KR20200107686A - Brake system and control method thereof - Google Patents

Abstract

Provided are a brake system that determines fading of the brake system based on a change in a required amount of brake fluid and a change in deceleration according to the temperature of the brake system, and compensates for a decrease in braking force due to the fading of the brake system, and a control method thereof. The brake system according to an embodiment includes: a piston for generating hydraulic pressure of brake fluid in the brake system; a sensor unit including an acceleration sensor that measures the deceleration of a vehicle and a pressure sensor that measures the hydraulic pressure of the brake fluid; a storage unit for storing information on a required reference amount of fluid according to the hydraulic pressure and information on reference deceleration according to the hydraulic pressure when the temperature of the brake fluid is at room temperature; and a control unit that determines the temperature of the brake fluid, determines the required amount of the brake fluid, and determines whether or not brake fading has occurred based on a difference value between the required amount of fluid and a pre-stored reference required amount of fluid corresponding to the measured hydraulic pressure and a difference value between the deceleration and pre-stored reference deceleration corresponding to the measured hydraulic pressure, when the determined temperature is higher than a preset high temperature reference value and the deceleration is less than road surface limit deceleration.

Description

Brake system and control method thereof {BRAKE SYSTEM AND CONTROL METHOD THEREOF}

The present invention relates to a brake system for determining fading of a brake system and a control method thereof.

In general, the brake system includes a hydraulic pressure supply device that receives the driver's braking intention as an electrical signal from a pedal position sensor that senses the displacement of the brake pedal when the driver depresses the brake pedal and supplies the pressure of the brake fluid to the wheel cylinder.

However, the hydraulic pressure of the brake fluid supplied from the hydraulic pressure supply device increases as the required amount of brake fluid supplied to the caliper increases, and the hydraulic pressure of the brake fluid compared to the required amount of brake fluid may vary depending on the temperature of the brake fluid.

In addition, when the temperature of the brake system increases due to the accumulation of frictional heat in the disks and pads of the brake system, a fading phenomenon may occur in which the friction coefficient of the friction material decreases.

In general, due to the fading phenomenon, compared to normal brake operation, the brake pedal stroke becomes longer and the braking force is lowered.

Accordingly, in recent years, research on a method of detecting fading of a brake system and compensating for a decrease in braking force due to fading has been continuously conducted.

A brake system and a control method thereof that determine fading of a brake system based on a change in a required amount of brake fluid according to a temperature of a brake system and a change in a vehicle deceleration rate, and compensate for a decrease in braking force due to the fading of the brake system are provided.

A brake system according to an embodiment includes: a piston generating hydraulic pressure of brake fluid in the brake system; A sensor unit including an acceleration sensor measuring a deceleration of a vehicle and a pressure sensor measuring a hydraulic pressure of the brake fluid; When the temperature of the brake fluid is at room temperature, a storage unit for storing reference required amount of liquid information according to hydraulic pressure and reference deceleration information according to hydraulic pressure; And determining the temperature of the brake fluid, determining the required amount of the brake fluid, and if the determined temperature is higher than a preset high temperature reference value and the deceleration is less than the road surface limit deceleration, the required amount of fluid and the measured hydraulic pressure And a control unit that determines whether or not brake fading occurs based on a difference value between a pre-stored reference required amount of liquid corresponding to and a difference value between the deceleration rate and a pre-stored reference deceleration rate corresponding to the measured hydraulic pressure.

The control unit is configured such that a difference value between the required liquid amount and a pre-stored reference required liquid amount corresponding to the measured hydraulic pressure is greater than or equal to a preset first fading determination reference value, and the deceleration rate and a pre-stored reference deceleration corresponding to the measured hydraulic pressure If the difference between the degrees is greater than or equal to a preset second fading determination reference value, it may be determined that the break fading has occurred.

When it is determined that the brake fading has occurred, the control unit may increase the hydraulic pressure of the brake fluid so that the deceleration is consistent with the reference deceleration.

The controller may control the piston to advance in order to increase the hydraulic pressure of the brake fluid.

The brake system further includes a pumping unit that pumps a hydraulic pressure of the brake fluid, and the control unit may control the pumping unit to increase a hydraulic pressure of the brake fluid.

The sensor unit may further include a pedal position sensor measuring a displacement of a pedal, and the control unit may determine the required amount of liquid based on pedal displacement information measured from the pedal position sensor.

The brake system further includes a motor that transmits rotational force to the piston, and the sensor unit further includes a motor position sensor that measures the position of the motor, and the control unit includes a motor position measured from the motor position sensor. The amount of movement of the piston may be calculated based on the information, and the required amount of liquid may be determined based on the amount of movement of the piston.

The control method of a brake system according to an embodiment comprising a piston generating hydraulic pressure of brake fluid in a brake system, an acceleration sensor measuring a deceleration rate of a vehicle, and a pressure sensor measuring a hydraulic pressure of the brake fluid, When the temperature of the brake fluid is at room temperature, information on a reference required amount of liquid according to the hydraulic pressure and information on a reference deceleration according to the hydraulic pressure are stored; Determining the temperature of the brake fluid; Determining the required amount of the brake fluid; If the determined temperature is greater than or equal to a preset high temperature reference value and the deceleration is less than or equal to the road surface limit deceleration, the difference between the required liquid amount and the pre-stored reference required liquid amount corresponding to the measured hydraulic pressure, and the deceleration and the measured And determining whether or not brake fading has occurred based on a difference value between pre-stored reference decelerations corresponding to the hydraulic pressure.

Determining whether or not the brake fading has occurred may include a difference value between the required liquid amount and a pre-stored reference required liquid amount corresponding to the measured hydraulic pressure is equal to or greater than a preset first fading determination reference value, and the deceleration and the measured hydraulic pressure And determining that the brake fading has occurred if the difference value between the pre-stored reference deceleration rates corresponding to is equal to or greater than the preset second fading determination reference value.

The control method of the brake system may further include, when determining that the brake fading has occurred, increasing the hydraulic pressure of the brake fluid so that the deceleration is consistent with the reference deceleration.

Increasing the hydraulic pressure of the brake fluid may include controlling the piston to advance.

The brake system may further include a pumping unit that pumps the hydraulic pressure of the brake fluid, and increasing the hydraulic pressure of the brake fluid may include controlling the pumping unit.

The sensor unit further includes a pedal position sensor for measuring a displacement of the pedal, and the determining of the required amount of brake fluid may include determining the required amount of liquid based on pedal displacement information measured from the pedal position sensor; It may include.

The brake system further includes a motor for transmitting rotational force to the piston, and the sensor unit further includes a motor position sensor for measuring a position of the motor, and determining the required amount of the brake fluid may include the motor Calculating the amount of movement of the piston based on the motor position information measured from the position sensor; It may include; determining the required amount of liquid based on the amount of movement of the piston.

According to the brake system and its control method according to an embodiment, the accuracy of brake fading determination of the brake system by determining the fading of the brake system based on the change in the amount of brake fluid required and the change in the deceleration rate of the vehicle according to the temperature of the brake system. Can improve.

In addition, according to the brake system and the control method thereof according to an exemplary embodiment, a safer and more efficient braking can be provided by compensating for a decrease in braking force due to fading of the brake system.

1 is a hydraulic circuit diagram showing a state in a non-braking state of a brake system according to an exemplary embodiment.
2 is a block diagram showing the configuration of a brake system according to an embodiment.
3 is a graph showing characteristics of a required liquid amount of a brake system according to an exemplary embodiment.
4 is a graph showing deceleration characteristics of a brake system according to an exemplary embodiment.
5 is a flowchart illustrating a case of determining brake fading in a method for controlling a brake system according to an exemplary embodiment.
6 is a flowchart illustrating a case of adjusting hydraulic pressure in a brake fading situation in a method for controlling a brake system according to an exemplary embodiment.

The same reference numerals refer to the same elements throughout the specification. This specification does not describe all elements of the embodiments, and general content or content overlapping between the embodiments in the technical field to which the present invention pertains will be omitted. The term'unit, module, member, block' used in the specification may be implemented as software or hardware, and according to embodiments, a plurality of'units, modules, members, blocks' may be implemented as one component, It is also possible for one'unit, module, member, block' to include a plurality of components.

In addition, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

Terms such as first and second are used to distinguish one component from other components, and the component is not limited by the above-described terms.

Singular expressions include plural expressions, unless the context clearly has exceptions.

In each step, the identification code is used for convenience of explanation, and the identification code does not describe the order of each step, and each step may be implemented differently from the specified order unless a specific sequence is clearly stated in the context. have.

Hereinafter, embodiments will be described with reference to the accompanying drawings.

