Electric braking device

Abstract

To sensitively grasp that force for pressing a friction member becomes zero.SOLUTION: An electric braking device (1) includes an acquisition unit (103) that acquires a reference timing at which a magnitude of at least one of a time displacement amount which is a displacement amount of a moving body (12 or the like) per unit time, a time change rate which is a change amount of the time displacement amount per unit time, an angle displacement amount which is a displacement amount of the moving body (12 or the like) per unit rotation angle of an electric motor (80), and an angle change rate which is a change amount of the angle displacement amount per unit angle becomes equal to or larger than a predetermined threshold value, and a determination unit (104) that determines at least one of transition from a contact state in which a piston (30) is in contact with a friction member (40) to a separation state in which the piston (30) is separated from the friction member (40) and transition from the separation state to the contact state based on the reference timing acquired by the acquisition unit (103).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electric braking system. [Background technology]

[0002] Generally, in an electric braking device that does not have an axial force sensor that directly detects the pressing force of a friction member, a technology is known in which the pressing force of the friction member is estimated by measuring the displacement of a rotating member using a displacement sensor. In the disc brake disclosed in Patent Document 1, the thrust sensor that detects the reaction force against the pressing force on the braking member due to the thrust of the piston is composed of a conductive member that moves linearly under the influence of the reaction force, and a non-contact proximity sensor that includes a first coil and a second coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-100368 Summary of the Invention [Problem to be solved by the invention]

[0004] In the disc brake disclosed in Patent Document 1, a disc spring receives the reaction force against the pressing force on the braking member, and the conductive member attached as the target of the proximity sensor moves linearly according to the reaction force and the spring constant of the disc spring. The proximity sensor estimates the pressing force based on the displacement of the conductive member that follows the deformation of the disc spring, but because the change in the displacement is small near the point where the estimated pressing force becomes zero, the proximity sensor may not be able to sensitively detect the displacement of the rotating member where the pressing force becomes zero. An object of one aspect of the present disclosure is to detect with high sensitivity when the force pressing the friction member becomes zero. [Means for solving the problem]

[0005] In order to solve the above problems, an electric braking device according to one aspect of the present disclosure is an electric braking device that drives a piston in a forward or backward direction by the driving force of an electric motor and presses a friction member against a rotating member to generate a braking force on a wheel, and is equipped with: an acquisition unit that acquires a reference timing that is the point in time at which the magnitude of at least one of a time displacement amount that is the displacement amount of the moving body per unit time, a time change rate that is the change amount of the time displacement amount per unit time, an angular displacement amount that is the displacement amount of the moving body per unit rotation angle of the electric motor, and an angular change rate that is the change amount of the angular displacement amount per unit angle becomes equal to or exceeds a predetermined threshold; and a determination unit that determines, based on the reference timing acquired by the acquisition unit, at least one of a transition from a contact state in which the piston is in contact with the friction member to a separated state in which the piston is separated from the friction member, and a transition from the separated state to the contact state. The electric braking device according to each aspect of the present disclosure may be realized by a computer. In this case, the control program for the electric braking device that causes the computer to operate as each part (software element) of the electric braking device to realize the electric braking device, and the computer-readable recording medium on which the control program is recorded, also fall within the scope of the present disclosure. [Effects of the Invention]

[0006] According to one aspect of the present disclosure, it is possible to detect with high sensitivity when the force pressing the friction member becomes zero. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of an electric braking device according to a first embodiment of the present disclosure. [Figure 2] FIG. 10 is a diagram used to explain the processing of a determination unit. [Figure 3] FIG. 10 is a diagram used to explain the processing of a determination unit in an electric braking device according to a second embodiment of the present disclosure. [Figure 4] FIG. 10 is a diagram used to explain the processing of a determination unit in an electric braking device according to a third embodiment of the present disclosure. [Figure 5] FIG. 4 is a diagram used to explain a first restricting portion. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Embodiment 1] FIG. 1 is a schematic diagram of an electric braking device according to a first embodiment of the present disclosure. The electric braking device 1 shown in Fig. 1 includes a linear motion conversion mechanism 10, a cylinder 20, a piston 30, a friction member 40, a piston seal 50, a control board 60, a first sensor 70, an electric motor 80, a parking brake mechanism 90, and a control unit 100. The electric braking device 1 is used, for example, in an electric caliper disposed on the wheels of a vehicle. Hereinafter, the forward direction and reverse direction will be defined as shown by the arrows in Fig. 1.

[0009] The linear motion conversion mechanism 10 has a linear motion member 11 and a screw shaft 12. The linear motion member 11 is, for example, a nut and has a cylindrical shape. The outer circumferential surface of the linear motion member 11 faces the inner circumferential surface of the piston 30. The screw shaft 12 is screwed into the linear motion member 11. The cylinder 20 has a cylindrical shape with a bottom, with a bottom 21 on the retraction side. The piston 30 slides inside the cylinder 20. When the piston 30 slides in the retraction direction, it approaches the bottom 21 of the cylinder 20, and when it slides in the forward direction, it moves away from the bottom 21 of the cylinder 20. The screw shaft 12 of the linear motion conversion mechanism 10 penetrates the bottom 21 from the inside to the outside of the cylinder 20.

[0010] The screw shaft 12 is provided with a flange portion 13 inside the cylinder 20. The flange portion 13 protrudes inside the cylinder 20 in the direction of the rotation diameter of the screw shaft 12. A thrust bearing 14 is provided between the flange portion 13 and the bottom 21 of the cylinder 20. The screw shaft 12 is inserted into the thrust bearing 14. The thrust bearing 14 allows the screw shaft 12 to rotate relative to the cylinder 20. In the state shown in FIG. 1 , a gap exists between the thrust bearing 14 and the bottom 21 of the cylinder 20.

[0011] A gear 15 is provided on the outside of the cylinder 20. The gear 15 is provided, for example, on a portion of the screw shaft 12 outside the cylinder 20. Rotational motion generated by the electric motor 80 is transmitted to the gear 15 via a gear 82 or the like. The rotational motion of the gear 15 is transmitted to the linear motion member 11 that is screwed with the screw shaft 12. The linear motion member 11 converts the rotational motion of the screw shaft 12 into linear motion. When the gear 15 rotates in a predetermined forward direction, the linear motion member 11 moves linearly forward, and when the gear 15 rotates in a reverse direction, the linear motion member 11 moves linearly backward. The linear motion member 11 is connected to the piston 30 by a key member 31. The piston 30 is driven linearly by the linear motion member 11.

