Electronic braking system

Abstract

Electronic braking system comprising a reservoir (30) in which oil is stored, a master cylinder (20) with a first oil pressure port (24a) and a second oil pressure port (24b) coupled to the reservoir (30) to receive the oil, a pedal displacement sensor (11) configured to detect a displacement of a brake pedal (10), and a simulation device (50) connected to the master cylinder (20) and arranged to obtain a response according to a pedal actuation of the brake pedal (10), which electronic braking system has: a hydraulic pressure supply unit (100) configured to output an electrical signal through the pedal displacement sensor (11) to actuate a motor (140) when the brake pedal (10) is actuated, and configured to convert rotational energy of the motor (140) into linear motion; an oil pressure control unit (200) with a first oil pressure circuit (201) and a second oil pressure circuit (202) connected to the hydraulic pressure supply unit (100) by a main oil pressure path (210), each of which is configured to control two wheels such that a hydraulic pressure is received using a force generated by the hydraulic pressure supply unit (100) to perform braking; and an electronic control unit configured to control the motor (140) and valves based on hydraulic pressure information and pedal displacement information, the oil pressure control unit (200) contains: a first inlet valve (221) and a second inlet valve (222), each arranged upstream of two wheel cylinders (40) to control the two wheels arranged in the first oil pressure circuit (201); a third inlet valve (223) and a fourth inlet valve (224), each arranged upstream of two wheel cylinders (40) to control the two wheels arranged in the second oil pressure circuit (202); a first balancing valve (241) configured to connect or disconnect the two wheel cylinders (40) to which the first inlet valve (221) and the second inlet valve (222) are connected; a second balancing valve (242) configured to connect or disconnect the two wheel cylinders (40) to which the third inlet valve (223) and the fourth inlet valve (224) are connected; a first discharge valve (231) connected to a wheel cylinder (40) located below the two wheel cylinders (40) present in the first oil pressure circuit (201), and configured to control a flow of oil discharged from the connected wheel cylinder (40); and a second discharge valve (232) connected to a wheel cylinder (40) located below the two wheel cylinders (40) present in the second oil pressure circuit (202), and configured to control a flow of oil discharged from the connected wheel cylinder (40).

Description

BACKGROUND1. Area

[0001] Embodiments of the present invention relate to an electronic braking system, and more particularly to an electronic braking system capable of achieving structural simplification and performing accurate pressure control. 2. Description of the state of the art

[0002] The document DE 10 2013 002 378 A1 discloses an electric braking system for vehicles having a pressure supply device connected to a reservoir through a hydraulic passage for receiving the oil, wherein the brake supply device outputs a braking intention of a driver as an electrical signal through the pedal displacement sensor when the driver depresses the brake pedal to operate a motor and convert a rotational force of the motor into a linear movement.Further, the electric braking system comprises a hydraulic control unit including a first circuit including at least a first vehicle wheel and a second circuit including at least a second vehicle wheel for receiving a hydraulic pressure having a force generated by the pressure supply device to thereby perform braking, a lock valve for controlling the hydraulic pressure from the master cylinder to a wheel cylinder located in each vehicle wheel, a simulation device connected to the master cylinder for providing a reaction force response to the pedal force of the brake pedal, and an electronic control unit for controlling the motor and the valves based on pressure information and pedal displacement information.

[0003] WO 2014 / 068660 A1 discloses a brake control device having a front-wheel cross-connection passage that enables communication between wheel cylinders for a left front wheel and a right front wheel via a front-wheel connection switching valve, and a rear-wheel cross-connection passage that enables communication between wheel cylinders for a left rear wheel and a right rear wheel via a rear-wheel connection switching valve. The brake control device performs hydraulic control by keeping the front-wheel connection switching valve and the rear-wheel connection switching valve open. The front-wheel connection switching valve is of the normally closed type, and the rear-wheel connection switching valve is of the normally open type. With this configuration, the brake control device can solve a problem caused by operating fluid leakage and reduce energy consumption.

[0004] Every vehicle requires braking capability and thus requires a braking system. Recently, various types of braking systems have been proposed to realize stronger and more stable braking forces. Examples of braking systems include an anti-lock braking system (ABS), which prevents wheel slippage during braking; a brake friction control system (BTCS), which prevents drive wheels from slipping when a vehicle experiences sudden acceleration or rapid acceleration; and an electronic stability control system (ECS), which, together with ABS and BTSC, controls the hydraulic pressure of a braking system to maintain a stable driving condition.

[0005] Such an electronic brake system includes a plurality of solenoid valves for controlling brake oil pressure transmitted to wheel cylinders (referred to as hydraulic brakes or disc brakes) mounted on the wheels of a vehicle, a pair of low-pressure accumulators for temporarily storing oil discharged from the wheel cylinders, a motor and a pump for forcibly pumping the oil stored in the low-pressure accumulators, a plurality of check valves for preventing backflow of oil, and an electronic control unit (ECU) for controlling the operations of the solenoid valves and the motor, which are compactly installed in an oil pressure block formed of aluminum.Furthermore, a hydraulic pressure supply unit is provided and used, which receives an electrical signal from a pedal displacement sensor for detecting a displacement of the brake pedal according to the braking intention of a driver when the driver steps on a brake, and supplies pressure to the wheel cylinders.

[0006] The electronic brake system equipped with the aforementioned hydraulic pressure supply unit is disclosed as European Patent No. EP 2 520 473 B1. According to this disclosure, the hydraulic pressure supply unit is designed to generate braking pressure by actuating a motor in accordance with a pressure on the brake pedal. Here, the braking pressure is generated by converting the rotational energy of the motor into a linear motion to push a piston.

[0007] However, in the electronic brake system having the above-described structure, the arrangement of the plurality of solenoid valves provided for controlling the pressure transmitted to the wheel cylinders is complex, and in addition, the solenoid valves are individually operated to control a hydraulic pressure supplied to the wheel cylinder provided in each wheel, thereby increasing vibrations and noises due to the operation of the solenoid valves.

