Electromechanical brake and method of operation thereof

Abstract

Disclosed is an electromechanical brake and a method for operating the same. The electromechanical brake of the present embodiment includes a piston configured to advance and retreat in a manner to pressurize a brake pad, a power conversion unit that converts rotational motion into linear motion to provide the piston with driving force received from an actuator, and a position adjustment portion that adjusts the relative position of the piston with respect to the power conversion unit. The power conversion unit includes a main shaft that receives driving force from the actuator to rotate, and a nut that is connected to the main shaft to advance or retreat on the inside of the piston to advance or retreat the piston by rotating in a first direction or a second direction of the main shaft. The position adjustment portion includes a first thread formed on the outer circumferential surface of the nut, a second thread formed on the inner circumferential surface of the piston and engaged with the first thread, and an adjuster provided between the main shaft and the nut to advance or retreat the relative position of the piston by rotating the nut in the first direction or the second direction by rotation of the main shaft.

Description

Technical Field

[0001] This invention relates to electromechanical brakes and their operating methods, and more specifically, to an electromechanical disc brake and its operating method that utilizes the rotational driving force of a motor to perform braking of a vehicle. Background Technology

[0002] Vehicles are inevitably equipped with braking systems to perform braking, and various braking systems have been developed for the safety of drivers and passengers.

[0003] In the past, braking systems primarily relied on mechanically connected boosters to supply the hydraulic pressure required for braking to the wheel cylinders when the driver pressed the brake pedal. However, as a second-generation braking system, electromechanical braking systems have been developed that receive the driver's braking intention via electrical signals and, based on this, activate electric devices such as motors to provide braking force to the vehicle.

[0004] Such an electromechanical braking system converts the rotational force of the motor into linear motion through a motor and a reducer, thereby providing clamping pressure on the brake disc and performing service braking and parking braking of the vehicle.

[0005] On the other hand, brake pads, which are in direct contact with the vehicle's brake discs and apply pressure, gradually wear down with repeated braking actions. In order to maintain the vehicle's braking performance independently of brake pad wear, it is necessary to compensate for the wear of the brake pads. However, in this case, the size of the braking system or its length in the axial direction increases, leading to a decrease in the vehicle's usability. Summary of the Invention

[0006] Technical issues

[0007] This embodiment provides an electromechanical braking system and its operation method that can maintain and improve the braking performance of a vehicle regardless of brake pad wear.

[0008] This embodiment provides an electromechanical braking system and its operating method that can stably perform vehicle braking under various operating conditions.

[0009] This embodiment provides an electromechanical braking system and its operating method that reduce the size and weight of a vehicle, thereby improving its applicability and enabling greater space utilization.

[0010] This embodiment provides an electromechanical braking system and its operation method that can easily compensate for brake pad wear with a simple structure.

[0011] This embodiment provides an electromechanical braking system and its operation method that reduces drag, improves braking performance, and suppresses braking noise and vibration.

[0012] means of solving technical problems

[0013] According to one aspect of the present invention, an electromechanical brake is provided, comprising: a piston configured to pressurize brake pads and retract; a power conversion unit receiving driving force from an actuator to convert rotational motion into linear motion to provide to the piston; and a position adjustment unit adjusting the relative position of the piston with respect to the power conversion unit, the power conversion unit comprising: a spindle receiving driving force from the actuator and rotating; and a nut connected to the spindle and moving the piston forward or backward by rotating the spindle in a first or second direction, the position adjustment unit comprising: a first thread formed on the outer peripheral surface of the nut; a second thread formed on the inner peripheral surface of the piston and engaging with the first thread; and an adjuster disposed between the spindle and the nut and moving the nut in the first or second direction by rotating the spindle to move the relative position of the piston forward or backward.

[0014] The aforementioned adjuster includes: a flange that extends radially outward from the outer periphery of the main shaft; a first protrusion that protrudes from the flange; and a second protrusion that protrudes from the nut, which is engaged by the first protrusion when the main shaft rotates in a first direction, thereby guiding the nut to rotate in the first direction and thus advancing the relative position of the piston.

[0015] When the vehicle's brakes are released, the first angle between the first protrusion and the second protrusion is greater than the second angle of rotation of the first protrusion from the state of brake release to the state of brake application.

