Electric brake device

Abstract

Provided is an electric brake device capable of improving a current reduction effect. The electric brake has: a first region in which the braking force increases when the motor current of the electric motor increases; a second region in which the braking force is maintained when the motor current decreases from an increase to a prescribed current; and a third region in which the braking force decreases when the motor current decreases from the predetermined current. The electric brake is controlled such that the braking force of the at least one or more wheels is maintained as the braking force generated along the third region.

Description

Technical Field

[0001] The present invention relates to an electric brake device for applying a braking force to a vehicle such as an automobile. Background Art

[0002] The electric brake device includes a brake mechanism that presses a brake pad (braking member) against a brake disc (braked member) and a motor that drives the brake mechanism (Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-129812 Summary of the Invention

[0006] Technical problem to be solved by the invention

[0007] The conventional electric brake device described in Patent Document 1 maintains braking force by using a switching range between positive and negative efficiency in the relationship between current and braking force—that is, a braking force retention range where the braking force remains constant even when the current is reduced. This conventional technology suppresses current consumption and improves power efficiency. However, because the degree to which current should be reduced is unknown, this conventional technology suffers from the problem of not being able to maximize the current reduction effect if variations are present.

[0008] The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to provide an electric brake device capable of improving the current reduction effect.

[0009] Technical solutions to technical problems

[0010] In order to solve the above technical problems, the electric braking device of the present invention comprises: a braking mechanism, which presses the braking component toward the braked component; an electric motor, which drives the braking mechanism, and is characterized in that the electric braking device has: a first region in which the braking force increases when the current of the electric motor increases; a second region in which the braking force is maintained until the current switches from increase to decrease and reaches a specified current; and a third region in which the braking force is reduced when the current decreases from the specified current, and the braking force of at least one wheel is controlled to maintain the braking force generated along the third region.

[0011] According to the electric brake device according to one embodiment of the present invention, the current reduction effect can be enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram showing a system configuration of a vehicle to which the electric brakes according to the first and second embodiments of the present invention are applied.

[0013] Figure 2 It is a cross-sectional view showing the electric brake according to the first embodiment.

[0014] Figure 3 This is a characteristic diagram showing the relationship between the braking force and the motor current in the first embodiment.

[0015] Figure 4 This is a characteristic diagram showing temporal changes in the required braking force, motor current, motor position, and braking force for the first embodiment and the comparative example.

[0016] Figure 5 This is a characteristic diagram showing time changes in the required braking force, motor current, motor position, and braking force for the first modification and the comparative example.

[0017] Figure 6 This is a characteristic diagram showing time changes in the required braking force, motor current, motor position, and braking force for the second modification and the comparative example.

[0018] Figure 7 It is a cross-sectional view showing an electric brake according to a second embodiment.

[0019] Figure 8 This is a characteristic diagram showing the relationship between the braking force and the motor current in the second embodiment.

[0020] Figure 9 This is a characteristic diagram showing temporal changes in the required braking force, motor current, motor position, and braking force for the second embodiment and the comparative example.

[0021] Figure 10 This is a characteristic diagram showing time changes in the required braking force, motor current, motor position, and braking force for the third modification and the comparative example.

[0022] Figure 11 This is a characteristic diagram showing time changes in the required braking force, motor current, motor position, and braking force for the fourth modification and the comparative example. DETAILED DESCRIPTION

[0023] Hereinafter, a case where the electric brake device according to the embodiment is applied to a four-wheeled vehicle will be described as an example with reference to the drawings.

[0024] Figure 1This diagram shows the system configuration of a vehicle 1 employing an electric brake 20 serving as an electric brake system according to an embodiment. The brake system 2 installed in vehicle 1 includes hydraulic brakes 4 (front brake mechanism) provided for the left front wheel 3L and the right front wheel 3R in the vehicle's travel direction, and electric brakes 20 (rear brake mechanism) provided for the left rear wheel 5L and the right rear wheel 5R. Furthermore, a main ECU 9 is connected to a hydraulic pressure sensor 7 and a pedal stroke sensor 8, which measure the driver's operation amount on the brake pedal 6. The main ECU 9 receives input signals from the hydraulic pressure sensor 7 and the pedal stroke sensor 8 and calculates target braking forces for each wheel (all four wheels) using a predetermined control program. Based on the calculated braking forces, the main ECU 9 transmits braking commands for each of the two front wheels to the hydraulic system ECU 10 via the CAN (Controller Area Network) 12. Based on the calculated braking forces, the main ECU 9 transmits braking commands for each of the two rear wheels to the electric brake ECU 11 via the CAN 12. Furthermore, the main ECU 9 is connected to wheel speed sensors 13 provided near each of the front wheels 3L, 3R and the rear wheels 5L, 5R, and can detect the wheel speed of each wheel.