[0012] The bearing 16 is fixed to the cylinder 20. The bearing 16 is formed, for example, by combining a radial bearing and a thrust bearing. In the state shown in FIG. 1 , the bearing 16 abuts against the gear 15 on the outside of the cylinder 20. The screw shaft 12 is inserted through the bearing 16. The bearing 16 allows the screw shaft 12 to rotate relative to the cylinder 20.

[0013] The friction member 40 is, for example, a brake pad. When the piston 30 moves linearly forward, the axial force of the screw shaft 12 is applied to the friction member 40, and the friction member 40 is pressed against a rotating member such as a disc rotor that rotates together with the wheel, generating a braking force on the wheel.

[0014] The piston seal 50 is provided between the cylinder 20 and the piston 30 to prevent foreign matter from entering the inside of the cylinder 20. The piston seal 50 is deformed when the piston 30 moves linearly. The cylinder 20 moves forward or backward due to the restoring force of the piston seal 50. For example, when the piston 30 moves linearly forward, the restoring force of the piston seal 50 moves the cylinder 20 forward, and the bottom 21 of the cylinder 20 abuts against the thrust bearing 14.

[0015] The parking brake mechanism 90 has a ratchet gear 91 and a pawl portion 92. The pawls of the pawl portion 92 engage with the teeth of the ratchet gear 91, thereby restricting reverse rotation of the screw shaft 12, which moves the piston 30 linearly backward. As a result, the piston 30 is restricted from moving in a direction away from the rotating member, and the state in which the friction member 40 presses the rotating member is maintained.

[0016] The first sensor 70 is used to detect the displacement of the screw shaft 12. The first sensor 70 has a detectable portion 71 and a displacement detection portion 72. The detectable portion 71 is, for example, a conductive member provided at the tip of the screw shaft 12. When the screw shaft 12 rotates in the forward direction, the detectable portion 71 moves linearly forward, and when the screw shaft 12 rotates in the reverse direction, the detectable portion 71 moves linearly backward. The displacement detection unit 72 is, for example, a plurality of coils attached to the control board 60, and an excitation current is supplied to the displacement detection unit 72 under the control of the control unit 100. The displacement detection unit 72 is magnetically coupled to the detected unit 71, which is a conductive member. When the detected unit 71 moves, the magnetic coupling between the detected unit 71 and the displacement detection unit 72 changes, and the inductance of the plurality of coils changes. A second sensor 81 is provided coaxially with the electric motor 80. The second sensor 81 outputs a detection signal corresponding to the rotation angle of the electric motor 80 to the control unit 100. The second sensor 81 is provided on the control board 60. The second sensor 81 may detect the rotation of a gear 82 provided coaxially with the electric motor 80, or may detect the rotation of gear 15.

[0017] The control unit 100 is, for example, a microcomputer provided on the control board 60. The control unit 100 functions as a detection unit 101, a rotation angle detection unit 102, an acquisition unit 103, a determination unit 104, and a threshold setting unit 105.

[0018] The detection unit 101 detects the amount of displacement over time, which is the amount of displacement per unit time, of a moving body that moves due to a reaction force against the pressing force on the friction member 40 caused by the driving of the piston 30. In FIG. 1, the moving bodies are the screw shaft 12, the thrust bearing 14, and the bearing 16. The detection unit 101 detects the amount of displacement over time of these moving bodies based on the detection signal of the first sensor 70. The rotation angle detection unit 102 detects the rotation angle of the electric motor 80. The rotation angle detection unit 102 detects the rotation angle of the electric motor 80 based on the detection signal of the second sensor 81, for example.

[0019] The acquiring unit 103 according to the first embodiment acquires a reference time point, which is the time point at which the magnitude of the amount of time displacement of the moving object becomes equal to or greater than a predetermined threshold value X1. The judgment unit 104 judges, based on the reference timing acquired by the acquisition unit 103, that the piston 30 has transitioned from a contact state in which the piston 30 is in contact with the friction member 40 to a separation state in which the piston 30 is separated from the friction member 40.

[0020] The threshold setting unit 105 derives an estimate of the amount of displacement over time of the moving body based on the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102, and sets the threshold X1 based on the estimate. The threshold setting unit 105 sets the threshold X1 by correcting the threshold X1 from its reference value based on, for example, the difference between the estimate of the amount of displacement over time of the moving body and the amount of displacement over time detected by the detection unit 101. By setting the threshold X1 based on the estimate of the amount of displacement over time of the moving body, the acquisition unit 103 can appropriately acquire the reference timing even if wear of the friction member 40 progresses.

[0021] The control unit 100 determines the timing to release the braking force applied to the wheels based on the determination result of the determination unit 104. By properly determining the timing to release the braking force applied to the wheels, the occurrence of so-called brake drag, in which braking force continues to be applied to the wheels even when the brake pedal is not depressed, is suppressed.

[0022] Fig. 2 is a diagram used to explain the processing of the determination unit. Fig. 2 illustrates the change over time in the displacement of the screw shaft 12 from the state of the electric braking device 1 shown in Fig. 1 when the piston 30 is linearly moved forward to press the friction member 40, and then when the piston 30 is linearly moved backward to separate the piston 30 from the friction member 40. The horizontal axis of Fig. 2 represents time, and the vertical axis represents the displacement of the screw shaft 12.

[0023] 1, the piston 30 is in a separated state in which it is separated from the friction member 40. Therefore, the pressing force pressing the friction member 40 is zero. At timing T0, under the control of the control unit 100, the screw shaft 12 starts to rotate in the forward direction, and the piston 30 starts to move linearly forward, starting to deform the piston seal 50. At this time, the restoring force of the piston seal 50 moves the cylinder 20 forward, and the screw shaft 12 is displaced backward relative to the cylinder 20.

[0024] At timing T1, the piston 30 is in contact with the friction member 40. The amount of displacement of the screw shaft 12 relative to the cylinder 20 at timing T1 is defined as A. The gap between the bottom 21 of the cylinder 20 and the thrust bearing 14 becomes narrower by the amount of displacement A than in the state shown in FIG. 1, and the thrust bearing 14 abuts against the bottom 21 of the cylinder 20. The gap between the bearing 16 and the gear 15 becomes larger by the amount of displacement A.