[0016] The aforementioned regulator also includes a third protrusion formed on the aforementioned flange, which is engaged by the third protrusion when the aforementioned main shaft rotates in the second direction, thereby guiding the aforementioned nut to rotate in the second direction and thus causing the relative position of the aforementioned piston to retract.

[0017] When the vehicle is braking, the third angle between the second protrusion and the third protrusion is greater than the fourth angle of rotation of the third protrusion from the braking state of the vehicle to the braking release state of the vehicle.

[0018] An internal thread is formed on the inner circumferential surface of the nut. The spindle includes: a first end on one side, which has an external thread on its outer circumferential surface that engages with the internal thread; a second end on the other side, which is connected to the actuator; and a central portion located between the first end and the second end, wherein the flange is fixedly disposed on the outer circumferential surface of the central portion.

[0019] The first and third protrusions are formed separately and protrudingly on the front surface of the flange opposite to the nut, and the second protrusion is formed protrudingly on the back surface of the nut opposite to the front surface of the flange.

[0020] The aforementioned electromechanical brake further includes: an electronic control unit that controls the operation of the aforementioned actuator; and a sensing unit that detects the connection force between the disc rotating with the wheel and the aforementioned brake pads.

[0021] When the connection force between the disc and the brake pads detected by the sensor is less than a preset value while the vehicle is braking, the electronic control unit determines that the brake pads are worn and enters a first mode that advances the relative position of the piston.

[0022] If the connection force between the disc and the brake pad detected by the sensor unit is greater than a preset value when the vehicle's brakes are released, the electronic control unit determines that there is drag and enters a second mode that causes the relative position of the piston to retract.

[0023] In the first mode described above, the actuator is controlled to rotate the main shaft in the first direction from the vehicle's brake release state to the vehicle's braking state. This additional rotation of the main shaft in the first direction causes the first protrusion to connect with the second protrusion and rotate, thereby guiding the nut to rotate in the first direction. The piston's relative position to the nut is advanced by the rotation of the nut in the first direction.

[0024] After the first mode described above, the electronic control unit restores the main shaft or the first protrusion to its original position when the vehicle's brakes are released.

[0025] In the second mode described above, the actuator is controlled to rotate the main shaft in the second direction from the vehicle's braking state to the vehicle's brake release state. This additional second-direction rotation causes the third protrusion to connect with and rotate the second protrusion, thereby guiding the nut to rotate in the second direction. The second-direction rotation of the nut causes the piston to retract relative to the nut.

[0026] Invention Effects

[0027] The electromechanical braking system and its operating method according to this embodiment can maintain and improve the braking performance of a vehicle regardless of the wear of the brake pads.

[0028] According to the electromechanical braking system and its operating method of this embodiment, the vehicle braking can be stably performed under various operating conditions.

[0029] According to the electromechanical braking system and its operation method in this embodiment, the size and weight are reduced, thereby improving the applicability of the vehicle and realizing the space utilization of the vehicle.

[0030] The electromechanical braking system and its operating method according to this embodiment can easily compensate for brake pad wear with a simple structure.

[0031] According to the electromechanical braking system and its operating method in this embodiment, drag phenomenon is reduced, braking performance is improved, and braking noise and vibration are suppressed. Attached Figure Description

[0032] Figure 1 This is a side cross-sectional view showing the electromechanical brake of this embodiment.

[0033] Figure 2 This is a side cross-sectional view showing the main part of the electromechanical brake in this embodiment, enlarged.

[0034] Figure 3 This is an exploded perspective view showing the main parts of the electromechanical brake of this embodiment.

[0035] Figure 4 As Figure 2 The A-A' cross-sectional view shows the positions of the first, second, and third protrusions before braking or when the vehicle is in the brake-released state.

[0036] Figure 5 This is a side cross-sectional view showing the operation of the electromechanical brake of this embodiment under the braking state of the vehicle.

[0037] Figure 6 As Figure 5 The B-B' cross-sectional view shows the positions of the first, second, and third protrusions under braking conditions.

[0038] Figure 7 This is a side cross-sectional view showing the operation of the electromechanical brake of this embodiment in a first mode state for compensating for brake pad wear.

