Electric brake device

Abstract

According to the present invention, a braking mechanism drives an electric motor to press a brake pad toward a disk rotor. An electric brake ECU estimates a position of contact between the brake pad and the disk rotor on the basis of a braking characteristic (for example, a relationship between a motor current and a motor position of the electric motor). The electric brake ECU estimates the position of contact and / or stiffness by using as a reference (zero) the motor current at a position a predetermined value back from the motor position at which the motor current reaches a predetermined current as a result of contact between the brake pad and the disk rotor.

Description

Electric brake device

[0001] The present invention relates to an electric brake device that applies braking force to a vehicle such as an automobile.

[0002] Patent Document 1 describes an electric disc brake that estimates the pad contact position (contact position between the brake pad and the disc rotor) based on the current value of the electric motor (motor current).

[0003] JP 2010-83282 A

[0004] The technology described in Patent Document 1 improves the accuracy of pad contact position estimation by subtracting (removing) noise (pulsation) with a period corresponding to one rotation of the electric motor in the clearance area from the relationship between the measured motor position and motor current (braking characteristics). However, in this case, it is not possible to remove noise (pulsation) with a period corresponding to more than one rotation of the electric motor.

[0005] An object of the present invention is to provide an electric brake device that can improve the accuracy of estimating the contact position and the accuracy of estimating the stiffness.

[0006] An electric brake device according to one embodiment of the present invention comprises an actuator that presses a braking member toward a member to be braked by driving an electric motor, and a contact position estimation unit that estimates a contact position between the braking member and the member to be braked based on the braking characteristics of the electric brake device, wherein when a physical quantity corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical quantity due to contact between the braking member and the member to be braked, the contact position estimation unit moves the actuator position back by a predetermined value from the actuator position at that time, and estimates the contact position based on the physical quantity at the actuator position moved back by the predetermined value.

[0007] Moreover, an electric brake device according to one embodiment of the present invention includes an actuator that presses a braking member toward a member to be braked by driving an electric motor, and a stiffness estimation unit that estimates stiffness of the braking member, the member to be braked, and the actuator based on the braking characteristics of the electric brake device, and when a physical quantity corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical quantity due to contact between the braking member and the member to be braked, the stiffness estimation unit moves the actuator position back by a predetermined value from the actuator position at that time, and estimates the stiffness based on the physical quantity at the actuator position moved back by the predetermined value.

[0008] According to one embodiment of the present invention, it is possible to improve the accuracy of estimating the contact position and the accuracy of estimating the stiffness.

[0009] 6 is a schematic diagram showing a vehicle equipped with an electric brake device according to an embodiment. FIG. 1 is a perspective view showing the electric brake device in FIG. 1. FIG. 2 is a cross-sectional view showing the electric brake device in FIG. 1. FIG. 3 is a flowchart showing a process for offsetting a reference for braking characteristics. FIG. 4 is a flowchart (modified version) similar to FIG. 4 but adding a process for updating a predetermined value for return amount. FIG. 6 is a characteristic diagram showing an example of braking characteristics (20 types in total, including four types of low-frequency pulsation and five types of stiffness). FIG. 7 is a characteristic diagram showing an enlarged view (approximately 10 times) of section A in FIG. 6 only in the vertical direction. FIG. 8 is a characteristic diagram showing braking characteristics according to a comparative example (20 types in total, including four types of low-frequency pulsation and five types of stiffness). FIG. 9 is a characteristic diagram showing braking characteristics according to an embodiment (braking characteristics in which the braking characteristics according to the comparative example in FIG. 8 are offset). FIG. 10 is an explanatory diagram (characteristic diagram) explaining a change (advancement) in braking characteristics with pad wear. FIG. 11 is an explanatory diagram (characteristic diagram) showing braking characteristics (C1, C2) obtained by the processes from S3 to S6 of FIG. 4. FIG. 5 is an explanatory diagram (characteristic diagram) showing braking characteristics (C1, C2) obtained when the processing from S4 to S6 in FIG. 4 is performed on a memory.

[0010] An electric brake device according to an embodiment will be described below with reference to the accompanying drawings, taking as an example a case where it is installed in a four-wheeled vehicle. Each step in the flow charts shown in Figures 4 and 5 is represented by the letter "S" (for example, step 1 = "S1"). In Figure 1, a line with two diagonal lines represents an electrical system line. The suffix "L" corresponds to "left," and the suffix "R" corresponds to "right."

[0011] Fig. 1 shows a vehicle system. In Fig. 1, the vehicle 1 is equipped with a brake system 4 that applies braking forces to wheels 2, 3 (front wheels 2L, 2R and rear wheels 3L, 3R) to brake the vehicle 1. The brake system 4 includes left and right front-wheel electric brake devices 5L, 5R (front braking devices) provided corresponding to the left front wheel 2L (left front wheel 2L) and the right front wheel 2R (right front wheel 2R), left and right rear-wheel electric brake devices 6L, 6R (rear braking devices) provided corresponding to the left rear wheel 3L (left rear wheel 3L) and the right rear wheel 3R (right rear wheel 3R), a brake pedal 7 (operating device) as a brake operating member, a pedal reaction force device 8 (hereinafter referred to as pedal simulator 8) that generates a kickback reaction force in response to operation (depression) of the brake pedal 7, and a pedal stroke sensor 9 as an operation detection sensor that measures the amount of operation of the brake pedal 7 by the driver.

[0012] The left and right front-wheel electric brake devices 5L, 5R and the left and right rear-wheel electric brake devices 6L, 6R (hereinafter also referred to as electric brake devices 5, 6) are configured as, for example, electric disc brakes (electric disc brakes). The electric brake devices 5, 6 apply braking force to the wheels 2, 3 (front wheels 2L, 2R, rear wheels 3L, 3R) by driving an electric motor 26. Furthermore, for example, the left and right rear-wheel electric brake devices 6L, 6R are equipped with a parking mechanism (not shown).

[0013] The pedal stroke sensor 9 is provided, for example, in the pedal simulator 8. The pedal stroke sensor 9 may also be provided in the brake pedal 7. Furthermore, instead of the pedal stroke sensor 9, a pedal force sensor that measures a pedal force corresponding to the amount of operation of the brake pedal 7 may be used. The pedal stroke sensor 9 is connected to a first brake control ECU 10 and a second brake control ECU 11, which are ECUs (Electronic Control Units) for brake control.