[0025] After timing T1, the pressure with which the piston 30 presses the friction member 40 increases, pressing the friction member 40 against a rotating member such as a disc rotor. At this time, the piston 30 receives a reaction force against the pressure with which the piston 30 presses the friction member 40. This reaction force can also be described as a reaction force against the axial force of the screw shaft 12. The reaction force that the piston 30 receives from the friction member 40 deforms moving bodies such as the screw shaft 12, thrust bearing 14, and bearing 16, resulting in the screw shaft 12 being displaced in the backward direction. This further widens the gap between the bearing 16 and the gear 15. By timing T2, when the screw shaft 12 starts to rotate in the reverse direction, the screw shaft 12 has been displaced in the backward direction by A+B.

[0026] At timing T2, when the screw shaft 12 starts to rotate in the reverse direction, the pressing force of the piston 30 against the friction member 40 decreases, and the moving bodies such as the screw shaft 12, thrust bearing 14, and bearing 16 start to return to their original shape from the deformation caused by the reaction force of the axial force. At timing T3, the piston 30 moves away from the friction member 40 and transitions to a separated state. As the piston 30 moves away from the friction member 40, the pressing force of the piston 30 pressing the friction member 40 becomes zero.

[0027] Between timings T3 and T4, when the screw shaft 12 rotates in the reverse direction, the piston 30 separates from the friction member 40. At timing T4, when the piston 30 retreats to the position shown in FIG. 1, the piston seal 50 returns to its original state. At this time, the reaction force and restoring force acting on the screw shaft 12 become zero, and the screw shaft 12 suddenly changes direction in the forward direction until the gear 15 abuts against the bearing 16.

[0028] The threshold value X1 is set to a value that exceeds the amount of time displacement of the moving body including the screw shaft 12 during a sudden change in the screw shaft 12, but does not exceed the amount of time displacement of the moving body during any period other than the sudden change in the screw shaft 12. The acquisition unit 103 acquires, as a reference timing, the timing at which the amount of time displacement of the moving body including the screw shaft 12 during the sudden change in the screw shaft 12 becomes equal to or greater than the threshold value X1. When the acquisition unit 103 acquires the reference timing, the determination unit 104 determines that the piston 30 has transitioned from the approaching state to the separating state.

[0029] The threshold setting unit 105 derives an estimate of the amount of displacement over time of the moving object during the sudden change of the screw shaft 12, based on the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102 during the sudden change of the screw shaft 12. The threshold setting unit 105 corrects the threshold X1, for example, based on the difference between the estimate of the amount of displacement over time derived during the sudden change of the screw shaft 12 and the amount of displacement over time of the moving object detected by the detection unit 101.

[0030] [Embodiment 2] A second embodiment of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the first embodiment, and the description thereof will not be repeated.

[0031] An electric braking device 1 according to a second embodiment of the present disclosure differs from the first embodiment in that the key member 31 is not connected to the linearly moving member 11, and the relative position of the linearly moving member 11 with respect to the piston 30 changes. The moving body according to the second embodiment is the linearly moving member 11, the screw shaft 12, the thrust bearing 14, the bearing 16, etc. When the bearing 16 is fixed to the cylinder 20, the bearing 16 is not included in the moving body, and when the bearing 16 is not fixed to the cylinder 20, the bearing 16 is included in the moving body.

[0032] The key member 31 according to the second embodiment is an example of a first restricting portion, and is, for example, a ring stopper such as a C-ring. The key member 31 according to the second embodiment is located on the rearward direction side of the linear moving member 11. The key member 31 restricts the amount of change in the relative position of the linear moving member 11 with respect to the piston 30 according to the second embodiment to within a range equal to or less than a predetermined first distance (hereinafter, referred to as the first range). The first range includes, for example, at least a position where the linear moving member 11 abuts against the piston 30, a position where the linear moving member 11 abuts against the key member 31, and a position therebetween. For example, when the linear moving member 11 moves forward relative to the piston 30, it abuts against the piston 30, and when the linear moving member 11 moves backward relative to the piston 30, it abuts against the key member 31.

[0033] The gear 15 according to the second embodiment is an example of a second regulating portion. The gear 15 is connected to the screw shaft 12 outside the cylinder 20. A side surface of the gear 15 faces the bottom 21 of the cylinder 20 and the bearing 16. The gear 15 according to the second embodiment regulates the amount of forward movement of the screw shaft 12 to within a range equal to or less than a predetermined second distance (hereinafter, referred to as the second range). The second range includes, for example, at least the position of the screw shaft 12 when the side surface of the gear 15 abuts against the bearing 16, the position where the thrust bearing 14 abuts against the bottom 21 of the cylinder 20, and a position between them.

[0034] In the second embodiment, at timing T3, after the piston 30 separates from the friction member 40, and before the restoring force of the piston seal 50 becomes zero, not only does the screw shaft 12 suddenly change direction in the forward direction and the gear 15 abuts against the bearing 16, but also the linear moving member 11 moves backward relative to the piston 30 and abuts against the key member 31.

[0035] The electric braking device 1 according to the second embodiment is designed so that the static friction force between the screw shaft 12 and the bearing 16 is smaller than the static friction force between the linearly moving member 11 and the piston 30. Therefore, before the linearly moving member 11 starts to move backward relative to the piston 30, the screw shaft 12 starts to displace in the forward direction. Hereinafter, the static friction force generated between the linearly moving member 11 and the piston 30 will be referred to as a first static friction force, and the static friction force generated between the screw shaft 12 and the bearing 16 will be referred to as a second static friction force. The electric braking device 1 according to the second embodiment is designed so that the second static friction force is smaller than the first static friction force.

[0036] 3 is a diagram used to explain the processing of the determination unit in an electric braking device according to a second embodiment of the present disclosure. At timing T2 according to the second embodiment, the screw shaft 12 starts to rotate in the reverse direction. At this time, the linear motion member 11 abuts against the piston 30 and is separated from the key member 31. The flange portion 13 of the screw shaft 12 abuts against the thrust bearing 14, and the thrust bearing 14 abuts against the bottom 21 of the cylinder 20. The restoring force of the piston seal 50 is applied to the piston 30 in the backward direction. The axial force of the screw shaft 12 is applied from the linear motion member 11 to the piston 30 in the forward direction, and from the thrust bearing 14 to the bottom 21 of the cylinder 20 in the backward direction.

[0037] Between timings T2 and T3, the force with which the piston 30 presses the friction member 40 gradually decreases as the screw shaft 12 rotates in the reverse direction. At timing T3, the force with which the piston 30 presses the friction member 40 becomes zero.

