Electric braking system for vehicles

Abstract

An electric braking system for a vehicle is disclosed, comprising a reservoir (30), a master cylinder (20), an input rod (12), and a pedal displacement sensor (11). The electric braking system includes a pressure supply unit (110) for receiving oil and outputting an electrical signal through the pedal displacement sensor, a hydraulic control unit for braking a wheel, a first and a second switching valve (131, 132) connected by a channel connecting the pressure supply unit to the hydraulic control unit, a simulator (150) connected to the master cylinder, and an electronic control unit for controlling the motor (114) and the valves.The pressure supply unit comprises a pressure chamber (111), a hydraulic piston (112) arranged in the pressure chamber, a hydraulic spring (113) for elastically supporting the hydraulic piston, the motor for generating a rotary force, and a ball screw component (115) for converting the rotary motion of the motor into a linear motion. The hydraulic piston is connected to the screw (115a).

Description

BACKGROUND 1. Area

[0001] Exemplary embodiments of the present invention relate to an electric braking system that has a simplified structure and enables precise pressure control. 2. Description of the state of the art

[0002] A braking system for slowing a vehicle is essentially attached to the vehicle, and various systems have been proposed in recent times to achieve stronger and more consistent braking force. Examples of braking systems include an anti-lock braking system (ABS), a brake traction control system (BTCS), and a dynamic vehicle control system (VDC). ABS prevents wheels from slipping during braking. BTCS prevents drive wheels from slipping during rapid acceleration from a standstill or during sudden acceleration of a vehicle. VDC maintains a stable driving condition by controlling brake fluid pressure through a combination of ABS and BTCS.

[0003] Such a braking system contains several solenoid valves for controlling brake fluid pressure, which is transmitted to a wheel cylinder attached to a vehicle wheel (a hydraulic brake), a low-pressure accumulator and a high-pressure accumulator pair for temporarily storing oil flowing from the wheel cylinder, a motor and pump for forcibly pumping the oil into the low-pressure accumulator, several shut-off valves to prevent backflow of oil, and an electronic control unit (ECU) for controlling the actuation of the solenoid valves and the motor. These components are compactly installed in a hydraulic block made of aluminum.

[0004] The structure of such a braking system is disclosed in Korean patent KR 10 1 090 910 B1. According to this document, the braking system drives the motor and the pump to fill the high-pressure accumulator and / or the low-pressure accumulator with hydraulic pressure, and controls the increase, decrease, and maintenance of the hydraulic pressure by opening and closing the electric solenoid valves. Accordingly, the structure of the braking system is complex.

[0005] Additionally, there is a predetermined gap between an input rod, which exerts pressure on a master cylinder according to the foot force applied to the brake pedal, and the master cylinder itself. Consequently, when a driver activates the braking system, a lost portion of the pedal travel is generated. This can cause the driver to feel that the brakes are not functioning properly, leading to dissatisfaction with the braking performance and potentially even resulting in an accident. Furthermore, the pedal feel may be impaired.

[0006] An electric braking system according to the preamble of the main claim is described in publication DE 10 2011 089 869 A1. SUMMARY

[0007] It is therefore an object of the present invention to provide an electric braking system for a vehicle which has a simplified configuration, provides a stable pedal feel during braking and enables precise pressure control.

[0008] Another object of the present invention is to provide an electric braking system for a vehicle that enables braking by the foot force of a driver even when the braking system is operating anomalously, and allows for the immediate generation of pressure according to the foot force exerted on the brake pedal without any lost movement phase.

[0009] Additional aspects of the invention are partly described below and partly become apparent from the description, or can be discovered by carrying out the invention.

