Electric braking system for vehicles

Abstract

An electric braking system for a vehicle is disclosed, comprising a reservoir (30), an input rod (12) and a pedal displacement sensor (11) for detecting a displacement of a brake pedal (10).The electric brake system includes a pressure supply unit (110) connected to the reservoir and a hydraulic channel (116) for outputting an electrical signal via the pedal displacement sensor, a hydraulic control unit (120) with a first circuit (121) and a second circuit (122), a starting valve (143, 144) for controlling the hydraulic pressure transmitted to a wheel cylinder (40), a switching valve (133, 134) connected to a channel connecting the pressure supply unit to the hydraulic control unit, a compliance unit (160) installed in a channel connecting the starting valve and the switching valve and containing a compliance chamber (161), a piston (162) and an elastic part (163), a simulator (150) connected to the master cylinder for providing a reaction force, and an electronic control unit for controlling the motor (114) and the valves.

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 recently been proposed to achieve stronger and more consistent braking force. Examples of braking systems include an anti-lock braking system (ABS), a brake drive control system (BTCS), and a dynamic vehicle control system (VDC). ABS prevents wheels from slipping during braking. BTCS prevents drive wheel slippage during hard acceleration from a standstill or during sudden acceleration of a vehicle. VDC maintains a stable driving condition of a vehicle by controlling brake fluid pressure through a combination of ABS and BTCS.

[0003] Such an electric 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 and a high-pressure accumulator pair for temporarily storing oil flowing from the wheel cylinder, a motor and pump for forcibly pumping the oil to the low-pressure accumulator, several shut-off valves to prevent backflow of oil, and an electronic control unit (ECU) for controlling the operations 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 1090910 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 that can have a simplified configuration, can provide a stable braking feel during braking and enables precise pressure control.

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

[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 according to the invention 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 according to the foot force of a driver, and a pedal displacement sensor for detecting a displacement of a brake pedal connected to the input rod, further comprising a pressure supply unit connected to the reservoir and a hydraulic channel to receive oil and output an electrical signal through the pedal displacement sensor to actuate a motor when the driver depresses the brake pedal, such that...that a rotational force of the engine is converted into a linear motion, a hydraulic control unit equipped with a first circuit, which is fitted with at least one first wheel, and a second circuit, which is fitted with at least one second wheel, to perform the braking of a wheel with hydraulic pressure supplied according to the force generated by the pressure supply unit, a starting valve for controlling the hydraulic pressure transmitted from the master cylinder to a wheel cylinder installed on each wheel, a switching valve connected to a channel connecting the pressure supply unit to the hydraulic control unit, in order to control the hydraulic pressure, a compliance unit installed in a channel connected to the starting valve and the switching valve and containing a compliance chamber with a predetermined volume that changes according to a pressure change,and a piston and an elastic part located in the compliance chamber, a simulator connected to the main cylinder to provide a reaction force according to the foot force applied to the brake pedal, and an electronic control unit to control the motor and valves based on information about pressure and pedal displacement.

[0011] The compliance unit may also include a compliance valve located at an inlet of the compliance chamber.

[0012] 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.

[0013] The pressure supply unit may include: a pressure chamber connected to the hydraulic channel to receive oil supplied to it, a hydraulic piston arranged in the pressure chamber, a hydraulic spring arranged in the pressure chamber to elastically support the hydraulic piston, the motor being provided to generate 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 rotational force from the motor into a linear motion, the hydraulic piston being able to be connected to the screw designed for linear motion, such that the oil in the pressure chamber is pressurized by the screw.

[0014] 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 returns.

[0015] The electric braking system according to the invention further comprises a first channel for connecting the pressure supply unit to the first circuit and a second supply channel branching off from the first supply channel and connected to the second circuit. The switching valve comprises a first switching valve installed in the first supply channel to control the hydraulic pressure and a second switching valve installed in the second supply channel to control the hydraulic pressure.