[0008] Furthermore, since the configuration of the multiple solenoid valves and the flow paths for controlling the pressure according to different control modes becomes complex, and in addition, the weight and volume of the system are increased because a motor, a pump, and a low-pressure accumulator are additionally provided, the ease of assembly and efficient use of space are impaired, and vibration and noise due to the operation of the motor and the pump increase.

[0009] These problems are solved by an electronic braking system according to claim 1. Possible embodiments are set out in the subclaims. SUMMARY OF THE INVENTION

[0010] It is therefore an aspect of the present invention to provide an electronic brake system capable of performing braking in accordance with a pedal operation by a driver even when a brake system operates abnormally, and whose configuration is simplified by minimizing the number of valves for controlling a flow of oil pressure and accurately controlling the pressure therein.

[0011] Additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

[0012] According to one aspect of the present invention, an electronic brake system includes a reservoir in which oil is stored, a master cylinder having a first oil pressure port and a second oil pressure port, coupled to the reservoir to receive the oil, a pedal displacement sensor configured to detect a displacement of a brake pedal, and a simulation device connected to the master cylinder and provided to obtain a response according to a pedal operation of the brake pedal. The electronic brake system includes a hydraulic pressure supply unit configured to output an electrical signal through the pedal displacement sensor to actuate a motor when the brake pedal is actuated, and configured to convert rotational energy of the motor into rectilinear motion, an oil pressure control unit having a first oil pressure circuit and a second oil pressure circuit.which are connected to the hydraulic pressure supply unit through an oil pressure main path, and each configured to control two wheels such that hydraulic pressure is received by using a force generated by the hydraulic pressure supply unit to perform braking, and an electronic control unit configured to control the motor and valves based on hydraulic pressure information and pedal displacement information, wherein the oil pressure control unit includes: a first inlet valve and a second inlet valve, each arranged upstream of two wheel cylinders to control the two wheels arranged in the first oil pressure circuit, a third inlet valve and a fourth inlet valve, each arranged upstream of two wheel cylinders to control the two wheels present in the second oil pressure circuit, a first balance valve,which is configured to connect or disconnect the two wheel cylinders to which the first inlet valve and the second inlet valve are connected, a second balance valve configured to connect or disconnect the two wheel cylinders to which the third inlet valve and the fourth inlet valve are connected, a first discharge valve connected to each wheel cylinder of the two wheel cylinders present in the first oil pressure circuit and configured to control a flow of oil discharged from the connected wheel cylinder, and a second discharge valve connected to each wheel cylinder of the two wheel cylinders present in the second oil pressure circuit and configured to control a flow of oil discharged from the connected wheel cylinder.

[0013] The hydraulic pressure output from the wheel cylinder connected to each of the unloading valves can be controlled by opening and closing operations of the unloading valves, and the hydraulic pressure output from the wheel cylinder not connected to the unloading valves can be controlled by rotation in a direction opposite to the rotation direction of the motor of the hydraulic pressure supply unit during braking.

[0014] The first balance valve and the second balance valve may be closed when the discharge valve is opened, and the hydraulic pressure is output from the wheel cylinder connected to each of the discharge valves, and the first balance valve and the second balance valve may be closed when the motor of the hydraulic pressure supply unit is rotated in the reverse direction and the hydraulic pressure is output from the wheel cylinder not connected to each of the discharge valves.

[0015] The discharge valves may be provided with normally closed type solenoid valves which are opened when an opening signal is received in a state where the valve is normally closed.

[0016] One of the intake valves of the first and second intake valves may be opened, one of the intake valves of the third and fourth intake valves may be opened, and the hydraulic pressure may be transmitted to the wheel cylinder of each wheel.

[0017] The intake valves may be provided with normally closed type solenoid valves which are operated to open when an opening signal is received in a state in which the valve is normally closed.

[0018] The first and second relief valves may be provided with normally open type solenoid valves which are operated to close when a closing signal is received from the electronic control unit in a state in which the valve is normally closed.

[0019] The electronic brake system may further include a first backup path configured to connect the first oil pressure port and the first compensation valve so that oil is directly supplied to the wheel cylinders when the electronic brake system operates abnormally, and a second backup path configured to connect the second oil pressure port and the second compensation valve, a first shut-off valve disposed in the first backup path and configured to control a flow of the oil, and a second shut-off valve disposed in the second backup path and configured to control a flow of the oil.

[0020] The first and second shut-off valves may be provided with normally open type solenoid valves which are operated to close when a closing signal is received from the electronic control unit in the normal state in which the valve is open.

[0021] The hydraulic pressure supply unit may include: a motor configured to generate rotational power by the electrical signal of the pedal displacement sensor, an energy converter configured to convert the rotational motion of the motor into rectilinear motion, and an oil pressure piston connected to the energy converter and configured to perform rectilinear motion, a pressure chamber slidably disposed with the oil pressure piston and connected to the first and second oil pressure circuits through the oil pressure main path, and an oil pressure spring disposed in the pressure chamber and configured to elastically support the oil pressure piston, wherein the pressure chamber is connected to the reservoir through an oil path to receive the oil.