[0010] To solve the aforementioned problems, an electric braking system according to the main claim is proposed according to the invention. Accordingly, an electric braking system for a vehicle comprises a reservoir for storing oil, a master cylinder equipped with two hydraulic circuits and configured to generate hydraulic pressure using the oil stored in the reservoir, an input rod arranged to contact the master cylinder for forward movement in accordance with the foot force of a driver, and a pedal displacement sensor for detecting a displacement of a brake pedal connected to the input rod. The electric braking system further comprises: a pressure supply unit connected to the reservoir and a hydraulic channel for receiving oil and outputting an electrical signal through the pedal displacement sensor for actuating a motor when the driver depresses the brake pedal, such that...that a rotational force of the motor is converted into a linear motion, a hydraulic control unit for performing the braking of a wheel with hydraulic pressure supplied according to the force generated by the pressure supply unit, a first and a second switching valve connected in series with a channel connecting the pressure supply unit to the hydraulic control unit to control the transmission of hydraulic pressure to a wheel cylinder by opening and closing operations, a simulator connected to the master cylinder to provide a reaction force according to the foot force exerted on the brake pedal, and an electronic control unit for controlling the motor and the valves based on information about the pressure and pedal displacement, wherein the pressure supply unit comprises a pressure chamber connected to the hydraulic channel for receiving oil supplied to it, a hydraulic piston arranged in the pressure chamber,The device includes a hydraulic spring arranged in the pressure chamber for elastically supporting the hydraulic piston, a motor for generating a rotational force according to the electrical signal from the pedal displacement sensor, and a ball screw part designed with a screw and a bolt to convert a rotary motion of the motor into a linear motion, wherein the hydraulic piston is connected to the screw, which is designed for linear movement such that the oil in the pressure chamber is pressurized by the screw.

[0011] According to the invention, the first and second switching valves are installed and connected in series in the channel connecting the pressure supply unit to the hydraulic control unit in order to control the transmission of the hydraulic pressure generated by the pressure supply unit to the hydraulic control unit by means of opening and closing operations, wherein the first switching valve controls the hydraulic pressure supplied to the first circuit of the hydraulic control unit, and the second switching valve controls the hydraulic pressure supplied to the second circuit of the hydraulic control unit.

[0012] A shut-off valve can be installed in the hydraulic channel to prevent backflow of pressure from the pressure chamber and to allow the oil to be drawn into and stored in the pressure chamber when the hydraulic piston is retracted.

[0013] A pressure sensor for detecting pressure can be arranged in a channel connected to the pressure chamber and the main cylinder.

[0014] The hydraulic control unit may include: a normally open solenoid valve located upstream of the wheel cylinder to control the transmission of hydraulic pressure to the wheel cylinder, a normally closed solenoid valve located downstream of the wheel cylinder to control the release of hydraulic pressure from the wheel cylinder, and a return channel to connect the normally closed solenoid valve to the hydraulic channel.

[0015] According to the invention, the hydraulic control unit is provided with two wheel brake circuits, comprising a first circuit which is provided with at least one first wheel to receive the hydraulic pressure supplied to it for carrying out the braking, and a second circuit which is provided with at least one second wheel.

[0016] The electric braking system may include: a first and a second safety channel for connecting two hydraulic circuits of the master cylinder to the wheel cylinder to control the oil if the electric braking system malfunctions, a first starting valve for controlling the connection between the first safety channel and the master cylinder, and a second starting valve for controlling the connection between the second safety channel and the master cylinder.

[0017] The first and second starting valves can be normally open solenoid valves that remain open in a normal state and close upon receiving a signal for a closing operation from the electronic control unit.

[0018] The simulator may include: a simulation chamber for storing the oil dispensed by the main cylinder, a reaction piston located in the simulation chamber, a reaction spring for elastically supporting the reaction piston, and a simulation valve located at an inlet of the simulation chamber.

[0019] The simulation valve can be a normally closed solenoid valve that remains closed in a normal state and is opened upon receiving a signal for an opening process from the electronic control unit.

[0020] The first switching valve can be a normally open solenoid valve, and the second switching valve can be a normally closed solenoid valve that remains closed in a normal state and is opened upon receiving a signal for an opening operation from the electronic control unit.

[0021] The first and second switching valves can be normally closed solenoid valves that remain closed in a normal state and are opened upon receiving a signal for an opening operation from the electronic control unit.

[0022] The electric braking system may further include a compliance unit arranged in the channel connected to the first switching valve and the second switching valve to store a predetermined quantity of oil by changing its volume according to the hydraulic pressure.