[0016] A shut-off valve can be installed in parallel with the first and second switching valves.

[0017] 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.

[0018] 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.

[0019] The electric braking system may further include a first and a second safety channel to connect the two hydraulic circuits of the master cylinder to the wheel cylinder to control the oil when the electric braking system fails, wherein the starting valve may include a first starting valve installed in the first safety channel to control the connection between the first safety channel and the master cylinder, and a second starting valve installed in the second safety channel to control the connection between the second safety channel and the master cylinder.

[0020] 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.

[0021] 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.

[0022] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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 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

[0024] Reference will now be made in detail to the exemplary embodiments of the present invention, which are illustrated in the accompanying drawings, whereby identical reference numerals consistently refer to identical elements.

[0025] 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.

[0026] 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 braking 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.

[0027] Here, the master cylinder 20 can be provided with at least one chamber for generating hydraulic pressure. According to FIG. 1, the master cylinder 20 is provided with a first cylinder 21a and a second cylinder 22a to provide two hydraulic circuits and contacts the inlet rod 12. By providing the master cylinder 20 with two hydraulic circuits, it 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 of the hydraulic circuits 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 of the hydraulic circuits 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 malfunctions.

[0028] The first cylinder 21a and the second cylinder 22a of the master cylinder 20, configured as above, are each provided with a first spring 21b and a second spring 22b. 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.

[0029] 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 is pressed, the master cylinder 20 is directly pressed with the lost movement portion.

[0030] 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 a driver intention to brake in the form of an electrical signal from the pedal displacement sensor 11, which detects a displacement of the brake pedal 10; a hydraulic pressure control unit 120 for performing the braking of the wheels using the force generated by the pressure supply unit 110; switching valves 133 and 134, which are installed in a channel connecting the pressure supply unit 110 with the hydraulic pressure control unit 120 to control hydraulic pressure; starting valves 143 and 144 for controlling the hydraulic pressure transmitted from the master cylinder 20 to the wheel cylinders 40; and a compliance unit, which is installed in the channel containing the starting valves 143 and 144 and the associated switching valves 133 and 134 and has a volume ofwhich varies according to a change in pressure, and a simulator 150 which is connected to the master cylinder 20 to provide a reaction force to the brake pedal 10.

[0031] The pressure supply unit 110 comprises 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 for connecting the reservoir 20 to the pressure chamber 111 to allow 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.

[0032] 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 a linear movement of the screw 115a. The hydraulic spring 113 serves to return the hydraulic piston 112 to its initial position.

[0033] 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 the torque into linear motion, not only functions as a pivot point for motor 114 but also drives screw 115a in a straight line. 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 through the spiral groove and several balls. That is to say, as disclosed above, the hydraulic piston 112 is pushed by linear movement of the screw 115a to generate hydraulic pressure.

[0034] 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 prevents 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.

[0035] The reference number '118' designates a first pressure sensor for measuring the hydraulic pressure in pressure chamber 111.

[0036] The hydraulic pressure control unit 120 is equipped with a first circuit 121 for receiving hydraulic pressure supplied to it in order to control the braking of at least one first wheel, and with a second circuit 122 for receiving hydraulic pressure supplied to it in order to control 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 hydraulic pressure.

[0037] According to Fig. 1. The valves 123 and 124 are divided into a normally open solenoid valve 123 (hereinafter referred to as 'NO type') 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') 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.

[0038] 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 output and transferred to the reservoir 30 or the pressure supply unit 110.

