Electro-Mechanical Brake

Abstract

Initiates the electric brake. According to one embodiment of the present disclosure, an electric brake is provided comprising: a wheel disc; a brake pad disposed on the side of the wheel disc; a piston configured to push the brake pad toward the wheel disc; a motor that supplies power to the piston; a hysteresis data storage unit that stores function information for an upward section in which braking force increases as the piston moves toward the wheel disc, and function information for a downward section in which braking force decreases as the piston moves toward the opposite side of the wheel disc; a position detection unit that detects the position of the piston; a calculation unit that calculates the derivative value of the piston's position with respect to time; a past state data storage unit that stores information for the previous section corresponding to the previous piston position; and a braking force calculation unit that calculates the braking force based on the derivative value of the piston's position and the information for the previous section.

Description

Technology Field

[0001] The present disclosure relates to an electric brake. Background Technology

[0002] The content described in this section merely provides background information regarding the present disclosure and does not constitute prior art.

[0003] Electro-mechanical brakes (EMBs) are widely used. Although originally developed as Electronic Parking Brakes (EPBs), their application is expanding to serve as primary brakes, replacing conventional hydraulic brakes. An EMB is a device in which a motor-driven actuator is mounted on the brake caliper to directly brake the vehicle using motor power, without the medium of brake fluid. While EMBs possess a mechanism similar to that of the Electronic Parking Brake (EPB), they require higher braking responsiveness and operational durability than EPBs because they are primarily used for main braking. Compared to hydraulic brakes, EMBs have a simpler structure, faster braking response speeds, and enable more precise control, thereby improving braking stability.

[0004] Electric brakes equipped with load sensors can accurately measure clamping force. However, if the EMB is equipped with a load sensor, the design of the sensor mounting section becomes more complex, and manufacturing costs increase. An increase in the size of the EMB due to the sensor installation is also inevitable.

[0005] To address the issues of rising manufacturing costs and increasing EMB size, clamping force can be estimated using a current sensor instead of a load sensor. The EMB can be designed so that the current sensor measures the current flowing through the motor generating the braking force, and the clamping force is estimated based on the measured current value. However, the method of estimating clamping force by measuring the current flowing through the motor suffers from lower estimation accuracy compared to using a load sensor due to measurement noise from the current sensor.

[0006] FIG. 11 is a schematic diagram showing the configuration of a conventional electric brake.

[0007] Referring to FIG. 11, the EMB includes a wheel disc (11_c), a pair of brake pads (11_b) positioned on both sides of the wheel disc (11_c), and a piston (11_a) configured to press the brake pads (11_b) toward the wheel disc (11_c). As the piston (11_a) moves toward the wheel disc (11_c), the braking force increases. However, even if the relative positions of the piston (11_a) and the brake pads (11_b) are the same, the braking force has different values ​​depending on the movement path of the piston (11_a). That is, the braking force with respect to the position of the piston (11_a) has hysteresis characteristics. Therefore, the braking force of the EMB cannot be accurately estimated without considering the movement path of the piston (11_a). The problem to be solved

[0008] An electric brake according to one embodiment can estimate the clamping force with high accuracy by estimating the clamping force based on the position of a piston where a specific current value is detected.

[0009] An electric brake according to one embodiment can calculate the braking force more accurately by considering the hysteresis characteristics of the braking force with respect to the position of the piston.

[0010] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0011] According to one embodiment of the present disclosure, an electric brake is provided comprising: a wheel disc; a brake pad disposed on the side of the wheel disc; a piston configured to push the brake pad toward the wheel disc; a motor that supplies power to the piston; a hysteresis data storage unit that stores function information for an upward section in which braking force increases as the piston moves toward the wheel disc, and function information for a downward section in which braking force decreases as the piston moves toward the opposite side of the wheel disc; a position detection unit that detects the position of the piston; a calculation unit that calculates the derivative value of the piston's position with respect to time; a past state data storage unit that stores information for the previous section corresponding to the previous piston position; and a braking force calculation unit that calculates the braking force based on the derivative value of the piston's position and the information for the previous section. Effects of the invention

[0012] According to one embodiment, the electric brake has the effect of estimating the clamping force with high accuracy by estimating the clamping force based on the position of the piston where a specific current value is detected.