1 is a hydraulic circuit diagram showing a state of a brake system 1 in a non-braking state according to an exemplary embodiment.

Referring to FIG. 1, the brake system 1 typically includes a master cylinder 20 that generates hydraulic pressure, a reservoir 30 that is coupled to an upper portion of the master cylinder 20 to store brake fluid, and a brake pedal ( An input rod 12 that pressurizes the master cylinder 20 according to the foot force of 10), a wheel cylinder 40 that brakes each wheel (RR, RL, FR, FL) by transmitting hydraulic pressure, and a brake pedal A pedal position sensor 11 that senses the displacement of (10) and a simulation device 50 that provides a reaction force according to the foot force of the brake pedal 10 are provided.

In addition, although not shown in FIG. 1, a wheel speed sensor is provided in each wheel cylinder 40 to measure the speed of each wheel FL, RR, RL, and FR.

The master cylinder 20 is configured to have at least one chamber to generate hydraulic pressure. For example, the master cylinder 20 is configured to have two chambers, a first piston 21a and a second piston 22a are provided in each chamber, and the first piston 21a is an input rod 12 ) Can be connected. In addition, the master cylinder 20 may form first and second hydraulic ports 24a and 24b through which hydraulic pressure is discharged from the two chambers, respectively.

On the other hand, the master cylinder 20 can secure safety in case of failure by having two chambers. For example, one of the two chambers may be connected to the right front wheel FR and the left rear wheel RL of the vehicle, and the other chamber may be connected to the left front wheel FL and the right rear wheel RR. In this way, by configuring the two chambers independently, it is possible to brake the vehicle even if one chamber fails.

In addition, a first spring (21b) is provided between the first piston (21a) and the second piston (22a) of the master cylinder (20), and between the end of the second piston (22a) and the master cylinder (20). 2 springs 22b may be provided.

The first spring 21b and the second spring 22b are provided in each of the two chambers, and as the displacement of the brake pedal 10 varies, the first piston 21a and the second piston 22a are compressed. The elastic force is stored in the spring 21b and the second spring 22b. And when the force pushing the first piston (21a) is less than the elastic force, the first and second pistons (21a, 22a) are pushed to the original state by using the stored elastic force of the first spring (21b) and the second spring (22b). I can.

Meanwhile, the input rod 12 for pressing the first piston 21a of the master cylinder 20 may be in close contact with the first piston 21a. That is, there may not be a gap between the master cylinder 20 and the input rod 12. Therefore, when the brake pedal 10 is released, the master cylinder 20 can be directly pressed without a pedal invalid stroke section.

The simulation device 50 may be connected to a first backup passage 251 to be described later to provide a reaction force according to the foot force of the brake pedal 10. As reaction force is provided to compensate for the foot pressure provided by the driver, the driver can finely adjust the braking force as intended.

Referring to FIG. 1, the simulation device 50 includes a simulation chamber 51 provided to store brake fluid flowing out of the first hydraulic port 24a of the master cylinder 20 and a reaction force piston provided in the simulation chamber 51. It includes a pedal simulator having 52 and a reaction spring 53 for elastically supporting the same, and a simulator valve 54 connected to the rear end of the simulation chamber 51.

The reaction force piston 52 and the reaction force spring 53 are installed to have a certain range of displacement within the simulation chamber 51 by the brake fluid flowing into the simulation chamber 51.

The simulator valve 54 may be provided in a flow path connecting the rear end of the simulation chamber 51 and the reservoir 30. The front end of the simulation chamber 51 may be connected to the master cylinder 20, and the rear end of the simulation chamber 51 may be connected to the reservoir 30 through the simulator valve 54. Therefore, even when the reaction force piston 52 returns, the brake fluid of the reservoir 30 flows through the simulator valve 54, so that the entire interior of the simulation chamber 51 may be filled with the brake fluid.

Meanwhile, in the drawing, several reservoirs 30 are shown, and each reservoir 30 uses the same reference numeral. However, these reservoirs may be provided with the same parts or different parts. For example, the reservoir 30 connected to the simulation device 50 is the same as the reservoir 30 connected to the master cylinder 20, or stores brake fluid separately from the reservoir 30 connected to the master cylinder 20. It can be a store that can be.

Meanwhile, the simulator valve 54 may be configured as a normally closed solenoid valve that maintains a normally closed state. The simulator valve 54 is opened when the driver applies a pedal effort to the brake pedal 10 and can transmit the brake fluid in the simulation chamber 51 to the reservoir 30.

In addition, a simulator check valve 55 may be installed between the simulation chamber 51 and the reservoir 30 so as to be connected in parallel with the simulator valve 54. The simulator check valve 55 allows the brake fluid of the reservoir 30 to flow into the simulation chamber 51, but the brake fluid in the simulation chamber 51 passes through the flow path in which the check valve 55 is installed, and the reservoir 30 Can be blocked from flowing into. When the pedal effort of the brake pedal 10 is released, the brake fluid may be supplied into the simulation chamber 51 through the simulator check valve 55, so that a rapid return of the pedal simulator pressure may be ensured.

The hydraulic pressure supply device 100 includes a hydraulic pressure supply unit 110 that provides hydraulic pressure of brake fluid delivered to the wheel cylinder 40, a motor 120 that generates rotational force by an electrical signal from the pedal position sensor 11, and , It may include a power conversion unit 130 that converts the rotational motion of the motor 120 into linear motion and transmits it to the hydraulic pressure providing unit 110. Alternatively, the hydraulic pressure providing unit 110 may be operated not by a driving force supplied from the motor 120 but by a pressure supplied from a high pressure accumulator.

The brake system 1 according to an embodiment includes a hydraulic pressure supply device 100 that mechanically operates by receiving the driver's braking intention as an electrical signal from the pedal position sensor 11 that senses the displacement of the brake pedal 10, The hydraulic control unit 200 consisting of first and second hydraulic circuits 201 and 202 for controlling the flow of hydraulic pressure delivered to the wheel cylinder 40 provided in each of the two wheels RR, RL, FR, and FL. And, a first cut valve 261 provided in a first backup passage 251 connecting the first hydraulic port 24a and the first hydraulic circuit 201 to control the flow of hydraulic pressure, and a second hydraulic port ( A second cut valve 262 provided in the second backup passage 252 connecting the 24b) and the second hydraulic circuit 202 to control the flow of hydraulic pressure, and a hydraulic pressure supply device based on hydraulic pressure information and pedal displacement information ( 100) and valves (54, 60, 221a, 221b, 221c, 221d, 222a, 222b, 222c, 222d, 233, 235, 236, 243) and the electronic control unit (2000) for controlling.

The overall control of the brake system 1 of the electronic control unit 2000 may be performed.

As shown in FIG. 1 again, the hydraulic pressure providing unit 110 includes a cylinder block 111 in which a pressure chamber for receiving and storing brake fluid is formed, a hydraulic piston 114 accommodated in the cylinder block 111, and Sealing members 115 (115a, 115b) provided between the hydraulic piston 114 and the cylinder block 111 to seal the pressure chamber, and the power output from the power conversion unit 130 by being connected to the rear end of the hydraulic piston 114 It includes a drive shaft 133 for transmitting to the hydraulic piston (114).

The pressure chamber is a first pressure chamber 112 located in front of the hydraulic piston 114 (forward direction, left direction in the drawing), and a first pressure chamber 112 located in the rear (reverse direction, right direction in the drawing) of the hydraulic piston 114. It may include a second pressure chamber (113). That is, the first pressure chamber 112 is partitioned by the front end of the cylinder block 111 and the hydraulic piston 114, and is provided to change the volume according to the movement of the hydraulic piston 114, and the second pressure chamber 113 ) Is divided by the cylinder block 111 and the rear end of the hydraulic piston 114, and is provided so that the volume is changed according to the movement of the hydraulic piston 114.

The first and second pressure chambers 112 and 113 are connected to the reservoir 30 by the dump passages 116 and 117, respectively, and receive and store brake fluid from the reservoir 30 or store the first or second pressure chamber. Brake fluid of (112, 113) can be delivered to the reservoir (30).

Next, passages 211, 212, 213, 214, 215, 216, 217 and valves 231, 232, 233, 234 connected to the first pressure chamber 112 and the second pressure chamber 113, 235, 236, 241, 242, 243) will be described.

The second hydraulic passage 212 may communicate with the first hydraulic circuit 201, and the third hydraulic passage 213 may communicate with the second hydraulic circuit 202. Accordingly, hydraulic pressure may be transmitted to the first hydraulic circuit 201 and the second hydraulic circuit 202 by the advance of the hydraulic piston 114.

In addition, the brake system 1 according to an embodiment is provided in the second and third hydraulic flow paths 212 and 213, respectively, and a first control valve 231 and a second control valve 232 for controlling the flow of brake fluid. It may include.