[0039] According to this embodiment, the electronic brake system includes inlet channels 131 and 132 that connect the pressure supply unit 110 to the first and second circuits 121 and 122 of the hydraulic pressure control unit 120. The first switching valve 133, which controls the transmission of hydraulic pressure to the wheel cylinder 40 of the first circuit 121 by means of an opening and closing operation, is installed in the first inlet channel 131. The second switching valve 134, which controls the transmission of hydraulic pressure to the wheel cylinder 40 of the second circuit 122 by means of an opening and closing operation, is installed in the second inlet channel 132. Here, the second inlet channel 132 branches off from the first inlet channel and is connected to the second circuit 122.The opening and closing of the first and second switching valves 133 and 134 are controlled by the ECU to transmit the hydraulic pressure generated by the pressure supply unit 110 directly to the wheel cylinders 40. That is, the first switching valve 133 controls the hydraulic pressure supplied to the first circuit 121, and the second switching valve 134 controls the hydraulic pressure supplied to the second circuit 122.

[0040] The first and second switching valves 133 and 134 are normally closed (NC) type solenoid valves, which remain closed in their normal state and are actuated to open when they receive an opening signal from the ECU. Although not shown, the first switching valve 133 could be a normally open (NO) type solenoid valve, which remains open in its normal state and closes upon receiving a closing signal. That is, if the first switching valve 133 is an NO valve, its actuation can be simplified, as it opens without the need for electrical energy.

[0041] The shut-off valves 135 and 136 are connected in parallel to the first and second switching valves 133 and 134, which are located at the points where the pressure chamber 111 is connected to the circuits 121 and 122. The shut-off valves comprise a first shut-off valve 135, connected in parallel to the first switching valve 133, and a second shut-off valve 135, connected in parallel to the second switching valve 134. The shut-off valves 135 and 136 are one-way shut-off valves that allow hydraulic pressure to be transmitted only to the wheel cylinders 40 and serve to prevent a pressure increase due to the delayed actuation of the first and second switching valves 133 and 134.

[0042] 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 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 starting valve 143 and the second starting valve 144, and the braking intended by the driver can be determined by the pressure sensor 148.

[0043] 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.

[0044] According to this embodiment, the compliance units are installed in the channels to which the switching valves 133 and 134 and the starting valves 143 and 144 are connected. In the illustrated embodiment, the compliance units are installed between the first switching valve 133 and the first starting valve 143, and between the second switching valve 134 and the second starting valve 144. Here, the compliance units are designed to store the hydraulic pressure generated by the pressure supply unit 110. The compliance units have the same configuration and the same function. That is, the two compliance units independently supply hydraulic pressure to the first circuit 121 and the second circuit 122.

[0045] Each of the compliance units is equipped with a compliance chamber 161 with a predetermined volume for storing hydraulic pressure and a compliance valve 165 located at the inlet of the compliance chamber 161. A piston 162 and an elastic element 163 are arranged within the compliance chamber 161 such that the volume of the compliance chamber 161 is changed within a specific range by the hydraulic pressure introduced into the compliance chamber 161. The compliance valve 165 is a normally closed (NC) type solenoid valve that remains closed in its normal state and opens upon receiving a signal from the ECU.

[0046] If the ABS cycle 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 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 133 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 compresses the oil, the hydraulic pressure is transferred from the compliance unit 116 to the wheel cylinders 40. This prevents a drop in the supplied pressure.Accordingly, problems in the control of the ABS mode and the braking of the vehicle, caused by a drop in the supplied pressure, can be overcome.

[0047] While the compliance unit is illustrated as being equipped with the compliance valve 165 to store hydraulic pressure in the compliance chamber 161 so that the stored hydraulic pressure is supplied to the wheel cylinders 40 according to the opening and closing of the valve, embodiments of the present invention are not limited to this. The compliance unit can be used without the compliance valve 165. For example, a structure without a compliance valve is shown in Fig. 3 shown. In Fig. 3 denote reference figures that are identical to those in the Fig. 1 and Fig. 2 are parts with the same functions as those in the Fig. 1 and Fig. 2 shown.

[0048] According to Fig. 3. The compliance unit 260 is provided with a compliance chamber with a predetermined volume of hydraulic pressure reservoirs, and an elastic component (not shown) is arranged in the chamber. This allows the compliance unit 260 to temporarily store oil (hydraulic oil). That is, the compliance unit 260 supplies hydraulic pressure to the wheel cylinders 40 even without opening and closing the valve when the hydraulic pressure supplied to the wheel cylinders 40 is reduced.