[0039] Figure 8 As Figure 7 The C-C' cross-sectional view shows the positions of the first protrusion, the second protrusion, and the third protrusion in the first mode state.

[0040] Figure 9 This is a side cross-sectional view showing the operation of the electromechanical brake of this embodiment in the brake release state of the vehicle after the first mode.

[0041] Figure 10 As Figure 9The D-D' cross-sectional view shows the positions of the first, second, and third protrusions in the brake-released state of the vehicle after the first mode.

[0042] Figure 11 This is a side cross-sectional view showing the operation of the electromechanical brake of this embodiment in the second mode state for reducing drag.

[0043] Figure 12 As Figure 11 The cross-sectional view along the E-E' direction shows the positions of the first, second, and third protrusions in the second mode state. Detailed Implementation

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are disclosed to fully convey the spirit of the present invention to those skilled in the art. The present invention is not limited to the embodiments disclosed herein, and may be implemented in other forms. For clarity of explanation, figures are omitted for parts unrelated to the description, and the sizes of the constituent elements are shown enlarged to aid in understanding the invention.

[0045] Figure 1 This is a side cross-sectional view showing the electromechanical brake 100 of this embodiment.

[0046] Reference Figure 1 The electromechanical brake 100 of this embodiment includes: a bracket (not shown) having a pair of pads 11, 12 for applying pressure to a disc (not shown) that rotates with the wheel; a caliper housing 20 slidably disposed on the bracket to actuate the pair of pads 11, 12; a piston 110 retractably disposed inside the caliper housing 20; an actuator (not shown) generating and providing a driving force for moving the piston 110; and a power conversion unit 120 receiving the rotational drive force provided from the actuator. Power is converted into linear motion and transmitted to piston 110, thereby performing forward and backward movement of piston 110 in the axial direction; position adjustment unit 130 adjusts the relative position of piston 110 with respect to power conversion unit 120 to compensate for wear of brake pad 10 or reduce drag phenomenon; sensing unit 140 detects the contact force between disc and brake pad 10 or the connection force of brake pad 10; and electronic control unit (not shown) controls the operation of actuator based on information provided from sensing unit 140.

[0047] Brake pads 10 are attached to the inner surfaces of a pair of gaskets 11 and 12. The pair of gaskets are connected from their outer surfaces to the front surface of the piston 110 (within...). Figure 1 An inner pad 11, which is configured to be in contact with the left side of the caliper housing (based on the reference), and an outer pad 12, which is configured to be in contact with the finger-shaped portion 22 of the caliper housing 20, are slidably disposed on the bracket.

[0048] The caliper housing 20 includes a finger-like portion 22 for actuating the outer pad 12 and a cylinder portion 21 on which a piston 110 is provided, and is slidably connected to the bracket. In the caliper housing 20, as the caliper housing 20 slides from the bracket toward the disc side due to the reaction force generated by the movement of the piston 110 during vehicle braking, the outer pad 12 applies pressure to the disc side by approaching the disc side via the finger-like portion 22.

[0049] Figure 2 and Figure 3 The side cross-sectional view and exploded perspective view are shown in the enlarged view of the main part of the electromechanical brake 100 of the embodiment, with reference to Figures 1 to 3 Piston 110 is formed on the rear side ( Figure 1 and Figure 2 The cup-shaped part (right side) is slidably inserted into the cylinder section 21. The piston 110 receives power via the actuator and power conversion unit 120 (described later) to press the inner pad 11 towards the disc side. A second thread 132 is formed on the inner circumferential surface of the piston 110, engaging with a first thread 131 formed on the outer circumferential surface of the nut 125 (described later). Furthermore, as described later, the piston 110 is provided with a rotation prevention part (not shown) so that when the nut 125 is rotated via the position adjustment part 130, the piston 110 does not rotate with the nut 125 but performs a linear movement towards the pad side. Regarding the operation of adjusting the relative position of the piston 110 with respect to the main shaft 121 or the nut 125 via the position adjustment part 130, please refer to... Figures 4 to 12 Then it will be discussed.