[0023] The compliance unit may include: a compliance chamber provided with a predetermined volume, a piston and an elastic part arranged in the compliance chamber, and a compliance valve arranged at an inlet of the compliance chamber.

[0024] The compliance valve can be a normally closed solenoid valve that remains closed in a normal state and opens upon receiving a signal for an opening operation from the electronic control unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] These and / or other aspects of the invention will become apparent and easier to understand with reference to the following description of the exemplary embodiments, which is given in conjunction with the accompanying drawings, of which: Fig. 1 is a view showing hydraulic circuits of an electric braking system for a vehicle according to an embodiment of the present invention, which is not in operation; Fig. 2 is a hydraulic circuit diagram illustrating an electric braking system for a vehicle according to an embodiment of the present invention, which is in normal operation; and Fig. 3 is a hydraulic circuit diagram illustrating an electric braking system for a vehicle according to another embodiment of the present invention. DETAILED DESCRIPTION

[0026] Reference will now be made in detail to the embodiments of the present invention, which are illustrated in the accompanying drawings. The terms used in the description and the appended claims should not be interpreted as being limited to general and dictionary meanings, but should be interpreted on the basis of the meanings and concepts in accordance with the spirit of the present invention, based on the principle that the inventor is permitted to define suitable terms for the best explanation. The preferred embodiments described in the description and shown in the drawings are purely illustrative and are not intended to represent all aspects of the invention. Therefore, it should be noted that various equivalents and modifications may be made without departing from the spirit of the invention at the time of filing this application.

[0027] Fig. Figure 1 is a view showing a hydraulic circuit of an electric braking system for a vehicle according to an embodiment of the present invention, which is not in operation.

[0028] According to Fig. 1 comprises an electric braking system for a vehicle, generally comprising a master cylinder 20 for generating hydraulic pressure, a reservoir 30 coupled to the upper part of the master cylinder 20 for storing oil, an input rod 12 for applying pressure to the master cylinder 20 in accordance with a foot force applied to a brake pedal 10, wheel cylinders 40 for performing the braking of the respective wheels RR, RL, FR and FL when the oil in the reservoir 30 is transferred to them, and a pedal displacement sensor 11 for detecting a displacement of the brake pedal 10.

[0029] Here, the main cylinder 20 can be equipped with at least one chamber to generate hydraulic pressure. According to Fig. The master cylinder 20 is equipped with a first cylinder 20a and a second cylinder 22a to form two hydraulic circuits and is in contact with the input rod 12. Providing the master cylinder 20 with two hydraulic circuits is intended to ensure safety in the event of a malfunction. For example, the first of the two hydraulic circuits is connected to the front right wheel FR and the rear left wheel RL of the vehicle, and the other hydraulic circuit is connected to the front left wheel FL and the rear right wheel RR. Typically, the first of the two hydraulic circuits is connected to the two front wheels FR and FL, and the other hydraulic circuit is connected to the two rear wheels RR and RL. By designing the two circuits to be independent of each other, it remains possible to brake the vehicle even if one of the hydraulic circuits fails.

[0030] The first cylinder 21a and the second cylinder 22a of the master cylinder 20, configured as above, are equipped with a first spring 21b and a second spring 22b, respectively. The first spring 21b and the second spring 22b store an elastic force when the first cylinder 21a and the second cylinder 22a are compressed. When the force pushing the first cylinder 21a becomes weaker than the elastic force, the elastic force pushes the first and second pistons 21a and 22a back to their initial positions.

[0031] The input rod 12 for exerting pressure on the first cylinder 21a of the master cylinder 20 is in close contact with the first cylinder 21a. This means there is no gap between the master cylinder 20 and the input rod 12. Therefore, when the brake pedal 10 is pressed, the master cylinder 20 is directly pressed with the lost movement portion.

[0032] The electric braking system for a vehicle according to an embodiment of the present invention comprises a pressure supply unit 110 for actuation by receiving an intention of the driver to perform braking, in the form of an electrical signal from the pedal sensing sensor 11, which detects the displacement of the brake pedal 10; a hydraulic pressure control unit 120 for performing braking of the wheels using the force generated by the pressure supply unit 110; a first and a second switching valve 131 and 132, which are connected in series in a channel that connects the pressure supply unit 110 to the hydraulic pressure control unit 120; and a simulator 150, which is connected to the master cylinder 20 to provide a reaction force to the brake pedal 10.