[0014] A first brake control ECU 10 (also referred to as first ECU 10) and a second brake control ECU 11 (also referred to as second ECU 11) are provided in the vehicle 1. The first ECU 10 and the second ECU 11 are configured to include a microcomputer having a central processing unit (CPU), a storage device (memory), a control board, etc. The first ECU 10 and the second ECU 11 receive a signal from the pedal stroke sensor 9 and calculate the braking force (target braking force) for each wheel (four wheels) according to a predetermined control program.

[0015] The first ECU 10 calculates, for example, target braking forces to be applied to the left front wheel 2L and the right rear wheel 3R. Based on the calculated target braking forces, the first ECU 10 outputs (transmits) braking commands (control commands) for each of the left front wheel 2L and the right rear wheel 3R to the electric brake ECUs 31, 31 via a CAN 12 (Controller Area Network) serving as a vehicle data bus.

[0016] The second ECU 11 calculates, for example, target braking forces to be applied to the right front wheel 2R and the left rear wheel 3L. Based on the calculated target braking forces, the second ECU 11 outputs (transmits) braking commands (control commands) for each of the right front wheel 2R and the left rear wheel 3L to the electric brake ECUs 31, 31 via the CAN 12.

[0017] In order to perform such braking control, the first ECU 10 and the second ECU 11 are provided with control units 10A, 11A that perform calculations based on input information (e.g., a signal from the pedal stroke sensor 9, etc.) and output the calculation results (e.g., a control command according to a target thrust). The first ECU 10 and the second ECU 11 receive vehicle information transmitted via the CAN 12 from other ECUs mounted on the vehicle 1 (e.g., a prime mover ECU, a transmission ECU, a steering ECU, an automatic driving ECU, etc., not shown).

[0018] For example, the first ECU 10 and the second ECU 11 can acquire various vehicle information via the CAN 12, such as information on the AT range position or MT shift position, ignition on / off information, engine speed information, powertrain torque information, transmission gear ratio information, steering wheel operation information, clutch operation information, accelerator operation information, vehicle-to-vehicle communication information, information on the surroundings of the vehicle from an on-board camera, and information from an acceleration sensor (longitudinal acceleration, lateral acceleration).

[0019] A parking brake switch 13 is provided near the driver's seat. The parking brake switch 13 is connected to the first ECU 10 (and the second ECU 11 via the CAN 12). The parking brake switch 13 transmits a signal (an actuation request signal) corresponding to a request to actuate the parking brake (an apply request, which is a request to hold the parking brake, or a release request, which is a request to release the parking brake) in response to an operation instruction from the driver to the first ECU 10 and the second ECU 11. The first ECU 10 and the second ECU 11 transmit parking brake commands for each of the two rear wheels (rear wheels 3L, 3R) to the electric brake ECUs 31, 31 based on the operation (actuation request signal) of the parking brake switch 13. The parking brake switch 13 corresponds to a switch that actuates a parking mechanism.

[0020] 2 and 3 show the electric brake devices 5, 6. The electric brake devices 5, 6 include a braking mechanism 21 and an electric motor 26 that constitute actuators, and an electric brake ECU 31. The electric brake devices 5, 6 apply braking force to the vehicle 1 by controlling the position and thrust of the braking mechanism 21. To this end, the braking mechanism 21 includes a rotation angle sensor 32 ( FIG. 3 ) as position detection means that detects the motor rotation position, a thrust sensor 33 ( FIG. 3 ) as thrust detection means that detects the thrust generated in the piston 24 (piston thrust), and a current sensor 34 as current detection means that detects the current of the electric motor 26 (motor current).

[0021] The braking mechanism 21 includes, for example, a carrier 22, a caliper 23 serving as a cylinder (wheel cylinder), a piston 24 serving as a pressing member, and brake pads 25 serving as braking members (friction pads). The braking mechanism 21 includes an electric motor 26 for driving the braking mechanism 21, i.e., for generating a braking force by the braking mechanism 21. The braking mechanism 21 also includes a speed reduction mechanism 27, a rotary-to-linear motion conversion mechanism 28, and a return spring 29 serving as a fail-open mechanism. The speed reduction mechanism 27, together with an ECU board 31B of the electric brake ECU 31, are covered by a housing 30. The housing 30, the speed reduction mechanism 27, the electric motor 26, the rotation angle sensor 32, and the ECU board 31B constitute a driving member for driving the braking mechanism 21.

[0022] The carrier 22 is fixed to the body of the vehicle 1. The caliper 23 is supported (floatingly supported) by the carrier 22 to allow movement in the axial direction of the disc rotor D. The electric motor 26 rotates when supplied with electric power and propels the piston 24. In this way, the electric motor 26 applies a braking force. The electric motor 26 is controlled by the electric brake ECU 31 based on a braking command (control command) from the first ECU 10 or the second ECU 11. The speed reduction mechanism 27 is formed, for example, by a gear reduction mechanism, and reduces the rotation of the electric motor 26 before transmitting it to the rotary-to-linear motion conversion mechanism 28.

[0023] The rotary-linear motion conversion mechanism 28 converts the rotation of the electric motor 26, transmitted via the reduction gear mechanism 27, into axial displacement (linear displacement) of the piston 24. The piston 24 is driven by the electric motor 26 to move the brake pad 25. The brake pad 25 is pressed against the disc rotor D by the piston 24. The pair of brake pads 25, 25 are located on both axial sides of the disc rotor D and are each supported by the carrier 22. The disc rotor D, which serves as a braked member (rotor), rotates together with the wheels 2L, 2R, 3L, 3R.

[0024] When braking is applied, the return spring 29 applies a rotational force in the brake release direction to the rotating member of the rotary-to-linear motion conversion mechanism 28. In the braking mechanism 21, the piston 24 is driven by the electric motor 26 to press the brake pad 25 against the disc rotor D. That is, based on a braking request (braking command), the braking mechanism 21 transmits thrust generated by driving the electric motor 26 to the piston 24, which moves the brake pad 25. In this way, the braking mechanism 21 presses the brake pad 25 against the disc rotor D.