[0050] The power conversion unit 120 includes: a main shaft 121 that receives driving force from an actuator (not shown) and rotates therein; a nut 125 disposed inside a piston 110 and screwed to the main shaft 121, which moves forward with the piston 110 by rotating the main shaft 121 in a first direction or moves backward with the piston 110 by rotating the main shaft 121 in a second direction; and a plurality of balls (not shown) sandwiched between the main shaft 121 and the nut 125. This power conversion unit 120 is constituted by a ball screw type conversion device that converts the rotational motion of the main shaft 121 into linear motion.

[0051] The first direction of rotation of the spindle 121 described below refers to the direction of rotation in which the nut 125 moves forward by rotating the spindle 121. The second direction of rotation of the spindle 121 refers to the direction of rotation in which the nut 125 moves backward by rotating the spindle 121, which is the opposite direction to the first direction.

[0052] The spindle 121 is divided into a first end 121a on one side with an external thread 122 formed on its outer circumferential surface, a second end 121c on the other side connected to an actuator and receiving driving force, and a central portion 121b disposed between the first end 121a and the second end 121c to fix the flange 136 (described later). The first end 121a of the spindle 121 is inserted into the inside of the nut 125, and the second end 121c is provided with a bearing 150 to enable smooth rotation of the flange 136 (described later) and a sensing part 140 to sense the load applied to the spindle 121 and detect the connection force between the disc and the brake pad 10.

[0053] The nut 125 is formed as a hollow cylinder to be inserted into the first end 121a of the main shaft 121, and an internal thread 126 is formed on its inner circumferential surface to engage with the external thread 122 of the main shaft 121 using balls (not shown) as the medium. Such a ball screw type power conversion device is a well-known and widely used technology, therefore, a detailed description of its operation is omitted.

[0054] On the other hand, a first thread 131 is formed on the outer peripheral surface of the nut 125, which engages with the second thread 132 formed on the inner peripheral surface of the piston 110, which will be described in detail later.

[0055] The actuator (not shown) comprises a motor and a reduction gear with multiple reduction gears, receiving power from a power supply unit located in the vehicle to generate and supply driving force. The actuator is connected to the second end 121c of the main shaft 121 to transmit the generated driving force to the rotational motion of the main shaft 121. The actuator is located on the outside of the caliper housing 20 and, as a reduction gear, utilizes various structures such as planetary gear assemblies or worm gear structures to reduce the power of the motor and supply it to the main shaft 121.

[0056] The position adjustment unit 130 adjusts the relative position of the piston 110 with respect to the power conversion unit 120, thereby advancing the relative position of the piston 110 to compensate for the wear of the brake pads 10 or retracting the relative position of the piston 110 to reduce drag.

[0057] The position adjustment part 130 includes: a first thread 131 formed on the outer peripheral surface of the nut 125; a second thread 132 formed on the inner peripheral surface of the piston 110 and engaging with the first thread 131; and an adjuster 135 disposed between the main shaft 121 and the nut 125, which rotates the nut 125 in a first direction to advance the relative position of the piston 110 or rotates the nut 125 in the opposite direction of the first direction, i.e., a second direction, to retract the relative position of the piston 110.

[0058] The first direction of rotation of the nut 125 described below, which is the same as the first direction of rotation of the main shaft 121 described above, refers to the direction of rotation in which the piston 110 is advanced by rotating the nut 125. Furthermore, the second direction of rotation of the nut 125, which is the opposite direction to the first direction, is the same as the second direction of rotation of the main shaft 121 described above, and refers to the direction of rotation in which the piston 110 is retracted by rotating the nut 125.

[0059] A first thread 131 is formed on the outer peripheral surface of the nut 125, and a second thread 132 is formed on the inner peripheral surface of the piston 110. The first thread 131 and the second thread 132 are interlocked. Thus, the piston 110 and the nut 125 are screwed together, and the nut 125 and the piston 110 move linearly together. Therefore, during normal vehicle braking, the nut 125 and the piston 110 move forward together, or when the vehicle brakes are released, the nut 125 and the piston 110 move backward together. Simultaneously, the piston 110 and the nut 125 can rotate relative to each other. Rotation of the nut 125 in a first direction causes the piston 110 to move forward relative to the nut 125 or the spindle 121, and rotation of the nut 125 in the opposite direction (a second direction) causes the piston 110 to move backward relative to the nut 125 or the spindle 121.