[0013] According to one embodiment, the electric brake calculates the braking force by considering the hysteresis characteristics of the braking force with respect to the position of the piston, thereby having the effect of calculating the braking force more accurately. Brief explanation of the drawing

[0014] FIG. 1 is a schematic diagram showing the configuration of an electric brake according to one embodiment of the present disclosure. FIG. 2 is a diagram showing the driving state of an electric brake according to one embodiment of the present disclosure. Figure 3 is a graph showing the actual current according to the operating distance of the brake pad. Figure 4 is a graph illustrating a method for estimating the location of a contact point. Figure 5 is a graph showing the motor control timing for contact point detection. Figure 6 is a graph showing the magnitude of the braking force according to the position and direction of movement of the piston. FIG. 7 is a graph for explaining the process of determining a function that an electric brake follows to calculate braking force according to one embodiment of the present disclosure. FIG. 8 is a graph for explaining a transition interval function according to one embodiment of the present disclosure. FIG. 9 is a graph showing an ascending section function, a descending section function, and a transition section function according to one embodiment of the present disclosure. Figure 10 is a graph illustrating the change in the braking force function according to the position of the piston when the brake pad is worn out. Figure 11 is a schematic diagram showing the configuration of a conventional electric brake. Specific details for implementing the invention

[0015] Some embodiments of the present disclosure are described in detail below with reference to the exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the present disclosure, if it is determined that a detailed description of related known components or functions could obscure the essence of the present disclosure, such detailed description is omitted.

[0016] In describing the components of the embodiments according to the present disclosure, symbols such as first, second, i), ii), a), b), etc., may be used. These symbols are intended only to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the symbols. When a part in the specification is described as 'comprising' or 'having' a component, this means that, unless explicitly stated otherwise, it does not exclude other components but may include additional components.

[0017] FIG. 1 is a schematic diagram showing the configuration of an electric brake according to one embodiment of the present disclosure.

[0018] Referring to FIG. 1, an electric brake according to one embodiment of the present disclosure comprises all or part of a wheel disc (150), a brake pad (140), a piston (131), a motor (120), a current detection unit (180), a position detection unit (170), a hysteresis data storage unit (161), a calculation unit (162), a past state data storage unit (163), a transition section function data generating unit (164), a contact point calculation unit (165), a braking force calculation unit (166), and a motor controller (167).

[0019] The wheel disc (150) is attached to the wheel of the vehicle. The wheel disc (150) rotates together with the wheel of the vehicle. The vehicle can be braked by restricting the rotation of the wheel disc (150). A brake pad (140) is positioned on the side of the wheel disc (150). A piston (131) is configured to push the brake pad (140) toward the wheel disc (150) by driving the motor (120). As the piston (131) presses the brake pad (140) toward the wheel disc (150), frictional force is generated between the brake pad (140) and the wheel disc (150). Due to the frictional force generated between the brake pad (140) and the wheel disc (150), the rotation of the wheel disc (150) is restricted. The motor (120) supplies power to the piston (131).

[0020] The process of the piston (131) receiving power from the motor (120) and driving is described. The driving gear (134) rotates together with the rotation axis (121) of the motor (120) by the driving of the motor (120). The driving gear (134) meshes with the driven gear (133). When the driving gear (134) rotates, the driven gear (133) also rotates together. The driven gear (133) is coupled with the screw shaft (132). The screw shaft (132) rotates in conjunction with the rotation of the driven gear (133). A screw thread is formed on the outer surface of the screw shaft (132). A groove corresponding to the shape of the screw thread of the screw shaft (132) is formed on the inner surface of the piston (131). When the screw shaft (132) rotates together with the driven gear (133), the piston (131) moves in a straight line while engaging / unengaging with the screw shaft (132). When the piston (131) moves in a straight line toward the wheel disc (150), the brake pad (140) is pushed toward the wheel disc (150) by the piston (131).