[0025] Next, refer to Figure 1 and Figure 2 The specific structure of the electric brake 20 according to the first embodiment will be described.

[0026] The electric brake 20 includes a brake mechanism 21 that transmits the thrust generated by the motor 39 to the piston 32. The piston 32 moves the brake pads 22 and 23, pressing the disc rotor D (disc); a thrust sensor 44 that detects the thrust on the piston 32; a rotation angle sensor 46 that detects the rotational position of the motor 39; and an electric brake ECU 11, which serves as a control device and controls the driving of the motor 39 based on a braking command. In this case, the disc rotor D is the braked component. The brake pads 22 and 23 are the braking components. The brake mechanism 21 is the braking mechanism.

[0027] like Figure 2 As shown, the brake mechanism 21 includes a pair of inner and outer brake pads 22 and 23, and a caliper 24. The inner and outer brake pads 22 and 23 are arranged axially on opposite sides of a disc rotor D mounted on a rotating portion of the vehicle 1. The electric brake 20 is a floating caliper type. The inner and outer brake pads 22 and 23, as well as the caliper 24, are supported by a bracket 25 fixed to a non-rotating portion of the vehicle 1, such as a steering knuckle. The bracket 25 includes an inner support portion 26 and an outer support portion 27 that independently support the inner and outer brake pads 22 and 23, respectively.

[0028] The caliper 24 includes a caliper body 28, which is the main body of the caliper 24, and an electric motor 39 arranged in parallel with the caliper body 28. A cylindrical cylinder portion 29 and a claw portion 30 are integrally formed in the caliper body 28. The cylinder portion 29 is arranged at a base end portion on the vehicle inner side, facing the inner brake pad 22, and is open to face the inner brake pad 22. The claw portion 30 extends outward from the cylinder portion 29 across the disc rotor D and is arranged at a front end side on the vehicle outer side, facing the outer brake pad 23.

[0029] The cylinder portion 29 includes a bottomed cylinder 31. A piston 32 is formed in a bottomed cup shape to press the inner brake pad 22. The piston 32 is housed in the cylinder 31 with its bottom 33 facing the inner brake pad 22.

[0030] A gear box 34 is disposed on the bottom wall side of the cylinder portion 29 of the caliper body 28. The gear box 34 houses a spur gear multi-stage reduction mechanism 35, a planetary gear reduction mechanism 36, and a control board 38. The control board 38 is provided with an electric brake ECU 11, which serves as a control device and is comprised of, for example, a microcomputer. The electric brake ECU 11 controls the driving of the electric motor 39 based on a braking command.

[0031] The caliper body 28 includes: an electric motor 39; a spur gear multi-stage reduction mechanism 35 and a planetary gear reduction mechanism 36 as transmission mechanisms for amplifying the rotational torque from the electric motor 39; a ball screw mechanism 41 that transmits the rotation from the spur gear multi-stage reduction mechanism 35 and the planetary gear reduction mechanism 36 and applies thrust to the piston 32; a thrust sensor 44 that detects the reaction force to the thrust (pressing force) from the piston 32 toward the inner and outer brake pads 22 and 23; a return mechanism 45 that accumulates a rotational force in the rearward direction relative to the push rod 42 when the push rod 42 of the ball screw mechanism 41 pushes the piston 32; a rotation angle sensor 46 that detects the rotation angle of the rotating shaft 40 of the electric motor 39; and a thrust retaining mechanism 47 that maintains the thrust from the piston 32 toward the inner and outer brake pads 22 and 23 during braking. The spur gear multi-stage reduction mechanism 35 and the planetary gear reduction mechanism 36 constitute a reduction mechanism.

[0032] The thrust sensor 44 is a thrust detection unit that detects the thrust generated by the brake mechanism 21 (brake mechanism). Specifically, the thrust sensor 44 detects the thrust applied to the piston 32. The thrust sensor 44 is sandwiched between the base nut 43 and the bottom of the cylinder 31 that constitute the ball screw mechanism 41.

[0033] The spur gear multi-stage reduction mechanism 35 and the planetary gear reduction mechanism 36 reduce and intensify the rotation of the motor 39 at a predetermined reduction ratio and transmit it to the planetary carrier 37 of the planetary gear reduction mechanism 36. The rotation from the planetary carrier 37 is transmitted to the push rod 42 of the ball screw mechanism 41.