[0025] As shown in Fig. 1, an electric brake ECU 31 is provided for each brake mechanism 21. The electric brake ECU 31 includes, for example, a microcomputer having a central processing unit (CPU), a storage device (memory), a control board, etc., and a drive circuit (e.g., an inverter) for supplying power to the electric motor 26. As shown in Fig. 3, the electric brake ECU 31 includes an ECU board 31B in which the arithmetic circuit, etc. are incorporated. The electric brake ECU 31 controls the electric motor 26 that operates the brake mechanism 21 based on commands from the first ECU 10 or the second ECU 11.

[0026] The electric brake ECU 31 includes a control unit 31A (in other words, an ECU board 31B) that performs calculations based on input information (e.g., signals corresponding to control commands) and outputs the calculation results (e.g., electric motor drive commands corresponding to the control commands). The electric brake ECU 31, together with the first ECU 10 and the second ECU 11, constitutes a control device (brake control device) that controls the electric motor 26. In this case, the electric brake ECU 31 controls the drive of the electric motor 26 based on a braking command (control command) input to the electric brake ECU 31. The electric brake ECU 31 for the rear wheels controls the drive (apply, release) of the parking mechanism based on a parking operation command input to the electric brake ECU 31. A signal corresponding to the braking command and a signal corresponding to the parking operation command are input to the electric brake ECU 31 from the first ECU 10 or the second ECU 11.

[0027] The rotation angle sensor 32 detects the rotation angle (motor rotation angle) of the rotating shaft 26A of the electric motor 26. The rotation angle sensor 32 is provided corresponding to each electric motor 26 of each braking mechanism 21, and constitutes position detection means for detecting the rotation position (motor rotation position) of the electric motor 26 and, by extension, the position (piston position) of the piston 24. The rotation angle sensor 32 is, for example, composed of a magnet 32A, which is a magnetic member attached to the rotating shaft 26A of the electric motor 26, and a magnetic detection IC chip 32B, which is a magnet signal receiver provided in the electric brake ECU 31 (ECU board 31B). The electric brake ECU 31 (ECU board 31B) can calculate and detect the rotation angle of the rotating shaft 26A of the electric motor 26 by detecting changes in the magnetic flux of the rotating magnet 32A using the magnetic detection IC chip 32B.

[0028] The thrust sensor 33 detects a reaction force against the thrust (pressing force) from the piston 24 to the brake pad 25. The thrust sensor 33 is provided in each braking mechanism 21, and constitutes thrust detection means that detects the thrust (piston thrust) generated in the piston 24. The thrust sensor 33 is provided in the rotary-to-linear motion conversion mechanism 28. The current sensor 34 detects the current (motor current) supplied to the electric motor 26. The current sensor 34 is provided corresponding to each electric motor 26 of each braking mechanism 21, and constitutes current detection means that detects the current (motor current, motor torque current) supplied to the electric motor 26. The rotation angle sensor 32, the thrust sensor 33, and the current sensor 34 are connected to the electric brake ECU 31.

[0029] The electric brake ECU 31 (and the first ECU 10 and the second ECU 11 connected to this electric brake ECU 31 via the CAN 12) can obtain the rotation angle of the electric motor 26 based on a signal from the rotation angle sensor 32. The electric brake ECU 31 (and the first ECU 10 and the second ECU 11) can obtain the thrust generated in the piston 24 based on a signal from the thrust sensor 33. The electric brake ECU 31 (and the first ECU 10 and the second ECU 11) can obtain the motor current supplied to the electric motor 26 based on a signal from the current sensor 34.

[0030] Next, the braking and braking release operations of the electric brake devices 5, 6 will be described. Note that the following description will be given taking as an example the operation when the driver operates the brake pedal 7. However, in the case of automatic braking, the operation is almost the same except that, for example, an automatic braking command is output from the automatic driving ECU, the automatic braking ECU, the first ECU 10, or the second ECU 11 to the electric brake ECU 31.

[0031] For example, when the driver depresses the brake pedal 7 while the vehicle 1 is traveling, the first ECU 10 and the second ECU 11 output a command corresponding to the depression of the brake pedal 7 (a control command corresponding to the target thrust command value) to the electric brake ECU 31 based on a detection signal input from the pedal stroke sensor 9. The electric brake ECU 31 drives (rotates) the electric motor 26 in the forward direction, i.e., the braking direction, based on the command from the first ECU 10 and the second ECU 11. The rotation of the electric motor 26 is transmitted to the rotary-to-linear motion conversion mechanism 28 via the reduction mechanism 27, and the piston 24 moves forward toward the brake pads 25.

[0032] This presses the brake pads 25 against the disc rotor D, applying a braking force. At this time, the driving of the electric motor 26 is controlled based on detection signals from the pedal stroke sensor 9, the rotation angle sensor 32, the thrust sensor 33, etc., thereby establishing a braking state. During this braking, a force in the braking release direction is applied to the rotating member 28A of the rotary-to-linear motion conversion mechanism 28, and ultimately to the rotating shaft 26A of the electric motor 26, by the return spring 29 provided in the braking mechanism 21.

[0033] On the other hand, when the brake pedal 7 is operated to the release side, the first ECU 10 and the second ECU 11 output a command corresponding to this operation (a control command corresponding to the target thrust command value) to the electric brake ECU 31. The electric brake ECU 31 drives (rotates) the electric motor 26 in the reverse direction, i.e., the direction of braking release, based on the command from the first ECU 10 and the second ECU 11. The rotation of the electric motor 26 is transmitted to the rotary-to-linear motion conversion mechanism 28 via the speed reducer 27, and the piston 24 moves backward in a direction away from the brake pads 25. Then, when the brake pedal 7 is completely released, the brake pads 25 move away from the disc rotor D, and the braking force is released. In this non-braking state where the braking is released, the return spring 29 provided in the braking mechanism 21 returns to its initial state.

[0034] Next, thrust control and position control by the electric brake devices 5 and 6 will be described.

[0035] The first ECU 10 and the second ECU 11 calculate the braking force to be generated by the electric brake devices 5, 6, i.e., the target thrust to be generated by the piston 24, based on detection data from various sensors (e.g., the pedal stroke sensor 9), an automatic brake command, etc. The first ECU 10 and the second ECU 11 output braking commands (control commands) corresponding to the target thrust to the electric brake ECU 31. The electric brake ECU 31 performs thrust control on the electric motor 26 using feedback of the piston thrust detected by the thrust sensor 33, and position control on the electric motor 26 using feedback of the motor rotational position detected by the rotation angle sensor 32, so that the piston 24 generates the target thrust.