[0033] The pressure supply unit 10 includes a pressure chamber 111 with a predetermined space for storing the oil supplied to it, a hydraulic piston 112 and a hydraulic spring 113 arranged in the pressure chamber 111, a motor 114 for generating a rotary force according to an electrical signal from the pedal displacement sensor 11, a ball screw part 115 equipped with a screw 115a and a ball nut 115b to convert the rotary motion of the motor 114 into a linear motion, and a hydraulic channel 116 to connect the reservoir 20 to the pressure chamber 111, thus enabling the oil to be supplied to the pressure chamber 111. Here, a signal detected by the pedal displacement sensor 11 is transmitted to an electronic control unit (ECU) (not shown). The ECU controls the motor 114 and the valves provided in the braking system according to the present invention, as will be described later.The control of several valves according to the displacement of the brake pedal 10 is described below.

[0034] As discussed above, the pressure chamber 111 is connected to the reservoir 30 via the hydraulic channel 116 to store the oil supplied to it. The pressure chamber 111 is equipped with the hydraulic piston 112 and the hydraulic spring 113 for elastically supporting the hydraulic piston 112. The hydraulic piston 112 is connected to the screw 115a of the ball screw part 115 so that pressure is exerted on the pressure chamber 111 by linear movement of the screw 115a. The hydraulic spring 113 serves to return the hydraulic piston 112 to its initial position.

[0035] Motor 114 is an electric motor that generates a torque based on a signal output by the ECU. The ECU causes motor 114 to generate a torque for forward or reverse rotation. Here, the ball nut 115b of the ball screw part 115, which converts a torque into linear motion, not only functions as a rotation axis for motor 114, but also provides the linear motion for screw 115a. Although this in Fig. As not shown in Figure 1, a spiral groove is formed in the outer circumferential surface of the screw 115a. The ball nut 115b is rotatably coupled by the spiral groove and several balls. That is to say, as disclosed above, the hydraulic piston 112 is pressurized by linear movement of the screw 115a in order to generate hydraulic pressure.

[0036] According to this embodiment, a shut-off valve 117 is installed in the hydraulic channel 116 to prevent backflow of pressure into the pressure chamber 111. The shut-off valve 117 not only serves to prevent backflow of pressure into the pressure chamber 111, but also ensures that oil is drawn into and stored in the pressure chamber 111 when the hydraulic piston 112 is retracted.

[0037] The reference number '118' designates a first pressure sensor for detecting hydraulic pressure in pressure chamber 111.

[0038] The hydraulic pressure control unit 120 is equipped with a first circuit 121 for receiving hydraulic pressure supplied to it for controlling the braking of at least one wheel, and a second circuit 122 for receiving hydraulic pressure supplied to it for controlling the braking of at least one second wheel. Thus, the hydraulic pressure control unit 120 contains two wheel brake circuits. Here, the at least one first wheel can include front wheels FR and FL, while the at least one second wheel can include rear wheels RR and RL. Each of the wheels FR, FL, RR, and RL is equipped with a wheel cylinder 40 to perform braking when hydraulic pressure is supplied to it. That is, each of the circuits 121 and 122 contains a channel connected to the wheel cylinders 40. The channel is equipped with several valves 123 and 124 to control the hydraulic pressure.

[0039] According to Fig. 1. The valves 123 and 124 are divided into a normally open solenoid valve 123 (hereinafter referred to as 'NO type'), which is located upstream of the wheel cylinders 40 to control the transmission of hydraulic pressure to the wheel cylinders, and a normally closed solenoid valve 124 (hereinafter referred to as 'NC type'), which is located downstream of the wheel cylinders 40 to control the release of hydraulic pressure from the wheel cylinders 40. The opening and closing of such solenoid valves 123 and 124 are controlled by the ECU.