[0060] Adjuster 135 rotates nut 125, causing piston 110 to move forward or backward relative to nut 125. Adjuster 135 includes: flange 136, which is fixed to the central portion 121b of main shaft 121 and extends radially; first protrusion 137, which protrudes from the front surface of flange 136 (to... Figure 2 (Based on the left side); the second protrusion 138, which is formed prominently on the back of the nut 125 (to... Figure 2 (Based on the right side), when the main shaft 121 rotates in the first direction, it is locked by the first protrusion 137 and guides the nut 125 to rotate in the first direction; and the third protrusion 139, which is formed protrudingly on the front surface of the flange 136, is locked by the second protrusion 138 when the main shaft 121 rotates in the second direction and guides the nut 125 to rotate in the second direction.

[0061] The flange 136 extends radially from the central portion 121b of the main shaft 121 and is fixed to the main shaft 121, rotating integrally with it. The first protrusion 137 and the third protrusion 139, described later, are separated from each other at a predetermined angle and protrude from the front surface of the flange 136. Figure 2 (based on the left side), on the back side of flange 136 (with) Figure 2 The right side (based on the reference) is provided with a bearing 150 to enable smooth rotation of the flange 136 and prevent wear between the flange 136 and surrounding components.

[0062] The first protrusion 137 and the third protrusion 139 are formed prominently on the front surface of the flange 136 opposite to the nut 125. Figure 2 (Based on the left side), when the main shaft 121 rotates, it rotates together with the flange 136 about the main shaft 121 as the axis, and the second protrusion 138 is formed protrudingly on the back of the nut 125 opposite to the flange 136 (with the left side as the reference). Figure 2 (based on the right side), thus being held in place by the first protrusion 137 or the third protrusion 139 to guide the rotation of the nut 125.

[0063] Figure 4 As Figure 2 The A-A' cross-sectional view shows the positions of the first to third protrusions 139 before braking or when the vehicle is released from braking. (Refer to...) Figure 4 A first protrusion 137 and a third protrusion 139 are provided on the front surface of the flange 136 and are formed protrudingly at an angle to each other, with a second protrusion 138 provided on the back of the nut 125 disposed therebetween.

[0064] Specifically, in the state before the action is performed or in the vehicle's brake-released state, the angle between the first protrusion 137 on the front surface of the flange 136 and the second protrusion 138 on the back surface of the nut 125 (hereinafter referred to as the 'first angle') is greater than the rotation angle of the first protrusion 137 from the vehicle's brake-released state to the vehicle's braking state (refer to...). Figure 6 (Hereinafter referred to as 'second angle'). When the second angle ② is greater than the first angle ①, even during normal vehicle braking, the second protrusion 138 is held by the first protrusion 137, causing the nut 125 to rotate in the first direction. As a result, the piston 110 advances relative to the nut 125 or the main shaft 121, causing a sharp increase in the connecting force between the piston 110 and the pad. Consequently, the vehicle's braking force exceeds the driver's braking demand, leading to drag and potentially reducing vehicle operating safety and fuel consumption. Therefore, by making the first angle ① greater than the second angle ②, the first protrusion 137 and the second protrusion 138 do not contact each other during normal vehicle braking, thereby keeping the relative position of the piston 110 relative to the nut 125 or the main shaft 121 constant, achieving improved braking operability and operational safety for the driver.

[0065] Additionally, when the vehicle is braked, the angle between the second protrusion 138 on the back of the nut 125 and the third protrusion 139 on the front surface of the flange 136 (refer to...) Figure 6 (hereinafter referred to as 'third angle') is greater than the rotation angle of the third protrusion 139 from the vehicle's braking state to the vehicle's brake release state (refer to... Figure 4 and Figure 6(Hereinafter referred to as the 'fourth angle'). When the fourth angle ④ is greater than the third angle ③, during normal vehicle brake release, the second protrusion 138 can be locked by the third protrusion 139, causing the nut 125 to rotate in the second direction. As a result, the relative position of the piston 110 with respect to the nut 125 or the main shaft 121 moves backward, reducing the connecting force between the piston 110 and the pad. Consequently, the braking force of the vehicle is less than the driver's braking demand, posing a risk of a safety accident. Therefore, by making the third angle ③ greater than the fourth angle ④, during normal vehicle brake release, the second protrusion 138 and the third protrusion 139 do not contact each other, thereby keeping the relative position of the piston 110 with respect to the nut 125 or the main shaft 121 constant, thus achieving driver braking operability and operational safety.