[0034] The ball screw mechanism 41 is a rotation-to-linear motion conversion mechanism. The ball screw mechanism 41 converts the rotational motion from the spur gear multi-stage reduction mechanism 35 and the planetary gear reduction mechanism 36, that is, the rotational motion of the motor 39, into linear motion (hereinafter referred to as linear motion for convenience), thereby applying thrust to the piston 32. The ball screw mechanism 41 is composed of a push rod 42 as a shaft component and a base nut 43 as a nut component. The push rod 42 transmits the rotational motion from the spur gear multi-stage reduction mechanism 35 and the planetary gear reduction mechanism 36. The base nut 43 is threadedly engaged with the outer circumferential surface of the push rod 42. The base nut 43 is engaged with the cylinder 31 via a mating portion (not shown) in a manner that prevents relative rotation. The push rod 42 can rotate relative to the base nut 43 and advance while pressing the base nut 43 against the thrust sensor 44. Furthermore, the push rod 42 is connected to the piston 32 via a thrust bearing mounted at its front end so that it can rotate relative to the piston 32. Therefore, the piston 32 can be moved forward, and the inner brake pad 22 can be pressed against the disc rotor D by the piston 32 .

[0035] The reset mechanism 45 is sometimes also referred to as a fail-safe release mechanism. The reset mechanism 45 releases the braking force of the piston 32 from the inner brake pad 22 and the outer brake pad 23 to the disc rotor D if the motor 39 or the control board 38 fails during braking.

[0036] The rotation angle sensor 46 is a motor position detector that detects the rotation angle of the rotating shaft 40 of the motor 39. The rotation angle sensor 46 includes a magnet member 46A attached to the rotating shaft 40 of the motor 39 and a magnetic detection IC chip 46B. By detecting changes in magnetic flux from the rotating magnet member 46A using the magnetic detection IC chip 46B, the rotation angle of the rotating shaft 40 of the motor 39 can be calculated and detected using the control board 38. The rotation angle sensor 46 constitutes rotation angle detection means for detecting the rotation position of the motor 39, which serves as the motor position.

[0037] Return spring 48 is composed of a coil spring. Return spring 48 can accumulate a rotational force in the backward direction relative to push rod 42. A current sensor 49 is mounted within the motor drive circuit on control board 38 so as to detect the motor current supplied to electric motor 39. Current sensor 49 outputs a signal corresponding to the motor current.

[0038] The main ECU 9 inputs a required braking force as a braking command to the electric brake ECU 11. In addition, the electric brake ECU 11 receives inputs of the thrust detected by the thrust sensor 44, the motor position detected by the rotation angle sensor 46, and the motor current detected by the current sensor 49. Based on the motor current, motor position, and thrust, the electric brake ECU 11 controls the driving of the electric motor 39 so that the braking force generated by the electric brake 20 matches the required braking force based on the braking command.

[0039] Next, the operation of the electric brake 20 during normal driving, braking and brake release, will be described.

[0040] During braking during normal driving, the electric motor 39 is driven by a command from the electric brake ECU 11. Its rotation in the forward direction, i.e., the braking direction (force-boosting direction), is reduced and amplified at a predetermined reduction ratio via the spur gear multi-stage reduction mechanism 35 and the planetary gear reduction mechanism 36, and then transmitted to the planetary carrier 37 of the planetary gear reduction mechanism 36. The rotation from the planetary carrier 37 is then transmitted to the push rod 42 of the ball screw mechanism 41.

[0041] Next, the push rod 42 begins to rotate as the planetary carrier 37 rotates. The push rod 42 presses the base nut 43 against the thrust sensor 44 and moves forward while rotating relative to the base nut 43. As the push rod 42 moves forward while rotating relative to the base nut 43, the piston 32 moves forward, pressing the inner brake pad 22 against the disc rotor D. Then, due to the reaction force of the piston 32 against the pressing force of the inner brake pad 22, the caliper body 28 moves relative to the bracket 25. Figure 2 The outer brake pad 23 mounted on the claw portion 30 is pressed against the disc rotor D. As a result, the disc rotor D is clamped between the inner brake pad 22 and the outer brake pad 23 to generate friction, thereby generating a braking force for the vehicle 1.

[0042] Next, when the disc rotor D is clamped by the inner brake pad 22 and the outer brake pad 23 and braking force begins to be generated, a reaction force is applied to the thrust sensor 44 from the inner brake pad 22 side via the push rod 42 and the base nut 43, and from the outer brake pad 23 side via the claw 30 and the bottom of the cylinder 31. The thrust sensor 44 then detects the thrust from the inner brake pad 22 and the outer brake pad 23 toward the disc rotor D caused by the forward movement of the piston 32.

[0043] Then, a rotational force in the backward direction with respect to the push rod 42 is accumulated in the return spring 48. Thereafter, the driving of the motor 39 is controlled based on detection signals from the rotation angle sensor 46 and the thrust sensor 44, etc., and the braking state is established.