In addition, the first and second control valves 231 and 232 allow only the flow of brake fluid in a direction from the first pressure chamber 112 to the first or second hydraulic circuit 201, 202, and brake in the opposite direction. Liquid flow may be provided with a check valve that blocks. That is, the first or second control valves 231 and 232 allow the hydraulic pressure of the first pressure chamber 112 to be transferred to the first or second hydraulic circuits 201 and 202, while It is possible to prevent the hydraulic pressure of the circuits 201 and 202 from leaking to the first pressure chamber 112 through the second or third hydraulic flow paths 212 and 213.

On the other hand, the fourth hydraulic flow path 213 may be branched into the fifth hydraulic flow path 215 and the sixth hydraulic flow path 216 on the way and communicate with both the first hydraulic circuit 201 and the second hydraulic circuit 202. . For example, the fifth hydraulic passage 215 branching from the fourth hydraulic passage 214 communicates with the first hydraulic circuit 201, and the sixth hydraulic passage 216 branched from the fourth hydraulic passage 214 is It may communicate with the second hydraulic circuit 202. Accordingly, hydraulic pressure can be transmitted to both the first hydraulic circuit 201 and the second hydraulic circuit 202 by the reverse of the hydraulic piston 114.

In addition, the brake system 1 according to an exemplary embodiment is provided in the fifth hydraulic passage 215 and provided in the third control valve 233 and the sixth hydraulic passage 216 to control the flow of brake fluid. It may include a fourth control valve 234 to control.

The third control valve 233 may be provided as a two-way control valve that controls the flow of brake fluid between the second pressure chamber 113 and the first hydraulic circuit 201. In addition, the third control valve 233 may be provided as a normal closed type solenoid valve that is normally closed and operates to open the valve upon receiving an open signal from the electronic control unit 2000.

In addition, the fourth control valve 234 is provided as a check valve that allows only the flow of brake fluid in a direction from the second pressure chamber 113 to the second hydraulic circuit 202, and blocks the flow of brake fluid in the opposite direction. I can. That is, the fourth control valve 234 prevents the hydraulic pressure of the second hydraulic circuit 202 from leaking into the second pressure chamber 113 through the sixth hydraulic flow path 216 and the fourth hydraulic flow path 214. I can.

In addition, the brake system 1 according to an embodiment is provided in the seventh hydraulic passage 217 connecting the second hydraulic passage 212 and the third hydraulic passage 213 to control the flow of brake fluid. It includes a valve 235 and a sixth control valve 236 provided in the eighth hydraulic flow path 218 connecting the second hydraulic flow path 212 and the seventh hydraulic flow path 217 to control the flow of brake fluid. I can. In addition, the fifth control valve 235 and the sixth control valve 236 are normally closed and are normally closed type solenoid valves that operate to open the valve upon receiving an open signal from the electronic control unit 2000. Can be provided.

When an abnormality occurs in the first control valve 231 or the second control valve 232, the fifth control valve 235 and the sixth control valve 236 operate to open to prevent the first pressure chamber 112. The hydraulic pressure may be transmitted to both the first hydraulic circuit 201 and the second hydraulic circuit 202.

In addition, the fifth control valve 235 and the sixth control valve 236 may be operated to be opened when the hydraulic pressure of the wheel cylinder 40 is removed and sent to the first pressure chamber 112. This is because the first control valve 231 and the second control valve 232 provided in the second hydraulic flow path 212 and the third hydraulic flow path 213 are provided as check valves that allow only one-way brake fluid flow.

In addition, the brake system 1 according to an embodiment is provided in the first and second dump passages 116 and 117, respectively, and a first dump valve 241 and a second dump valve 242 for controlling the flow of brake fluid. It may further include. The dump valves 241 and 242 may be check valves that open only a direction from the reservoir 30 to the first or second pressure chambers 112 and 113 and close the opposite direction. That is, the first dump valve 241 allows the brake fluid to flow from the reservoir 30 to the first pressure chamber 112, but the flow of the brake fluid from the first pressure chamber 112 to the reservoir 30 It may be a check valve that shuts off, and the second dump valve 242 allows the brake fluid to flow from the reservoir 30 to the second pressure chamber 113, but the reservoir 30 from the second pressure chamber 113 The flow of the brake fluid may be a check valve that blocks.

In addition, the second dump passage 117 may include a bypass passage, and the bypass passage includes a third dump valve 243 for controlling the flow of brake fluid between the second pressure chamber 113 and the reservoir 30. Can be installed.

The third dump valve 243 may be provided as a solenoid valve capable of controlling flow in both directions, and is open in a normal state, but is a normally open type that operates to close the valve when a closing signal is received from the electronic control unit 2000. It can be provided with a (Normal Open type) solenoid valve.

The hydraulic pressure providing unit 110 of the brake system 1 according to an embodiment may operate in a double acting type. That is, as the hydraulic piston 114 advances, the hydraulic pressure generated in the first pressure chamber 112 is transmitted to the first hydraulic circuit 201 through the first hydraulic flow path 211 and the second hydraulic flow path 212 to the right side. The wheel cylinder 40 installed on the front wheel FR and the left rear wheel LR can be operated, and transmitted to the second hydraulic circuit 202 through the first hydraulic flow path 211 and the third hydraulic flow path 213 As a result, the wheel cylinder 40 installed on the right rear wheel RR and the left front wheel FL can be operated.

Similarly, as the hydraulic piston 114 moves backward, the hydraulic pressure generated in the second pressure chamber 113 is transmitted to the first hydraulic circuit 201 through the fourth hydraulic passage 214 and the fifth hydraulic passage 215 to the right side. The wheel cylinder 40 installed on the front wheel FR and the left rear wheel LR can be operated, and transmitted to the second hydraulic circuit 202 through the 4th hydraulic channel 214 and the 6th hydraulic channel 216 As a result, the wheel cylinder 40 installed on the right rear wheel RR and the left front wheel FL can be operated.

In addition, as the hydraulic piston 114 moves backward, the negative pressure generated in the first pressure chamber 112 sucks the brake fluid of the wheel cylinder 40 installed in the right front wheel FR and the left rear wheel LR, It can be transmitted to the first pressure chamber 112 through the circuit 201, the second hydraulic flow path 212, and the first hydraulic flow path 211, and installed in the right rear wheel RR and the left front wheel FL. The brake fluid of the wheel cylinder 40 may be sucked and transmitted to the first pressure chamber 112 through the second hydraulic circuit 202, the third hydraulic passage 213, and the first hydraulic passage 211.

Next, the motor 120 and the power conversion unit 130 of the hydraulic pressure supply device 100 will be described.

The motor 120 is a device that generates rotational force by a signal output from the electronic control unit 2000 and may generate rotational force in a forward or reverse direction. The rotational angular speed and rotational angle of the motor 120 can be precisely controlled.

In addition, the motor position sensor MPS is a motor control sensor that controls the rotation angle of the motor 120 or the current of the motor.

That is, the motor position sensor (MPS) for measuring the rotational angular velocity and the rotational angle of the motor 120 may be further included, and the rotation angle and other position information of the motor 120 may be transmitted to the electronic control unit 2000.

Meanwhile, the electronic control unit 2000 includes a plurality of valves 54, 60, 221a, 221b, 221c, 221d, 222a, 222b, 222c, 222d, 233 provided in the brake system 1 including the motor 120 , 235, 236, 243).

In addition, an operation in which the electronic control unit 2000 controls a plurality of valves according to the displacement of the brake pedal 10 will be described later.

The driving force of the motor 120 generates displacement of the hydraulic piston 114 through the power conversion unit 130, and the hydraulic pressure generated as the hydraulic piston 114 slides in the pressure chamber is converted into the first and second hydraulic flow paths. It is transmitted to the wheel cylinder 40 installed on each wheel RR, RL, FR, and FL through (211, 212).

The power conversion unit 130 is a device that converts rotational force into linear motion, and may include, for example, a worm shaft 131, a worm wheel 132, and a drive shaft 133.

That is, while displacement occurs in the brake pedal 10, the signal sensed by the pedal position sensor 11 is transmitted to the electronic control unit 2000, and the electronic control unit 2000 drives the motor 120 in one direction. To rotate the worm shaft 131 in one direction. The rotational force of the worm shaft 131 is transmitted to the drive shaft 133 via the worm wheel 132, and the hydraulic piston 114 connected to the drive shaft 133 moves forward to generate hydraulic pressure in the first pressure chamber 112.