[0049] According to Fig. In the illustrated embodiment, a simulator 150 is provided, connected to the master cylinder 20, to generate a reaction force corresponding to the foot force applied to the brake pedal 10. 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 an NC-type solenoid valve that is normally in a closed state.This means that when the driver presses down the brake pedal 10, the simulation valve 155 is opened to allow the brake fluid to be transferred to the simulation chamber 151.

[0050] 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 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.

[0051] The following describes the operation of an electric braking system for a vehicle according to an embodiment of the present invention.

[0052] Fig. Figure 2 is a hydraulic circuit diagram illustrating an electric braking system for a vehicle in normal operation.

[0053] According to Fig. 2. When the driver initiates braking, the desired braking force can be detected by the pedal displacement sensor 11 based on information about the pressure applied by the driver to 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 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 friction braking force based on the difference between the braking force requested by the driver and the regenerative braking force. This allows the ECU to detect the magnitude of the increase or decrease in pressure at the wheel.

[0054] More precisely, 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 reservoir 30, which contains oil, via the hydraulic channel 116. Due to the linear motion of the ball screw component 115, which converts rotary motion into linear motion, hydraulic pressure is generated in the pressure chamber 111. Additionally, the first and second starting valves 143 and 140, 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 supply channels 131 and 132. That is, since the first and second switching valves 133 and 134 are opened by the ECU to control the hydraulic pressure supplied to each by the first and second circuits 121 and 122, hydraulic pressure is transmitted to the wheel cylinders 40 to generate braking force.

[0055] Additionally, the pressure generated by the foot force applied to the brake pedal 10, corresponding to the vacuuming of the master cylinder 20, is transmitted to the simulator 150 connected to the master cylinder 20. At this time, the normally closed (NC) simulation valve 155, located between the master cylinder 20 and the simulation chamber 151, opens, 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 generated in the simulation chamber 151, thus providing the driver with proper pedal feel.

[0056] If the ABS cycle is maintained for a prolonged period, thus blocking the generation of brake pressure by the pressure supply unit 110, 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 compresses the oil, the hydraulic pressure is transmitted from the compliance unit 116 to the wheel cylinders 40. This prevents a drop in the supplied pressure.

[0057] 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 at the same time, and the first cylinder 21a, which is in contact with the input rod 12, also moves forward to the left simultaneously. 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 emergency braking. In this, the first and second starting valves 143 and 144, which are installed in the first and second safety channels 141 and 142, are NO-type solenoid valves, while the simulation valve 155 and the first and second switching valves 133 and 134 are NC-type solenoid valves.Accordingly, hydraulic pressure is transmitted directly to the wheel cylinders 40. This enables stable braking and thus increases braking stability.

[0058] An electric braking system for a vehicle is designed to generate hydraulic pressure by detecting the driver's intention to brake according to the braking force applied to the brake pedal 10, controlling the motor 114 according to an electrical signal output, and converting the rotary motion of the motor 114 into linear motion, thus enabling precise control of the hydraulic pressure. 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.

[0059] As can be seen from the foregoing description, an electric braking system for a vehicle according to the present invention has the following effects.

[0060] Firstly, since the electric braking system is designed to generate hydraulic pressure by converting a motor's rotational force into linear motion, precise control of the pressure is possible, and the structure of the braking system can be simplified compared to conventional cases.

[0061] Secondly, in the event of a brake system failure, the driver's foot force is transferred directly to the master cylinder to enable the vehicle to brake. This ensures a stable braking force.

[0062] Thirdly, a compliance unit performs hydraulic damping by changing its volume and is filled with a specific quantity of oil from the pressure chamber during the ABS cycle. Accordingly, if the ABS cycle is maintained for a long time, the stored oil is supplied to the wheel cylinders during the oil intake process by the pressure supply unit. This prevents a sudden drop in the supplied pressure.