[0044] On the other hand, when the brake is released, the rotating shaft 40 of the electric motor 39 rotates in the reverse direction, i.e., the brake release direction (force reduction direction), according to a command from the electric brake ECU 11. This reverse rotation is transmitted to the push rod 42 via the spur gear multi-stage reduction mechanism 35 and the planetary gear reduction mechanism 36. As a result, the push rod 42 begins to move backward while relatively rotating in the reverse direction, thereby reducing the thrust to the disc rotor D. The caliper body 28 is moved relative to the bracket 25 by the restoring force of the inner brake pad 22 and the outer brake pad 23 compressed by the thrust. Figure 2 The piston 32 moves to the left in the middle, and the piston 32 retreats. As a result, the return spring 48 returns to its initial state, releasing the braking force of the inner brake pad 22 and the outer brake pad 23 on the disc rotor D.

[0045] The piston 32 retracts due to the restoring force of the pads until the restoring force of the inner and outer brake pads 22, 23 balances the sliding resistance between the pads and the bracket, and the sliding resistance between the piston 32 and the cylinder 31. To further retract the piston 32, the motor 39 must be driven in the force-reducing direction, causing the push rod 42 to retract further. This engages the groove on the inner wall of the piston, and the force is transmitted to the piston 32 via a retaining ring that limits the relative displacement between the piston 32 and the push rod 42 in the linear direction, causing the piston 32 to retract.

[0046] The inner and outer brake pads 22 and 23 are prevented from retracting due to sliding resistance between the pads and the bracket, and between the piston 32 and the cylinder 31. The resulting residual thrust between the inner and outer brake pads 22, 23, and the disc rotor D becomes resistance torque (drag torque) during vehicle travel, i.e., when the disc rotor D rotates, affecting the vehicle's power efficiency. Therefore, in the electric brake 20, when no braking command is received or issued from the main ECU 9, the electric motor 39 is driven in a deceleration direction to create a gap (clearance) between the piston 32 and the inner brake pad 22. This reduces the residual thrust and drag torque. Although not shown, a gap can also be created between the disc rotor D and the inner brake pad 22 by integrally engaging the piston 32 and the inner brake pad 22 for linear motion. Alternatively, a gap can be created between the disc rotor D and the outer brake pad 23 by, for example, providing a spring between the inner and outer brake pads 22, 23, biasing the inner and outer brake pads away from the disc rotor D. Through these methods, the drag torque can be further reduced.

[0047] During braking, if the motor 39 and the control board 38 fail, the push rod 42 moves backward while rotating relative to the opposite direction due to the force accumulated in the return spring 48 during braking, and the braking force from the inner brake pad 22 and the outer brake pad 23 to the disc rotor D is released.

[0048] Thus, to control the position and thrust of piston 32, electric brake 20 includes a rotation angle sensor 46 that detects the rotation angle of motor 39, a thrust sensor 44 that detects the thrust of piston 32, and a current sensor 49 that detects the motor current. Furthermore, to address any failure during thrust generation, a reset mechanism 45 (fail-safe mechanism) is included that releases the thrust.

[0049] In addition, the electric brake 20 is configured so that the reduction mechanism (spur gear multi-stage reduction mechanism 35, planetary gear reduction mechanism 36) and the rotation-to-linear motion conversion mechanism (ball screw mechanism 41) can be operated regardless of the input from either the input side or the output side. Figure 3 As shown, there is a first region where the braking force increases when the current of the motor 39 increases, a second region where the braking force is maintained until the current decreases from the increase to the specified current, and a third region where the braking force decreases when the current decreases from the specified current. The specified current is set to the current value at which the braking force switches from being maintained to being reduced. For example Figure 3 An example of the relationship between the motor current and the braking force when the braking force increases (increases) and decreases (decreases). In this case, the braking force is substantially consistent with the braking force obtained from the thrust detected by the thrust sensor 44.

[0050] like Figure 3 As shown by the dashed line, the relationship between motor current and braking force varies due to factors such as the efficiency of the reduction mechanism and the rotation-to-linear motion conversion mechanism. Specifically, variations in the efficiency of the moving parts of these mechanisms, such as the reduction mechanism and the rotation-to-linear motion conversion mechanism, lead to variations in the slope of the braking force relative to the motor current during force increase and force decrease. Furthermore, variations in the sliding resistance of the moving parts lead to variations in the difference in motor current during force increase and force decrease. Therefore, the second region is not constant.

[0051] To address this issue, the electric brake ECU 11 for the electric brake 20 controls the motor current supplied to the electric motor 39 to maintain the braking force generated along the third region when the electric brake 20 for the wheel receives a hold command from the host controller, the main ECU 9. This ensures reliable braking force maintenance while significantly reducing motor current. This control is applicable to constant braking, but it can also be applied to at least one wheel, such as the inside wheel during cornering or a wheel with a higher ECU temperature than the other wheels. Therefore, when the electric brake 20 is applied to all four wheels, the above control can also be applied to only the front or rear wheels. Furthermore, in addition to determining whether to maintain braking force based on a hold command from the host controller, the determination can also be made by the control device (electric brake ECU 11) that controls the electric brake 20 based on changes in the host controller's braking command (braking force command).