[0066] The sensing unit 140 detects the contact force or coupling force between the disc and the brake pad 10. The sensing unit 140 may be composed of a pressure sensor (force sensor) or similar device that senses the load on the spindle 121 or actuator to detect the coupling force between the disc and the brake pad 10, but is not limited to this type of device. The sensing unit 140 sends the detected coupling force information of the brake pad 10 to the electronic control unit, which determines the wear or drag of the brake pad 10 based on the coupling force information detected by the sensing unit 140.

[0067] The operation method of the electromechanical brake 100 system in this embodiment will now be described.

[0068] Figure 5 This is a side cross-sectional view showing the operation of the electromechanical brake 100 of this embodiment under vehicle braking conditions. Figure 6 As Figure 5 The B-B' cross-sectional view shows the positions of the first protrusion 137, the second protrusion 138, and the third protrusion 139 when the vehicle is under braking conditions.

[0069] Reference Figure 2 , Figures 4 to 6 When braking in normal mode (either the first or second mode described later) before engaging service braking or parking braking, from Figure 2 and Figure 4 The brake release state shown is changed to Figure 5 and Figure 6 The braking state is shown.

[0070] Specifically, when the driver applies pressure to the brake pedal (not shown) to brake the vehicle, the pedal displacement sensor (not shown) detects the driver's braking intention with an electrical signal and sends it to the electronic control unit. Based on this, the electronic control unit controls the actuator's movement, causing the disc and brake pads 10 to adhere tightly and perform vehicle braking.

[0071] When braking the vehicle, the main shaft 121 rotates in a first direction due to the action of the actuator, and the nut 125 moves forward with the rotation of the main shaft 121 in the first direction, thereby causing the piston 110 to also move towards the pad side. The brake pad 10 mounted on the pad comes into close contact with the disc, thereby generating a connecting force, which in turn causes the vehicle to brake.

[0072] At this time, the first protrusion 137 of the flange 136 provided on the main shaft 121 rotates by a second angle from the vehicle's brake-released state to the vehicle's braking state as the main shaft 121 rotates in the first direction. However, in the state where the vehicle's brakes are released, the first angle ① between the first protrusion 137 of the flange 136 and the second protrusion 138 of the nut 125 increases, so that under normal braking conditions, the first protrusion 137 of the flange 136 and the second protrusion 138 of the nut 125 do not contact each other. Therefore, the relative position of the piston 110 with respect to the nut 125 or the main shaft 121 remains constant.

[0073] When releasing the vehicle's brakes, from Figure 5 and Figure 6 The braking state shown has changed to Figure 2 and Figure 4 The brake release state is shown. Specifically, the main shaft 121 rotates in the second direction by the action of the actuator, and the nut 125 retracts as the main shaft 121 rotates in the second direction, thereby causing the piston 110 to also separate from and retract from the pads 11 and 12. The brake pads 10 mounted on the pads 11 and 12 separate from the disc, thereby releasing the vehicle's brakes. The first protrusion 137 of the flange 136 provided on the main shaft 121 returns to its original position as the main shaft 121 rotates in the second direction.

[0074] The following describes a first mode in which the electromechanical brake 100 of this embodiment compensates for the wear of the brake pads 10 in order to maintain the braking performance of the vehicle regardless of the wear of the brake pads 10.

[0075] If the contact force or connection force between the disc and the brake pads 10 detected by the sensing unit 140 during vehicle braking is less than a preset normal range value, the electronic control unit determines that there is wear on the brake pads 10 and enters the first mode to compensate for it.

[0076] Figure 7 This is a side cross-sectional view showing the operation of the electromechanical brake 100 of this embodiment in a first mode state for compensating for wear of the brake pads 10. Figure 8 As Figure 7 The C-C' cross-sectional view shows the positions of the first protrusion 137, the second protrusion 138, and the third protrusion 139 in the first mode state.