[0036] That is, the brake mechanism 21 adjusts the thrust of the piston 24 based on a braking command (target thrust) from the first ECU 10 and the second ECU 11 and a feedback signal from a thrust sensor 33 that measures the thrust of the piston 24. To determine the thrust, torque control of the electric motor 26 is performed via the rotary-to-linear motion conversion mechanism 28 and the speed reduction mechanism 27, i.e., current control is performed based on a feedback signal from a current sensor 34 that measures the amount of current flowing to the electric motor 26. There is a correlation between the braking force, piston thrust (thrust), torque of the electric motor 26 (motor torque), current value, and piston position (measurement value of the rotation speed of the electric motor 26 by the rotation angle sensor 32).

[0037] Braking force (braking force) by the electric brake devices 5, 6 is generated by pressing the brake pads 25 against the disc rotor D. At this time, the driver's braking request is detected by the pedal stroke sensor 9. The driver's braking request detected by the pedal stroke sensor 9 is input to the electric brake ECU 31 (ECU board 31B) as a braking command from the first ECU 10 and the second ECU 11. The electric brake ECU 31 (ECU board 31B) controls the electric motor 26 based on the braking command corresponding to the driver's request and a signal (signal corresponding to thrust) from the thrust sensor 33.

[0038] The torque generated by the electric motor 26 is amplified by the reduction gear mechanism 27 and converted into thrust by the rotary-to-linear motion conversion mechanism 28, i.e., thrust in the axial direction of the piston 24, causing the piston 24 to press the brake pad 25 against the disc rotor D. The electric motor 26 is controlled by a rotation angle sensor 32 detecting the rotation angle of a rotating shaft 26A, which is the rotation angle of the electric motor 26. That is, the electric motor 26 is controlled by a magnetic detection IC chip 32B, which serves as a magnet signal receiver, detecting changes in the magnetic flux of a magnet 32A that rotates together with the rotating shaft 26A. At this time, the rotation angle of the electric motor 26 detected by the rotation angle sensor 32 is used to control the position of the piston 24, thereby adjusting the amount of clearance between the brake pad 25 and the disc rotor D.

[0039] Incidentally, to control an electric brake device with high precision, it is necessary to accurately estimate the contact position between the braking member and the braked member. Furthermore, the stiffness of the braking member, the braked member, and the actuator (braking mechanism, electric motor) also needs to be accurately estimated depending on the specifications of the thrust sensor, or for control without using a thrust sensor (thrust sensorless control). That is, the contact position is necessary for accurately controlling the pad clearance, and the stiffness is necessary for accurately controlling the braking force (thrust) (more specifically, for accurately controlling the thrust without using a thrust sensor). Therefore, to control an electric brake device with high precision, it is necessary to accurately estimate the contact position and / or stiffness. However, if noise (pulsation) is introduced into the sensor values ​​of the controlled object, the accuracy of estimating the contact position and the stiffness decreases.

[0040] Therefore, in this embodiment, a position backed by a predetermined value set so as to always maintain clearance from the position where a predetermined motor current is reached is set as the reference position. Then, the contact position and stiffness are estimated based on the braking characteristics (the relationship between the piston position or motor position and the piston thrust or motor current) in which the motor current at this reference position is offset to zero (0). This reduces the influence of low-frequency pulsation and improves the accuracy of contact position and stiffness estimation. This reduces contact position variation and stiffness variation, and prevents the gap (clearance) between the braking member and the braked member from becoming too small or too large. As a result, the drag torque between the braking member and the braked member can be reduced, and responsiveness when applying braking force can be improved. These points are explained in detail below.

[0041] FIG. 6 shows the braking characteristics of the electric brake devices 5, 6, specifically, the braking characteristics expressed by the "motor position," which is the rotational position of the electric motor 26, and the "motor current," which is the current value of the electric motor 26. As an example, FIG. 6 shows a total of 20 types of characteristics, including four types of low-frequency pulsation and five types of stiffness. The position where the motor current suddenly increases corresponds to the position (contact position) where the braking member (brake pad 25) and the member to be braked (disc rotor D) come into contact with each other. In the clearance region before the contact position, the four types of low-frequency pulsation appear, and after the contact position, the five types of stiffness appear in a superimposed manner. The "motor position" is detected by, for example, the rotation angle sensor 32, and the "motor current" is detected by the current sensor 34.

[0042] The "motor position" correlates with the "piston position," which is the axial position of the piston 24. Therefore, the "piston position" may be used instead of the "motor position" as the braking characteristic. In this case, the "piston position" may be detected or calculated from the "motor position." When detecting the "piston position," for example, a displacement sensor that detects the displacement of the piston 24 may be provided in the braking mechanism 21. Furthermore, the "motor current" correlates with the "motor torque," which is the torque of the electric motor 26, or the "piston thrust," which is the thrust of the piston 24. Therefore, the "motor torque" or the "piston thrust" may be used instead of the "motor current" as the braking characteristic. In this case, the "motor torque" or the "piston thrust" may be detected or calculated from the "motor current." When detecting the "motor torque," for example, a torque sensor that detects the torque of the electric motor 26 (rotating shaft 26A) may be provided. When detecting the "piston thrust," it may be detected by the thrust sensor 33.

[0043] In either case, as shown in Figure 6, the motor current (motor torque, piston thrust) rises sharply as the brake pad 25 (braking member) comes into contact with the disc rotor D (brake receiving member). The braking characteristics at this time, i.e., the relationship between the "motor position (piston position)" and the "motor current (motor torque, piston thrust)", correspond to the rigidity of the brake pad 25, disc rotor D, and braking mechanism 21. For example, when the change (increase) in the motor current (motor torque, piston thrust) relative to the displacement (advance) of the motor position (piston position) is large, the rigidity is high, and when the change (increase) in the motor current (motor torque, piston thrust) relative to the displacement (advance) of the motor position (piston position) is small, the rigidity is low.

