Electric braking device

Abstract

An electric braking device (10) comprises: a piston (14) that has an exposed part (14A) that is exposed from a cylinder (13) over an entire range of movement for movement in response to the linear motion of a linear motion part (15B); a restrictable part (19) that extends further outward than the outer circumference of the piston (14) in the radial direction of the piston (14); and a restriction part (18) that restricts, relative to the cylinder (13), the rotation of the restrictable part (19) around the axis of the piston (14).

Description

electric braking device

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

[0002] Patent Document 1 discloses an electric braking device including a rotating member that rotates in response to rotation of an electric motor, a linearly moving member that moves linearly in response to the rotation of the rotating member, and a piston that moves linearly together with the linearly moving member to press a friction member against a brake rotor. The electric braking device disclosed in Patent Document 1 has a groove formed on the inner wall surface of a cylinder that extends in the direction of movement of the linearly moving member, an engaging member that engages with the groove is attached to the piston, and engagement of the engaging member with the groove restricts rotation of the piston around the rotation axis of the rotating member.

[0003] Japanese Patent Application Laid-Open No. 2023-25962

[0004] An electric braking device may be provided with a piston seal that seals the gap between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder. When attempting to restrict the rotation of the piston around the rotation axis of a rotating member by forming a groove on the inner wall surface of the cylinder and attaching an engaging member to the piston, as in Patent Document 1, the electric braking device must be designed so that the groove and engaging member do not interfere with the piston seal. The piston's axial length must be longer than the sum of the clearance where the piston seal slides with the piston and the clearance where the engaging member moves linearly while engaging with the groove, making it difficult to reduce the size of the electric braking device in the axial length direction. One aspect of the present disclosure aims to reduce the size of an electric braking device.

[0005] In order to solve the above problems, an electric braking device according to one aspect of the present disclosure provides an electric braking device in which a rotating part of a linear motion conversion mechanism rotates in response to the rotational motion of an electric motor, the rotational motion of the rotating part is converted into linear motion in a forward or backward direction of a linear motion part of the linear motion conversion mechanism, and a piston sliding within a cylinder and a friction material are driven by the linear motion in the forward direction of the linear motion part, causing the friction material to be pressed against a rotating body that rotates together with the vehicle wheel, thereby applying a braking force to the wheel. The piston has an exposed part that is exposed from the cylinder over its entire range of motion in response to the linear motion of the linear motion part, and is provided with a regulated part that is provided on the exposed part and extends radially of the piston outward beyond the outer periphery of the piston, and a regulating part that regulates the relative rotation of the regulated part with respect to the cylinder around the axis of the piston.

[0006] According to one aspect of the present disclosure, the electric braking device can be made smaller.

[0007] Fig. 1 is a schematic cross-sectional view of an electric braking device according to a first embodiment of the present disclosure. Fig. 2 is a diagram schematically showing a cross section taken along the line AA in Fig. 1. Fig. 3 is a schematic cross-sectional view of an electric braking device according to a third embodiment of the present disclosure. Fig. 4 is a schematic cross-sectional view of an electric braking device according to a fourth embodiment of the present disclosure.

[0008] [Embodiment 1] Fig. 1 is a schematic cross-sectional view of an electric braking device according to a first embodiment of the present disclosure. The electric braking device 10 shown in Fig. 1 includes an electric motor 11, a reduction gear mechanism 12, a cylinder 13, brake pads 16 and 17, a restricting portion 18, a restricted portion 19, a claw portion 20, and a bridge portion 21. The cylinder 13 has a piston 14 and a linear motion conversion mechanism 15 therein. The linear motion conversion mechanism 15 has a nut 15A and a threaded shaft 15B. The brake pads 16 and 17 face each other across a brake rotor 40. The brake rotor 40 is an example of a rotating body that rotates together with a vehicle wheel. The claw portion 20 is positioned opposite the cylinder 13. The bridge portion 21 is a beam portion of a caliper that straddles the brake rotor 40 and connects the cylinder 13 and the claw portion 20. A mount 22 is attached to a non-rotating member of the vehicle and supports the brake pads 16 and 17.

[0009] The electric motor 11 generates rotational torque using an external power supply. The reduction mechanism 12 reduces the rotation of the electric motor 11 and transmits it to the linear motion conversion mechanism 15. The nut 15A is an example of a rotating part, and receives the rotation of the electric motor 11 transmitted via the reduction mechanism 12 to perform rotational motion. The screw shaft 15B is an example of a linear motion part, and performs linear motion in the forward or backward direction in accordance with the rotation of the nut 15A. Hereinafter, the forward or backward direction will be referred to as the forward-backward direction. Within the forward-backward movable range of the screw shaft 15B, the forward end will be referred to as the foremost position, and the backward end will be referred to as the rearward end.