[0077] Reference Figure 7 and Figure 8 In order to enter the first mode, the electronic control unit controls the actuator's operation, thereby causing the spindle 121 to rotate in the first direction. At this time, the electronic control unit rotates the spindle 121 in the first direction, which is used to achieve a normal braking state (see reference). Figure 5 and Figure 6 Based on the second angle, an additional first directional rotation (exceeding) is generated. Figure 4 The first protrusion 137 of the flange 136 on the main shaft 121 engages with the second protrusion 138 of the nut 125 and rotates. The second protrusion 138 is engaged by the first protrusion 137 and rotates together in the first direction, thereby causing the nut 125 to also rotate in the first direction. The piston 110 advances relative to the nut 125 by the rotation of the nut 125 in the first direction, thereby compensating for the wear of the brake pad 10.

[0078] After completing the first mode of compensating for the wear of the brake pads 10, the electromechanical brake 100 of this embodiment returns to the state before the vehicle's brakes are released or applied.

[0079] Figure 9 This is a side cross-sectional view showing the operation of the electromechanical brake 100 of this embodiment in the brake-released state of the vehicle after the first mode. Figure 10 As Figure 9 The D-D' cross-sectional view shows the positions of the first protrusion 137, the second protrusion 138, and the third protrusion 139 in the vehicle's brake-released state after the first mode.

[0080] Reference Figure 9 and Figure 10 The electronic control unit compensates for the wear of the brake pads 10 in a first mode, and then controls the actuator to rotate the main shaft 121 in a second direction. Specifically, as shown... Figure 2 and Figure 4 As shown, the actuator rotates the main shaft 121 in the second direction to restore it to the state before the vehicle's brakes are released or applied. As described above, in the first mode, the main shaft 121 undergoes an additional rotation in the first direction, but the electronic control unit rotates the main shaft 121 in the second direction by an amount corresponding to the additional rotation performed in the first mode, thereby restoring the main shaft 121 and nut 125 to their original positions.

[0081] After executing the first mode, the main shaft 121, which returns to its original position, rotates a second angle when the vehicle brakes again, so that the relative position of the piston 110 with respect to the main shaft 121 or the nut 125 is adjusted to perform braking action in a state that compensates for the wear of the brake pads 10, thereby performing stable braking of the vehicle.

[0082] The following describes the operation of the electromechanical brake 100 in this embodiment in order to reduce the drag phenomenon that the piston 110 cannot quickly return to its original position after the vehicle is braked.

[0083] If the contact force or connection force between the disc and the brake pad 10 detected by the sensing unit 140 when the vehicle's brakes are released is greater than the preset normal range value, the electronic control unit determines that there is a drag phenomenon that the piston 110 has not returned to its original position and enters the second mode.

[0084] Figure 11 This is a side cross-sectional view showing the operation of the electromechanical brake 100 of this embodiment in the second mode state to reduce drag. Figure 12 As Figure 11 The cross-sectional view along the E-E' direction shows the positions of the first protrusion 137, the second protrusion 138, and the third protrusion 139 in the second mode state.

[0085] Reference Figure 11 and Figure 12 In order to enter the second mode, the electronic control unit controls the actuator to rotate the spindle 121 in the second direction. At this time, the electronic control unit performs an additional second-direction rotation (exceeding) on ​​top of the second-direction rotation of the spindle 121 used to achieve the normal brake release state. Figure 4 The third protrusion 139 of the flange 136 on the main shaft 121 is engaged by the second protrusion 138 of the nut 125. The second protrusion 138, engaged by the third protrusion 139, rotates together in the second direction, causing the nut 125 to rotate in the second direction as well. This second-direction rotation of the nut 125 causes the piston 110 to retract relative to the nut 125, thereby separating the piston 110 from the pad and reducing drag.