Conversely, when the pedal effort is removed from the brake pedal 10, the electronic control unit 2000 drives the motor 120 in the opposite direction so that the worm shaft 131 rotates in the opposite direction. Accordingly, the worm wheel 132 also rotates in the opposite direction, and the hydraulic piston 114 connected to the drive shaft 133 returns (while moving backward) to generate negative pressure in the first pressure chamber 112.

On the other hand, it is possible to generate hydraulic pressure and negative pressure in the opposite direction. That is, while displacement occurs in the brake pedal 10, the signal sensed by the pedal position sensor 11 is transmitted to the electronic control unit 2000, and the electronic control unit 2000 drives the motor 120 in the opposite direction. To rotate the worm shaft 131 in the opposite direction. The rotational force of the worm shaft 131 is transmitted to the drive shaft 133 via the worm wheel 132, and the hydraulic piston 114 connected to the drive shaft 133 moves backward to generate hydraulic pressure in the second pressure chamber 113.

Conversely, when the pedal effort is removed from the brake pedal 10, the electronic control unit 2000 drives the motor 120 in one direction so that the worm shaft 131 rotates in one direction. Accordingly, the worm wheel 132 also rotates in the opposite direction and the hydraulic piston 114 connected to the drive shaft 133 returns (while moving forward) to generate negative pressure in the second pressure chamber 113.

As described above, the hydraulic pressure supply device 100 serves to transmit the hydraulic pressure to the wheel cylinder 40 or suck the hydraulic pressure to the reservoir 30 according to the rotational direction of the rotational force generated from the motor 120.

On the other hand, when the motor 120 rotates in one direction, hydraulic pressure may be generated in the first pressure chamber 112 or negative pressure may be generated in the second pressure chamber 113. Whether to brake by using the hydraulic pressure or to reduce the negative pressure Whether to release the braking using the control valves (54, 60, 221a, 221b, 221c, 221d, 222a, 222b, 222c, 222d, 233, 235, 236, 243) constituting the plurality of valves 800 Can be determined.

In addition, it should be understood that the power conversion unit 130 according to an embodiment can be adopted in any structure as long as it can convert rotational motion into linear motion other than the structure of the ball screw nut assembly.

A first cut valve 261 for controlling the flow of brake fluid is provided in the first backup passage 251, and a second cut valve 262 for controlling the flow of brake fluid is provided in the second backup passage 252 Can be. In addition, the first backup passage 251 connects the first hydraulic port 24a and the first hydraulic circuit 201, and the second backup passage 252 has a second hydraulic port 24b and a second hydraulic circuit ( 202) can be connected.

In addition, the first and second cut valves 261 and 262 are normally open type solenoid valves that are open in a normal state and then operate to close when a closing signal is received from the electronic control unit 2000. Can be provided.

Next, the hydraulic control unit 200 according to an embodiment will be described with reference to FIG. 1.

The hydraulic control unit 200 may include a first hydraulic circuit 201 and a second hydraulic circuit 202 that respectively control two wheels by receiving hydraulic pressure. As an example, the first hydraulic circuit 201 may control the right front wheel FR and the left rear wheel RL, and the second hydraulic circuit 202 may control the left front wheel FL and the right rear wheel RR. . In addition, a wheel cylinder 40 is installed on each of the wheels FR, FL, RR, and RL, and braking is performed by receiving hydraulic pressure.

The first hydraulic circuit 201 is connected to the first hydraulic flow path 211 and the second hydraulic flow path 212 to receive hydraulic pressure from the hydraulic pressure supply device 100 or the master cylinder 20, and the second hydraulic flow path 212 ) Is branched into two flow paths connected to the right front wheel (FR) and the left rear wheel (RL). Likewise, the second hydraulic circuit 202 is connected to the first hydraulic channel 211 and the third hydraulic channel 213 to receive hydraulic pressure from the hydraulic pressure supply device 100, and the third hydraulic channel 213 is the left front wheel. It diverges into two flow paths connected to the (FL) and the right rear wheel (RR).

The hydraulic circuits 201 and 202 may include a plurality of inlet valves 221 (221a, 221b, 221c, 221d) to control the flow of hydraulic pressure. As an example, the first hydraulic circuit 201 may be provided with two inlet valves 221a and 221b connected to the first hydraulic flow path 211 and respectively controlling hydraulic pressure transmitted to the two wheel cylinders 40. . In addition, the second hydraulic circuit 202 may be provided with two inlet valves 221c and 221d that are connected to the second hydraulic flow path 212 and respectively control the hydraulic pressure delivered to the wheel cylinder 40.

In addition, the inlet valve 221 is disposed on the upstream side of the wheel cylinder 40, is open in a normal state, and operates to close the valve when a closing signal is received from the electronic control unit 2000 (Normal Open type). It can be provided with a solenoid valve.

In addition, the hydraulic circuits 201 and 202 include check valves 223a, 223b, 223c, and 223d provided in the bypass flow path connecting the front and rear of the respective inlet valves 221a, 221b, 221c, and 221d. I can. Check valves (223a, 223b, 223c, 223d) allow only the flow of brake fluid from the wheel cylinder 40 to the hydraulic pressure providing unit 110, and from the hydraulic pressure providing unit 110 to the wheel cylinder 40 The flow of brake fluid can be provided to limit. Check valves (223a, 223b, 223c, 223d) can be able to quickly remove the braking pressure of the wheel cylinder (40), and when the inlet valves (221a, 221b, 221c, 221d) do not operate normally, the wheel cylinder The hydraulic pressure of 40 may be introduced into the hydraulic pressure providing unit 110.

In addition, the hydraulic circuits 201 and 202 may further include a plurality of outlet valves 222 (222a, 222b, 222c, 222d) connected to the reservoir 30 to improve performance when braking is released. The outlet valves 222 are respectively connected to the wheel cylinders 40 to control the discharge of hydraulic pressure from the respective wheels RR, RL, FR, and FL. That is, the outlet valve 222 senses the braking pressure of each wheel RR, RL, FR, and FL, and is selectively opened when depressurized braking is required to control the pressure.

In addition, the outlet valve 222 may be provided as a normal closed type solenoid valve that is normally closed and operates to open the valve upon receiving an open signal from the electronic control unit 2000.

In addition, the hydraulic control unit 200 may be connected to the backup passages 251 and 252. As an example, the first hydraulic circuit 201 is connected to the first backup flow path 251 to receive hydraulic pressure from the master cylinder 20, and the second hydraulic circuit 202 is connected to the second backup flow path 252. Hydraulic pressure may be provided from the master cylinder 20.

At this time, the first backup passage 251 may join the first hydraulic circuit 201 upstream of the first and second inlet valves 221a and 221b. Likewise, the second backup passage 252 may join the second hydraulic circuit 202 upstream of the third and fourth inlet valves 221c and 221d. Therefore, when the first and second cut valves 261 and 262 are closed, the hydraulic pressure provided from the hydraulic pressure supply device 100 is supplied to the wheel cylinder 40 through the first and second hydraulic circuits 201 and 202. In the case of opening the first and second cut valves 261 and 262, the hydraulic pressure provided from the master cylinder 20 may be supplied to the wheel cylinder 40 through the first and second backup passages 251 and 252. I can. At this time, since the plurality of inlet valves 221a, 221b, 221c, and 221d are open, there is no need to change the operating state.

At least one component may be added or deleted corresponding to the performance of the components of the brake system 1 shown in FIG. 1. In addition, it will be readily understood by those of ordinary skill in the art that the mutual positions of the components may be changed corresponding to the performance or structure of the system.

Hereinafter, the operation of the brake system 1 according to an embodiment will be described in detail.

First, FIG. 2 is a block diagram showing the configuration of a brake system 1 according to an embodiment.

As shown in FIG. 2, the brake system 1 according to an embodiment is capable of controlling a plurality of valves in the hydraulic pressure supply device 100 and the hydraulic control unit 200 shown in FIG. 1. Based on the sensor unit 1000 including the motor position sensor (MPS), the pedal position sensor 11, and the pressure sensors PS1 and PS2 included in the circuit of the, and the detection signal obtained from the sensor unit 1000 And an electronic control unit 2000 that controls the brake system 1.

Specifically, the sensor unit 1000 according to an embodiment includes a wheel speed sensor 1100, a motor position sensor 1200, an acceleration sensor 1300, a pedal position sensor 1400, and a pressure sensor 1500.

The wheel speed sensor 1100 transmits the measured wheel speed to the electronic control unit 2000 by being positioned at each wheel FL, RR, RL, and FR of the vehicle.

The motor position sensor 1200 includes a motor position sensor MPS shown in FIG. 1, and includes a motor control sensor that controls a rotation angle of the motor 120 or a current of the motor.

That is, the motor position sensor 1200 for measuring the rotational angular speed and the rotational angle of the motor 120 may transmit rotational angle and other position information of the motor 120 to the electronic control unit 2000.