[0044] FIG. 7 shows a magnified view (e.g., approximately 10 times) of portion A in FIG. 6 only in the vertical direction (up and down direction). The contact position where the motor current (motor torque, piston thrust) begins to rise sharply gradually advances due to wear of the brake pad 25 and disc rotor D, etc. For example, as shown in FIG. 10 , contact positions P1, P2, and P3 gradually move to the right in the order P1 → P2 → P3 as wear of the brake pad 25 and disc rotor D progresses. Furthermore, as shown by multiple characteristic lines after the contact positions, the stiffness of the brake pad 25, disc rotor D, and braking mechanism 21 varies not only due to wear and uneven wear of the brake pad 25 and disc rotor D, but also due to the temperature and efficiency of the actuator (brake mechanism 21, electric motor 26), etc. Furthermore, when low-frequency pulsation caused by the meshing of the gears of the reduction mechanism 27 is added, the motor current (thrust force) varies by four times the amplitude of the pulsation even with the same rigidity, as shown in the characteristics of "+low-frequency single-sided swing upper limit side" and "+low-frequency single-sided swing lower limit side" in Figures 6 and 7. Therefore, if the contact position and / or rigidity are estimated based on this characteristic, the estimation results will also vary.

[0045] Therefore, in this embodiment, the influence of low-frequency pulsation is reduced by offsetting (correcting) the braking characteristics from those shown in FIG. 8 to those shown in FIG. 9 by performing the process shown in FIG. 4 . Similar to FIGS. 6 and 7 , FIGS. 8 and 9 also show a total of 20 types of characteristics, including four types of low-frequency pulsation and five types of stiffness, for the same contact position. As a comparative example, FIG. 8 shows the braking characteristics before the process shown in FIG. 4 is performed. In contrast, FIG. 9 shows the braking characteristics after the variation is reduced by performing the process shown in FIG. 4 . The process shown in FIG. 4 offsets (corrects) the braking characteristics from those shown in FIG. 8 to those shown in FIG. 9 . As shown in FIG. 8 , if the point A is the point at which the motor current (motor torque, piston thrust) reaches a predetermined current T (predetermined torque T, predetermined thrust T) and the point B is the point at which the motor current (motor torque, piston thrust) has returned a predetermined amount S from point A, the process shown in FIG. 4 offsets (corrects) the braking characteristics so that the motor current (motor torque, piston thrust) at point B becomes a reference value (e.g., zero). As a result, the braking characteristics (corrected braking characteristics) shown in FIG. 9 can be obtained by offsetting (correcting) the braking characteristics shown in FIG. 8.

[0046] Next, the process shown in Fig. 4 will be described with reference to Fig. 11 in addition to Fig. 8 and Fig. 9. The process in Fig. 4 is performed, for example, by the electric brake ECU 31 (control unit 31A). In this case, the electric brake ECU 31 can start the process in Fig. 4 based on a command (offset command) from, for example, the first ECU 10 or the second ECU 11. The specific timing for starting the process will be described later.

[0047] In S1, a predetermined return amount value S (piston return amount S, motor return amount S) is determined (calculated) in advance. This determined predetermined value S is stored, for example, in the memory of the electric brake ECU 31. The predetermined value S is the return amount of the electric motor 26 (piston 24) used in the process of S4, which will be described later. The predetermined value S can be stored in memory in advance, such as during the manufacture of the vehicle 1 (before the electric brake devices 5, 6 are put into use), and the process of S1 does not need to be performed every time. The magnitude of the predetermined value S will be described later. In the following S2, a contact position estimation and stiffness estimation mode is started. That is, a process for offsetting the braking characteristics is started. Specifically, the process proceeds to S3, where the electric motor 26 is driven in the forward direction, i.e., in the direction in which the brake pads 25 contact the disc rotor D (the direction in which braking force is applied). As a result, the piston 24 advances, the brake pads 25 contact the disc rotor D, and the brake pads 25 press (clamp) the disc rotor D, and the motor current begins to increase. FIG. 11 shows two characteristics C1 and C2, that is, the characteristic C1 of "+low frequency one-sided swing upper limit side" and the characteristic C2 of "+low frequency one-sided swing lower limit side".

[0048] In S3, the electric motor 26 is driven in the forward direction until the physical quantity (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force reaches a predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T). Point A in FIGS. 8 and 11 corresponds to the point at which the predetermined current T, which corresponds to the predetermined physical quantity, is reached. The magnitude of the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T) will be described later. In the following S4, the electric motor 26 is returned a predetermined value S in the X-axis direction from the position at which the motor current (piston thrust, motor torque) reaches the predetermined current T (predetermined thrust T, predetermined torque T). That is, the electric motor 26 is stopped at a position corresponding to point A, and then driven in the reverse direction from this position, i.e., in the direction in which the brake pads 25 move away from the disc rotor D (the direction in which the application of the braking force is released), to return to a position corresponding to point B. As shown in FIG. 8, if the position in the X-axis direction of point A where the motor current (piston thrust, motor torque) reaches a predetermined current T (predetermined thrust T, predetermined torque T) is defined as xa, and the position in the X-axis direction of point B is defined as xb, then xa - S = xb.

[0049] In the next step S5, the motor current (piston thrust, motor torque) at point B is offset to a reference value (e.g., zero). That is, as indicated by the arrows in FIGS. 8 and 11, the motor current (piston thrust, motor torque) at point B is offset to zero. In other words, if the value in the Y-axis direction (motor current, piston thrust, motor torque) at point B is yb, yb is set to 0. In the next step S6, the electric motor 26 is driven in the forward direction again, and the contact position and stiffness are estimated based on the characteristics at that time (i.e., the braking characteristics in FIG. 9 and the characteristics C1 and C2 after offset in FIG. 11). That is, in S6, "-yb" is subtracted from the motor current (piston thrust, motor torque) measured (detected) when the electric motor 26 is driven in the forward direction again. The relationship between the motor current (piston thrust, motor torque) and the motor position (piston position) obtained in this way is set as the post-correction (post-offset) characteristics C1 and C2, and the contact position and stiffness are estimated using these post-correction (post-offset) characteristics C1 and C2. Figure 9 corresponds to the post-offset (post-correction) braking characteristics (post-correction braking characteristics) in which all of the braking characteristics in Figure 8 are offset.