Claims

1. An electromechanical brake comprising: a piston capable of advancing and retreating to pressurize a brake pad; a power conversion unit that converts rotational motion into linear motion to provide to the piston from a driver; a position adjustment section that adjusts a relative position of the piston with respect to the power conversion unit, the power conversion unit including: a main shaft that receives driving force from the driver to rotate; and a nut connected to the main shaft, which advances or retreats inside the piston to advance or retreat the piston by rotating the main shaft in a first direction or a second direction, the position adjustment section including: a first thread formed on an outer circumferential surface of the nut; a second thread formed on an inner circumferential surface of the piston and engaged with the first thread; and an adjuster provided between the main shaft and the nut, which advances or retreats the relative position of the piston by rotating the nut in the first direction or the second direction by rotation of the main shaft, the adjuster including: a flange formed so as to expand in a radial direction on an outer circumferential surface of the main shaft; a first protrusion protrusively formed on the flange; and a second protrusion protrusively formed on the nut, which is caught by the first protrusion to guide the nut to rotate in the first direction when the main shaft rotates in the first direction, thereby advancing the relative position of the piston.

2. The electromechanical brake according to claim 1, wherein a first angle between the first protrusion and the second protrusion is larger than a second angle by which the first protrusion rotates from a brake release state of a vehicle to a brake state of the vehicle in a state in which the brake of the vehicle is released.

3. The electromechanical brake according to claim 1, wherein the adjuster further includes a third protrusion protrusively formed on the flange, the second protrusion is caught by the third protrusion to guide the nut to rotate in the second direction when the main shaft rotates in the second direction, thereby retreating the relative position of the piston.

4. The electromechanical brake according to claim 3, wherein a third angle between the second protrusion and the third protrusion is larger than a fourth angle by which the third protrusion rotates from the brake state of the vehicle to the brake release state of the vehicle in the brake state of the vehicle.

5. The electromechanical brake according to claim 3, wherein an internal thread is formed on an inner circumferential surface of the nut, the main shaft includes a first end portion on one side, which has an external thread engaged with the internal thread formed on an outer circumferential surface, a second end portion on the other side, which is connected to the driver, and a central portion between the first end portion and the second end portion, the flange is fixedly provided on an outer circumferential surface of the central portion.

6. The electromechanical brake according to claim 5, wherein the first protrusion and the third protrusion are formed apart from each other and protrusively on a front surface of the flange opposite to the nut, the second protrusion is protrusively formed on a back surface of the nut opposite to the front surface of the flange.

7. The electromechanical brake according to claim 3, further comprising: an electronic control unit that controls an operation of the driver; and an electronic control unit that controls an operation of the driver. a sensing unit that detects a coupling force between a disc that rotates together with a wheel and the brake pad.

8. An operation method of an electromechanical brake according to claim 7, wherein, when the coupling force between the disc and the brake pad detected by the sensing unit in the braking state of the vehicle is less than a predetermined value, the electronic control unit determines that there is wear in the brake pad and enters a first mode in which the relative position of the piston is advanced.

9. The operation method of the electromechanical brake according to claim 8, wherein, when the coupling force between the disc and the brake pad detected by the sensing unit in the braking release state of the vehicle is greater than a predetermined value, the electronic control unit determines that there is drag and enters a second mode in which the relative position of the piston is retracted.

10. The operation method of the electromechanical brake according to claim 8, wherein, in the first mode, the operation of the actuator is controlled so that the main shaft rotates in the first direction from the braking release state of the vehicle to the braking state of the vehicle, the main shaft is caused to rotate by the additional first direction rotation of the main shaft so that the first protrusion and the second protrusion are brought into contact, thereby causing the nut to rotate in the first direction, and the relative position of the piston with respect to the nut is advanced by the first direction rotation of the nut.

11. The operation method of the electromechanical brake according to claim 10, wherein, after the first mode, the electronic control unit causes the main shaft or the first protrusion to return to the original position in the braking release state of the vehicle.

12. The operation method of the electromechanical brake according to claim 9, wherein, in the second mode, the operation of the actuator is controlled so that the main shaft rotates in the second direction from the braking state of the vehicle to the braking release state of the vehicle, the main shaft is caused to rotate by the additional second direction rotation of the main shaft so that the third protrusion and the second protrusion are brought into contact, thereby causing the nut to rotate in the second direction, and the relative position of the piston with respect to the nut is retracted by the second direction rotation of the nut.

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