[0040] The hydraulic pressure control unit 120 includes a return channel 126 that connects the NC-type solenoid valve 124 to the hydraulic channel 116. The return channel 126 allows the hydraulic pressure transmitted to the wheel cylinders 40 to be discharged through them and transferred to the reservoir 30 or the pressure supply unit 110.

[0041] According to this embodiment, the first and second switching valves 131 and 132, connected in series to perform an opening and closing operation for controlling the transmission of hydraulic pressure to the wheel cylinders 40, are installed in the channel connecting the pressure supply unit 110 to the hydraulic pressure control unit 120. The first and second switching valves 131 and 132 are opened and closed by the ECU and are connected to the two wheel brake circuits, i.e., the first and second circuits 121 and 122, to transmit the hydraulic pressure generated by the pressure supply unit 110 directly to the wheel cylinders 40. That is, the first switching valve 131 controls the hydraulic pressure supplied to the first circuit 121, and the second switching valve 132 controls the hydraulic pressure supplied to the second circuit 122.

[0042] The first and second switching valves 131 and 132 are normally closed (NC) type solenoid valves, which remain closed in their normal state and are actuated to open when they receive a signal to open from the ECU. Although not shown, the first switching valve 131 could be a normally open (NO) type solenoid valve, which remains open in its normal state and closes upon receiving a signal to close. That is, if the first switching valve 131 is an NO valve, its actuation can be simplified, as it opens without the need for electrical energy.

[0043] According to this embodiment, in the event of a malfunction of the electric braking system of a vehicle, a first safety channel 141 and a second safety channel 142 can be arranged between the master cylinder 20 with two hydraulic circuits and the wheel cylinders 40. A first starting valve 143 for opening and closing the first safety channel 141 is provided in the middle of the first safety channel 141, and a second starting valve 144 for opening and closing the second safety channel 142 is provided in the middle of the second safety channel 142. The first safety channel 141 is connected to the first circuit 121 via the first starting valve 143, and the second safety channel 142 is connected to the second circuit 122 via the second starting valve 144. In particular, a second pressure sensor 148 for measuring the oil pressure of the master cylinder 20 can be provided between the first starting valve 143 and the master cylinder 20.When braking is performed by the driver, the safety channels 141 and 142 can be interrupted by the first start valve 143 and the second start valve 144, and the braking intended by the driver can be determined by the pressure sensor 148.

[0044] The first and second starting valves 143 and 144 are NC type solenoid valves that remain open in the normal state and are closed upon receiving a signal for the closing process from the ECU.

[0045] Additionally, a simulator 150, connected to the master cylinder 20 to provide a reaction force corresponding to the foot force applied to the brake pedal 10, is provided. According to the illustrated embodiment, the channel connecting the master cylinder 20 to the simulator 150 is connected to the first safety channel 141. The simulator 150 includes a simulation chamber 151, designed to store oil discharged through the outlet of the master cylinder 20, and a simulation valve 155 located at the inlet of the simulation chamber 151. A reaction piston 152 and a reaction spring 153 for elastically supporting the reaction piston 152 are provided in the simulation chamber 151. The oil introduced into the simulation chamber 151 causes the reaction piston 152 and the reaction spring 153 to move within a specific range.The simulation valve 155 is a normally closed (NC) solenoid valve, which is normally in a closed state. This means that when the driver presses down the brake pedal 10, the simulation valve 155 opens to allow the brake fluid to be transferred to the simulation chamber 151.

[0046] Additionally, a simulation shut-off valve 157 is provided between the simulator 150 and the master cylinder 20, i.e., between the simulation chamber 151 and the simulation valve 155. The simulation shut-off valve 157 is connected to the master cylinder 20. The simulation shut-off valve 157 allows the pressure corresponding to the foot force exerted on the brake pedal 10 to be transmitted to the simulation chamber 151 only via the simulation valve 155.

[0047] The following describes the operation of an electric braking system for a vehicle according to an embodiment of the present invention.

[0048] Fig. Figure 2 is a hydraulic pie chart illustrating an electric braking system for a vehicle in normal operation.