[0038] Between timing T3 and timing T4 in the second embodiment, as the screw shaft 12 rotates in the reverse direction, the piston 30 moves away from the friction member 40. As the piston 30 moves away from the friction member 40, the shape of the piston seal 50 gradually returns to its original shape, and the restoring force of the piston seal 50 gradually decreases. At timing T4 in the second embodiment, the piston 30 moves back to the position shown in FIG. 1, and the restoring force of the piston seal 50 and the frictional force between the piston 30 and the cylinder 20 balance each other.

[0039] Between timings T4 and T6 according to the second embodiment, the moving body according to the second embodiment returns from its deformed state in accordance with the rotation of the screw shaft 12 in the reverse direction. In the electric braking device 1 according to the second embodiment, the second static friction force is designed to be smaller than the first static friction force, and therefore the screw shaft 12 begins to displace relative to the bearing 16 before the linearly moving member 11 begins to move relative to the piston 30. Between timings T4 and T5 according to the second embodiment, the screw shaft 12 displaces in the forward direction, and at timing T5, the gear 15 abuts against the bearing 16. Between timings T5 and T6, the linearly moving member 11 moves backward relative to the piston 30 and abuts against the key member 31.

[0040] Between timings T6 and T7, the axial force of the screw shaft 12 is applied from the linear motion member 11 to the key member 31 in the backward direction, and from the gear 15 to the bearing 16 in the forward direction. At this time, the piston 30 linearly moves backward, generating a restoring force in the piston seal 50. This restoring force of the piston seal 50 is applied to the piston 30 in the forward direction. At this time, the screw shaft 12 is displaced in the forward direction. At timing T7, the screw shaft 12 starts to rotate in the normal direction. At timing T0, the piston 30 advances to the position shown in FIG.

[0041] Between timings T0 to T9 according to the second embodiment, as the screw shaft 12 rotates in the forward direction, the moving body according to the second embodiment begins to return to its original shape. In the electric braking device 1 according to the second embodiment, the second static friction force is designed to be smaller than the first static friction force, and therefore the screw shaft 12 begins to displace relative to the bearing 16 before the linearly moving member 11 begins to move relative to the piston 30. Between timings T0 to T8 according to the second embodiment, the screw shaft 12 displaces in the backward direction, and at timing T8, the gear 15 moves away from the bearing 16. Between timings T8 to T9, the linearly moving member 11 moves forward relative to the piston 30 and comes into contact with the piston 30.

[0042] Between timings T9 and T1, the axial force of the screw shaft 12 is applied from the linear motion member 11 to the piston 30 in the forward direction, and from the thrust bearing 14 to the bottom 21 of the cylinder 20 in the backward direction. At this time, the linear movement of the piston 30 in the forward direction generates a restoring force in the piston seal 50. At timing T1, the restoring force of the piston seal 50 is applied to the piston 30 in the backward direction.

[0043] At timing T1, the piston 30 is in contact with the friction member 40. The amount of displacement of the screw shaft 12 relative to the displacement detection unit 72 at timing T1 is designated as A. The gap between the bottom 21 of the cylinder 20 and the thrust bearing 14 becomes narrower by the amount of displacement A than in the state shown in FIG. 1, and the thrust bearing 14 comes into contact with the bottom 21 of the cylinder 20.

[0044] After timing T1, the pressing force of the piston 30 against the friction member 40 increases, and the friction member 40 is pressed against a rotating member such as a disc rotor. At this time, the piston 30 receives a reaction force against the pressing force of the piston 30 against the friction member 40. The reaction force that the piston 30 receives from the friction member 40 deforms moving bodies such as the screw shaft 12, the bottom 21 of the cylinder 20, the thrust bearing 14, and the bearing 16, and as a result, the screw shaft 12 is displaced in the backward direction. This further widens the gap between the bearing 16 and the gear 15.

[0045] In the periods from timing T4 to T5 and T0 to T8 in embodiment 2, the amount of time displacement of the moving body detected by the detection unit 101 tends to match the amount of time displacement of the moving body estimated from the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102. During the periods from timing T5 to T6 and from timing T8 to T9, the moving body does not move even though the electric motor 80 rotates. During the periods from timing T6 to T7 and from T9 to T1, the amount of time displacement of the moving body detected by the detection unit 101 tends to not match the amount of time displacement of the moving body estimated from the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102.

[0046] Therefore, the acquiring unit 103 according to the second embodiment acquires at least one of the following as the reference timing according to the second embodiment. (1) The time T4 and T0 when the amount of displacement of the moving body detected by the detection unit 101 and the amount of displacement of the moving body estimated from the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102 start to match. (2) Timings T5 and T8 when the moving body stops moving even when the electric motor 80 rotates (3) Timing T6 when the screw shaft 12 begins to move forward (4) After the timing T8, the electric motor 80 is rotated and the moving body starts to move again at the timing T9.

[0047] For example, if the displacement amount per unit time of the screw shaft 12 changes significantly before and after timing T4, the acquisition unit 103 according to embodiment 2 may acquire the point in time at which the displacement amount of the screw shaft 12 over time becomes equal to or greater than a predetermined threshold value X1 as the reference timing (timing T4). If timing T4 cannot be accurately obtained based on the amount of displacement of the screw shaft 12 over time before and after timing T4, timing T5 when the screw shaft 12 stops displacing, timing T6 when the screw shaft 12 starts to displace in the forward direction, or the like may be obtained as the reference timing. Timing T5 is the point in time when the amount of displacement of the screw shaft 12 over time becomes equal to or greater than a predetermined threshold value −Y1 and equal to or less than +Y1. The predetermined threshold value Y1 is, for example, approximately zero. If the amount of displacement of the screw shaft 12 per unit time changes significantly before and after timing T6, the obtaining unit 103 according to the second embodiment may obtain the timing when the amount of displacement of the screw shaft 12 over time becomes equal to or greater than a predetermined threshold value as the reference timing (timing T6). Alternatively, if the displacement amount per unit time of the screw shaft 12 begins to change around timing T9, the acquisition unit 103 according to embodiment 2 may acquire the point in time at which the displacement amount of the screw shaft 12 over time becomes equal to or greater than a predetermined threshold value A1 as the reference timing (timing T9). If timing T9 cannot be accurately obtained based on the amount of displacement of the screw shaft 12 before and after timing T9, timing before T9, such as timing T8 when the screw shaft 12 stops displacing or timing T0 when the amount of displacement of the screw shaft 12 per unit time changes significantly, may be obtained as the reference timing. Timing T8 is the point in time when the amount of displacement of the screw shaft 12 per unit time is equal to or greater than a predetermined threshold value −B1 and equal to or less than a predetermined threshold value +B1. The predetermined threshold value B1 is, for example, approximately zero. If the amount of displacement of the screw shaft 12 per unit time changes significantly before and after timing T0, the obtaining unit 103 according to the second embodiment may obtain the time when the amount of displacement of the screw shaft 12 per unit time becomes equal to or greater than a predetermined threshold value as the reference timing (timing T0).