[0021] The position detection unit (170) detects the position of the piston (131). The position of the piston (131) represents the distance from the lowest point of the stroke of the piston (131) to the piston (131). Here, the lowest point of the stroke refers to the position of the brake pad (140) when the brake pad (140) is maximally separated from the wheel disc (150).

[0022] The position detection unit (170) may include an angle sensor. The angle sensor measures the angular displacement of the rotation axis (121) of the motor (120). The position detection unit (170) can calculate the linear travel distance of the piston (131) using the angular displacement of the rotation axis (121) detected by the angle sensor. The linear travel distance of the piston (131) according to the rotation angle of the motor (120) may vary depending on the design of the electric brake. For example, an electric brake can be designed in which the linear travel distance of the piston (131) is 1 mm while the rotation axis (shaft, 121) of the motor (120) rotates 360 degrees.

[0023] FIG. 2 is a diagram showing the driving state of an electric brake according to one embodiment of the present disclosure.

[0024] Referring to FIG. 2, when the brake pad (140) is separated from the wheel disc (150) as in FIG. 2 (a), no braking force is formed. Here, braking force is a force that brakes the vehicle. When the piston (131) pushes the brake pad (140) and the brake pad (140) and the wheel disc (150) come into contact as in FIG. 2 (b), frictional force is generated between the brake pad (140) and the wheel disc (150). The frictional force generated between the brake pad (140) and the wheel disc (150) acts as a braking force. The position of the piston (131) when the brake pad (140) and the wheel disc (150) begin to come into contact is called the contact point. As in FIG. 2 (c), when the piston (131) moves past the contact point toward the wheel disc (150), the force with which the piston (131) presses the brake pad (140) increases. Here, the force with which the piston (131) presses the brake pad (140) is called the clamping force. As the clamping force increases, the frictional force generated between the brake pad (140) and the wheel disc (150) increases. In other words, the braking force increases.

[0025] An electric brake according to one embodiment of the present disclosure can estimate the clamping force using a current sensor and a position sensor without a load sensor.

[0026] The position detection unit (170) can precisely measure the position of the piston (131) using an angle sensor. However, since the contact point changes depending on the wear condition of the brake pad (140), the position of the contact point cannot be determined solely from the position of the piston (131). If the contact point cannot be determined, it is difficult to accurately estimate the clamping force based on the position of the piston (131).

[0027] The current detection unit (180) detects the current value flowing through the motor (120). The control unit (160) receives feedback on the current value detected by the current detection unit (180) and controls the motor (120). An electric brake device according to one embodiment of the present disclosure identifies the location of a contact point using current control.

[0028] Figure 3 is a graph showing the actual current according to the operating distance of the brake pad.

[0029] Referring to FIG. 3, the magnitude of the current flowing through the motor (120) increases in proportion to the strength of the clamping force. However, since the measurement value of the current sensor has a large error range, it is difficult to accurately estimate the clamping force. Referring to FIG. 3, the current sensor If the case where a value is detected is determined to be a contact point, a large error range (e) occurs due to measurement noise of the current sensor. A current detection unit (180) according to one embodiment of the present disclosure includes a current sensor that measures the current flowing through the motor (120) and a low-pass filter (not shown) that removes noise from the current value measured using the current sensor. If only the current sensor is used, the first current value may be measured at a plurality of piston (131) positions due to measurement noise. The contact point calculation unit (165) identifies the first position using the current value with reduced noise using the low-pass filter.

[0030] Figure 4 is a graph illustrating a method for estimating the location of a contact point.

[0031] Referring to FIG. 4, the horizontal axis of the graph represents the position of the piston (131), and the vertical axis represents the current value flowing through the motor (120). As you move to the right along the horizontal axis of the graph, the gap (g, see FIG. 1) between the brake pad (140) and the wheel disc (150) decreases.

[0032] The current value of the motor (120) is generally maintained at a constant value in the section prior to the contact point (X), but increases non-linearly during the non-linear section (a) shown in FIG. 4 after the contact point. If the operating distance is further increased past the non-linear section (a), the current value increases linearly during the linear section (b) shown in FIG. 4. Here, the linear section (b) refers to a section in which the current value detected using the current detection unit (180) changes linearly within a predetermined error range with respect to the position of the piston (131).

