking. The brake force distribution is carried out so that the brake fluid pressure on the rear wheel 5 is inversely proportional to the speed relative to the obstacle.

This configuration ensures the maximum braking force while adjusting 5 the distribution of braking force between the front and rear wheels 4 and 5 during the autonomous actuation of the braking system 3.

Although the various implementations have been described, it will appear to those skilled in the art that modifications can be made without departing from the scope of the present invention.

10 4 Front wheel 5 Rear wheel 50 Braking force control system 51 AEB control unit 52 ESP control unit 15 Lal, Lbl First brake force distribution map La2, Lb2 Second braking force distribution card

Claims (7)

1. Braking force control system (50) of a vehicle, the vehicle comprising a plurality of wheels, the system being configured for: perform an autonomous actuation of a braking system (3) of the vehicle by increasing a brake fluid pressure on each of the wheels in the case where a decision strategy generates a request for collision avoidance by braking; and performing a braking force distribution, the braking force distribution performed during the autonomous actuation of the braking system (3) being different from that during a non-autonomous actuation of the braking system (3) in that, during the 'independent actuation of the braking system (3), the magnitude of the brake fluid pressure on at least one of the wheels may increase more significantly than during the non-autonomous actuation of the braking system (3). 2. System (50) according to claim 1, in which At least one of the wheels is a rear wheel (5), and the brake force distribution is carried out so that the brake fluid pressure on the rear wheel (5) during the autonomous actuation of the braking system (3) can be higher than during the non-autonomous actuation of the braking system (3). 3. System (50) according to claim 2, further comprising: a first braking force distribution card (La 1, Lbl) used to distribute the braking force during non-autonomous actuation of the braking system (3); and a second braking force distribution card (La2, Lb2) used to effect the braking force distribution during the autonomous actuation of the braking system (3), in which the second braking force distribution card (La2 , Lb2) allows the magnitude of the brake fluid pressure on the rear wheel (5) to increase more than the first braking force distribution map (Lal, Lbl) allows, and sets an upper limit of the magnitude of the brake fluid pressure on the rear wheel (5) so that it is less than an upper limit of the magnitude of the brake fluid pressure on a front wheel (4) of the wheels. 4. The system (50) according to claim 2 or 3, wherein the pressure maintenance event of preventing the brake fluid pressure on the rear wheel (5) from further increasing is delayed from the start of the autonomous actuation of the braking system (3) more than the pressure maintenance event of preventing the brake fluid pressure on the rear wheel (5) from increasing further is delayed from the start of the actuation not autonomous braking system (3) to allow the magnitude of the brake fluid pressure on the rear wheel (5) to increase during autonomous actuation of the braking system (3) more than during non-autonomous actuation of the braking system (3). 5. System (50) according to any one of the preceding claims 2 to 4, in which the brake fluid pressure on the rear wheel is maintained in the case where a slip ratio of the rear wheel (5) increases and reaches a predetermined pressure maintenance slip ratio, and the predetermined pressure maintenance slip ratio is higher during the autonomous actuation of the braking system (3) than during the non-autonomous actuation of the braking system (3). 6. System (50) according to any one of the preceding claims 2 to 5, in which, on the basis of the distance to an obstacle, the decision strategy generates the collision avoidance request by braking, and the distribution braking force is achieved so that the brake fluid pressure on the rear wheel (5) is inversely proportional to the distance to the obstacle. 7. System (50) according to any one of the preceding claims 2 to 5, in which, on the basis of the speed relative to an obstacle, the decision strategy generates the collision avoidance request by braking, and the distribution braking force is achieved so that the brake fluid pressure on the rear wheel (5) is inversely proportional to the speed with respect to 5 the obstacle. 1/6