[0048] The determination unit 104 according to the second embodiment determines that the piston 30 has transitioned from the contact state to the separated state based on the reference timing acquired by the acquisition unit 103 according to the second embodiment. If the reference timing is timing T5 or T6, the determination unit 104 may determine that the piston 30 has transitioned from the contact state to the separated state by subtracting a predetermined time from the reference timing to estimate timing T4. Here, the predetermined time may be determined based on a first range (first distance) and a second range (second distance) defined in the design stage of the electric braking device 1. The acquisition unit 103 may also acquire timings T5 and T6 as the reference timings. For example, if the reference timing is timing T5, the determination unit 104 may estimate timing T4 by subtracting a predetermined time based on the second range from the reference timing. If the reference timing is timing T6, the determination unit 104 may estimate timing T4 by subtracting a predetermined time based on the first range and the second range from the reference timing. Alternatively, it can be determined that the piston 30 has transitioned from the separated state to the contact state as follows. If the reference timing is timing T8 or T0, the predetermined time is added to the reference timing to estimate timing T9, thereby determining that the piston 30 has transitioned from the separated state to the contact state. The acquisition unit 103 may also acquire timings T8 and T0 as the reference timing. For example, if the reference timing is timing T8, the predetermined time based on the first range is added to the reference timing to estimate timing T0. If the reference timing is timing T0, the predetermined time based on the first and second ranges is added to the reference timing to estimate timing T0.

[0049] [Embodiment 3] A third embodiment of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the first and second embodiments, and the description thereof will not be repeated. The electric braking device 1 according to the third embodiment of the present disclosure differs from the second embodiment in that it is designed so that the first static friction force is smaller than the second static friction force.

[0050] FIG. 4 is a diagram used to explain the processing of the determination unit in the electric braking device according to the second embodiment of the present disclosure. Between timings T4 and T6 in the third embodiment, when the moving body in the third embodiment returns from the deformed state in accordance with the rotation of the screw shaft 12 in the reverse direction, the linear motion conversion mechanism 10 starts to move relative to the piston 30 before the screw shaft 12 is displaced. Between timings T4 and T5 in the third embodiment, the linear motion member 11 moves backward relative to the piston 30. At timing T5 in the third embodiment, the linear motion member 11 abuts against the key member 31. Between timings T5 and T6 in the third embodiment, the screw shaft 12 is displaced forward, and the gear 15 abuts against the bearing 16.

[0051] Between timings T0 to T9 according to the third embodiment, the moving body according to the third embodiment begins to return from deformation as the screw shaft 12 rotates in the forward direction. Between timings T0 to T8 according to the third embodiment, the linear moving member 11 moves forward relative to the piston 30. At timing T8 according to the third embodiment, the linear moving member 11 abuts against the piston 30. Between timings T8 to T9 according to the third embodiment, the screw shaft 12 is displaced backward, and the gear 15 moves away from the bearing 16.

[0052] In the periods from timing T4 to T5 and from timing T0 to T8 according to the third embodiment, the moving body does not move even if the electric motor 80 rotates. In the periods from timing T5 to T6 and from timing T8 to T9 in embodiment 3, the amount of time displacement of the moving body detected by the detection unit 101 tends to match the amount of time displacement of the moving body estimated from the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102. In the periods from timing T6 to T7 and from timing T9 to T1 in embodiment 3, the amount of time displacement of the moving body detected by the detection unit 101 tends to not match the amount of time displacement of the moving body estimated from the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102.

[0053] Therefore, the acquiring unit 103 according to the third embodiment acquires at least one of the following as the reference timing according to the third embodiment. (1) The timings T4 and T0 when the electric motor 80 stops rotating but the moving body stops moving. (2) The timings T5 and T8 at which the amount of displacement over time of the moving body detected by the detection unit 101 and the amount of displacement over time of the moving body estimated from the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102 begin to match. (3) Timing T6 when the screw shaft 12 begins to move forward (4) After the timing T8, the time difference between the amount of displacement of the moving body over time detected by the detection unit 101 and the amount of displacement of the moving body over time estimated from the rotation angle of the electric motor 80 detected by the rotation angle detection unit 102 begins to diverge at the timing T9.

[0054] For example, the acquiring unit 103 according to the third embodiment may acquire the time point at which the amount of displacement of the screw shaft 12 over time becomes equal to or greater than a predetermined threshold value −Y1 and equal to or less than a predetermined threshold value +Y1 as the reference timing (timing T4). The judgment unit 104 according to the third embodiment judges that the piston 30 has transitioned from a contact state to a separated state, or that the piston 30 has transitioned from a separated state to a contact state, based on the reference timing acquired by the acquisition unit 103 according to the third embodiment.

[0055] [Software implementation example] The functions of the electric braking device 1 (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly each part included in the control unit 100). In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments. The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium. In addition, some or all of the functions of each of the control blocks can be realized by logic circuits. For example, integrated circuits in which logic circuits that function as each of the control blocks are formed are also included in the scope of the present disclosure. In addition, the functions of each of the control blocks can also be realized by, for example, a quantum computer. Furthermore, each process described in each of the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may run on the control device or on another device (for example, an edge computer or a cloud server).