The acceleration sensor 1300 included in the vehicle's brake system 1 may include a lateral acceleration sensor and a vertical acceleration sensor, and the lateral acceleration sensor refers to the moving direction of the vehicle as the X axis, and the vertical axis of the moving direction ( Y-axis) direction is called the lateral direction and the acceleration in the lateral direction is measured.

The vertical acceleration sensor can measure the acceleration in the X-axis direction of the vehicle's moving direction.

The acceleration sensor 1300 is an element that detects a change in velocity per unit time, and detects dynamic forces such as acceleration, vibration, and impact, and can be measured using the principle of inertia force, electrical deformation, and gyro.

The pedal position sensor 1400 includes the pedal position sensor 11 shown in FIG. 1. That is, the pedal position sensor 1400 measures the driver's foot pressure applied to the pedal.

The pressure sensor 1500 measures the hydraulic pressure in the brake system 1 and may include a plurality of pressure sensors.

Specifically, it is possible to measure the pressure of each wheel through a pressure sensor (not shown) included in each wheel (FR, FL, RR, RL) and transmit the pressure value to the electronic control unit 20, The illustrated PS1 is a hydraulic oil pressure sensor that senses the hydraulic pressure of the hydraulic circuits 201 and 202 to measure the hydraulic pressure of the brake fluid, and PS2 is a backup flow pressure sensor that measures the oil pressure of the master cylinder 20. It is possible to measure the hydraulic pressure of brake fluid in 20).

Next, the electronic control unit 2000 collectively controls the brake system 1 of the vehicle according to an exemplary embodiment, and based on various sensor values measured by the sensor unit 1000, the vehicle deceleration and brake fluid The hydraulic pressure of the vehicle and the temperature of the brake fluid are determined, and the brake fading occurs based on the determined vehicle deceleration, the hydraulic pressure of the brake fluid, and the temperature of the brake fluid. It includes a control unit 2100 for compensating for and a storage unit 2200 for storing various types of data necessary for the operation of the control unit 2100.

The controller 2100 may be integrated in a system on chip (SOC) within the brake system 1 together with the storage unit 2200. However, since there is not only one system-on-chip embedded in the brake system 1, but there may be a plurality of system-on-chips, it is not limited to being integrated into only one system-on-chip.

The controller 2100 may include at least one memory in which a program for performing the above-described operation and an operation described later is stored, and at least one processor for executing the stored program. When there are a plurality of memories and processors, they may be integrated on one chip, or may be provided in physically separate locations.

In addition, the storage unit 2200 includes a cache, a read only memory (ROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), and a flash memory to store various types of information. A nonvolatile memory device such as, or a volatile memory device such as random access memory (RAM), or at least one of a storage medium such as a hard disk drive (HDD) or a CD-ROM, but is not limited thereto.

At least one component may be added or deleted corresponding to the performance of the components of the brake system 1 shown in FIG. 2. In addition, it will be readily understood by those of ordinary skill in the art that the mutual positions of the components may be changed corresponding to the performance or structure of the system.

Meanwhile, some of the components illustrated in FIG. 2 may be software and/or hardware components such as a Field Programmable Gate Array (FPGA) and an Application Specific Integrated Circuit (ASIC).

Hereinafter, a detailed operation process of the controller 2100 will be described with reference to FIGS. 3 and 4. 3 is a graph showing characteristics of the amount of liquid required of the brake system 1 according to an embodiment, and FIG. 4 is a graph showing the characteristics of a deceleration rate of the brake system 1 according to an embodiment.

Referring to FIG. 3, the required liquid amount/hydraulic pressure curve is the hydraulic pressure generated according to the volume of the liquid amount (the volume of brake fluid required; the vertical axis of FIG. 3) that the controller 2100 flows into the caliper (not shown) of each wheel. It shows the required hydraulic pressure of the brake fluid; the horizontal axis in FIG. 3). The required liquid amount/hydraulic pressure curve may be a brake pressure curve applied to the brake according to the volume of the liquid amount.

Here, the volume of the liquid amount increases as the piston of the cylinder advances (ie, as the piston pushes the brake fluid), the vertical axis of FIG. 3 may be the amount of movement of the piston. The pistons include the first piston 21a, the second piston 22a of the master cylinder 20 described in FIG. 1, the hydraulic piston 114 of the hydraulic pressure providing unit 110, and the piston of the wheel cylinder 40 (not shown). City) may be at least one of.

On the other hand, the required liquid amount/hydraulic pressure curve shows different characteristics depending on the temperature of the brake fluid. As the temperature increases, the liquid pressure loss occurs and the change value of the liquid pressure generated according to the volume change of the amount of liquid flowing into the caliper decreases. see. That is, as shown in FIG. 3, as the temperature of the brake fluid increases, the volume of the brake fluid required to obtain the same hydraulic pressure increases.

In other words, comparing the required liquid amount/hydraulic pressure curve 3000 at room temperature and the required liquid amount/hydraulic pressure curve 3500 at high temperature, when the temperature of the brake fluid corresponds to high temperature, the brake fluid required to obtain the same hydraulic pressure It can be seen that the required liquid amount is higher than that at room temperature.

In this case, the room temperature may generally correspond to a temperature within a range in which brake fading does not occur due to a decrease in braking force of the brake system 1, and may vary according to the type of the brake system 1.

In addition, the high temperature corresponds to a higher temperature than room temperature, and may correspond to a temperature at which brake fading may occur due to a decrease in braking force of the brake system 1.

As such, brake fading may occur when the temperature of the brake system 1 increases due to the accumulation of frictional heat in the disks and pads on the brake system 1, and accordingly, the temperature of the brake fluid in the brake system 1 may increase. have.

That is, brake fading may mean a phenomenon in which the friction material between the disk and the pad is hardened as the temperature of the brake system 1 increases, thereby reducing the friction coefficient of the friction material, thereby reducing the braking force of the vehicle.

Referring to FIG. 4, the deceleration/hydraulic curve represents the deceleration rate (vertical axis of FIG. 4) of the vehicle in which the brake system 1 is provided according to the hydraulic pressure of the brake fluid in the brake system 1 (the horizontal axis in FIG. 4). Show.

In general, as the hydraulic pressure of the brake fluid increases, the deceleration of the vehicle may increase in proportion thereto. In this case, the deceleration of the vehicle may represent a speed amount that changes in a direction opposite to the moving direction of the vehicle.

As described above, when the temperature of the brake system 1 rises from room temperature to a high temperature, brake fading may occur in the brake system 1. In this case, the brake system 1 can provide a lower braking force to the vehicle. That is, as the temperature increases, the brake system 1 may provide a lower braking force. In other words, as the temperature increases, the deceleration rate at the same hydraulic pressure may decrease.

As shown in FIG. 4, the deceleration/hydraulic pressure curve 4500 at high temperature may have a lower slope than the deceleration/hydraulic pressure curve 4000 at room temperature. That is, the deceleration rate at the same hydraulic pressure may decrease as the temperature of the brake system 1 increases.

Accordingly, the control unit 2100 of the brake system 1 according to an embodiment is based on the characteristics of the required liquid amount according to the hydraulic pressure that varies according to the temperature change of the brake fluid and the characteristics of the vehicle deceleration rate that varies according to the temperature change of the brake fluid. Thus, it is possible to determine whether or not brake fading, which may occur due to a change in the temperature of the brake fluid, occurs. Hereinafter, the operation of the control unit 2100 for determining whether or not break fading has occurred will be described in detail.

The control unit 2100 according to an embodiment may consider a temperature of a brake fluid and a deceleration rate of a vehicle as a precondition for determining whether brake fading occurs.

The controller 2100 according to an embodiment may obtain a deceleration rate of a vehicle, a hydraulic pressure of brake fluid, and a wheel speed of the vehicle from the sensor unit 1000.

Specifically, the sensor unit 1000 includes the wheel speed of the vehicle measured from the wheel speed sensor 1100, the deceleration rate of the vehicle measured from the acceleration sensor 1300, and the brake system 1 measured from the pressure sensor 1500. The hydraulic pressure of the internal brake fluid may be transmitted to the control unit 2100.

The controller 2100 according to an embodiment may determine the temperature of the brake fluid.

Specifically, the controller 2100 may determine the temperature of the brake fluid based on the wheel speed measured from the wheel speed sensor 1100 and the hydraulic pressure of the brake fluid measured from the pressure sensor 1500. The temperature of the brake fluid may be a value set in advance by the wheel speed and the hydraulic pressure of the brake fluid, and may be a value proportional to a speed value measured by the wheel speed sensor 1100 and a hydraulic pressure value measured by the pressure sensor 1500.