[0033] The current detection unit (180) detects the first current value ( The position of the piston (131) when ) is detected is defined as the first position (Y1). The first current value ( ) can be a preset value and a current value on the linear section (b). The first current value ( When the current value is on the linear section (b), the error range occurring in the linear section (b) is narrower than the error range (e) occurring in the non-linear section (a), so the contact point can be calculated more accurately.

[0034] The control unit (160) includes all or part of a hysteresis information storage unit (161), a calculation unit (162), a past state information storage unit (163), a transition section function information generation unit (164), a contact point calculation unit (165), a braking force calculation unit (166), and a motor controller (167).

[0035] The contact point calculation unit (165) calculates the contact point (X) based on the first position (Y1), which is the position of the piston (131) when the first current value is detected using the current detection unit (180). The contact point calculation unit (165) calculates the contact point (X) based on a preset distance ( A second position spaced apart from the opposite side of the wheel disc (150) by ) is calculated as the contact point (X). Pre-set distance ( The value of ) is an experimentally measured value and may vary depending on the specifications of the electric brake. The control unit (160) can determine the relative position of the brake pad (140) and the wheel disc (150) and the size of the air gap, etc., using a position sensor based on the determined contact point (X).

[0036] The motor controller (167) drives the motor (120) for a preset time when the vehicle is stopped to move the piston (131) toward the wheel disc (150). The motor controller (167) can drive the motor (120) for a preset time to move the piston (131) toward the wheel disc (150) when the vehicle is parked and the vehicle door is open. The motor controller (167) can drive the motor (120) at a preset angular velocity for a preset time when the door is open while the vehicle is parked. Based on the current value information regarding the position of the piston (131) collected during the preset time, the contact point calculation unit (165) can calculate the contact point (X).

[0037] If the driver presses the brake pedal before the preset time has elapsed, the motor controller (167) drives the motor (120) at a preset angular velocity for a preset time after the vehicle door is opened, thereby moving the piston (131) toward the wheel disc (150). Immediately after the preset time has elapsed, the motor controller (167) controls the motor (120) to generate a braking force corresponding to the braking signal.

[0038] Figure 5 is a graph showing the motor control timing for contact point detection.

[0039] Referring to FIG. 5, when the door is opened while the vehicle is stationary, the motor controller (167) drives the motor (120) at a constant angular velocity for about 2 seconds to move the piston (131) toward the wheel disc (150). In this disclosure, the motor controller (167) driving the motor (120) at a constant angular velocity for a preset time is referred to as ramp driving. The contact point calculation unit (165) identifies the contact point based on current value information regarding the position of the piston (131) obtained through ramp driving.

[0040] If the driver presses the pedal before the ramp drive ends, the motor controller (167) controls the motor (120) to generate a braking force corresponding to the braking signal input using the brake pedal immediately after the ramp drive ends. The ramp drive is performed while the vehicle is parked. Therefore, even if a braking force not corresponding to the braking signal generated by the driver is generated during the ramp drive, the driver cannot know that a braking force not corresponding to the braking signal has been generated.

[0041] The motor controller (167) controls the motor (120) so that the electric brake generates the required braking force based on the braking force calculated by the braking force calculation unit (166).

[0042] Figure 6 is a graph showing the magnitude of the braking force according to the position and direction of movement of the piston.

[0043] Referring to FIG. 6, the horizontal axis of the graph represents the position of the piston (131). The position of the piston (131) is set to 0 when the piston (131) is at the lowest point of the stroke. The vertical axis of the graph represents the braking force. The braking force is not determined solely by the position of the piston (131). Even if the piston (131) is in the same position, the braking force differs when the piston (131) moves toward the wheel disc (150) versus when the piston (131) moves toward the opposite side of the wheel disc (150). Therefore, in order to accurately estimate the braking force, not only the position of the piston (131) but also the movement path of the piston (131) must be considered. In the present disclosure, a function for the rising section in which the braking force increases as the piston (131) moves toward the wheel disc (150) is a rising section function ( (see FIG. 6), a function for a descending section in which the braking force decreases as the piston (131) moves to the opposite side of the wheel disc (150) descending section function ( It is called (see Fig. 6).