[0022] A check valve may be installed in the oil path to prevent reverse flow of pressure of the pressure chamber and to suck and store the oil in the pressure chamber when the oil pressure piston is moved back. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] While the present invention will be described in detail with reference to the accompanying drawings, since the following drawings describe embodiments of the present invention, the spirit and scope of the present invention should not be limited by the following drawings: Fig. 1 is an oil pressure circuit diagram illustrating an unbraked state of an electronic braking system according to an embodiment of the present invention; Fig. 2 is a diagram of an oil pressure circuit when a brake of an electronic brake system operates normally according to an embodiment of the present invention; Fig. 3 is a diagram of an oil pressure circuit when a brake of an electronic brake system is normally released according to an embodiment of the present invention; Fig. 4 is an oil pressure circuit diagram for describing an anti-lock braking system (ABS) applied to an electronic braking system according to an embodiment of the present invention; Fig. 5 is an oil pressure circuit diagram for describing an operation performed by a reverse movement in a discharge mode by a hydraulic pressure supply unit using an electronic brake system according to an embodiment of the present invention; Fig. 6 is an oil pressure circuit diagram for describing an operation by actuating a discharge valve in a discharge mode using an electronic brake system according to an embodiment of the present invention; and Fig. 7 is a diagram of an oil pressure circuit when an electronic brake system operates abnormally according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments are provided to fully explain the spirit and scope of the present invention to those skilled in the art. Thus, the present invention should not be construed as limited to the embodiments described herein, and may be embodied by various other embodiments. Parts not relevant to the description are omitted from the drawings in order to clearly explain the present invention. The size of the respective elements in the drawings may be exaggerated to facilitate understanding.

[0025] Fig. 1 is an oil pressure circuit diagram illustrating an unbraked state of an electronic braking system according to an embodiment of the present invention.

[0026] According to Fig. 1, the electronic brake system generally includes a master cylinder 20 that generates hydraulic pressure, a reservoir 30 coupled to an upper portion of the master cylinder 20 to store oil, an input rod 12 that applies pressure to the master cylinder 20 according to a pedal operation of a brake pedal 10, a wheel cylinder 40 to which the hydraulic pressure is transmitted to perform a braking operation of each wheel RR, RL, FR, and FL, a pedal displacement sensor 11 that detects a displacement of the brake pedal 10, and a simulation device 50 that provides a response against the pedal operation of the brake pedal 10.

[0027] Here, the master cylinder 20 is formed with at least one chamber to generate hydraulic pressure. As shown in the drawing, a first piston 21a and a second piston 22a form two chambers, and the first piston 21a is in contact with the input rod 12. To ensure safety in the event of a failure, the master cylinder 20 has two chambers. For example, one of the two chambers is connected to a right front wheel FR and a left rear wheel RL of a vehicle, and the other chamber is connected to a left front wheel FL and a right rear wheel RR thereof. Alternatively, one of the two chambers may be connected to two front wheels FR and FL, and the other chamber may be connected to two rear wheels RR and RL. The reason why two chambers are independently formed as described above is that a vehicle is braked even if one chamber fails.In the master cylinder 20, first and second oil pressure ports 24a and 24b are formed to discharge the hydraulic pressure of the two chambers.

[0028] Furthermore, a first spring 21b is provided between the first piston 21a and the second piston 22a of the master cylinder 20, and a second spring 22b is arranged between ends of the second piston 22a and the master cylinder 20. That is, the first spring 21b and the second spring 22b are provided for the two chambers, respectively, to store an elastic force due to the compression of the first piston 21a and the second piston 22a. The elastic force pushes the first and second pistons 21a and 22a to return them to their original positions when the force pushing the first piston 21a is smaller than the elastic force.

[0029] There is no gap between the master cylinder 20 and the input rod 12 by pressing the input rod 12 to press the first piston 21a of the master cylinder 20 against the first piston 21a to be in contact with each other. That is, when the brake pedal 10 is pressed, the master cylinder 20 is directly pressed without an invalid pedal stroke portion.

[0030] The simulation device 50 for providing a response based on the pedal operation of the brake pedal 10 is connected to a first backup path 251, which will be described below. As shown in the drawing, the simulation device 50 includes a simulation chamber 51 that stores oil discharged from the first oil pressure port 24a of the master cylinder 20, a reaction piston 52 disposed in the simulation chamber 51, a pedal simulator including a reaction spring 53 that elastically supports the reaction piston 52, and a simulation valve 54 connected to a rear end of the simulation chamber 51. Here, the simulation chamber 51 is installed to have a displacement within a predetermined range determined by the oil flowing into the simulation chamber 51 due to the reaction piston 52 and the reaction spring 53.

[0031] The simulation valve 54 is formed to connect the rear end of the simulation chamber 51 and the reservoir 30. That is, an inlet of the simulation chamber 51 is connected to the master cylinder 20, the rear end of the simulation chamber 51 is connected to the simulation valve 54, and the simulation valve 54 is connected to the reservoir 30, and thus the pedal simulation, that is, the entire internal volume of the simulation chamber 51, is filled with oil.

[0032] The simulation valve 54 is formed with a normally closed type solenoid valve that is closed in the normal state, and when a driver steps on the brake pedal 10, the simulation valve 54 is opened to transfer brake oil to the simulation chamber 51.

[0033] Furthermore, a simulation check valve 55 is installed in parallel with the simulation valve 54. The simulation check valve 55 allows the oil to flow from the reservoir 30 only into the simulation chamber 51. That is, the reaction piston 52 of the pedal simulator compresses the reaction spring 53, and oil within the simulation chamber 51 is transferred to the reservoir 30 through the simulation valve 54. Thus, since the simulation chamber 51 is filled with oil when the simulation device 50 is actuated, the friction of the reaction piston 52 is minimized, and thus the durability of the simulation device 50 is improved, and the structure thereof blocks the intrusion of foreign matter from the outside.

[0034] Furthermore, when the pedal operation of the brake pedal 10 is released, the supply of oil through the simulation check valve 55 to the simulation chamber 51 ensures that the pressure of the pedal simulator returns quickly.

[0035] The electronic brake system according to the embodiment of the present invention includes a mechanically operated hydraulic pressure supply unit 100 that receives an electrical signal from the pedal displacement sensor 11 for detecting a displacement of the brake pedal 10 when a driver steps on a brake, an oil pressure control unit 200 formed with first and second oil pressure circuits 201 and 202, each having two wheels, that control the flow of hydraulic pressure supplied to wheel cylinders 40 arranged at each wheel RR, RL, FR, and FL, a first shut-off valve 261 arranged in the first backup path 251 to connect the first oil pressure port 24a and the first oil pressure circuit 201 and controls a flow of the hydraulic pressure, a second shut-off valve 262 arranged in a second backup path 252 to connect the second oil pressure port 24b and the second oil pressure circuit 202, and a Controls the flow of hydraulic pressure,and an electronic control unit (ECU) (not shown) that controls the hydraulic pressure supply unit 100 and the valves 54, 221, 222, 223, 224, 241, 242, 261, and 262 based on the hydraulic pressure information and the pedal displacement information.