[0010] The piston 14 is connected to one end of the threaded shaft 15B and slides forward and backward together within the cylinder 13. When the piston 14 is driven forward, the brake pads 16 are pressed against the brake rotor 40, applying a braking force to the vehicle wheels. To prevent the threaded shaft 15B from rotating relative to the piston 14, the piston 14 and the threaded shaft 15B are provided with a rotation stopper (not shown), such as a keyway, a width across flats, or a D-cut. As a result, if the rotation of the piston 14 relative to the cylinder 13 is restricted, the rotation of the threaded shaft 15B relative to the cylinder 13 is also restricted.

[0011] The piston 14 has an exposed portion 14A. The exposed portion 14A is exposed from the cylinder 13 throughout the entire movable range of the linear motion of the screw shaft 15B. That is, the exposed portion 14A of the piston 14 is exposed from the cylinder 13 regardless of whether the screw shaft 15B is in any position from the frontmost position to the rearmost position.

[0012] The regulated portion 19 is formed of a rod material having sufficient rigidity so as not to be deformed by the rotational torque of the electric motor 11. In FIG. 1 , the regulated portion 19 has an L-shape. One end of the regulated portion 19 is connected to the exposed portion 14A in the radial direction of the piston 14 and extends outward from the outer periphery of the piston 14. Here, the radial direction of the piston 14 includes not only a direction perpendicular to the central axis of the piston 14 but also a direction parallel to the direction perpendicular to the central axis of the piston 14. The other end 19A of the regulated portion 19 is located outside the cylinder 13. In FIG. 1 , a connecting portion 14B is provided on a side surface of the exposed portion 14A of the piston 14, and one end of the regulated portion 19 is connected to the connecting portion 14B in the radial direction of the axis of the piston 14.

[0013] The restricting portion 18 is disposed outside the cylinder 13. In Fig. 1, the restricting portion 18 is disposed on the outer periphery of the cylinder 13. The restricted portion 19 passes through the restricting portion 18 on an extension path from one end connected to the connecting portion 14B to the other end 19A. The other end 19A of the restricted portion 19 is disposed at a position spaced a predetermined distance from the restricting portion 18 in the retraction direction.

[0014] Fig. 2 is a diagram that schematically shows a cross section taken along line A-A in Fig. 1. Note that Fig. 2 omits detailed illustration of the cross section of the cylinder 13. Fig. 2(a) shows a schematic cross section of the restricting portion 18 of the electric braking device 10 according to the first embodiment of the present disclosure.

[0015] 2A, the restricting portion 18 has a U-shaped cross section and includes a pair of restricting walls 18A and a bottom surface 18B. The restricting portion 18 is disposed so that the bottom surface 18B contacts the outer periphery of the cylinder 13. The restricting portion 18 is fixed so as not to rotate relative to the cylinder 13 due to the rotational torque of the electric motor 11.

[0016] The pair of restricting walls 18A face each other. The pair of restricting walls 18A are perpendicular to the bottom surface 18B and are substantially parallel to the direction from the rotation axis of the cylinder 13 toward the bottom surface 18B. A space is provided between the pair of restricting walls 18A, into which the restricted portion 19 can be inserted. The space between the pair of restricting walls 18A extends in the front-to-rear direction. The other end 19A of the restricted portion 19 is located further backward than the restricting portion 18, regardless of whether the screw shaft 15B is in a position between the rearmost position and the frontmost position.

[0017] The screw shaft 15B may rotate when it moves linearly in the forward and backward directions in response to the rotation of the nut 15A. When the screw shaft 15B rotates, the piston 14 and the regulated portion 19 rotate. In the electric braking device 10, when the screw shaft 15B rotates relative to the cylinder 13 by a predetermined angle or more, the regulated portion 19 abuts against one of the pair of regulating walls 18A, thereby locking the rotation of the screw shaft 15B, the piston 14, and the regulated portion 19. This efficiently converts the rotation of the nut 15A into linear motion of the screw shaft 15B. The regulated portion 19 can slide in the forward and backward directions while abutting against the pair of regulating walls 18A. The pair of regulating walls 18A may be provided with rollers, bearings, or lubricant-coated surfaces on the surfaces that abut against the regulated portion 19, allowing the regulated portion 19 to slide smoothly in the forward and backward directions.

[0018] Because the electric braking device 10 is disposed on the wheels of a vehicle, it is disposed in an environment where foreign objects can easily enter, and there is a risk that foreign objects kicked up from the road by the wheels may enter the space between the pair of restricting walls 18A. The restricting portion 18 is provided with an outlet 18C on the entire surface opposite the bottom surface 18B. The space between the pair of restricting walls 18A is connected to the outside of the space via the outlet 18C. When the electric braking device 10 is in a position where it is mounted on a vehicle, the restricting portion 18 may be provided with the outlet 18C positioned further in the direction of gravity than the bottom surface 18B. Because the space between the pair of restricting walls 18A is connected to the outside of the space in the direction of gravity, foreign objects that have entered the space can be easily discharged.