However, the present invention is not limited thereto, and when the brake system 1 further includes a separate temperature sensor, the controller 2100 may determine the temperature of the brake fluid based on the output value of the temperature sensor.

The controller 2100 according to an embodiment may compare the determined temperature of the brake fluid with a temperature corresponding to the high temperature reference value.

That is, the controller 2100 may determine whether the determined temperature of the brake fluid is higher than or equal to a high temperature reference value. In this case, the high temperature reference value may correspond to a temperature at which brake fading may occur due to hardening of the friction material in the brake system 1, and may be preset in the design stage and stored in the storage unit 2200.

As such, the control unit 2100 may determine whether or not brake fading occurs when there is a possibility that brake fading may occur, such as when the determined temperature of the brake fluid is equal to or higher than a high temperature reference value.

The controller 2100 according to an embodiment may determine whether the measured deceleration is less than or equal to the road surface limit deceleration.

In this case, the road surface limit deceleration refers to the maximum deceleration allowed for the vehicle so as not to cause slip between the tire and the road surface of the respective wheels RR, RL, FR, and FL. That is, when the vehicle deceleration is equal to or greater than the road surface limit deceleration, the vehicle may slip on the road surface, and braking force control according to the hydraulic pressure of the brake fluid may be limited, thereby impairing braking safety.

In other words, the more bright the brake pedal is, the higher the braking force can be obtained. The depression of the brake over the vehicle causes the vehicle to slip and reduce the braking power.

As described above, the road surface limit deceleration is a deceleration of the vehicle corresponding to the road surface limit, and the depression of the brake for causing a deceleration exceeding the road surface limit acceleration may cause the vehicle to slip and reduce the braking force.

The road surface limit deceleration may be determined based on the road surface limit friction force and the vehicle body weight. At this time, the road surface limit friction force may be calculated from a road surface friction coefficient of a driving road surface contacted by the tires of each wheel RR, RL, FR, and FL, and a load applied from the vehicle to the road surface.

In addition, the road friction coefficient may be previously stored in the storage unit 2200 according to the type of road, and may be calculated by dividing the deceleration of the vehicle by the gravitational acceleration. However, the method is not limited to the above method, and any method for calculating the road surface friction coefficient may be included without limitation.

That is, the control unit 2100 according to an exemplary embodiment may determine whether the measured deceleration is less than or equal to the road surface limit deceleration that may cause the vehicle to slip, and the hydraulic pressure of the brake fluid and It is possible to determine whether or not brake fading occurs when a certain functional relationship is established between the decelerations.

In this way, the controller 2100 according to an embodiment may determine whether or not brake fading occurs when the determined temperature is higher than the high temperature reference value and the measured deceleration is less than the road surface limit deceleration.

In this case, the controller 2100 according to an exemplary embodiment may determine whether or not brake fading occurs based on a change in a required amount of liquid and a change in deceleration according to the temperature of the brake fluid.

To this end, the control unit 2100 according to an embodiment may determine the required amount of brake fluid according to the hydraulic pressure measured by the pressure sensor 1500.

Specifically, the controller 2100 according to an embodiment may determine the amount of movement of the hydraulic piston 114 based on a change in the rotation angle of the motor 120 measured from the motor position sensor 1200, and the hydraulic piston 114 ) It is possible to determine the required amount of brake fluid based on the amount of movement and the cross-sectional area of the cylinder block 111.

In addition, according to an embodiment, the brake system 1 receives the driver's braking intention as an electrical signal from the pedal position sensor 1400 and drives the motor 120 to supply hydraulic pressure to the wheel cylinder 40. Instead of including 100, it is possible to provide a braking force by supplying hydraulic pressure generated in the master cylinder 20 to the wheel cylinder 40 including only the master cylinder 20.

In this case, the controller 2100 according to an exemplary embodiment may determine the required amount of brake fluid based on the pedal displacement information measured from the pedal position sensor 1400 and the cross-sectional area of the master cylinder 20.

The control unit 2100 according to an embodiment includes a difference value between the determined required liquid amount and a pre-stored reference required liquid amount corresponding to the measured hydraulic pressure, and the deceleration measured from the acceleration sensor 1300 and a pre-stored corresponding to the measured hydraulic pressure. It is possible to determine whether or not brake fading occurs based on a difference value between the reference decelerations.

To this end, the storage unit 2200 according to an embodiment may store reference required amount of liquid information according to the hydraulic pressure and reference deceleration information according to the hydraulic pressure when the temperature of the brake fluid is at room temperature. At this time, the reference required liquid amount information according to the hydraulic pressure may correspond to the required liquid amount/hydraulic pressure curve 3000 at room temperature shown in FIG. 3, and the reference deceleration information according to the liquid pressure is at room temperature shown in FIG. It can correspond to the deceleration/hydraulic pressure curve 4000.

The control unit 2100 according to an embodiment may determine whether a difference value between the determined required liquid amount and a reference required liquid amount corresponding to the measured hydraulic pressure is greater than or equal to the first fading determination reference value.

As described above, the amount of brake fluid required to generate the same fluid pressure may increase as the temperature increases based on the fluid pressure loss according to the temperature.

The controller 2100 may determine whether or not brake fading occurs based on a change in the amount of the brake fluid required according to the temperature change as described above.

That is, the controller 2100 corresponds to the current required amount of liquid determined based on the measured value of the motor position sensor 1200 or the measured value of the pedal position sensor 1400 and the current hydraulic pressure measured from the pressure sensor 1500. By comparing the difference value between the reference required amount of liquid with the first fading determination reference value, it is possible to check whether the current temperature of the brake fluid corresponds to a temperature capable of causing brake fading.

At this time, the first fading determination reference value corresponds to the difference between the required liquid amount at the temperature when brake fading starts and the reference required liquid amount at the same hydraulic pressure, and is set at the design stage and stored in the storage unit 2200. Can be. Also, the first fading determination reference value may be defined as a different value according to the hydraulic pressure.

In addition, the control unit 2100 according to an embodiment may determine whether a difference value between the measured deceleration rate and the reference deceleration rate corresponding to the measured hydraulic pressure is greater than or equal to the second fading determination reference value.

As described above, the deceleration rate at the same hydraulic pressure may decrease as the temperature increases as the friction coefficient decreases due to hardening of the friction material.

The control unit 2100 may determine whether or not brake fading occurs based on a change in the degree of reduction according to the temperature change as described above.

That is, the control unit 2100 determines the second fading difference between the current deceleration determined based on the measured value of the acceleration sensor 1300 and the reference deceleration corresponding to the current hydraulic pressure measured from the pressure sensor 1500. By comparing with the reference value, it is possible to determine whether or not break fading has occurred.

At this time, the second fading determination reference value corresponds to a difference value between the deceleration when brake fading starts and the reference deceleration at the same hydraulic pressure, and may be set at the design stage and stored in the storage unit 2200. . Also, the second fading determination reference value may be defined as a different value according to the hydraulic pressure.

Accordingly, the control unit 2100 according to an exemplary embodiment has a difference value between the determined current required liquid amount and the pre-stored reference required liquid amount corresponding to the measured current liquid pressure is equal to or greater than the preset first fading determination reference value, and the measured current If the difference value between the deceleration rate of and the previously stored reference deceleration rate corresponding to the measured current hydraulic pressure is greater than or equal to the preset second fading determination reference value, it may be determined that brake fading has occurred.

As described above, the brake system 1 is based on a change in the amount of brake fluid required for generating hydraulic pressure according to a temperature change of the brake fluid in the brake system 1 and a change in the deceleration rate of the vehicle according to the temperature change of the brake fluid. By determining the break fading, it is possible to determine the break fading with higher accuracy.

Also, when it is determined that brake fading has occurred, the controller 2100 according to an exemplary embodiment may control the brake system 1 to compensate for a decrease in braking force due to brake fading.

That is, the controller 2100 according to an embodiment adjusts the hydraulic pressure of the brake fluid so that the current deceleration measured from the acceleration sensor 1300 matches the reference deceleration corresponding to the current hydraulic pressure measured from the pressure sensor 1500. I can.

Specifically, the control unit 2100 according to an embodiment may control the motor 120 to control the hydraulic piston 114 to advance. Through this, the hydraulic pressure of the brake fluid increases, so that the current deceleration measured by the acceleration sensor 1300 may increase to match the reference deceleration corresponding to the current hydraulic pressure measured by the pressure sensor 1500.

In addition, the brake system 1 according to an embodiment includes a pump unit (not shown) that pumps hydraulic pressure, a motor (not shown) that transmits rotational force to the pump unit (not shown), and a pump unit (not shown). The hydraulic pressure pumped by the pump unit (not shown) and at least one redundancy flow path (not shown) connecting the wheel cylinders 40 provided in each of the wheels (RR, RL, FR, FL) It may include at least one inlet valve (not shown) that is opened to transmit to 40).