[0036] The hydraulic pressure supply unit 100 includes a pressure chamber 110 in which a predetermined space is provided for receiving and storing oil, a pressure piston 120 and an oil pressure spring 122 provided in the pressure chamber 110, a motor 140 that generates rotational energy by the electrical signal from the pedal displacement sensor 11, and an energy converter 130 that converts rotational motion of the motor 140 into rectilinear motion to move the oil pressure piston 120 rectilinearly. Here, the reservoir 30 and the pressure chamber 110 are connected by an oil path 103 to supply the oil to the pressure chamber 110. In addition, the signal detected by the pedal displacement sensor 11 is transmitted to the ECU, and the ECU controls the motor 140 and the valves included in the electronic brake system according to the embodiment of the present invention, which will be described below.The operations for controlling a plurality of valves due to displacement of the brake pedal 10 are described below.

[0037] As described above, the pressure chamber 110 is connected to the reservoir 30 through the oil path 103 and receives and stores the oil. As described above, the oil pressure piston 120 and the oil pressure spring 122, which elastically supports the oil pressure piston 120, are provided in the pressure chamber 110. Here, the hydraulic pressure generated by the pressure of the oil pressure piston 120 is transmitted through a main oil pressure path 210 to the wheel cylinder 40 installed in each wheel RR, RL, FR, and FL.

[0038] The oil pressure piston 120, which exerts pressure on the pressure chamber 110, is connected to the energy converter 130, which converts the rotational energy of the motor 140 into a rectilinear motion in the pressure chamber 110, and moves in a sliding manner.

[0039] The energy converter 130 is a device that converts rotational energy into rectilinear motion and is formed, for example, with a recirculating screw-ball nut assembly. For example, the energy converter 130 may be formed with a screw integrally formed with a rotating shaft of the motor 140 (not shown) and a ball nut screw-coupled to the screw with restricted rotation and performing rectilinear motion according to the rotation of the screw. That is, the screw serves as the rotating shaft of the motor 140 and is used to perform rectilinear motion of the ball nut. Here, the oil pressure piston 120 is connected to the ball nut of the energy converter 130 to press the pressure chamber 110 through the rectilinear motion of the ball nut, and the oil pressure spring 120 serves to return the oil pressure piston 120 to its original position when the ball nut returns to its original position.

[0040] Although not shown, the energy converter 130 may also be formed with a ball nut that is rotatable by receiving rotational power from the rotating shaft of the motor 140, and a screw that is screw-coupled to the ball nut with limited rotation and performs rectilinear motion according to the rotation of the ball nut. Such a screw-ball nut assembly structure is known in the art for a device that converts rotational motion into rectilinear motion, and thus, a detailed description thereof will be omitted. Furthermore, it should be noted that the energy converter 130 according to the embodiment of the present invention may include any structure capable of converting rotational motion into rectilinear motion other than the screw-ball nut assembly.

[0041] The motor 140 is an electric motor that generates rotational power in response to a signal output from the ECU and generates the rotational power in a normal or reverse direction depending on the ECU. Here, precise control is possible by controlling a rotation angle or speed of the motor 140. Such a motor 140 is known in the art, and thus a detailed description thereof is omitted.

[0042] Additionally, a check valve 120 is installed in the oil path 103 to prevent backflow of the pressure of the pressure chamber 110. The check valve 102 serves to prevent backflow of the pressure of the pressure chamber 110 and also to suck the oil into the pressure chamber 110 and store the oil therein when the oil pressure piston 120 is reset.

[0043] When an electronic brake system including the aforementioned hydraulic pressure supply unit 100 is used, the hydraulic pressure supply unit 100 may be configured to prevent cases where the pressure in the pressure chamber 110 does not return to atmospheric pressure during the process of sucking oil into the pressure chamber 110 while the oil pressure piston 120 is being reset. For example, a shut-off hole 111 is formed in the pressure chamber 110, and a communication path 101 connecting the shut-off hole 111 and the oil path 103 is formed between the pressure chamber 110 and the oil path 103. Here, the shut-off hole 111 is formed at a position corresponding to the initial position of the oil pressure piston 120. Thus, when the oil pressure piston 120 is reset, the oil pressure piston 120 is automatically connected to the reservoir 30 through the communication path 101, and thus the pressure of the pressure chamber 110 returns to the atmospheric pressure.

[0044] The oil pressure control unit 200 is formed with the first oil pressure circuit 201 and the second oil pressure circuit 202, which receive hydraulic pressure to control two wheels, respectively. As shown in the drawing, the wheel controlled by the first oil pressure circuit 201 may be formed with a right front wheel FR and a left rear wheel RL, and the wheel controlled by the second oil pressure circuit 202 may be formed with a left front wheel FL and a right rear wheel RR. The wheel cylinder 40 is installed in each of the wheels FR, FL, RR, and RL and receives hydraulic pressure to perform braking. That is, the oil pressure control unit 200 receives the hydraulic pressure from the hydraulic pressure supply unit 100 through the oil pressure main path 210 connected to the first and second oil pressure circuits 201 and 202, and each of the oil pressure circuits 201 and 202 includes a plurality of valves 221, 222, 223, 224, 241, and 242 to control a flow of the hydraulic pressure.