[0049] According to Fig. 2. When the driver initiates braking, the force of the braking desired by the driver can be detected by the pedal displacement sensor 11 based on information about the pressure exerted by the driver on the brake pedal 10. The ECU (not shown) receives an electrical signal output by the pedal displacement sensor 11 and drives the motor 114. Additionally, the ECU can receive the magnitude of the regenerative braking from the second pressure sensor 148, located at the outlet of the master cylinder 20, and the first pressure sensor 118, located at the outlet of the pressure supply unit 110, and calculate the force of friction braking according to the difference between the braking desired by the driver and the regenerative braking. This allows the ECU to detect the magnitude of the increase or decrease in pressure at the wheel.

[0050] Essentially, when the driver presses the brake pedal 10 in the initial stage of braking, the motor 114 is actuated, and the rotary force of the motor 114 is converted into linear motion to exert pressure on the pressure chamber 111. At this time, the pressure chamber 111 is connected to the oil reservoir 30 via the hydraulic channel 116. Due to the linear motion of the ball screw component 115, which converts the rotary motion into linear motion, hydraulic pressure is generated in the pressure chamber 111. Additionally, the first and second starting valves 143 and 144, installed in the first and second safety channels 141 and 142, which are connected to the outlets of the master cylinder 20, are closed, thus preventing the hydraulic pressure generated in the master cylinder 20 from being transmitted to the wheel cylinders 40.This transmits the hydraulic pressure generated in the pressure chamber 111 to the wheel cylinders 40 via the first and second switching valves 131 and 132. The first and second switching valves 131 and 132 are arranged in series to control the hydraulic pressure supplied to each by the first and second circuits 121 and 122. That is, the first and second switching valves 131 and 132 are opened by the ECU.

[0051] The pressure generated by the vacuuming of the master cylinder 20 by the foot force exerted on the brake pedal 10 is transmitted to the simulator 150 connected to the master cylinder 20. At this time, the simulation valve 155 located between the master cylinder 20 and the simulation chamber 151 is open, and hydraulic pressure is supplied to the simulation chamber 151. This moves the reaction piston 152, and a pressure corresponding to the load exerted on the reaction spring 153 supporting the reaction piston 152 is created in the simulation chamber 151, thus providing the driver with proper pedal feel.

[0052] Next, a description of the electric brake, which is not in normal operation, will be given. According to Fig. When the driver applies pressure to the brake pedal 10, the input rod 12 connected to the brake pedal 10 moves forward to the left, and the first cylinder 21a, which is in contact with the input rod 12, also moves forward to the left. At this time, braking can be carried out quickly because there is no gap between the input rod 12 and the first cylinder 21a. That is, the hydraulic pressure generated by vacuuming the master cylinder 20 is transmitted through the first and second safety channels 141 and 142 to the wheel cylinders 40 to generate a braking force for the safety brakes. Here, the first and second starting valves 143 and 144, which are installed in the first and second safety channels 141 and 142, are designed as NO-type solenoid valves, while the simulation valve 155 and the first and second switching valves 131 and 132 are designed as NC-type solenoid valves.Accordingly, hydraulic pressure is transmitted directly to the wheel cylinders 40. This enables stable braking and thus increases braking stability.

[0053] Since such an electric braking system for a vehicle is configured to generate hydraulic pressure by detecting the driver's braking intention according to the foot force applied to the brake pedal 10, controls the motor 114 according to the output of an electrical signal, and converts the rotary motion of the motor 114 into linear motion, precise control of the hydraulic pressure is possible. Additionally, in the event of a braking system failure, the hydraulic brake pressure generated by the driver's foot force is transmitted directly to the wheel cylinders 40 via the safety channels 141 and 142. This improves braking stability. By using such an electric braking system for a vehicle, the braking system can be designed to supply hydraulic pressure to the wheel cylinders 40 by storing a predetermined pressure to ensure more stable braking. For example, [reference to relevant figure] Fig. 3 an electric braking system for a vehicle according to another embodiment of the present invention. In Fig. 3 denotes reference figures that correspond to those in the Fig. 1 and Fig. 2 are identical, parts that have the same functions as those in the Fig. 1 and Fig. 2 shown.