The controller 2100 according to an embodiment may control a pump unit (not shown) to pump hydraulic pressure by controlling a motor (not shown) that transmits rotational force to the pump unit (not shown). Through this, the hydraulic pressure of the brake fluid increases, so that the current deceleration measured by the acceleration sensor 1300 may increase to match the reference deceleration corresponding to the current hydraulic pressure measured by the pressure sensor 1500.

Hereinafter, a method of controlling the brake system 1 according to an exemplary embodiment will be described. The brake system 1 according to the above-described embodiment may be applied to a method of controlling the brake system 1 to be described later. Accordingly, the contents described above with reference to FIGS. 1 to 4 are equally applicable to the control method of the brake system 1 according to an exemplary embodiment, even if there is no special mention.

5 is a flowchart illustrating a case of determining brake fading in a method of controlling the brake system 1 according to an exemplary embodiment.

Referring to FIG. 5, the controller 2100 according to an exemplary embodiment may consider a temperature of a brake fluid and a deceleration rate of a vehicle as prerequisites for determining whether brake fading occurs.

Accordingly, the brake system 1 according to an embodiment may measure a vehicle deceleration rate and a hydraulic pressure of the brake fluid (510).

Specifically, the sensor unit 1000 of the brake system 1 may measure the deceleration of the vehicle using the acceleration sensor 1300, and the brake fluid in the brake system 1 may be measured using the pressure sensor 1500. You can measure the hydraulic pressure. In addition, the sensor unit 1000 may measure the wheel speed using the wheel speed sensor 1100.

The brake system 1 according to an embodiment may determine the temperature of the brake fluid (520 ). That is, the control unit 2100 according to an embodiment may determine the temperature of the brake fluid.

Specifically, the controller 2100 may determine the temperature of the brake fluid based on the wheel speed measured from the wheel speed sensor 1100 and the hydraulic pressure of the brake fluid measured from the pressure sensor 1500. The temperature of the brake fluid may be a value set in advance by the wheel speed and the hydraulic pressure of the brake fluid, and may be a value proportional to a speed value measured by the wheel speed sensor 1100 and a hydraulic pressure value measured by the pressure sensor 1500.

However, the present invention is not limited thereto, and when the brake system 1 further includes a separate temperature sensor, the controller 2100 may determine the temperature of the brake fluid based on the output value of the temperature sensor.

In the brake system 1 according to an embodiment, if the determined temperature is higher than the high temperature reference value (example of 530), and the measured deceleration is less than or equal to the road surface limit deceleration (example of 540), the required liquid amount according to the measured hydraulic pressure is calculated. Can be determined (550). However, there is no limit to the timing of determining the required liquid amount according to the measured hydraulic pressure, and may be determined before considering the determined temperature and the measured deceleration.

To this end, the controller 2100 according to an embodiment may compare the determined temperature of the brake fluid with a temperature corresponding to the high temperature reference value.

That is, the controller 2100 may determine whether the determined temperature of the brake fluid is higher than or equal to a high temperature reference value. In this case, the high temperature reference value may correspond to a temperature at which brake fading may occur due to hardening of the friction material in the brake system 1, and may be preset in the design stage and stored in the storage unit 2200.

As such, the control unit 2100 may determine whether or not brake fading occurs when there is a possibility that brake fading may occur, such as when the determined temperature of the brake fluid is equal to or higher than a high temperature reference value.

In addition, the controller 2100 according to an embodiment may determine whether the measured deceleration is less than or equal to the road surface limit deceleration.

That is, the control unit 2100 according to an exemplary embodiment may determine whether the measured deceleration is less than or equal to the road surface limit deceleration that may cause the vehicle to slip, and the hydraulic pressure of the brake fluid and It is possible to determine whether or not brake fading occurs when a certain functional relationship is established between the decelerations.

In this way, the controller 2100 according to an embodiment may determine whether or not brake fading occurs when the determined temperature is higher than the high temperature reference value and the measured deceleration is less than the road surface limit deceleration.

In this case, the brake system 1 according to an exemplary embodiment may determine whether or not brake fading occurs based on a change in a required amount of liquid and a change in deceleration according to the temperature of the brake fluid.

To this end, the control unit 2100 according to an embodiment may determine the required amount of brake fluid according to the hydraulic pressure measured by the pressure sensor 1500.

Specifically, the controller 2100 according to an embodiment may determine the amount of movement of the hydraulic piston 114 based on a change in the rotation angle of the motor 120 measured from the motor position sensor 1200, and the hydraulic piston 114 ) It is possible to determine the required amount of brake fluid based on the amount of movement and the cross-sectional area of the cylinder block 111.

In addition, according to an embodiment, the brake system 1 receives the driver's braking intention as an electrical signal from the pedal position sensor 1400 and drives the motor 120 to supply hydraulic pressure to the wheel cylinder 40. Instead of including, the hydraulic pressure generated in the master cylinder 20 including only the master cylinder 20 may be supplied to the wheel cylinder 40 to provide a braking force.

In this case, the controller 2100 according to an exemplary embodiment may determine the required amount of brake fluid based on the pedal displacement information measured from the pedal position sensor 1400 and the cross-sectional area of the master cylinder 20.

The control unit 2100 according to an embodiment includes a difference value between the determined required liquid amount and a pre-stored reference required liquid amount corresponding to the measured hydraulic pressure, and the deceleration measured from the acceleration sensor 1300 and a pre-stored corresponding to the measured hydraulic pressure. It is possible to determine whether or not brake fading occurs based on a difference value between the reference decelerations.

Specifically, in the brake system 1 according to an embodiment, the difference value between the determined required liquid amount and the pre-stored reference required liquid amount corresponding to the measured hydraulic pressure is equal to or greater than a preset first fading determination reference value (example of 560), If the difference between the measured deceleration and the pre-stored reference deceleration corresponding to the measured hydraulic pressure is greater than or equal to the preset second fading determination reference value (YES in 570), it may be determined that brake fading has occurred (580).

To this end, the storage unit 2200 according to an embodiment may store reference required amount of liquid information according to the hydraulic pressure and reference deceleration information according to the hydraulic pressure when the temperature of the brake fluid is at room temperature. At this time, the reference required liquid amount information according to the hydraulic pressure may correspond to the required liquid amount/hydraulic pressure curve 3000 at room temperature shown in FIG. 3, and the reference deceleration information according to the liquid pressure is at room temperature shown in FIG. It can correspond to the deceleration/hydraulic pressure curve 4000.

The control unit 2100 according to an embodiment may determine whether a difference value between the determined required liquid amount and a reference required liquid amount corresponding to the measured hydraulic pressure is greater than or equal to the first fading determination reference value.

As described above, the amount of brake fluid required to generate the same fluid pressure may increase as the temperature increases based on the fluid pressure loss according to the temperature.

The controller 2100 may determine whether or not brake fading occurs based on a change in the amount of the brake fluid required according to the temperature change as described above.

That is, the controller 2100 corresponds to the current required amount of liquid determined based on the measured value of the motor position sensor 1200 or the measured value of the pedal position sensor 1400 and the current hydraulic pressure measured from the pressure sensor 1500. By comparing the difference value between the reference required amount of liquid with the first fading determination reference value, it is possible to check whether the current temperature of the brake fluid corresponds to a temperature capable of causing brake fading.

At this time, the first fading determination reference value corresponds to the difference value between the required liquid amount at the temperature when brake fading starts and the reference required liquid amount at the same hydraulic pressure, and is set in the design stage and stored in the storage unit 2200. Can be. Also, the first fading determination reference value may be defined as a different value according to the hydraulic pressure.

In addition, the control unit 2100 according to an embodiment may determine whether a difference value between the measured deceleration rate and the reference deceleration rate corresponding to the measured hydraulic pressure is greater than or equal to the second fading determination reference value.

As described above, the deceleration rate at the same hydraulic pressure may decrease as the temperature increases as the friction coefficient decreases due to hardening of the friction material.

The control unit 2100 may determine whether or not brake fading occurs based on a change in the degree of reduction according to the temperature change as described above.

That is, the control unit 2100 determines the second fading difference between the current deceleration determined based on the measured value of the acceleration sensor 1300 and the reference deceleration corresponding to the current hydraulic pressure measured from the pressure sensor 1500. By comparing with the reference value, it is possible to determine whether or not break fading has occurred.

At this time, the second fading determination reference value corresponds to a difference value between the deceleration when brake fading starts and the reference deceleration at the same hydraulic pressure, and may be set at the design stage and stored in the storage unit 2200. . Also, the second fading determination reference value may be defined as a different value according to the hydraulic pressure.