[0044] FIG. 7 is a graph for explaining the process of determining a function that an electric brake follows to calculate braking force according to one embodiment of the present disclosure.

[0045] Referring to FIG. 7, the vertical axis of the graph in FIG. 7 represents the position of the piston (131). The position of the piston (131) is set to 0 when the piston (131) is at the lowest point of the stroke. The horizontal axis of the graph represents the elapsed time.

[0046] The movement state of the piston (131) of the electric brake can be classified into four types. In this case, the piston (131) moves toward the wheel disc (150). That is, the derivative of the piston (131) position with respect to time is positive. State In this case, the position of the piston (131) decreases over time. That is, the derivative of the position of the piston (131) with respect to time is negative. State and state In this case, the position of the piston (131) does not change. That is, the derivative of the position of the piston (131) with respect to time is 0. State and state It is distinguished according to the movement state of the piston (131) just before the piston (131) stops. If the derivative value of the position of the piston (131) is positive before the piston (131) stops, the state Distinguish by, and if the derivative value of the piston (131) position is negative before the piston (131) stops, the state It can be distinguished as such. The movement state of the piston (131) is the state or state In this case, the braking force for the position of the piston (131) is determined according to the rising section function. The movement state of the piston (131) is a state or state In this case, the braking force for the position of the piston (131) is determined according to the descending section function.

[0047] The hysteresis information storage unit (161) is a rising interval function for the rising interval ( (see Fig. 6) information and a descent interval function for the descent interval ( (See Fig. 6) Stores information.

[0048] The calculation unit (162) calculates the derivative value of the piston (131) position with respect to time. The past state information storage unit (163) stores information about the previous section corresponding to the previous piston (131) position.

[0049] The braking force calculation unit (166) can calculate the braking force based on the derivative value of the piston (131) position and information regarding the previous section. When the derivative value of the piston (131) position with respect to time is positive, the braking force calculation unit (166) calculates the braking force by following the rising section function. When the derivative value of the piston (131) position with respect to time is negative, the braking force calculates the braking force by following the falling section function. When the derivative value of the piston (131) position with respect to time is 0 and the section corresponding to the previous piston (131) position is the rising section, the braking force calculates the braking force by following the rising section function. When the derivative value of the piston (131) position with respect to time is 0 and the section corresponding to the previous piston (131) position is the falling section, the braking force calculates the braking force by following the falling section function. By doing this, the braking force can be calculated using an appropriate function according to the movement state of the piston (131). By using an appropriate function to calculate the braking force, it is possible to calculate the braking force more accurately.

[0050] FIG. 8 is a graph for explaining a transition interval function according to one embodiment of the present disclosure.

[0051] Referring to FIG. 8, when the direction of movement of the piston (131) is changed at a position other than the maximum or minimum point of the braking force, the actual braking force follows a path that follows a transition section function. It changes continuously along the path. Here, the transition section refers to a section where the braking force is transferred from any point in either the rising section or the falling section to another section as the direction of movement of the piston (131) changes.

[0052] Figure 8 (a) is a graph showing the path of change in braking force according to the distance traveled by the piston when the piston moves in the direction of the wheel disc and then moves in the opposite direction of the wheel disc.

[0053] When the piston moves toward the wheel disc and then moves toward the opposite direction of the wheel disc, the magnitude of the braking force according to the distance traveled by the piston follows the path while moving toward the wheel disc. Eul, path in the transition section after the direction is changed , path after the transition section It changes according to.

[0054] Figure 8 (b) is a graph showing the path of change in braking force according to the distance traveled by the piston when the piston moves in the opposite direction of the wheel disc and then moves in the direction of the wheel disc.

[0055] When the piston moves from the opposite direction of the wheel disc to the direction of the wheel disc, the magnitude of the braking force according to the distance traveled by the piston follows the path while moving in the opposite direction of the wheel disc. Eul, path in the transition section after the direction is changed , path after the transition section It changes according to.