[0056] [Modification] In the above-described first and second embodiments, the acquisition unit 103 acquires the reference timing at which the amount of displacement over time of a moving body such as the screw shaft 12 becomes equal to or greater than a predetermined threshold value X1, and the determination unit 104 determines that the piston 30 has transitioned from a contact state to a separated state or that the piston 30 has transitioned from a separated state to a contact state based on the reference timing acquired by the acquisition unit 103. However, the timing acquired by the acquisition unit 103 as the reference timing may be a time point other than the time point at which the magnitude of the amount of displacement over time of a moving body such as the screw shaft 12 becomes equal to or greater than the predetermined threshold value X1. For example, the acquiring unit 103 may acquire, as the reference timing, a time point at which the magnitude of the time change rate, which is the amount of change per unit time in the amount of time displacement of the moving object, becomes equal to or greater than a predetermined threshold value X2. The threshold value X2 is set to a value such that the time change rate of the moving object including the screw shaft 12 exceeds this value during a sudden change in the screw shaft 12, but does not exceed this value during periods other than when the screw shaft 12 is suddenly changing. The threshold value setting unit 105 may derive an estimate of the time change rate based on the rotation angle of the electric motor 80 detected by the rotation angle detecting unit 102, and set the threshold value X2 based on this estimate. For example, the acquiring unit 103 may derive the magnitude of the angular displacement, which is the displacement of the moving body per unit rotation angle of the electric motor 80, based on the rotation angle of the electric motor 80 detected by the rotation angle detecting unit 102, and acquire the time point at which the magnitude of the angular displacement becomes equal to or greater than a predetermined threshold X3 as the reference timing. The threshold X3 may be set to a value that exceeds the angular displacement of the electric motor 80 during a sudden change in the screw shaft 12, but does not exceed the angular displacement of the electric motor 80 during periods other than when a sudden change in the screw shaft 12 is occurring. The threshold setting unit 105 may derive an estimated value of the angular displacement based on the rotation angle of the electric motor 80 detected by the rotation angle detecting unit 102, and set the threshold X3 based on the estimated value. For example, the acquiring unit 103 may acquire, as the reference timing, a time point when the magnitude of the angle change rate, which is the amount of change per unit angle of the angular displacement, becomes equal to or greater than a predetermined threshold value X4. The threshold value X4 may be set to a value such that the angle change rate of the electric motor 80 exceeds this value during a sudden change in the screw shaft 12 and does not exceed this value during periods other than when a sudden change in the screw shaft 12 is occurring. The threshold value setting unit 105 may derive an estimated value of the angle change rate based on the rotation angle of the electric motor 80 detected by the rotation angle detecting unit 102, and set the threshold value X4 based on this estimated value. The acquiring unit 103 may acquire the reference timing based on a plurality of parameters among the amount of time displacement, the rate of time change, the amount of angular displacement, and the rate of angular change of the moving object. The threshold setting unit 105 may set thresholds for a plurality of parameters among the amount of time displacement, the rate of time change, the amount of angular displacement, and the rate of angular change of the moving object that the acquiring unit 103 uses to acquire the reference timing. For example, the acquiring unit 103 may acquire, as the reference timing, a time point at which the magnitude of the amount of time displacement of the moving object is equal to or greater than a predetermined threshold X1 and the magnitude of the rate of time change is equal to or greater than a predetermined threshold X2. In this case, the threshold setting unit 105 may set the threshold X1 and the threshold X2 based on the rotation angle of the electric motor 80.

[0057] In the above embodiments 1 to 3, the judgment unit 104 judges that the piston 30 has transitioned from a close state to a separated state, or that the piston 30 has transitioned from a separated state to a contact state, based on the reference timing acquired by the acquisition unit 103. The determination unit 104 may determine both that the piston 30 has transitioned from a contact state to a separated state and that the piston 30 has transitioned from a separated state to a contact state, based on the reference timing acquired by the acquisition unit 103. The reference timing for determining that the piston 30 has transitioned from a separated state to a contact state may be different from the reference timing for determining that the piston 30 has transitioned from a contact state to a separated state. The threshold setting unit 105 may set a threshold used by the acquisition unit 103 to acquire the reference timing at which the piston 30 transitions from the separated state to the contact state separately from the threshold used by the acquisition unit 103 to acquire the reference timing at which the piston 30 transitions from the contact state to the separated state.

[0058] The acquisition unit 103 may perform processing to acquire the reference timing when the restriction on the rotation of the screw shaft 12 in the reverse direction by the parking brake mechanism 90 is released. This is because the piston 30 does not transition from a contact state to a separation state while the rotation of the screw shaft 12 in the reverse direction is restricted by the parking brake mechanism 90.

[0059] The control unit 100 may store in a predetermined storage unit the reference timing acquired by the acquisition unit 103 for the piston 30. The determination unit 104 may determine, based on the reference timing stored in the predetermined storage unit, that the piston has transitioned from a contact state to a separated state and / or that the piston has transitioned from a separated state to a contact state.

[0060] In the above-described first to third embodiments, the displacement detecting unit 72 of the first sensor 70 is a plurality of coils, and the detected unit 71 is a conductive member. The first sensor 70 detects the displacement of the screw shaft 12 based on a change in magnetic coupling between the displacement detecting unit 72 and the detected unit 71. However, the method of detecting the displacement of the screw shaft 12 is not limited to a method based on a change in magnetic coupling between a conductive member and a plurality of coils. For example, a magnet may be used as the detected unit 71, and a Hall sensor may be used as the displacement detecting unit 72, and the displacement of the screw shaft 12 may be detected based on a change in the magnetic field caused by the detected unit 71.

[0061] When the timings T5 and T8 according to the second embodiment or the timings T4 and T0 according to the third embodiment are acquired as the reference timings, the time points at which the amount of displacement over time of the screw shaft 12 becomes equal to or greater than a predetermined threshold value −Y1 and equal to or less than +Y1 are acquired as the reference timings. However, the acquiring unit 103 may acquire the timings T5 and T8 according to the second embodiment or the timings T4 and T0 according to the third embodiment as the reference timings based on something other than the amount of displacement over time of a moving body such as the screw shaft 12. For example, the acquiring unit 103 may acquire the time points at which the rate of change over time, which is the amount of change per unit time in the amount of displacement over time of the moving body, becomes equal to or greater than a predetermined threshold value −Y2 and equal to or less than +Y2.

[0062] The acquisition unit 103 according to the third embodiment acquires the timings T4 and T9 according to the third embodiment as the reference timings. However, the acquisition unit 103 may acquire the timings T5, T6, T0, or T8 according to the third embodiment as the reference timings. When the timing T5 according to the third embodiment is the reference timing, it is possible to determine that the piston 30 has transitioned from the contact state to the separated state by subtracting a predetermined time from the reference timing to estimate the timing T4. For example, when the reference timing according to the third embodiment is timing T5, it is possible to estimate the timing T4 by subtracting a predetermined time based on the first range from the reference timing. When the reference timing according to the third embodiment is timing T6, it is possible to estimate the timing T4 by subtracting a predetermined time based on the first and second ranges from the reference timing. When the reference timing according to the third embodiment is timing T8, it is possible to determine that the piston 30 has transitioned from the separated state to the contact state by adding a predetermined time to the reference timing to estimate the timing T9. For example, when the reference timing according to the third embodiment is timing T8, it is possible to estimate the timing T9 by adding a predetermined time based on the second range to the reference timing. When the reference timing according to the third embodiment is timing T0, timing T9 can be estimated by adding a predetermined time based on the first range and the second range to the reference timing.