[0045] The first oil pressure circuit 201 includes first and second inlet valves 221 and 222 connected to the oil pressure main path 210 for controlling the hydraulic pressure transmitted to the wheel cylinders 40, a first unloader valve 231 connected to each of the two wheel cylinders 40 included in the first oil pressure circuit 201 to control a flow of oil discharged from the wheel cylinder 40, and a first balance valve 241 connecting or disconnecting two wheel cylinders 40 connected to the first inlet valve 221 and the second inlet valve 222, respectively. More specifically, the first inlet valve 221 is arranged in the first oil pressure path 211 connecting the oil pressure main path 210 and the right front wheel FR, and the second inlet valve 222 is arranged in the second oil pressure path 212 connecting the oil pressure main path 210 and the left rear wheel RL.The first relief valve 231 is connected to the first oil pressure path 211 to control the hydraulic pressure output from the wheel cylinder 40 of the right front wheel FR. The first balance valve 241 is arranged in a path connecting the first oil pressure path 211 and the second oil pressure path 212, and serves to connect or disconnect the first and second oil pressure paths 211 and 212 according to an opening or closing operation thereof.

[0046] The second oil pressure circuit 201 includes third and fourth inlet valves 223 and 224 connected to the oil pressure main path 210 to control hydraulic pressure transmitted to the wheel cylinders 40, a second unloading valve 232 connected to each of the two wheel cylinders 40 included in the second oil pressure circuit 202 to control a flow of oil discharged from the wheel cylinder 40, and a second balance valve 242 connecting or disconnecting two wheel cylinders 40 connected to the third inlet valve 223 and the fourth inlet valve 224, respectively. More specifically, the third inlet valve 223 is arranged in the third oil pressure path 213 connecting the oil pressure main path 210 and the right rear wheel RR, and the fourth inlet valve 224 is arranged in the fourth oil pressure path 214 connecting the oil pressure main path 210 and the left front wheel FL.The second relief valve 231 is connected to the fourth oil pressure path 214 to control the hydraulic pressure output from the wheel cylinder 40 of the left front wheel FL. The second balance valve 242 is arranged in a path connecting the third oil pressure path 213 and the fourth oil pressure path 214, and serves to connect or disconnect the third and fourth oil pressure paths 213 and 214 according to an opening or closing operation thereof.

[0047] The opening and closing operations of the first to fourth inlet valves 221, 222, 223, and 224 are independently controlled by the ECU, and they are performed to transmit the hydraulic pressure generated by the hydraulic pressure supply unit 100 to the wheel cylinders 40. That is, the first and second inlet valves 221 and 222 are configured to control the hydraulic pressure supplied to the first oil pressure circuit 201, and the third and fourth inlet valves 223 and 224 are configured to control the hydraulic pressure supplied to the second oil pressure circuit 202.

[0048] According to an embodiment of the present invention, the hydraulic pressure can be transmitted to each wheel cylinder 40 of the wheels FR, FL, RR and RL by opening two inlet valves of the four inlet valves 221, 222, 223 and 224. For example, as shown in Fig. 2, the hydraulic pressure can be transmitted to each wheel cylinder 40 of the wheels FR, FL, RR, and RL by opening the first inlet valve 221 of the first and second inlet valves 221 and 222 and opening the fourth inlet valve 224 of the third and fourth inlet valves 223 and 224. That is, the hydraulic pressure passing through the first and fourth inlet valves 221 and 224 is transmitted to adjacent wheel cylinders 40 through the first and second balance valves 241 and 242. Here, although the hydraulic pressure is transmitted to each wheel cylinder 40 by opening the inlet valves 221 and 224 in the first oil pressure circuit 201 and the second oil pressure circuit 202, respectively, the present invention is not limited to this, and the hydraulic pressure may be transmitted to each wheel cylinder 40 by opening two inlet valves 221 and 222 arranged in the first oil pressure circuit 201 according to the structure of the communication paths.If there is a need for emergency braking, the hydraulic pressure can also be quickly transmitted to each wheel cylinder 40 by opening all of the inlet valves 221, 222, 223 and 224.

[0049] The first to fourth intake valves 221, 222, 223, and 224 are provided with normally closed-type solenoid valves that are operated to open a valve when an opening signal is received in a normal state in which the valve is closed. Furthermore, the first and second balance valves 241 and 242 are provided with normally open-type solenoid valves that are operated to close a valve when a closing signal is received from the ECU in a normal state in which the valve is open.

[0050] The first and second unloading valves 231 and 232 are provided with normally closed solenoid valves that are operated to open the valve when an opening signal is received in a normal state in which the valve is closed. The first and second unloading valves 231 and 232 are opened or closed to control a flow of hydraulic pressure when the hydraulic pressure of a corresponding wheel cylinder is output. The operations of the first and second unloading valves 231 and 232 will be described below.

[0051] According to one aspect of the present invention, when the electronic brake system malfunctions, the first and second backup paths 251 and 252 are provided to supply oil pressure generated by the master cylinder 20 directly to each wheel cylinder 40. Specifically, the first shutoff valve 261 is disposed in the first backup path 251 to control the flow of oil, and the second shutoff valve 262 is disposed in the second backup path 252 to control the flow of oil. Furthermore, the first backup path 251 connects the first oil pressure port 24a and the first oil pressure circuit 201, and the second backup path 252 connects the second oil pressure port 25b and the second oil pressure circuit 202.As shown in the drawing, the first backup path 251 is connected to the first relief valve 241, which is connected to the first oil pressure path 211 and the second oil pressure path 212, and the second backup path 252 is connected to the second relief valve 242, which is connected to the third oil pressure path 213 and the fourth oil pressure path 214. The actuation configurations of the first and second shut-off valves 261 and 262 will be described below.

[0052] The first and second shut-off valves 261 and 262 are provided with normally open type solenoid valves which are operated to close the valve when a close signal is received from the ECU in a normal state in which the valve is open.

[0053] A reference symbol “PS1”, which is not described, refers to a first pressure sensor that detects a hydraulic pressure of the wheel cylinder 40, and a reference symbol “PS2”, which is not described, refers to a second pressure sensor that measures an oil pressure of the master cylinder 20.