[0050] Here, the predetermined value S is set to be equal to or greater than the maximum displacement amount until the predetermined physical quantity T is reached, which is assumed to include factors such as wear and uneven wear of the brake pads 25, tilt of the disc rotor D, temperature, efficiency of the braking mechanism 21, and pulsation. That is, the predetermined value S can be calculated based on the largest displacement amount (motor displacement amount, piston displacement amount) until the physical quantity (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force reaches the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T). The predetermined physical quantity T is set to be a value greater than the maximum amplitude of pulsation in the detected value of the physical quantity caused by the actuator (brake mechanism 21, electric motor 26), including pulsation, or a value greater than twice the maximum amplitude if the pulsation is unidirectional. That is, the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T) can be set to be a value greater than the maximum amplitude of pulsation in the detected value of the physical quantity (motor current, piston thrust, motor torque) caused by the actuator (brake mechanism 21, electric motor 26). Furthermore, the predetermined physical quantity T may be changed depending on the temperatures of the actuator (brake mechanism 21, electric motor 26), the brake pad 25, the disc rotor D, etc. In this way, when the predetermined value S is returned, the clearance between the brake pad 25 and the disc rotor D can be made equal to or greater than 0, and the variations in the physical quantities (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force at the contact position can be minimized.

[0051] Note that the processing from S4 onward in FIG. 4 may be performed in the memory of the electric brake ECU 31. In this case, as shown in FIG. 12 , the electric motor 26 continues to drive even after reaching a predetermined current T, which is a predetermined physical quantity. The characteristics stored in the memory at this time, i.e., the relationship between the motor current (piston thrust, motor torque) and the motor position (piston position), are offset in the memory. For example, if the thick solid line characteristic C1 is obtained by driving the electric motor 26, the motor current (piston thrust, motor torque) at point B, which is a predetermined amount S back from point A, is offset to zero. This allows the offset (corrected) thin solid line characteristic C1 to be obtained in the memory. Furthermore, for example, if the thick dashed line characteristic C2 is obtained by driving the electric motor 26, the motor current (piston thrust, motor torque) at point B, which is a predetermined amount S back from point A, is offset to zero. This allows the offset (corrected) thin dashed line characteristic C2 to be obtained in the memory.

[0052] As described above, in the embodiment, the electric brake devices 5, 6 include an actuator and a contact position estimator. The actuator presses the brake pads 25, which serve as braking members, toward the disc rotor D, which serves as a braked member, by driving the electric motor 26. The actuator corresponds to, for example, the brake mechanism 21 and the electric motor 26. The contact position estimator estimates the contact position between the brake pads 25 and the disc rotor D based on braking characteristics. The contact position estimator corresponds to, for example, the electric brake ECU 31 (control unit 31A). The contact position estimator (control unit 31A) returns the actuator position (e.g., motor position, piston position) by a predetermined value S from the position at which a physical quantity (e.g., motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force of the actuator (brake mechanism 21, electric motor 26) reaches a predetermined physical quantity T (e.g., predetermined current T, predetermined thrust T, predetermined torque T) due to contact between the brake pads 25 and the disc rotor D. Then, the contact position estimation unit (control unit 31A) estimates the contact position using the physical quantities (motor current, piston thrust, motor torque) at the position returned by the predetermined value S as a reference (for example, zero).

[0053] In the embodiments, the electric brake devices 5 and 6 each include a stiffness estimation unit. The stiffness estimation unit estimates stiffness of the brake pads 25, the disc rotor D, and the actuator (the brake mechanism 21, the electric motor 26) based on braking characteristics. The stiffness estimation unit corresponds to, for example, the electric brake ECU 31 (control unit 31A). The stiffness estimation unit (control unit 31A) returns a predetermined value S from the actuator position (e.g., the motor position, the piston position) when a physical quantity (e.g., the motor current, the piston thrust, the motor torque) corresponding to the magnitude of the braking force of the actuator (the brake mechanism 21, the electric motor 26) reaches a predetermined physical quantity T (e.g., the predetermined current T, the predetermined thrust T, the predetermined torque T) due to contact between the brake pads 25 and the disc rotor D. The stiffness estimation unit (control unit 31A) then estimates stiffness using the physical quantity (the motor current, the piston thrust, the motor torque) at the position returned by the predetermined value S as a reference (e.g., zero).

[0054] The predetermined physical quantity T (e.g., predetermined current T, predetermined thrust T, predetermined torque T) is set to a value greater than the maximum amplitude of pulsation in the detected value of a physical quantity (e.g., motor current, piston thrust, motor torque) caused by the actuator (brake mechanism 21, electric motor 26). For example, as shown in FIGS. 6 and 7 , the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T) is set to a value greater than the maximum amplitude of the "+ low-frequency single-ended swing upper limit side." Meanwhile, the predetermined value S is calculated, for example, based on the largest displacement (motor displacement, piston displacement) until the physical quantity (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force reaches the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T). For example, as shown in FIGS. 8 , 11 and 12 , the predetermined value S can be set to a displacement amount (motor displacement amount, piston displacement amount) that allows the physical quantity (motor current, piston thrust, motor torque) to return to the clearance region from a position where the physical quantity (motor current, piston thrust, motor torque) reaches a predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T) even when the low-frequency single-sided swing is on the “+ lower limit side.”

[0055] As described above, according to the embodiment, the electric brake ECU 31 (control unit 31A) estimates the contact position and / or stiffness using as a reference (zero) the motor current at a position that is a predetermined value S back from the motor position when the motor current reaches the predetermined current T, as shown in Figures 8, 11, and 12. Note that the electric brake ECU 31 (control unit 31A) may estimate the contact position and / or stiffness using as a reference (zero) the piston thrust at a position that is a predetermined value S back from the piston position when the piston thrust reaches the predetermined thrust T. Alternatively, the electric brake ECU 31 (control unit 31A) may estimate the contact position and / or stiffness using as a reference (zero) the motor torque at a position that is a predetermined value S back from the motor position when the motor torque reaches the predetermined torque T.

[0056] In either case, the contact position and / or stiffness can be estimated based on braking characteristics in which the motor current, piston thrust, or motor torque at a position returned by a predetermined value S is set to a reference (zero), i.e., braking characteristics in which variation in braking characteristics associated with low-frequency pulsation as shown in FIG. 9 is suppressed. This reduces the influence of low-frequency pulsation and improves the accuracy of estimating the contact position and / or stiffness. This reduces variation in the contact position and / or stiffness. Furthermore, because variation in the contact position can be reduced, the gap (clearance) between the brake pad 25 and the disc rotor D can be prevented from becoming too small or too large. As a result, the drag torque between the brake pad 25 and the disc rotor D can be reduced, and responsiveness when applying braking force can be improved. Furthermore, because variation in stiffness can be reduced, braking force can be controlled with high precision, enabling fine vehicle control.