[0052] Next, use Figure 4 The operation of the electric brake 20 will be described with reference to the timing chart of FIG. Figure 4 The figure shows the time variation of the requested braking force, motor current, motor position (thrust), and braking force when a trapezoidal braking force is requested by the host controller (main ECU 9 ). In this case, the motor position roughly corresponds to the thrust generated by the brake mechanism 21 . Figure 4The solid line in represents the characteristics of the first embodiment in which the motor current is supplied in the third region while the braking force is maintained. Figure 4 The dotted line in represents the characteristics of a comparative example in which the motor current is supplied in the first region while the braking force is maintained.

[0053] like Figure 4 As shown by the solid line in , when the braking force increases, the electric brake ECU 11 increases the motor current to meet the required braking force. Then, if it detects a request to maintain the braking force, the electric brake ECU 11 reduces the motor current. If it detects a decrease in motor position or thrust, the electric brake ECU 11 maintains the motor current at that point.

[0054] When the required braking force decreases, the electric brake ECU 11 controls the motor current in accordance with the slope, compensating for the difference between the required braking force and the braking force at zero current. However, when the required braking force decreases, the electric brake ECU 11 may also control the motor current in accordance with the required braking force after compensating for the difference between the required braking force and the braking force. This allows the braking force to be slightly less than the required braking force, or the braking feel is not affected by compensation provided by other wheels.

[0055] On the other hand, Figure 4 As shown by the dotted line in , in the comparative example, when the braking force is maintained, the motor current supplied when the braking force is increased is kept constant. Therefore, in the comparative example, the motor current when the braking force is maintained increases compared to the first embodiment. Therefore, in the first embodiment and the comparative example maintained in the first region, Figure 4 The difference between the solid line and the dotted line in FIG represents the current consumption reduction effect.

[0056] Thus, in the first embodiment, the electric brake 20 has a first region in which the braking force increases when the motor current of the electric motor 39 increases, a second region in which the braking force is maintained when the motor current decreases from an increase to a specified current, and a third region in which the braking force is reduced when the motor current decreases from a specified current, and the braking force of at least one wheel is controlled to be maintained as the braking force generated along the third region.

[0057] This reduces current consumption when maintaining braking force, thereby improving power efficiency. Furthermore, since the third region is detected, current consumption is significantly reduced while reliably maintaining braking force, regardless of fluctuations in efficiency. Furthermore, since the power-on time is shortened, self-heating and heat exposure time are reduced, thereby improving the reliability of the electric brake ECU 11.

[0058] The electric brake 20 includes a spur gear multi-stage reduction mechanism 35 and a planetary gear reduction mechanism 36 as a reduction mechanism that reduces the rotational motion from the electric motor 39; and a ball screw mechanism 41 as a rotation-to-linear motion conversion mechanism that converts the reduction mechanism's rotational motion into linear motion, thereby pushing the inner and outer brake pads 22 and 23 as braking components. The reduction mechanism and the rotation-to-linear motion conversion mechanism are operable regardless of input from either the input side (e.g., the electric motor 39 side) or the output side (e.g., the inner and outer brake pads 22 and 23 sides). The braking force generated in the third range is controlled so as to be maintained by maintaining the motor current of the electric motor 39. Therefore, compared to maintaining the braking force in the second range, the motor current supplied to the electric motor 39 can be reduced, thereby improving power efficiency.

[0059] The electric brake 20 includes a rotation angle sensor 46 as a motor position detection unit that detects the rotational position of the motor 39. The rotation angle sensor 46 determines whether a braking force is generated in the third range. The electric brake 20 generates a braking force corresponding to the rotational position of the motor 39. Therefore, the electric brake ECU 11 can determine whether a braking force is generated in the third range by detecting the rotational position of the motor 39.

[0060] The electric brake 20 also includes a thrust sensor 44, serving as a thrust detection unit, that detects the thrust generated by the brake mechanism 21, which serves as a braking mechanism. Therefore, the electric brake ECU 11 can also determine whether a braking force is being generated along the third region based on the thrust detected by the thrust sensor 44. Estimating the braking force based on the rotational position of the electric motor 39 can lead to estimation errors, which can reduce the accuracy of braking force detection. In contrast, using the thrust detected by the thrust sensor 44 eliminates these estimation errors, improving braking force detection accuracy.