[0054] The operation of the electronic braking system according to an embodiment of the present invention will be described in detail below.

[0055] Fig. 2 is a diagram of an oil pressure circuit when a brake of an electronic brake system operates normally.

[0056] According to Fig. 2, when a driver starts braking, a braking intensity requested by the driver can be detected using pressure information and the like via the pedal displacement sensor 11, which responds to the brake pedal 10 depressed by the driver. The ECU (not shown) drives the motor 140 by receiving an electrical signal output from the pedal displacement sensor 11. Furthermore, the ECU can detect the amount of regenerative braking via a second pressure sensor PS2 arranged at an outlet of the master cylinder 20 and a first pressure sensor PS1 arranged on the oil pressure main path 210, and calculate the amount of friction braking according to a difference between the amount of braking requested by the driver and the amount of regenerative braking, and thus determine the amount of increase or decrease in the pressure of the wheels.

[0057] Specifically, when a driver steps on the brake pedal 10 in an initial stage of braking, the motor 140 is actuated, the rotational energy of the motor 140 is converted into rectilinear motion by the energy converter 130 to move the oil pressure piston 120 forward, and hydraulic pressure is generated by applying pressure to the pressure chamber 110. Here, the first and second shutoff valves 261 and 262 installed in the first and second backup paths 251 and 252, respectively connected to the first and second oil pressure ports 24a and 24b of the master cylinder 20, are closed, so that oil pressure generated by the master cylinder 20 is not transmitted to each wheel cylinder 40.

[0058] Furthermore, the hydraulic pressure generated by the pressure chamber 110 is transmitted to the wheel cylinders 40 of the right front wheel FR and the left front wheel FL by opening the first and fourth inlet valves 221 and 224 to generate braking force. At this point, the hydraulic pressure flowing through the first and fourth inlet valves 221 and 224 is transmitted to the wheel cylinders 40 of the left rear wheel RL and the right rear wheel RR through the first and second balance valves 241 and 242, which are opened. That is, the hydraulic pressure is supplied to all the wheel cylinders 40 by the opening operations of the two inlet valves 221 and 224 selected from the four inlet valves 221, 222, 223, and 224.

[0059] Such an actuation is an actuation in a typical braking situation, and if the need for emergency braking arises, the hydraulic pressure can also be quickly transmitted to the wheel cylinders 40 by opening all of the inlet valves 221, 222, 223 and 224.

[0060] The pressure generated by a pedal operation of the brake pedal 10 acting on the master cylinder 20 is transmitted to the simulation device 50 connected to the master cylinder 20. Here, the normally closed type simulation valve 54 located at a rear end of the simulation chamber 51 is opened, and oil filled in the simulation chamber 51 is transferred to the reservoir 30 through the simulation valve 54. Further, the reaction piston 52 is moved, and a pressure corresponding to the weight of the reaction spring 53 supporting the reaction piston 52 is formed in the simulation chamber 51, thus providing appropriate pedal sensitivity to a driver.

[0061] Next, the case of brake release when the electronic brake system is operating normally will be discussed with reference to Fig. 3. As described in Fig. As shown in Fig. 3, when a pedal operation of the brake pedal 10 is released, rotational energy is generated in a direction opposite to a forward direction in which the motor 140 moves the oil pressure piston 120, and the oil pressure piston 120 returns to its original position. Here, the first to fourth intake valves 221, 222, 223, and 224, the first and second unloading valves 231 and 232, and the first and second compensating valves 241 and 242 are controlled by the same opening and closing operations during braking. That is, the first and second unloading valves 231 and 232 and the second and third intake valves 222 and 223 are in a closed state, and the first and fourth intake valves 221 and 224 are open.Accordingly, the hydraulic pressure output from the wheel cylinders 40 of the first oil pressure circuit 201 is transmitted into the pressure chamber 110 through the first balance valve 241 and the first inlet valve 221, and the hydraulic pressure output from the wheel cylinders 40 of the second oil pressure circuit 210 is transmitted into the pressure chamber 110 through the second balance valve 242 and the fourth inlet valve 224.

[0062] In the simulation device 50, the oil within the simulation chamber 51 is transferred to the master cylinder 20 by the reaction piston 52 returning to its original position by the reaction spring 53, and oil is refilled into the simulation chamber 51 through the simulation valve 54 and the simulation shut-off valve 55 connected to the reservoir 30, thereby ensuring that the pressure of the pedal simulator is quickly restored.

[0063] When the oil pressure piston 120 moves due to the hydraulic pressure supply unit 100 of the above-described electronic brake system, a flow of oil within the pressure chamber 110 is controlled through the oil path 103 and the communication path 101 connected to the reservoir 30.

[0064] The electronic brake system according to an embodiment of the present invention can specifically control a control range by controlling the valves 221, 222, 223, 224, 241, and 242 provided in the oil pressure control unit 200 according to the pressure required by the wheel cylinder 40 provided at the wheels RR, RL, FR, and FL of the two oil pressure circuits 201 and 202, respectively. For example, Fig. 4 shows the case where braking is performed on only the corresponding wheel cylinder while an anti-lock braking system (ABS) is operating, and illustrates the braking of only one front wheel.

[0065] According to Fig. 4, the motor 140 is driven according to a pedal operation of the brake pedal 10. The rotational energy of the motor 140 is converted into rectilinear motion, and thus hydraulic pressure is generated by moving the pressure piston 120 forward and applying pressure to the pressure chamber 110. Here, the first and second cutoff valves 261 and 262 are closed, and the oil pressure generated by the master cylinder 20 is not transmitted to the wheel cylinder 40. Furthermore, the second and third inlet valves 222 and 223, the first and second discharge valves 231 and 232, and the first and second relief valves 241 and 242 are controlled in a closed state. Thus, the hydraulic pressure generated by the pressure chamber 110 is transmitted to the wheel cylinder 40 of the right wheel FR through the first inlet valve 221, and is transmitted to the wheel cylinder 40 of the left front wheel FL through the fourth inlet valve 224.Accordingly, the hydraulic pressure is transmitted only to the front wheels FL and FR of the wheels RL, RR, FL and FR.