[0019] The other end 19A of the regulated portion 19 can be disposed in the space between the pair of regulating walls 18A of the regulating portion 18 through the discharge port 18C. By matching the direction in which the other end 19A of the regulated portion 19 passes through the discharge port 18C with the direction in which one end of the regulated portion 19 is connected to the connecting portion 14B of the exposed portion 14A, the regulated portion 19 can be easily assembled to the electric braking device 10.

[0020] [Embodiment 2] Embodiment 2 of the present disclosure will be described below. For ease of explanation, components having the same functions as those described in the first embodiment will be denoted by the same reference numerals, and their descriptions will not be repeated. (b) of FIG. 2 is a schematic diagram illustrating a cross section of an electric braking device according to the second embodiment of the present disclosure, taken along line A-A. As shown in (b) of FIG. 2, the restricting portion 18 in the second embodiment has a rectangular cross-sectional shape and includes a surface 18D facing a bottom surface 18B. This prevents the restricted portion 19 from escaping from the gap between the pair of restricting walls 18A in the radial direction of the cylinder 13, thereby reducing the angular deviation between the axial direction of the piston 14 and the axial direction of the cylinder 13.

[0021] 3 is a schematic cross-sectional view of an electric braking device according to a third embodiment of the present disclosure. In the first and second embodiments, the restricting portion 18 is disposed on the outer periphery of the cylinder 13, and the restricted portion 19 is L-shaped. In the third embodiment, the restricting portion 18 is a groove dug in the bridge portion 21. The restricted portion 19 is I-shaped and moves linearly within the groove of the restricting portion 18 in conjunction with the linear movement of the piston 14. Even if the restricted portion 19 attempts to rotate relative to the cylinder 13, the restricted portion 19 abuts against the side wall of the groove of the restricting portion 18, thereby restricting the relative rotation of the restricted portion 19 and the piston 14 with respect to the cylinder 13.

[0022] 4 is a schematic cross-sectional view of an electric braking device according to a fourth embodiment of the present disclosure. The restricting portion 18 according to the fourth embodiment is longer in the front-to-rear direction than the restricting portion 18 according to the first embodiment, and the other end 19A of the regulated portion 19 is housed inside the restricting portion 18. The restricting portion 18 according to the fourth embodiment is provided with a dust boot 30 at an opening 18E through which the regulated portion 19 is inserted, thereby preventing foreign matter from entering the inside of the restricting portion 18.

[0023] In the above-described first, second, and fourth embodiments, the restricting portion 18 is disposed on the outer periphery of the cylinder 13, and in the third embodiment, the restricting portion 18 is disposed in the gap between the bridge portion 21 and the brake rotor 40. However, the restricting portion 18 can be disposed in any position as long as the relative position with respect to the cylinder 13 does not change. For example, the restricting portion 18 may be disposed in a mount 22 attached to a non-rotating member of the vehicle.

[0024] In the above-described embodiments 1 to 4, the restricting portion 18 and the restricted portion 19 have a rectangular cross-sectional shape. However, the cross-sectional shapes of the restricting portion 18 and the restricted portion 19 are not limited to a rectangle. The cross-sectional shapes of the restricting portion and the restricted portion 19 may be, for example, circular. Furthermore, the restricted portion 19 may have a twisted shape like the tip of a drill to promote the discharge of foreign matter to the outside of the restricting portion 18.

[0025] The restricting portion 18 may be formed by providing a hole in the side wall of the cylinder 13. In this case, the restricted portion 19 has an L-shape so as to be inserted into the hole provided in the side wall of the cylinder 13.

[0026] [Summary] In one aspect of the present disclosure, an electric braking device includes a linear motion conversion mechanism that converts the rotational motion of a rotary part of the linear motion conversion mechanism into linear motion in a forward or backward direction of a linear motion part of the linear motion conversion mechanism. A piston sliding within a cylinder and a friction material are driven by the linear motion of the linear motion part in the forward direction, causing the friction material to press against a rotating body that rotates together with a vehicle wheel, thereby applying a braking force to the wheel. The electric braking device includes: an exposed portion that is exposed from the cylinder throughout its entire range of motion in response to the linear motion of the linear motion part; a regulated portion that is provided on the exposed portion and extends radially outward beyond the outer periphery of the piston; and a regulating portion that regulates the relative rotation of the regulated portion with respect to the cylinder around the axis of the piston. Because the regulated portion is provided on the exposed portion that is exposed from the cylinder throughout the entire range of motion of the piston, the linear motion of the piston does not interfere with components provided between the cylinder and the piston. Furthermore, because the restricted portion extends radially from the exposed portion of the piston, the friction material does not interfere with the restricted portion when the linear motion portion drives the piston and the friction material. By restricting the relative rotation of the restricted portion with respect to the cylinder, the axial length of the piston does not need to be increased to avoid interference between the components, and the electric braking device can be made smaller.