[0063] 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) arranged to be 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) which is provided with a first circuit (121) which is equipped with at least one first wheel and a second circuit (122) which is equipped with at least one second wheel, in order to perform the braking of a wheel with hydraulic pressure supplied according to the force generated by the pressure supply unit (110); a starting valve (143, 144) for controlling the hydraulic pressure transmitted from the main cylinder (20) to a wheel cylinder (40) installed on each wheel; a switching valve (133, 134) which includes a first switching valve (133) and a second switching valve (134); a compliance unit installed in a channel connected to the starting valve (143, 144) and the switching valve (133, 134) and comprising a compliance chamber (161) with a predetermined volume which varies according to a change in pressure, as well as a piston (162) and an elastic part (163) arranged in the compliance chamber (161); a simulator (150) connected to the main cylinder (20) to provide a reaction force in accordance with the foot force applied to the brake pedal (10); an electronic control unit for controlling the motor (114) and the valves based on information about pressure and pedal displacement; and a first inflow channel (131) that connects the pressure supply unit (110) to the first circuit (121) of the hydraulic control unit (120), characterized by a second inlet channel (132) branching off from the first inlet channel (131) and connecting the pressure supply unit (110) to the second circuit (121) of the hydraulic control unit (120), wherein the first switching valve (133) is installed in the first inlet channel (131) to control the transmission of the hydraulic pressure generated by the pressure supply unit (110) to the first circuit (121) of the hydraulic control unit (120), and wherein the second switching valve (134) is installed in the second inlet channel (132) to control the transmission of the hydraulic pressure generated by the pressure supply unit (110) to the second circuit (122) of the hydraulic control unit (120). [2] Electric braking system according to claim 1, wherein the compliance unit further comprises a compliance valve (165) arranged at an inlet of the compliance chamber (161). [3] Electric braking system according to claim 2, 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 operation from the electronic control unit. [4] Electric braking system according to one of claims 1 to 3, 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 rotary motion of the motor into a linear motion, wherein the hydraulic piston (112) is connected to the screw (115a) which is designed to move in a straight line in such a manner, that the oil in the pressure chamber (111) is pressurized by the screw (115a). [5] Electric braking system according to claim 4, 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 the oil to be drawn into and stored in the pressure chamber (111) when the hydraulic piston (112) is retracted. [6] Electric braking system according to one of the preceding claims, wherein a shut-off valve (135, 136) is installed in parallel to the first and the second switching valve (133, 134). [7] Electric braking system according to one of claims 5 or 6, wherein the first and second switching valves (133, 134) 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. [8] Electric braking system according to any one of claims 1 to 7, wherein the hydraulic control unit 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) located 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). [9] Electric braking system according to any one of claims 1 to 8, further comprising a first and a second safety channel (141, 142) for connecting the 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, wherein the starting valve (143, 144) comprises a first starting valve (143) installed in the first safety channel (141) to control the connection between the first safety channel (141) and the master cylinder (20), and a second starting valve (144) installed in the second safety channel (142) to control the connection between the second safety channel (142) and the master cylinder (20). [10] Electric braking system according to claim 9, 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. [11] Electric braking system according to one of claims 9 or 10, wherein the compliance unit comprises a first compliance unit and a second compliance unit, wherein the first compliance unit is installed between the first switching valve (133) and the first starting valve (143) and is configured to store the hydraulic pressure generated by the pressure supply unit (110) and to supply the hydraulic pressure to the first circuit (121), wherein the second compliance unit is installed between the second switching valve (134) and the second starting valve (144) and is configured to store the hydraulic pressure generated by the pressure supply unit (110) and to supply the hydraulic pressure to the second circuit (122). [12] Electric braking system according to any one of claims 1 to 11, 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). [13] Electric braking system according to claim 12, 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.

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