[0054] In this embodiment, the electric braking system further includes a compliance unit 160. According to Fig.3 The compliance unit 160 is located in the channel connecting the first switching valve 131 and the second switching valve 132 to store the hydraulic pressure generated by the pressure supply unit 110. The compliance unit 160 includes a compliance chamber 161, which has a predetermined volume for storing hydraulic pressure, and a piston 162 and an elastic part 163 arranged within the compliance chamber 161. This allows the compliance unit 160 to change the volume of the compliance chamber 161 within a specific range due to the hydraulic pressure introduced into it. A compliance valve 165 is provided at the inlet of the compliance unit 160. The compliance valve is an NC-type solenoid valve that remains closed in a normal state and opens upon receiving a signal from the ECU to initiate the opening process.

[0055] If the ABS mode is maintained for an extended period during braking, the generation of brake pressure by the pressure supply unit 110 is blocked. In this case, the ECU (not shown) detects the situation and causes the compliance unit 160 to supply hydraulic pressure to the wheel cylinders 40. More precisely, if the generation of brake pressure by the pressure supply unit 110 is blocked, the first switching valve 131 closes, and the pressure piston 112 in the pressure chamber 111 moves rapidly backward to draw oil from the reservoir 20 through the hydraulic channel 116, and then moves forward again to generate hydraulic pressure. During the time that the pressure chamber 111 draws in and pressurizes the oil, the hydraulic pressure is transmitted from the compliance unit 160 to the wheel cylinders 40.This prevents a drop in the supplied pressure. Consequently, problems with the control of the ABS mode and the vehicle's braking caused by a drop in the supplied pressure can be overcome.

[0056] As can be seen from the foregoing description, an electric braking system for a vehicle according to the present invention has the following effects.

[0057] Firstly, since the electric braking system is configured to generate hydraulic pressure by converting the rotational force of a motor into linear motion, precise control of the pressure is possible, and the structure of the braking system can be simplified compared to conventional cases.

[0058] Secondly, if the braking system malfunctions, the driver's foot force is transferred directly to the master cylinder to enable the vehicle to brake. This ensures a stable braking force.

[0059] Finally, regardless of how the pressure is set during braking, the pedal feel delivered to the driver can be stabilized.