[0056] The function value of the transition interval function is the descending interval function ( greater than the function value of (see Fig. 6) and the rising interval function ( It has a value smaller than the function value of (see Fig. 6). The braking force calculation unit (166) calculates the braking force using the rising section function ( (see Fig. 6) or descending interval function ( If calculated solely by (see FIG. 6), an error occurs between the braking force calculated using the braking force calculation unit (166) in the transition section and the actual braking force. Therefore, an electric brake according to one embodiment of the present disclosure includes a transition section function information generation unit (164) that generates information of a transition section function.

[0057] The transition section function information generated by the transition section function information generation unit (164) can be determined based on the amount of wear of the brake pad (140).

[0058] A transition section function information generation unit (164) according to one embodiment of the present disclosure may include a memory (not shown) for storing transition section function information for a transition section. Transition section function information may be experimentally obtained, converted into a Look-Up Table (LUT), and stored in the memory. Function information stored in the memory is retrieved and used to calculate braking force. Alternatively, a transition section function information generation unit (164) according to another embodiment of the present disclosure includes a transition section function data calculating unit (not shown) that generates a function by calculating the transition section function based on the position of the piston (131) in real time.

[0059] The braking force calculation unit (166) calculates the braking force based on the position of the piston (131).

[0060] When the piston (131) moves toward the wheel disc (150), the rising section function ( The braking force can be calculated by substituting the position of the piston (131) into the (see FIG. 6). However, if the piston (131) moves to the opposite side of the wheel disc (150) and then moves to the side of the wheel disc (150), the transition section function value is the rising section function ( (See FIG. 6) In the position range of the piston (131) that is smaller than the value, the braking force is calculated using a transition range function. That is, when the direction of movement of the piston (131) changes from the opposite direction of the wheel disc (150) to the direction of the wheel disc (150), the braking force calculation unit (166) uses a transition range function and an upward range function ( The braking force is calculated by following the function with the smaller function value among (see Fig. 6).

[0061] When the piston (131) moves to the opposite side of the wheel disc (150), the descending section function ( The braking force can be calculated by substituting the position of the piston (131) into the function (see FIG. 6). However, if the piston (131) moves toward the wheel disc (150) and then moves toward the opposite side of the wheel disc (150), the transition section function value is the descending section function ( (See Fig. 6) In the position interval of the piston (131) smaller than the value, the descending interval function ( (see FIG. 6) to calculate the braking force. That is, when the direction of movement of the piston (131) changes from the direction of the wheel disc (150) to the opposite direction of the wheel disc (150), the braking force calculation unit (166) uses a transition section function and a descent section function ( The braking force is calculated by following the function with the larger function value among (see Fig. 6). By configuring the electric brake device in this way, it is possible to accurately estimate the braking force even when the direction of movement of the piston (131) is changed.

[0062] FIG. 9 is a graph showing an ascending section function, a descending section function, and a transition section function according to one embodiment of the present disclosure.

[0063] Referring to FIG. 9, a transition section function ( ; ) can have a positive slope. At any piston (131) position, the transition interval function ( ; The derivative of ) is the rising interval function( The derivative of (see Fig. 9) and the descent interval function ( It can be larger than the derivative value of (see Fig. 9).

[0064] Transition interval function( ; To generate ) more easily, the transition interval function( ; ) can be a linear function with a positive slope. Multiple transition interval functions existing between the rising interval and the falling interval ( ; ) can be a linear function with the same slope.

[0065] A control unit (160) according to one embodiment of the present disclosure determines the degree of wear of the brake pad (140) by measuring the distance between the contact point and the lowest point of the stroke of the piston (131).

[0066] Figure 10 is a graph illustrating the change in the braking force function according to the position of the piston when the brake pad is worn out.

[0067] Referring to FIG. 10, S1 is a graph representing the magnitude of the current with respect to the position of the piston (131). S2 is a graph representing the magnitude of the current with respect to the position of the piston (131) when the brake pad (140) is more worn than in S1. In FIG. 10, hysteresis characteristics were not shown to simply represent the piston (131) position-braking force graph according to the degree of wear of the brake pad (140). However, the following description is for the rising interval function ( , see Fig. 6), transition interval function and descent interval function ( This applies to all cases (see Fig. 6).