Accordingly, the control unit 2100 according to an exemplary embodiment has a difference value between the determined current required liquid amount and the pre-stored reference required liquid amount corresponding to the measured current liquid pressure is equal to or greater than a preset first fading determination reference value, and the measured current If the difference value between the deceleration rate of and the previously stored reference deceleration rate corresponding to the measured current hydraulic pressure is greater than or equal to the preset second fading determination reference value, it may be determined that brake fading has occurred.

As described above, the brake system 1 is based on a change in the amount of brake fluid required for generating hydraulic pressure according to a temperature change of the brake fluid in the brake system 1 and a change in the deceleration rate of the vehicle according to the temperature change of the brake fluid. By determining the break fading, it is possible to determine the break fading with higher accuracy.

6 is a flowchart illustrating a case of adjusting hydraulic pressure in a brake fading situation in a control method of the brake system 1 according to an exemplary embodiment.

Referring to FIG. 6, the brake system 1 according to an embodiment may determine that brake fading has occurred (610 ).

In this case, the brake system 1 can compensate for a decrease in braking force due to brake fading.

Specifically, the brake system 1 according to an exemplary embodiment may adjust the hydraulic pressure so that the deceleration corresponds to a reference deceleration corresponding to the measured hydraulic pressure (620).

That is, the controller 2100 according to an embodiment adjusts the hydraulic pressure of the brake fluid so that the current deceleration measured from the acceleration sensor 1300 matches the reference deceleration corresponding to the current hydraulic pressure measured from the pressure sensor 1500. I can.

Specifically, the control unit 2100 according to an embodiment may control the motor 120 to control the hydraulic piston 114 to advance. Through this, the hydraulic pressure of the brake fluid increases, so that the current deceleration measured by the acceleration sensor 1300 may increase to match the reference deceleration corresponding to the current hydraulic pressure measured by the pressure sensor 1500.

In addition, the brake system 1 according to an embodiment includes a pump unit (not shown) that pumps hydraulic pressure, a motor (not shown) that transmits rotational force to the pump unit (not shown), and a pump unit (not shown). The hydraulic pressure pumped by the pump unit (not shown) and at least one redundancy flow path (not shown) connecting the wheel cylinders 40 provided in each of the wheels (RR, RL, FR, FL) It may include at least one inlet valve (not shown) that is opened to transmit to 40).

The controller 2100 according to an embodiment may control a pump unit (not shown) to pump hydraulic pressure by controlling a motor (not shown) that transmits rotational force to the pump unit (not shown). Through this, the hydraulic pressure of the brake fluid increases, so that the current deceleration measured by the acceleration sensor 1300 may increase to match the reference deceleration corresponding to the current hydraulic pressure measured by the pressure sensor 1500.

Some components of the above-described brake system 1 may be software and/or hardware components such as a Field Programmable Gate Array (FPGA) and an Application Specific Integrated Circuit (ASIC).

The disclosed embodiments may be implemented in the form of a recording medium storing instructions executable by a computer. The instruction may be stored in the form of a program code, and when executed by a processor, a program module may be generated to perform the operation of the disclosed embodiments. The recording medium may be implemented as a computer-readable recording medium.

Computer-readable recording media include all kinds of recording media in which instructions that can be read by a computer are stored. For example, there may be read only memory (ROM), random access memory (RAM), magnetic tape, magnetic disk, flash memory, optical data storage device, and the like.

As described above, the disclosed embodiments have been described with reference to the accompanying drawings. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention may be practiced in a form different from the disclosed embodiments without changing the technical spirit or essential features of the present invention. The disclosed embodiments are illustrative and should not be construed as limiting.

1: brake system
1000: sensor unit
1100: wheel speed sensor
1200: motor position sensor
1300: acceleration sensor
1400: pedal position sensor
1500: pressure sensor
2000: electronic control unit
2100: control unit
2200: storage

Claims (14)

A piston for generating hydraulic pressure of brake fluid in the brake system;
A sensor unit including an acceleration sensor measuring a deceleration of a vehicle and a pressure sensor measuring a hydraulic pressure of the brake fluid;
When the temperature of the brake fluid is at room temperature, a storage unit for storing reference required amount of liquid information according to hydraulic pressure and reference deceleration information according to hydraulic pressure; And
When the temperature of the brake fluid is determined, the required fluid amount of the brake fluid is determined, and the determined temperature is more than a preset high temperature reference value and the deceleration is less than the road surface limit deceleration, the required fluid amount and the measured hydraulic pressure are A brake system comprising: a control unit for determining whether or not brake fading occurs based on a difference value between a corresponding pre-stored reference required liquid amount and a difference value between the deceleration rate and a pre-stored reference deceleration rate corresponding to the measured hydraulic pressure. . The method of claim 1,
The control unit,
The difference between the required liquid amount and the pre-stored reference required liquid amount corresponding to the measured hydraulic pressure is greater than or equal to a preset first fading determination reference value, and the difference between the deceleration rate and the pre-stored reference deceleration rate corresponding to the measured hydraulic pressure A brake system configured to determine that the break fading has occurred when the value is greater than or equal to a preset second fading determination reference value. The method of claim 2,
The control unit,
When it is determined that the brake fading has occurred, the brake system increases the hydraulic pressure of the brake fluid so that the deceleration rate coincides with the reference deceleration rate. The method of claim 3,
The control unit,
A brake system for controlling the piston to advance in order to increase the hydraulic pressure of the brake fluid. The method of claim 3,
The brake system,
Further comprising; a pumping unit for pumping the hydraulic pressure of the brake fluid,
The control unit,
A brake system for controlling the pumping unit to increase the hydraulic pressure of the brake fluid. The method of claim 1,
The sensor unit,
Further comprising a pedal position sensor for measuring the displacement of the pedal,
The control unit,
A brake system that determines the required amount of liquid based on pedal displacement information measured from the pedal position sensor. The method of claim 1,
The brake system,
Further comprising a; motor for transmitting the rotational force to the piston,
The sensor unit,
Further comprising a motor position sensor for measuring the position of the motor,
The control unit,
A brake system that calculates a movement amount of the piston based on motor position information measured from the motor position sensor, and determines the required amount of liquid based on the movement amount of the piston. A method for controlling a brake system comprising a piston generating a hydraulic pressure of brake fluid in a brake system, an acceleration sensor measuring a deceleration rate of a vehicle, and a pressure sensor measuring a hydraulic pressure of the brake fluid,
Storing reference required liquid amount information according to the hydraulic pressure and reference deceleration information according to the hydraulic pressure when the temperature of the brake fluid is at room temperature;
Determining the temperature of the brake fluid;
Determining the required amount of the brake fluid;
If the determined temperature is greater than or equal to a preset high temperature reference value and the deceleration is less than or equal to the road surface limit deceleration, the difference between the required liquid amount and the pre-stored reference required liquid amount corresponding to the measured hydraulic pressure, and the deceleration and the measured A control method of a brake system comprising: determining whether or not brake fading has occurred based on a difference value between pre-stored reference decelerations corresponding to the hydraulic pressure. The method of claim 8,
Determining whether or not the break fading has occurred,
The difference between the required liquid amount and the pre-stored reference required liquid amount corresponding to the measured hydraulic pressure is greater than or equal to a preset first fading determination reference value, and the difference between the deceleration rate and the pre-stored reference deceleration rate corresponding to the measured hydraulic pressure And determining that the brake fading has occurred when the value is greater than or equal to the preset second fading determination reference value. The method of claim 9,
When it is determined that the brake fading has occurred, increasing the hydraulic pressure of the brake fluid so that the deceleration rate coincides with the reference deceleration rate. The method of claim 10,
Increasing the hydraulic pressure of the brake fluid,
Controlling the piston to advance; control method of a brake system comprising a. The method of claim 10,
The brake system,
Further comprising; a pumping unit for pumping the hydraulic pressure of the brake fluid,
Increasing the hydraulic pressure of the brake fluid,
Controlling the pumping unit; control method of a brake system comprising a. The method of claim 8,
The sensor unit,
Further comprising a pedal position sensor for measuring the displacement of the pedal,
To determine the required amount of brake fluid,
Determining the required amount of liquid based on pedal displacement information measured from the pedal position sensor. The method of claim 8,
The brake system,
Further comprising a; motor for transmitting the rotational force to the piston,
The sensor unit,
Further comprising a motor position sensor for measuring the position of the motor,
To determine the required amount of brake fluid,
Calculating the amount of movement of the piston based on the motor position information measured from the motor position sensor;
And determining the required amount of liquid based on the amount of movement of the piston.

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