Claims

[1] Electric braking system for a vehicle, comprising a reservoir (30) for storing oil, a master cylinder (20) equipped with two hydraulic circuits and designed to generate hydraulic pressure using the oil stored in the reservoir (30), an input rod (12) in contact with the master cylinder (20) to be moved forward according to the foot force of a driver, and a pedal displacement sensor (11) for detecting a displacement of a brake pedal (10) connected to the input rod (12), wherein the electric braking system comprises: a pressure supply unit (110) connected to the reservoir (30) and a hydraulic channel (116) to receive oil and output an electrical signal through the pedal displacement sensor (11) to actuate a motor (114) when the driver presses the brake pedal (10), such that a rotational force of the motor (114) is converted into a linear motion; a hydraulic control unit (120) for performing the braking of a wheel with hydraulic pressure supplied according to the force generated by the pressure supply unit (110), wherein the hydraulic control unit (120) is provided with two wheel brake circuits, comprising a first circuit (121) which is provided with at least one first wheel for receiving the hydraulic pressure supplied to it for carrying out the braking, and a second circuit (122) which is provided with at least one second wheel; a first and a second switching valve (131, 132); a channel connecting the pressure supply unit (110) to the hydraulic control unit (120); a simulator (150) connected to the main cylinder (20) to obtain a reaction force corresponding to the foot force exerted on the brake pedal (10); and an electronic control unit for controlling the motor (114) and the valves based on information about the pressure and a pedal offset, wherein the pressure supply unit (110) comprises: a pressure chamber (111) which is connected to the hydraulic channel (116) to receive oil supplied to it; a hydraulic piston (112) which is arranged in the pressure chamber (111); a hydraulic spring (113) which is arranged in the pressure chamber (111) to elastically support the hydraulic piston (112); the motor (114) to generate a rotational force in accordance with the electrical signal from the pedal displacement sensor (11); and a ball screw part (115) which is connected to a screw (115a) and is designed with a bolt to convert a rotational force of the motor (114) into a linear motion, wherein the hydraulic piston (112) is connected to the screw (115a), which is designed for linear movement, such that the oil in the pressure chamber (111) is pressurized by the screw (115a). characterized by , that the first and the second switching valve (131, 132) in the channel, The pressure supply unit (110) is connected to the hydraulic control unit (120), and the valves are installed and connected in series to control the transmission of the hydraulic pressure generated by the pressure supply unit (110) to the hydraulic control unit (120) by opening and closing operations, wherein the first switching valve (131) controls the hydraulic pressure supplied to the first circuit (121) of the hydraulic control unit (120), and the second switching valve (132) controls the hydraulic pressure supplied to the second circuit (122) of the hydraulic control unit (120). [2] Electric braking system according to claim 1, wherein a shut-off valve (117) is installed in the hydraulic channel (116) to prevent backflow of pressure from the pressure chamber (111) and to allow oil to be drawn into and stored in the pressure chamber (111) when the hydraulic piston (112) is retracted. [3] Electric braking system according to one of claims 1 or 2, wherein a pressure sensor (118) for detecting pressure is arranged in a channel which is connected to the pressure chamber (111) and the master cylinder (20). [4] Electric braking system according to any one of claims 1 to 3, wherein the hydraulic control unit (120) comprises: a normally open solenoid valve (123) located upstream of the wheel cylinder (40) to control the transmission of hydraulic pressure to the wheel cylinder (40); a normally closed solenoid valve (124) arranged downstream of the wheel cylinder (40) to control the release of hydraulic pressure from the wheel cylinder (40); and a return channel (126) for connecting the normally closed solenoid valve (124) to the hydraulic channel (116). [5] Electric braking system according to any one of claims 1 to 4, further comprising a first and a second safety channel (141, 142) for connecting two hydraulic circuits of the master cylinder (20) to the wheel cylinder (40) to control the oil when the electric braking system has a malfunction, a first starting valve (143) for controlling the connection between the first safety channel (141) and the master cylinder (20), and a second starting valve (144) for controlling the connection between the second safety channel (142) and the master cylinder (20). [6] Electric braking system according to claim 5, wherein the first and second starting valves (143, 144) are normally open solenoid valves which remain open in a normal state and are closed upon receiving a signal for a closing operation from the electronic control unit. [7] Electric braking system according to any one of claims 1 to 6, wherein the simulator (150) comprises: a simulation chamber (151) for storing the oil discharged by the main cylinder (20); a reaction flask (152) arranged in the simulation chamber (151); a reaction spring (153) for elastically supporting the reaction piston (152); and a simulation valve (155) arranged at an inlet of the simulation chamber (151). [8] Electric braking system according to claim 7, wherein the simulation valve (155) is a normally closed solenoid valve which remains closed in a normal state and is opened upon receiving a signal for an opening process from the electronic control unit. [9] Electric braking system according to any one of claims 1 to 8, wherein the first switching valve (131) is a normally open solenoid valve and the second switching valve (132) is a normally closed solenoid valve which remains closed in a normal state and is opened upon receiving a signal for an opening operation from the electronic control unit. [10] Electric braking system according to any one of claims 1 to 8, wherein the first and second switching valves (131, 132) are normally closed solenoid valves which remain closed in a normal state and are opened upon receiving a signal for an opening operation from the electronic control unit. [11] Electric braking system according to any one of claims 1 to 10, further comprising a compliance unit (160) arranged in the channel connected to the first switching valve (131) and the second switching valve (132) to store a predetermined quantity of oil by changing its volume according to the hydraulic pressure. [12] Electric braking system according to claim 11, wherein the compliance unit comprises: a compliance chamber (161) which is provided with a predetermined volume; a piston (162) and an elastic part (163) arranged in the compliance chamber (162); and a compliance valve (165) which is arranged at an inlet of the compliance chamber (161). [13] Electric braking system according to claim 12, wherein the compliance valve (165) is a normally closed solenoid valve which remains closed in a normal state and is opened upon receiving a signal for an opening process from the electronic control unit.

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