[0063] The electric braking device 1 according to the second embodiment is designed so that the second static friction force is smaller than the first static friction force. The electric braking device 1 according to the third embodiment is designed so that the first static friction force is smaller than the second static friction force. When functioning as the acquisition unit 103 and the determination unit 104, the control unit 100 may determine whether to function as the second embodiment or the third embodiment based on the magnitude relationship between the first static friction force and the second static friction force. That is, the determination unit 104 may determine that the piston 30 has transitioned from a contact state to a separated state or that the piston 30 has transitioned from a separated state to a contact state based on the magnitude relationship between the first static friction force and the second static friction force.

[0064] In the electric braking device 1 according to the second or third embodiment, the key member 31 is a wheel stopper such as a C-ring. However, the first restricting portion is not limited to the key member 31 located on the rearward direction side of the linearly moving member 11. FIG. 5 is a diagram used to explain the first restricting portion. In FIG. 5, the linear moving member 11 has a groove 31A on its side surface, and the piston 30 has a groove 31B on its surface (the inner peripheral side surface of the piston 30) facing the side surface of the linear moving member 11. In FIG. 5, the key member 31 is disposed so as to straddle the grooves 31A and 31B and is provided so as to be slidable in the grooves 31A and 31B. The key member 31, the groove 31A of the linear moving member 11, and the groove 31B of the piston 30 shown in FIG. 5 are a modified example of the first restricting portion. When the linear moving member 11 moves forward relative to the piston 30, the state shown in FIG. 5 is reached. In FIG. 5, the key member 31 abuts against the side wall of the groove 31A on the backward direction side and the side wall of the groove 31B on the forward direction side. When the linearly moving member 11 moves backward relative to the piston 30, the key member 31 comes into contact with the side wall of the groove 31A on the forward direction side and the side wall of the groove 31B on the backward direction side. The key member 31 may be fixed to either one of the grooves 31A or 31B.

[0065] 〔summary〕 An electric braking device according to one aspect of the present disclosure is an electric braking device that drives a piston in a forward or backward direction by the driving force of an electric motor and presses a friction member against a rotating member to generate a braking force on a wheel, and is equipped with: an acquisition unit that acquires a reference timing that is the point in time at which the magnitude of at least one of a time displacement amount that is the displacement amount of the moving body per unit time, a time change rate that is the change amount of the time displacement amount per unit time, an angular displacement amount that is the displacement amount of the moving body per unit rotation angle of the electric motor, and an angular change rate that is the change amount of the angular displacement amount per unit angle becomes equal to or exceeds a predetermined threshold; and a judgment unit that judges, based on the reference timing acquired by the acquisition unit, at least one of a transition from a contact state in which the piston is in contact with the friction member to a separated state in which the piston is separated from the friction member, and a transition from the separated state to the contact state. According to the present disclosure, at least one of the transition of the piston from a separated state to a contact state and the transition of the piston from a contact state to a separated state is determined based on the magnitude of at least one of the amount of displacement over time, the rate of change over time, the amount of angular displacement, and the rate of change of angle of the moving body, thereby making it possible to sensitively detect when the force pressing the friction member becomes zero.

[0066] In one aspect of the electric braking device of the present disclosure, the electric braking device includes a threshold setting unit that derives an estimated value of at least one of the time displacement amount, the time change rate, the angular displacement amount, and the angular change rate based on the rotation angle of the electric motor, and sets the threshold value based on the estimated value. According to the present disclosure, the threshold value can be adjusted so that the acquisition unit can properly acquire the reference timing even if the friction member is worn.

[0067] In one embodiment of the electric braking device of the present disclosure, the electric braking device includes a linear motion conversion mechanism that converts the rotational motion of the electric motor into linear motion of a linear motion part and linearly drives the piston in the forward direction or the backward direction using the linear motion part, and a first regulating unit that regulates the amount of change in the relative position of the linear motion part with respect to the piston to be equal to or less than a predetermined first distance, and the determining unit determines at least one of a transition to the separated state and a transition to the contact state based on the first distance in addition to the reference timing. According to the present disclosure, an electric braking device includes a first restriction unit that restricts the amount of change in the relative position of the linearly moving part with respect to the piston to a predetermined first distance or less, and a determination unit that determines whether the piston has transitioned from a contact state to a separated state or from a separated state to a contact state based on the first distance in addition to a reference timing. The reference timing is acquired after the piston transitions from the contact state to the separated state or before the piston transitions from the separated state to the contact state, and it is determined that the piston has transitioned from the contact state to the separated state or from the separated state to the contact state at a timing a predetermined time before the reference timing based on the first distance. Here, the first distance is a known parameter determined during the design phase of the electric braking device. Therefore, by having the determination unit determine whether the piston has transitioned from the contact state to the separated state based on the first distance, in addition to the reference timing, the accuracy of the determination can be improved.

[0068] In one aspect of the electric braking device of the present disclosure, the piston slides within a bottomed cylindrical cylinder portion, and approaches the bottom of the cylinder portion when sliding in the backward direction and moves away from the bottom of the cylinder portion when sliding in the forward direction. The electric braking device includes a linear motion conversion mechanism that is rotationally driven by the electric motor and has a screw shaft that penetrates the bottom of the cylinder portion from the inside to the outside, and a linear motion unit that converts the rotational motion of the screw shaft into linear motion and drives the piston in a linear motion. The second regulating unit is provided on the outer part of the cylinder portion of the screw shaft, protrudes in the rotational radial direction of the screw shaft, faces the bottom of the cylinder portion, and regulates the amount of movement of the screw shaft in the forward direction relative to the cylinder portion to be equal to or less than a predetermined second distance. The determining unit determines at least one of a transition to the separated state and a transition to the contact state based on the second distance in addition to the reference timing. According to the present disclosure, the electric braking device includes a second restriction unit that restricts the amount of forward movement of the screw shaft relative to the displacement of the screw shaft relative to the cylinder unit to a second distance or less, and the determination unit determines that the piston has transitioned from the contact state to the separated state or the piston has transitioned from the separated state to the contact state based on the second distance in addition to the reference timing. The reference timing is acquired after the piston transitions from the contact state to the separated state or before the piston transitions from the separated state to the contact state, and it is determined that the piston has transitioned from the contact state to the separated state or the piston has transitioned from the separated state to the contact state at a timing a predetermined time before the reference timing based on the second distance. Here, the second distance is a known parameter determined during the design phase of the electric braking device. By having the determination unit determine the transition from the contact state to the separated state or the transition from the separated state to the contact state based on the second distance, in addition to the reference timing, the accuracy of the determination can be improved.