[0066] According to one aspect of the present invention, since the operations of the first to fourth intake valves 221, 222, 223, and 224, the first and second discharge valves 231 and 232, and the first and second balance valves 241 and 242 are independently controlled as described above, the hydraulic pressure can be transmitted to only the right wheels RR and RL, or the hydraulic pressure can be transmitted to the wheel cylinders 40 of the left front and left rear wheels FL and RL, the right front and left rear wheels FR and RL, or any that require the oil pressure.

[0067] Furthermore, in the electronic brake system according to the embodiment of the present invention, the brake pressure supplied to the wheel cylinder 40 can be output only by the corresponding wheel cylinder 40. For example, Fig. 5 shows a case where the electronic brake system operates in a discharge mode to output only the hydraulic pressure of the corresponding wheel cylinder 40, and illustrates the discharge for only the rear wheels RR and RL.

[0068] According to Fig. 5, the motor 140 operates in accordance with a pedal operation of the brake pedal 10. The rotational energy of the motor 140 is converted into a rectilinear motion, and thus, hydraulic pressure is sucked into the pressure chamber 110 by moving the oil pressure piston 120 in the reverse direction. Here, the first and fourth intake valves 221 and 224, the first and second discharge valves 231 and 232, and the first and second relief valves 241 and 242 are controlled in a closed state. Thus, the hydraulic pressure transmitted to the wheel cylinder 40 of the right rear wheel RR and the wheel cylinder 40 of the left rear wheel RL is sucked into the pressure chamber 110 through the second and third oil pressure paths 212 and 213 and the oil pressure main path 210. Accordingly, the hydraulic pressure is discharged to only the rear wheels RR and RL among the wheels RL, RR, FL and FR, and is transmitted to the pressure chamber 110.

[0069] As described above, since the discharge valves 231 and 232 are connected to the front wheels FL and FR, the pressure piston 120 of the hydraulic pressure supply unit moves backward to discharge the hydraulic pressure to the wheel cylinders of the rear wheels RL and RR. That is, the hydraulic pressure output from the wheel cylinder 40 of each of the front wheels FL and FR can be output to the reservoir 30 through each of the discharge valves 231 and 232. For example, Fig. 6 shows a state in which the electronic brake system is operated in a discharge mode, and the hydraulic pressure is discharged to only the corresponding wheel cylinders 40, that is, the front wheels FL and FR. As shown in the drawing, the first to fourth inlet valves 221, 222, 223, and 224, and the first and second balance valves 241 and 242 are controlled in a closed state, and the first and second discharge valves 231 and 232 are opened. Thus, the hydraulic pressure output from the wheel cylinders 40 installed on the right front wheel FR and the left front wheel FL is transmitted to the reservoir 30 through the first and second discharge valves 231 and 232.

[0070] According to one aspect of the present invention, when the first and second discharge valves 231 and 232 are connected to the rear wheels RL and RR, the hydraulic pressure of the wheel cylinders 40 installed on the rear wheels RR and RL is controlled, and the hydraulic pressure of the wheel cylinders 40 installed on the front wheels FL and FR is controlled using a reverse movement of the hydraulic pressure supply unit 100. That is, the installation positions of the first and second discharge valves 231 and 232 can be selectively changed, and in addition, the hydraulic pressure of required and corresponding wheel cylinders 40 can be discharged.

[0071] Finally, the case of abnormal operation of the electronic braking system is described. According to Fig.6, when the electronic brake system is operating abnormally, each of the valves 54, 221, 222, 223, 224, 241, 242, 261, and 262 is in an initial non-braking state. Thus, when a driver presses the brake pedal 10, the input rod 12 connected to the brake pedal 10 moves to the left, and the first piston 21a, which is in contact with the input rod 12, is simultaneously moved to the left. Furthermore, the second piston 22a is also moved to the left by the first piston 21a. Therefore, since there is no gap between the input rod 12 and the first piston 21a, braking can be performed quickly. That is, the hydraulic pressure generated by pressing the master cylinder 20 is transmitted to the wheel cylinders 40 through the first and second backup paths 251 and 252 connected for braking in a backup mode to generate a braking force.Here, the first and second cutoff valves 261 and 262 installed in the first and second backup paths 251 and 252, and the first and second balance valves 241 and 242 connected to the first and second backup paths 251 and 252 are formed with normally open type solenoid valves, and the simulation valve 54 and the first to fourth inlet valves 221, 222, 223, and 224 are formed with normally closed type solenoid valves, and thus the hydraulic pressure is immediately transmitted to the wheel cylinders 40. Therefore, stable braking can be achieved, and braking stability can be improved.

[0072] As is apparent from the above description, the electronic brake system according to the embodiments of the present invention can have the following effects.

[0073] First, the electronic braking system has the advantage of structural simplification over conventional structures by minimizing the number of valves for controlling oil pressure flow. Therefore, the size of the braking system, i.e., the size of a modulator block in which the valves are installed, can be reduced, enabling the realization of the electronic braking system as a low-cost product.

[0074] Secondly, since pressure is applied to all wheel cylinders using only two intake valves among the four intake valves for controlling a flow of hydraulic pressure transmitted to each wheel cylinder, the operating noise and vibration of the valves can be minimized.

[0075] Third, since a motor and valves are controlled by interconnected systems, the electronic brake system can precisely control the pressure. Additionally, the electronic brake system is configured with two oil pressure circuits, each connected to each of two independently controlled wheels, and connected to a hydraulic pressure supply unit, which controls the pressure according to the pressure required by each wheel and a determination by priority determination logic, thereby improving controllability.