[0057] According to the embodiment, the predetermined current T is set to a value greater than the maximum amplitude of pulsation in the detected value of the motor current caused by the braking mechanism 21 (for example, the maximum amplitude of "+ low-frequency one-way swing upper limit side"). Also, the predetermined thrust T is set to a value greater than the maximum amplitude of pulsation in the detected value of the piston thrust caused by the braking mechanism 21 (for example, the maximum amplitude of "+ low-frequency one-way swing upper limit side"). Also, the predetermined torque T is set to a value greater than the maximum amplitude of pulsation in the detected value of the motor torque caused by the braking mechanism 21 (for example, the maximum amplitude of "+ low-frequency one-way swing upper limit side"). Therefore, pulsation in the detected values ​​of the physical quantities (motor current, piston thrust, motor torque) caused by the braking mechanism 21 can be removed.

[0058] According to this embodiment, the predetermined value S is calculated based on the largest displacement (motor displacement, piston displacement) until the physical quantity (motor current, piston thrust, motor torque) corresponding to the magnitude of the braking force reaches the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T). Therefore, the position returned by the predetermined value S can be set as a position (clearance region) where there is clearance before contact between the brake pad 25 and the disc rotor D.

[0059] Here, the thrust sensor 33 may be omitted. That is, the electric brake devices 5, 6 may be configured without the thrust sensor 33. In a configuration without the thrust sensor 33, the contact position, stiffness, and therefore the thrust can be estimated based on the braking characteristics between the motor position and the motor current. As shown in FIG. 9 , this reduces the variation in the braking characteristics between the motor position and the motor current, thereby improving the accuracy of estimating the contact position, stiffness, and therefore the thrust. On the other hand, in a configuration with the thrust sensor 33, for example, depending on the sensor specifications, the sensor mounting location, etc., pulsation due to the rolling of the balls in the thrust bearing and pulsation due to the meshing of the reducer may be incorporated into the sensor value. Even in this case, as shown in FIG. 9 , it is possible to reduce the variation in the braking characteristics between the motor position (or piston position) and the piston thrust.

[0060] Furthermore, the ideal timing for performing the process of FIG. 4 (the process of offsetting the reference braking characteristics) is, for example, when the vehicle 1 is stopped and not braking. For example, the process of FIG. 4 (the process of offsetting the reference braking characteristics) can be performed when the vehicle 1 is started (when the start switch is turned on or the engine is started). In contrast, when the process from S4 onward in FIG. 4 is performed in memory, it can be performed regardless of whether the vehicle 1 is stopped or not and during normal braking. Furthermore, the process of FIG. 4 (the process of offsetting the reference braking characteristics) can be performed simultaneously on the electric brake devices 5 and 6 of all four wheels when the vehicle 1 is reliably stopped and braking force is not required, such as in a pad replacement mode when replacing the brake pads 25. However, it is not preferable to perform the process simultaneously on all four wheels in other situations. For this reason, it is preferable to perform the process in a state where the vehicle can be reliably stopped, other than in a pad replacement mode. For example, wheels that do not have a parking mechanism (e.g., left front wheel 2L, right front wheel 2R) are parked when the parking brake is applied, and wheels that have a parking mechanism (e.g., left rear wheel 3L, right rear wheel 3R) are parked when stopping can be ensured even without the braking force of one of the wheels that have a parking mechanism.

[0061] In this embodiment, as shown in FIG. 4 , a preset value is always used as the predetermined value S. Alternatively, as shown in FIG. 5 , the predetermined value S may be updated. Note that the processes S1 to S6 in FIG. 5 are the same as those S1 to S6 in FIG. 4. In S11 following S1 in FIG. 5 , the contact position is learned in advance. That is, in the process in FIG. 5 , the contact position is assumed to have already been learned (for example, the contact position has been estimated or detected at least once before shipping). Then, when the contact position / rigidity estimation mode is started in S2, the electric motor 26 is driven in the forward direction (the direction in which the piston 24 advances) in S3. In S12 following S3, it is determined whether a predetermined physical quantity T is reached while the piston 24 advances by the predetermined value S from the contact position.

[0062] If S12 returns "YES," i.e., if the predetermined physical quantity T is reached while moving forward by the predetermined value S from the contact position, the process proceeds to S4. On the other hand, if S12 returns "NO," i.e., if the predetermined physical quantity T is not reached while moving forward by the predetermined value S from the contact position, the process proceeds to S13. In this case, in S13, the displacement amount (motor displacement amount, piston displacement amount) that corresponds to the stroke when the predetermined physical quantity T is reached is updated to a new predetermined value S. Thus, in the process of FIG. 5 , if it is determined in S12 that the predetermined physical quantity T is not reached while moving forward by the predetermined value S from the contact position, the displacement until the predetermined physical quantity T is reached is updated to a new predetermined value S in S13. When performing the process of FIG. 5 , the initial predetermined value S can be made smaller than the predetermined value S used in FIG. 4 . This can further reduce the effects of low-frequency pulsation.

[0063] According to the modification shown in FIG. 5 , if the physical quantity (motor current, piston thrust, motor torque) does not reach the predetermined physical quantity T (predetermined current T, predetermined thrust T, predetermined torque T) even when the predetermined value S is moved from the stored contact position, the displacement amount until the physical quantity reaches the predetermined physical quantity is set as a new predetermined value. This new predetermined value is stored in the memory of the electric brake ECU 31 as an updated predetermined value S. Therefore, the initial value of the predetermined value S, i.e., the predetermined value S for S1, can be set small. Then, the predetermined value S can be updated to an appropriate value. This makes it possible to further reduce the effects of low-frequency pulsation.

[0064] In the embodiment, an example has been described in which the control unit 10A of the first ECU 10 controls the left front wheel electric brake device 5L and the right rear wheel electric brake device 6R, and the control unit 11A of the second ECU 11 controls the right front wheel electric brake device 5R and the left rear wheel electric brake device 6L. However, this is not limiting, and for example, the control unit 10A of the first ECU 10 may control the right front wheel electric brake device 5R and the left rear wheel electric brake device 6L, and the control unit 11A of the second ECU 11 may control the left front wheel electric brake device 5L and the right rear wheel electric brake device 6R.