[0061] It should be noted that if Figure 4 As shown, in the first embodiment, the electric brake ECU 11 of the electric brake 20 reduces the motor current from the moment of recognizing that the braking force holding is requested from the host controller, the main ECU 9 , to hold the braking force in the third region.

[0062] The present invention is not limited to this, and can also be Figure 5As shown in the first modified example, upon recognizing a braking force hold request from the main ECU 9, the electric brake ECU 11 increases the motor current by a detection amount and then decreases it, considering the need to reduce the braking force in order to detect a shift to the third region. In the first embodiment, since the braking force is maintained after detecting the third region, there is a tendency for the braking force in the hold state to be lower than the required braking force. In contrast, in the first modified example, the braking force is increased by the amount required to detect the third region before the motor current is reduced to detect the third region. This allows the braking force in the hold state to approach the required braking force.

[0063] Furthermore, in the first modification, when the braking force increases, the braking force generated by the brake mechanism 21 is increased as the required braking force increases, similarly to the first embodiment. The present invention is not limited thereto, and may also be Figure 6 As shown in the second variant, when the braking force increases, the motor current is supplied by adding (increasing) the amount required to detect the third zone. Subsequently, if the main ECU 9 recognizes a request to maintain the braking force, the electric brake ECU 11 reduces the motor current and detects a transition to the third zone. After detecting the third zone, the electric brake ECU 11 fixes the motor current value to maintain the braking force in the third zone. In the second variant, as in the first variant, the braking force in the maintained state can be brought close to the requested braking force. Furthermore, in the second variant, the motor current can be reduced from the moment a request to maintain the braking force is recognized. Therefore, compared to the first variant, the braking force can be brought into the maintained state earlier.

[0064] Furthermore, in order to detect the third region, when detecting a decrease in the motor position or thrust, the motor current may be maintained after taking into account recognition errors, etc. Figures 4 to 6 In the description above, the braking force is reduced after the motor current is maintained (after the braking force is maintained). The present invention is not limited to this example. Alternatively, after the motor current is maintained, the motor current may be increased to the upper limit in the first range, for example, in response to a command from an Advanced Driver-Assistance Systems (ADAS) or in response to an emergency braking situation (e.g., a sudden decrease in the distance to a preceding or following vehicle).

[0065] then, Figure 1 、 Figures 7 to 9This represents a second embodiment. The second embodiment is characterized in that at least one of the reduction mechanism and the rotation-to-linear motion conversion mechanism is configured to be inoperable based on input from either the input side or the output side, and the braking force generated along the third region is controlled so as to be maintained by de-energizing the electric motor. It should be noted that in the second embodiment, components identical to those in the first embodiment are denoted by the same reference numerals, and their descriptions are omitted.

[0066] like Figure 1 and Figure 7 As shown, the electric brake 50 of the second embodiment, like the electric brake 20 of the first embodiment, includes a brake mechanism 51, a thrust sensor 44, a rotation angle sensor 46, and an electric brake ECU 53. The brake mechanism 51 is configured substantially the same as the brake mechanism 21 of the first embodiment. Therefore, the brake mechanism 51 includes a spur gear multi-stage reduction mechanism 35 and a planetary gear reduction mechanism 36 as reduction mechanisms, and a trapezoidal screw mechanism 52 as a rotation-to-linear conversion mechanism. However, the trapezoidal screw mechanism 52 is configured to be actuated by input from the input side, i.e., the motor 39 (reduction mechanism side), but not by input from the output side, i.e., the piston 32. Therefore, if the motor current supply to the motor 39 is stopped (the motor current reaches zero), the position of the piston 32 remains unchanged. Consequently, even when the motor current supply is stopped, the thrust from the inner and outer brake pads 22, 23 to the disc rotor D is maintained, maintaining the braking force.

[0067] It should be noted that the structure that cannot be operated based on input from the output side is not limited to the rotation-to-linear conversion mechanism. The structure that cannot be operated based on input from the output side may be included in the reduction mechanism, or in both the reduction mechanism and the rotation-to-linear conversion mechanism.

[0068] The electric brake ECU 53 is configured similarly to the electric brake ECU 11 of the first embodiment. The main ECU 9 inputs the required braking force as a braking command to the electric brake ECU 53. In addition, the electric brake ECU 53 receives inputs of the thrust detected by the thrust sensor 44, the motor position detected by the rotation angle sensor 46, and the motor current detected by the current sensor 49. Based on the motor current, motor position, and thrust, the electric brake ECU 53 controls the drive of the electric motor 39 so that the braking force generated by the electric brake 50 matches the required braking force based on the braking command.