[0069] In one aspect of the electric braking device of the present disclosure, the piston slides inside a cylindrical cylinder portion with a bottom, approaches a bottom of the cylinder portion when sliding in the backward direction, and moves away from the bottom of the cylinder portion when sliding in the forward direction, and includes a linear motion conversion mechanism that is rotationally driven by the electric motor and has a threaded shaft that penetrates the bottom from the inside to the outside of the cylinder portion, and a linear motion part that converts the rotational motion of the threaded shaft into linear motion and drives the piston in a linear motion; a first restriction part that restricts the displacement amount of the linear motion part relative to the piston to a predetermined first distance or less; and a second regulating portion provided on the outer portion of the cylinder portion, protruding in the direction of the rotational diameter of the screw shaft and facing the bottom portion of the cylinder portion, regulating the amount of movement of the screw shaft in the forward direction relative to the cylinder portion to a predetermined second distance or less, wherein the judgment portion determines a magnitude relationship between a first static friction force generated between the linear motion portion and the piston and a second static friction force generated between a bearing provided at the bottom portion and the screw shaft, and judges at least one of a transition to the separated state and a transition to the contact state based on the first distance, the second distance, and the magnitude relationship in addition to the reference timing. According to the present disclosure, the determination unit determines whether the contact state has transitioned to a separated state or whether the separated state has transitioned to a contact state based on the reference timing, the first distance, the second distance, and the magnitude relationship between the first static friction force and the second static friction force. Here, the first static friction force generated between the linearly moving part and the piston and the second static friction force generated between the bearing and the screw shaft are known parameters determined during the design stage of the electric braking device. Therefore, the order of the relative movement of the linearly moving part with respect to the piston and the relative movement of the piston with respect to the bearing is determined in advance during the design stage of the electric braking device. Therefore, by having the determination unit determine whether the contact state has transitioned to a separated state or whether the separated state has transitioned to a contact state based on the acquired reference timing and the known parameters, the first distance, the second distance, the first static friction force, and the second static friction force, the determination accuracy can be improved.

[0070] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0071] 1 Electric braking device 10. Linear motion conversion mechanism 11 Linear motion member 12 Screw shaft 14 Thrust bearing 16 Bearings 20 Cylinder (cylinder part) 30 pistons 40 Friction member 80 Electric Motor 81 Second Sensor 90 Parking brake mechanism 100 control section 101 Detector 102 Rotation angle detection unit 103 Acquisition Department 104 Judgment Department 105 Threshold setting unit T1, T2, T3, T4 timing

Claims

1. An electric braking device in which a piston is driven forward or backward by the driving force of an electric motor to press a friction member against a rotating member, thereby generating a braking force on a wheel, an acquisition unit that acquires a reference timing that is a time point at which the magnitude of at least one of a time displacement amount, which is a displacement amount of the moving body per unit time, a time change rate, which is a change rate of the time displacement amount per unit time, an angular displacement amount, which is a displacement amount of the moving body per unit rotation angle of the electric motor, and an angular change rate, which is a change rate of the angular displacement amount per unit angle, becomes equal to or greater than a predetermined threshold; a determination unit that determines, based on the reference timing acquired by the acquisition unit, at least one of a transition from a contact state in which the piston is in contact with the friction member to a separation state in which the piston is separated from the friction member and a transition from the separation state to the contact state; An electric braking device comprising:

2. 2. The electric braking device according to claim 1, further comprising a threshold setting unit that derives an estimated value of at least one of the time displacement amount, the time change rate, the angular displacement amount, and the angular change rate based on a rotation angle of the electric motor, and sets the threshold value based on the estimated value.

3. a linear motion conversion mechanism that converts the rotational motion of the electric motor into linear motion of a linear motion part, and causes the linear motion part to linearly drive the piston in the forward direction or the backward direction; a first restriction portion that restricts a change in the relative position of the linear moving portion with respect to the piston to a predetermined first distance or less, The electric braking device according to claim 1 , wherein the determination unit determines at least one of the transition to the separated state and the transition to the contact state based on the first distance in addition to the reference timing.

4. the piston slides in a cylindrical cylinder portion having a bottom, and approaches a bottom of the cylinder portion when sliding in the backward direction, and moves away from the bottom of the cylinder portion when sliding in the forward direction, a linear motion conversion mechanism including a screw shaft that is rotationally driven by the electric motor and penetrates the bottom portion from the inside to the outside of the cylinder portion, and a linear motion unit that converts the rotational motion of the screw shaft into linear motion and linearly drives the piston; A second regulating portion is provided on an outer portion of the cylinder portion of the screw shaft, protrudes in a rotational radial direction of the screw shaft, faces the bottom of the cylinder portion, and regulates the amount of movement of the screw shaft in the forward direction relative to the cylinder portion to a predetermined second distance or less. The electric braking device according to claim 1 , wherein the determination unit determines at least one of the transition to the separated state and the transition to the contact state based on the second distance in addition to the reference timing.

5. the piston slides in a cylindrical cylinder portion having a bottom, and approaches a bottom of the cylinder portion when sliding in the backward direction, and moves away from the bottom of the cylinder portion when sliding in the forward direction, a linear motion conversion mechanism including a screw shaft that is rotationally driven by the electric motor and penetrates the bottom portion from the inside to the outside of the cylinder portion, and a linear motion unit that converts the rotational motion of the screw shaft into linear motion and linearly drives the piston; a first restriction portion that restricts a displacement amount of the linear moving portion relative to the piston to a predetermined first distance or less; A second regulating portion is provided on an outer portion of the cylinder portion of the screw shaft, protrudes in a rotational radial direction of the screw shaft, faces the bottom of the cylinder portion, and regulates the amount of movement of the screw shaft in the forward direction relative to the cylinder portion to a predetermined second distance or less. a magnitude relationship between a first static friction force generated between the linear motion portion and the piston and a second static friction force generated between a bearing provided at the bottom portion and the screw shaft; 3. The electric braking device according to claim 1, wherein the determination unit determines at least one of a transition to the separated state and a transition to the contact state based on the first distance, the second distance, and the magnitude relationship in addition to the reference timing.

Images