[0068] When the brake pad (140) wears out, the contact point moves from X to X'. That is, the contact point moves toward the wheel disc (150). As the brake pad (140) wears out, the stiffness of the brake pad (140) increases, causing the slope to increase in the linear section (b, see FIG. 5). The first verification point moves from Y1 to Y1'. Therefore, the pre-set distance, which is the distance from the first position to the second position, also at It must be set differently. That is, the pre-set distance must be set differently depending on the degree of wear of the brake pad (140).

[0069] The control unit (160) can determine that the degree of wear of the brake pad (140) increases as the absolute distance of the contact point (X) increases, by measuring the absolute distance of the contact point (X). Here, the absolute distance of the contact point (X) refers to the operating distance from the lowest point of the stroke to the contact point. The control unit (160) [determines] the degree of wear of the brake pad (140). A value can be found and applied. Depending on the degree of wear of the brake pad (140). The amount of change can be experimentally determined, converted into a Look-Up Table (LUT), and stored in the memory of the control unit (160). That is, the control unit (160) can determine the degree of wear of the brake pad (140) by calculating the absolute distance of the brake pad (140), and accordingly value The contact point (X') of the worn brake pad (140) can be estimated by converting it into a value.

[0070] As the brake pad (140) wears down, the derivative of the braking force function with respect to the position of the piston (131) increases at any position of the piston (131). An electric brake according to one embodiment of the present disclosure has an upward section function ( , see Fig. 6), transition interval function and descent interval function ( (see FIG. 6) reflects the determination of a hysteresis information storage unit (161) according to one embodiment of the present disclosure, which is determined based on the amount of wear of the brake pad (140), a plurality of rising section functions ( (see FIG. 6) A plurality of descending section functions determined based on information and the amount of wear of the brake pad (140) (See Fig. 6) Stores information.

[0071] The amount of wear on the brake pad (140) is the position of the piston (131) when the brake pad (140) and the wheel disc (150) begin to contact from the lowest point of the stroke of the piston (131). , It can be determined by measuring the distance to ).

[0072] The above description is merely an illustrative explanation of the technical concept of the present embodiment, and a person skilled in the art to which the present embodiment belongs would be able to make various modifications and variations within the scope of the essential characteristics of the present embodiment. Accordingly, the present embodiments are intended to explain, not limit, the technical concept of the present embodiment, and the scope of the technical concept of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present embodiment. Explanation of the symbols

[0073] 100: Electric brake 120: Motor 131: Piston 140: Brake pads 150: Wheel disc 161: Hysteresis Information Storage Unit 162: Operation unit 163: Past state information storage unit 164: Transition Interval Function Information Generation Unit 165: Contact Point Calculation Unit 166: Braking force calculation unit 167: Motor Controller 170: Position detection unit 180: Current detection unit

Claims

Claim 1 An electric brake configured such that a piston pushes a brake pad toward a wheel disc by driving a motor, comprising: a hysteresis data storage unit storing function information for an upward section in which braking force increases as the piston moves toward the wheel disc, and function information for a downward section in which braking force decreases as the piston moves toward the opposite side of the wheel disc; a position detection unit detecting the position of the piston; a calculation unit calculating a differential value of the piston's position with respect to time; a past state data storage unit storing information for a previous section corresponding to the previous piston position; and a braking force calculation unit calculating a braking force based on the differential value of the piston's position and the information for the previous section. Claim 2 In claim 1, the braking force calculation unit calculates the braking force by following the rising section function when the derivative value of the piston position with respect to time is positive, an electric brake. Claim 3 An electric brake according to claim 1, wherein the braking force calculation unit calculates the braking force by following the rising section function if the derivative value of the piston position with respect to time is 0 and the preceding section corresponding to the preceding piston position stored in the past state information storage unit is the rising section. Claim 4 An electric brake according to claim 1, wherein the braking force calculation unit calculates the braking force by following the descending section function if the derivative value of the piston position with respect to time is 0 and the preceding section corresponding to the preceding piston position stored in the past state information storage unit is the descending section. Claim 5 An electric brake according to claim 1, wherein the braking force calculation unit calculates the braking force by following the descending section function when the derivative value of the piston position with respect to time is negative.

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