[0069] In addition, the electric brake 50 is configured so that at least one of the reduction mechanism (spur gear multi-stage reduction mechanism 35, planetary gear reduction mechanism 36) and the rotation-to-linear conversion mechanism (trapezoidal screw mechanism 52) cannot be actuated based on input from either the input side or the output side. Figure 8 As shown, there is a first region where the braking force increases when the forward current (the absolute value of the forward motor current) of the motor 39 increases, a second region where the braking force is maintained until the forward current decreases from increasing to a predetermined reverse current, and a third region where the braking force decreases when the reverse current (the absolute value of the reverse motor current) decreases from a predetermined current. The predetermined current is set to the current value at which the braking force switches from being maintained to being reduced. In other words, in the second embodiment, the third region is located in the second quadrant. For example Figure 8 An example of the relationship between the motor current and the braking force when the braking force increases (increases) and decreases (decreases). In this case, the braking force is substantially consistent with the braking force obtained from the thrust detected by the thrust sensor 44.

[0070] When the electric brake 50 is applied to a wheel for which a hold command has been input from the host controller, the main ECU 9, the electric brake ECU 53 controls the motor current supplied to the electric motor 39 to maintain the braking force generated along the third region. This ensures reliable braking force and significantly reduces motor current. As in the first embodiment, this control is applicable to constant braking and can also be applied to at least one wheel, such as the inner wheel during cornering or a wheel with a higher ECU temperature than the other wheels. Therefore, when the electric brake 20 is applied to all four wheels, the above control can also be applied to only the front or rear wheels. Furthermore, in addition to determining whether the braking force is maintained based on a hold command from the host controller, the control device (electric brake ECU 53) that controls the electric brake 50 based on changes in the host controller's braking command (braking force command) can also determine whether the braking force is maintained.

[0071] Next, use Figure 9 The operation of the electric brake 50 will be described with reference to the timing chart of FIG. Figure 9 When a trapezoidal-wave braking force is requested by the host controller (main ECU 9 ), the requested braking force, motor current, motor position (thrust), and temporal changes in the braking force are shown. Figure 9 The solid line in φ represents the characteristics of the second embodiment in which the motor current is controlled so as to maintain the braking force generated in the third region when the braking force is maintained. Figure 9 The dotted line in represents the characteristics of a comparative example in which the motor current is supplied in the first region while the braking force is maintained.

[0072] like Figure 9As shown by the solid line in , when the braking force increases, the electric brake ECU 53 increases the forward motor current to meet the required braking force. Then, if it detects that the required braking force is being maintained, the electric brake ECU 53 switches the absolute value of the forward motor current from increasing to decreasing, reaching zero, and then increases the absolute value of the reverse motor current. This causes the electric motor 39 to rotate in the reverse direction, displacing the inner and outer brake pads 22 and 23 away from the disc rotor D. Consequently, if a decrease in motor position or thrust is detected, the electric brake ECU 53 reduces the absolute value of the reverse motor current to zero, stopping the supply of motor current.

[0073] When the required braking force decreases, the electric brake ECU 11 increases the absolute value of the motor current in the opposite direction and then decreases it. At this point, the electric brake ECU 11 controls the motor current based on the slope of the required braking force to compensate for the difference between the required braking force and the braking force when the current is zero. However, this is not limiting. When the required braking force decreases, the electric brake ECU 11 may also control the motor current in line with the required braking force after compensating for the difference. This results in a braking force that is less than the required force, but only slightly, or with compensation provided by other wheels without affecting the feel.

[0074] Thus, the second embodiment also achieves substantially the same operational effects as the first embodiment. Furthermore, the electric brake 50 includes a spur gear multi-stage reduction mechanism 35 and a planetary gear reduction mechanism 36 as reduction mechanisms that reduce the rotational motion from the motor 39; and a trapezoidal screw mechanism 52 as a rotation-to-translation conversion mechanism that converts the reduction mechanism's rotational motion into linear motion and pushes the inner and outer brake pads 22 and 23 as braking members. At least one of the reduction mechanism and the rotation-to-translation conversion mechanism is inoperable based on input from either the input side (e.g., the motor 39 side) or the output side (e.g., the inner and outer brake pads 22 and 23 sides). The braking force generated along the third region is controlled so that it is maintained by de-energizing the motor current of the motor 39. Therefore, for example, when detecting the motor position, detection can be performed only between the motor 39 and the inoperable portion, compared to the first embodiment, minimizing variations in the braking force. Furthermore, since the braking force can be maintained even when the motor current is not supplied, the current consumption can be further reduced.

[0075] It should be noted that if Figure 9As shown in the second embodiment, the electric brake ECU 53 of the electric brake 50 reduces the motor current from the moment of recognizing that the upper controller, that is, the main ECU 9, requests the braking force to be maintained, and maintains the braking force in the third range. The present invention is not limited to this, and may also be as follows. Figure 10 As shown in the third modified example, when the electric brake ECU 53 recognizes that the main ECU 9 has requested the brake force to be maintained, it considers that the brake force should be reduced to detect the transition to the third region, increases the forward motor current by a detection amount, and then reduces the motor current.