[0076] Fourth, when the braking system fails, a pedal operation by a driver is directly transmitted to the master cylinder, so that braking of the vehicle is still possible, and thus a stable braking force can be obtained.

Claims

[1] An electronic brake system comprising a reservoir (30) in which oil is stored, a master cylinder (20) having a first oil pressure port (24a) and a second oil pressure port (24b) coupled to the reservoir (30) to receive the oil, a pedal displacement sensor (11) configured to detect a displacement of a brake pedal (10), and a simulation device (50) connected to the master cylinder (20) and arranged to obtain a response in accordance with a pedal operation of the brake pedal (10), which electronic brake system comprises: a hydraulic pressure supply unit (100) configured to output an electrical signal through the pedal displacement sensor (11) to actuate a motor (140) when the brake pedal (10) is actuated, and configured to convert rotational energy of the motor (140) into rectilinear motion; an oil pressure control unit (200) having a first oil pressure circuit (201) and a second oil pressure circuit (202) connected to the hydraulic pressure supply unit (100) through an oil pressure main path (210), each configured to control two wheels such that a hydraulic pressure is received using a force generated by the hydraulic pressure supply unit (100) to perform braking; and an electronic control unit configured to control the motor (140) and valves based on hydraulic pressure information and pedal displacement information, wherein the oil pressure control unit (200) contains: a first inlet valve (221) and a second inlet valve (222), each arranged upstream of two wheel cylinders (40) for controlling the two wheels arranged in the first oil pressure circuit (201); a third inlet valve (223) and a fourth inlet valve (224), each arranged upstream of two wheel cylinders (40) for controlling the two wheels arranged in the second oil pressure circuit (202); a first balance valve (241) configured to connect or disconnect the two wheel cylinders (40) to which the first intake valve (221) and the second intake valve (222) are connected; a second balance valve (242) configured to connect or disconnect the two wheel cylinders (40) to which the third intake valve (223) and the fourth intake valve (224) are connected; a first discharge valve (231) connected to one wheel cylinder (40) among the two wheel cylinders (40) provided in the first oil pressure circuit (201), and configured to control a flow of oil discharged from the connected wheel cylinder (40); and a second discharge valve (232) connected to one wheel cylinder (40) among the two wheel cylinders (40) included in the second oil pressure circuit (202), and configured to control a flow of oil discharged from the connected wheel cylinder (40). [2] An electronic brake system according to claim 1, wherein the hydraulic pressure output from the wheel cylinder (40) connected to the first unloading valve (231) and the second unloading valve (232) is controlled by opening and closing operations of the first unloading valve (231) and the second unloading valve (232), and the hydraulic pressure output from the wheel cylinder (40) not connected to the first unloading valve (231) and the second unloading valve (232) is controlled by rotation in a direction opposite to a rotation direction of the motor (140) of the hydraulic pressure supply unit (100) during braking. [3] The electronic brake system according to claim 2, wherein the first balance valve (241) and the second balance valve (242) are closed when the first unloading valve (231) and the second unloading valve (232) are opened and the hydraulic pressure is output from the wheel cylinder (40) connected to the first unloading valve (231) and the second unloading valve (232), and the first balance valve (241) and the second balance valve (242) are closed when the motor (140) of the hydraulic pressure supply unit rotates in the reverse direction and the hydraulic pressure is output from the wheel cylinder (40) not connected to the first unloading valve (231) and the second unloading valve (232). [4] An electronic brake system according to claim 1, wherein said first unloading valve (231) and said second unloading valve (232) are provided with normally closed type solenoid valves which are operated to open the valve when an opening signal is received in a normal state in which the valve is closed. [5] An electronic braking system according to claim 1, wherein one of the inlet valves (221,222) of the first and second inlet valves is opened, one of the inlet valves (223,224) of the third and fourth inlet valves is opened, and the hydraulic pressure is transmitted to the wheel cylinder (40) of each wheel. [6] An electronic brake system according to claim 1, wherein the inlet valves (221,222,223,224) are provided with normally closed type solenoid valves which are operated to open the valve when an opening signal is received in a normal state in which the valve is closed. [7] An electronic brake system according to claim 1, wherein said first and second compensating valves (241,242) are provided with normally open type solenoid valves which are operated to close the valve when a closing signal is received from said electronic control unit in a normal state in which the valve is open. [8] An electronic braking system according to claim 1, further comprising: a first backup path (251) configured to connect the first oil pressure port (24a) and the first compensation valve (241) so that oil is directly supplied to the wheel cylinders (40) when the electronic brake system operates abnormally; a second backup path (252) configured to connect the second oil pressure port (24b) and the second compensation valve (242); a first shut-off valve (261) arranged in the first backup path (251) and configured to control a flow of the oil; and a second shut-off valve (262) disposed in the second backup path (252) and configured to control a flow of the oil. [9] An electronic brake system according to claim 8, wherein said first and second cut-off valves (261,262) are provided with normally open type solenoid valves which are operated to close the valve when a closing signal is received from said electronic control unit in a normal state in which the valve is open. [10] An electronic brake system according to claim 1, wherein the hydraulic pressure supply unit (100) includes: a motor (140) configured to generate rotational energy by the electrical signal of the pedal displacement sensor (11); an energy converter (130) configured to convert the rotary motion of the motor (140) into a linear motion; an oil pressure piston (120) connected to the energy converter (130) and configured to perform a rectilinear movement; a pressure chamber (110) provided with the slidable oil pressure piston (120) and connected to the first and second oil pressure circuits (201, 202) through the oil pressure main path (210); and an oil pressure spring (122) arranged in the pressure chamber (110) and configured to elastically support the oil pressure piston (120), wherein the pressure chamber (110) is connected to the container (30) by an oil path to receive the oil. [11] An electronic brake system according to claim 10, wherein a check valve (102) is installed in the oil path to prevent a flow of a pressure of the pressure chamber (110) in the reverse direction and to suck and store the oil in the pressure chamber (110) when the oil pressure piston (120) is returned.

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