[0065] In the embodiment, the braking mechanism 21 has been described as a so-called floating caliper type disc brake in which the piston 24 is provided on the inner side of the caliper 23. However, the braking mechanism is not limited to this, and may be, for example, a so-called opposed piston type disc brake in which a piston is provided on each of the inner and outer sides of the caliper.

[0066] In the embodiment, the brake mechanism 21 is a disc brake. However, the brake mechanism is not limited to this. For example, the brake mechanism may be a drum brake in which a shoe (friction pad) is pressed against a drum rotor (rotor) that rotates together with the wheel.

[0067] In the embodiment, an example has been described in which all four wheels are equipped with electric brakes operated by the electric motor 26. However, the present invention is not limited to this, and for example, the front wheels may be equipped with hydraulic brakes and the rear wheels with electric brakes, or the front wheels may be equipped with electric brakes and the rear wheels with hydraulic brakes.

[0068] In the embodiment, an example has been described in which a vehicle braking control device (ECU) includes a first ECU 10, a second ECU 11, and an electric brake ECU 31. However, this is not limiting. For example, the first ECU 10 and the second ECU 11 may be configured as a single ECU, or the first ECU 10, the second ECU 11, and the electric brake ECU 31 may be configured as a single ECU. Furthermore, the contact position estimator and / or the stiffness estimator may be provided in the first ECU 10, the second ECU 11, the electric brake ECU 31, or another ECU. That is, the contact position estimator and / or the stiffness estimator may be provided in any ECU (control device, control unit) mounted on the vehicle.

[0069] According to the embodiment described above, the contact position estimator estimates the contact position by setting a predetermined value back from the actuator position when the physical quantity corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical quantity due to contact between the braking member and the braked member, and using the physical quantity at the position set back by the predetermined value as a reference. Therefore, the contact position can be estimated based on braking characteristics that are based on the physical quantity at the position set back by the predetermined value, i.e., braking characteristics in which variation in braking characteristics due to low-frequency pulsation is suppressed. This reduces the influence of low-frequency pulsation and improves the accuracy of contact position estimation. As a result, variation in the contact position can be reduced, and the gap (clearance) between the braking member and the braked member can be prevented from becoming too small or too large. This reduces the drag torque between the braking member and the braked member and improves responsiveness when applying braking force.

[0070] According to this embodiment, the stiffness estimator estimates stiffness by using the physical quantity at the position where the actuator position is set back by a predetermined value from the position where the physical quantity corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical quantity due to contact between the braking member and the braked member as a reference. Therefore, stiffness can be estimated based on braking characteristics that are adjusted to the physical quantity at the position where the actuator position is set back by the predetermined value as a reference, i.e., braking characteristics in which variation in braking characteristics due to low-frequency pulsation is suppressed. This reduces the influence of low-frequency pulsation and improves the accuracy of stiffness estimation. As a result, variation in stiffness can be reduced, and braking force can be controlled with high precision, enabling fine vehicle control.

[0071] According to the embodiment, the predetermined physical quantity is set to a value greater than the maximum amplitude of pulsation in the detected value of the physical quantity caused by the actuator, thereby making it possible to remove pulsation in the detected value of the physical quantity caused by the actuator.

[0072] According to this embodiment, the predetermined value is calculated based on the largest displacement amount until the physical quantity reaches the predetermined physical quantity, and therefore the position returned by the predetermined value can be set as a position (clearance region) where there is a clearance before contact between the braking member and the braked member.

[0073] According to the embodiment, if the physical quantity does not reach the predetermined physical quantity even when the physical quantity is moved by the predetermined amount from the stored contact position, the displacement amount until the physical quantity reaches the predetermined physical quantity is set as a new predetermined value. Therefore, the initial value of the predetermined value can be set small. Then, the predetermined value can be updated to an appropriate value. This can further reduce the influence of low-frequency pulsation.

[0074] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0075] This application claims priority to Japanese Patent Application No. 2023-110586, filed July 5, 2023. The entire disclosure of Japanese Patent Application No. 2023-110586, filed July 5, 2023, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0076] 5 Electric brake device 5L Left front wheel electric brake device 5R Right front wheel electric brake device 6 Electric brake device 6L Left rear wheel electric brake device 6R Right rear wheel electric brake device 21 Braking mechanism (actuator) 25 Brake pad (braking member) 26 Electric motor (actuator) 31 Electric brake ECU (contact position estimation unit, stiffness estimation unit) D Disc rotor (braked member)

Claims

1. An electric brake device comprising: an actuator that presses a braking member towards a member to be braked by driving an electric motor; and a contact position estimation unit that estimates a contact position between the braking member and the member to be braked based on the braking characteristics of the electric brake device, wherein when a physical quantity corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical quantity due to contact between the braking member and the member to be braked, the contact position estimation unit moves the actuator position back by a predetermined value from the actuator position at that time, and estimates the contact position based on the physical quantity at the actuator position moved back by the predetermined value.

2. An electric brake device comprising: an actuator that presses a braking member towards a braked member by driving an electric motor; and a stiffness estimation unit that estimates stiffness of the braking member, the braked member and the actuator based on the braking characteristics of the electric brake device, wherein when a physical quantity corresponding to the magnitude of the braking force of the actuator reaches a predetermined physical quantity due to contact between the braking member and the braked member, the stiffness estimation unit moves the actuator position back by a predetermined value from the actuator position at that time, and estimates the stiffness based on the physical quantity at the actuator position moved back by the predetermined value.

3. An electric brake device according to claim 1 or 2, wherein the predetermined physical quantity is a value greater than a maximum amplitude of pulsation in the detected value of the physical quantity caused by the actuator.

4. An electric brake device according to claim 1 or 2, wherein the predetermined value is calculated based on the largest amount of displacement until the physical quantity reaches the predetermined physical quantity.

5. An electric brake device as claimed in claim 1 or 2, wherein, if the physical quantity does not reach the predetermined physical quantity even when the physical quantity is moved by the predetermined amount from the stored contact position, the amount of displacement until the physical quantity reaches the predetermined physical quantity is set as a new predetermined value in place of the predetermined value.