[0076] Furthermore, in the third modified example, when the braking force increases, the braking force generated by the brake mechanism 51 is increased as the required braking force increases, similarly to the first embodiment. The present invention is not limited thereto, and may also be Figure 11 As shown in the fourth modified example, when the braking force increases, the motor current is supplied by an amount previously increased (increased) to the amount required for detecting the third range. Subsequently, if the main ECU 9 recognizes a request to maintain the braking force, the electric brake ECU 53 reduces the motor current and detects a transition to the third range. After detecting the third range, the electric brake ECU 53 de-energizes the motor current, maintaining the braking force in the third range.

[0077] Furthermore, in each of the above embodiments, the electric brake 20 is applied to the rear wheels 5L and 5R, but the electric brake 20 may be applied to the front wheels 3L and 3R, or to all four wheels. Furthermore, the electric brake may be an electric disc brake or an electric drum brake.

[0078] In the above embodiments, the electric brakes 20 and 50 used in four-wheeled vehicles are described as an example. However, the present invention is not limited thereto and can also be applied to two-wheeled or three-wheeled vehicles, work vehicles, trucks, buses, and the like as transport vehicles.

[0079] It should be noted that the present invention is not limited to the above-described embodiments and includes various variations. For example, the above-described embodiments are described in detail to facilitate understanding of the present invention and are not limited to all of the structures described. Furthermore, a portion of the structure of a particular embodiment can be replaced with the structure of another embodiment, and the structure of another embodiment can be added to the structure of a particular embodiment. Furthermore, for a portion of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0080] This application claims the benefit of priority based on Japanese Patent Application No. 2023-017512, filed on February 8, 2023. The entire disclosure of Japanese Patent Application No. 2023-017512, filed on February 8, 2023, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0081] Description of Reference Numerals

[0082] 11, 53: ECU (control unit) for electric brakes;

[0083] 20, 50: Electric brake (electric brake device);

[0084] 21, 51: brake mechanism (brake mechanism);

[0085] 22: inner brake pad (brake component);

[0086] 23: outer brake pad (brake component);

[0087] 32: piston;

[0088] 35: straight tooth multi-stage reduction mechanism (reduction mechanism);

[0089] 36: Planetary gear reduction mechanism (reduction mechanism);

[0090] 39: Electric motor;

[0091] 41: Ball screw mechanism (rotation-to-direct motion conversion mechanism);

[0092] 44: thrust sensor (thrust detection unit);

[0093] 46: Rotation angle sensor (motor position detection unit);

[0094] 49: current sensor;

[0095] 52: Trapezoidal screw mechanism (rotation-to-direct motion conversion mechanism);

[0096] D: Disc rotor (braked part).

Claims

1. An electric brake device, characterized in that: The electric brake device has: a brake mechanism that presses the braking member toward the braked member; an electric motor that drives the brake mechanism, The electric brake device has a first region in which the braking force increases when the electric current of the motor increases; a second region in which the braking force is maintained until the current reaches a predetermined current after switching from increasing to decreasing; and a third region in which the braking force decreases when the current decreases from the predetermined current. The braking force of at least one wheel is controlled so as to be maintained at the braking force generated along the third region.

2. The electric brake device according to claim 1, characterized in that have: a speed reduction mechanism that reduces the speed of rotation from the electric motor; a rotation-to-direct motion conversion mechanism, which converts the rotational motion of the reduction mechanism into a direct motion and pushes the braking component; The speed reduction mechanism and the rotation-to-linear conversion mechanism are structures capable of being operated regardless of input from either the input side or the output side. The braking force generated along the third region is controlled so as to be maintained by maintaining the current of the electric motor.

3. The electric brake device according to claim 1, wherein have: a speed reduction mechanism that reduces the speed of rotation from the electric motor; a rotation-to-direct motion conversion mechanism, which converts the rotational motion of the reduction mechanism into a direct motion and pushes the braking component; At least one of the speed reduction mechanism and the rotation-to-linear motion conversion mechanism is configured to be inoperable by input from either the input side or the output side. The braking force generated along the third region is controlled so as to be maintained by non-energizing the electric current of the electric motor.

4. The electric brake device according to any one of claims 1 to 3, characterized in that The electric brake device includes a motor position detection unit that detects a rotational position of the motor. Whether the braking force is generated along the third region is determined by the motor position detection unit.

5. The electric brake device according to any one of claims 1 to 3, characterized in that: The electric brake device includes a thrust detection unit that detects the thrust generated in the brake mechanism. Whether the braking force is generated along the third region is determined by the thrust detection unit.

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