[0027] In an electric braking device according to one aspect of the present disclosure, one end of the regulated portion is connected to the exposed portion, and the other end is disposed at a different position from the one end in the axial direction of the piston. With the above configuration, since the one end and the other end of the regulated portion are disposed at different positions in the axial direction of the piston, the position of the regulating portion in the axial direction of the piston can be set at a position different from the position of the one end of the regulated portion. This improves the degree of freedom in the position of the regulating portion.

[0028] In one aspect of the electric braking device according to the present disclosure, the restricting portion has a pair of restricting walls facing each other, and the restricted portion passes through the space between the pair of restricting walls from the exposed portion. When the exposed portion rotates relative to the cylinder by a predetermined angle, the restricted portion abuts against one of the pair of restricting walls, thereby restricting the relative rotation of the restricted portion with respect to the cylinder. When the electric braking device is mounted on a vehicle, the space between the pair of restricting walls is connected to the outside of the space between the pair of restricting walls in the direction of gravity. According to the above configuration, when the electric braking device is mounted on a vehicle, the space between the pair of restricting walls is open in the direction of gravity. This prevents a foreign object from remaining in the space between the pair of restricting walls even if it enters the space between the pair of restricting walls from the outside. Therefore, foreign objects are less likely to become trapped between the pair of restricting walls that constitute the restricting portion and the restricted portion, thereby preventing interference with the linear motion of the restricted portion and the piston.

[0029] In an electric braking device according to one aspect of the present disclosure, the regulated portion has a rigidity that prevents it from deforming due to the rotational torque generated by the electric motor when it abuts against one of the pair of regulating walls. According to the above configuration, the regulated portion has a rigidity that prevents it from deforming due to the rotational torque generated by the electric motor. Therefore, when the regulated portion abuts against one of the pair of regulating walls, the regulated portion does not deform, thereby effectively restricting the relative rotation of the regulated portion with respect to the cylinder.

[0030] In an electric braking device according to one aspect of the present disclosure, the regulating portion is disposed at a position where its relative position with respect to the cylinder does not change in accordance with the linear movement of the linear moving portion. In an electric braking device according to one aspect of the present disclosure, the regulating portion is disposed on the outer periphery of the cylinder. In an electric braking device according to one aspect of the present disclosure, the electric braking device includes a claw portion facing the cylinder and a beam portion connecting the claw portion and the cylinder and spanning the rotating body. The regulating portion is a groove carved in the beam portion. The regulating portion may be disposed between the rotating body and the beam portion. If the position of the regulating portion with respect to the cylinder changes in accordance with the linear movement of the linear moving portion, it is necessary to increase the length from one end to the other end of the regulated portion by the amount of the position change. According to the above configuration, since the position of the regulating portion does not change in accordance with the linear movement of the cylinder, it is not necessary to increase the length from one end to the other end of the regulated portion.

[0031] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

Claims

1. An electric braking device in which a rotating part of a linear motion conversion mechanism rotates in response to the rotational motion of an electric motor, the rotational motion of the rotating part is converted into linear motion in a forward or backward direction of a linear motion part of the linear motion conversion mechanism, and a piston sliding inside a cylinder and a friction material are driven by the linear motion in the forward direction of the linear motion part, thereby pressing the friction material against a rotating body that rotates together with the wheels of a vehicle, thereby applying a braking force to the wheels, wherein the piston has an exposed part that is exposed from the cylinder within its entire range of motion that moves in response to the linear motion of the linear motion part, a regulated part that is provided on the exposed part and extends radially of the piston outward beyond the outer periphery of the piston, and a regulating part that regulates the relative rotation of the regulated part with respect to the cylinder centered on the axis of the piston.

2. The electric braking device according to claim 1, wherein one end of the regulated portion is connected to the exposed portion, and the other end is disposed at a position different from the one end in the axial direction of the piston.

3. An electric braking device as described in claim 1 or 2, wherein the regulating portion has a pair of regulating walls facing each other, the regulated portion passes from the exposed portion through a space between the pair of regulating walls, and when the exposed portion rotates relative to the cylinder by a predetermined angle, the regulated portion abuts against one of the pair of regulating walls, thereby regulating the relative rotation of the regulated portion with respect to the cylinder, and when the electric braking device is in a position mounted on a vehicle, the space between the pair of regulating walls is connected to the outside of the space between the pair of regulating walls in the direction of gravity.

4. The electric braking device according to claim 1, wherein the regulating portion is disposed at a position where its relative position with respect to the cylinder does not change in accordance with the linear motion of the linear motion portion.

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