Electric braking device

Abstract

To suppress an eccentric load generated in a linear motion portion due to axial inclination of a piston with respect to an axial direction of a cylinder.SOLUTION: An electric braking device (1) includes: a first curved surface on at least one of a pressing surface (14) of a linear motion portion (11) and a pressed surface (32) of a piston (30); and a second curved surface in a region where a coupling member (50) engaging with a first engagement portion (31) and a second engagement portion (13) engages with the first engagement portion (31), for swinging such that a linear motion axis of the piston (30) inclines.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Generally, an electric braking device that uses a screw mechanism to move a piston in the axial direction of a cylinder requires a rotation prevention mechanism that restricts relative rotation of the linearly moving part and the piston with respect to the cylinder.Patent Document 1 discloses a ball screw device that includes a rotation prevention member that prevents relative rotation of the nut with respect to the housing, and a retaining ring that is engaged so as to span between the nut with a first retaining ring groove and the piston with a second retaining ring groove. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-82214 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the ball screw device disclosed in Patent Document 1, when a retaining ring is used to prevent relative displacement of the nut with respect to the piston, an unbalanced load may be generated on the nut due to the axial tilt of the piston relative to the axial direction of the cylinder, which may reduce the life of the screw mechanism. One aspect of the present disclosure aims to suppress an unbalanced load that occurs in a linear motion part of a linear motion conversion part due to an axial tilt of a piston with respect to an axial direction of a cylinder. [Means for solving the problem]

[0005] In order to solve the above problems, an electric braking device according to one embodiment of the present disclosure is an electric braking device that converts the rotational motion of an electric motor into linear motion of a linear motion part of a linear motion conversion mechanism, drives a piston that is in contact with the inner periphery of a cylinder using the linear motion, and presses a friction material against a rotating body that rotates together with the wheel of a vehicle, thereby applying a braking force to the wheel, wherein the piston has a first engagement part with which a connecting member engages on its inner periphery, and has a second engagement part that engages with the connecting member on its outer periphery of the linear motion part that faces the inner periphery of the piston, the connecting member engages with both the first engagement part and the second engagement part, a pressing surface of the linear motion part that presses the piston and a pressed surface of the piston that is pressed by the linear motion part are in contact, at least one of the pressing surface and the pressed surface has a first curved surface, and the connecting member has a second curved surface in the range engaged with the first engagement part so that the piston oscillates so that the linear motion axis of the linear motion is tilted.

[0006] In order to solve the above problems, one aspect of the present disclosure provides an electric braking device that converts the rotational motion of an electric motor into linear motion of a linear motion part of a linear motion conversion mechanism, drives a piston, and applies a braking force to a vehicle wheel by pressing a friction material against a rotating body that rotates together with the wheel, wherein the piston has a cylindrical shape with a bottom, is engaged with the friction material, and has an outer peripheral surface abutting a cylinder, the linear motion part has a cylindrical shape, an outer peripheral surface facing the inner peripheral surface of the piston, and has a pressing surface that abuts a predetermined pressed surface of the piston when the linear motion part moves linearly in accordance with the rotational motion of the electric motor, and is equipped with a connecting member that connects the piston to the linear motion part by engaging with the inner peripheral surface of the piston and the outer peripheral surface of the linear motion part, and at least one of the pressing surface and the pressed surface has a first curved surface so that the axial direction of the piston is inclined with respect to the axial direction of the cylinder, and the connecting member has a second curved surface in a range of its surface that engages with the inner peripheral surface of the piston. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, it is possible to suppress an unbalanced load that occurs in a linear moving part due to an inclination of the axial direction of the piston with respect to the axial direction of the cylinder. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of an electric braking device according to an embodiment of the present disclosure. [Figure 2] 10A and 10B are diagrams illustrating an example of a method for connecting a piston of an electric braking device according to an embodiment of the present disclosure to a linear moving part. DETAILED DESCRIPTION OF THE INVENTION

[0009] FIG. 1 is a cross-sectional view of an electric braking device according to one embodiment of the present disclosure. The electric braking device 1 shown in FIG. 1 includes a linear motion conversion mechanism 10, a cylinder 20, a piston 30, brake pads 40, and a connecting member 50, and is used, for example, in an electric caliper disposed on a vehicle wheel. Hereinafter, a forward direction and a reverse direction will be defined as shown by arrows in FIG. 1. In FIG. 1, the forward direction and the reverse direction are parallel to an axis A along which the cylinder 20 extends.

[0010] The linear motion conversion mechanism 10 has a linear motion part 11 and a rotating part 12. The linear motion part 11 is, for example, a nut and has a cylindrical shape. The rotating part 12 is a threaded shaft that is rotatable about a rotation axis that overlaps with the axis A of the cylinder 20. The linear motion part 11 has an outer circumferential surface that faces the inner circumferential surface of the piston 30, and the inner circumferential surface is screwed onto the rotating part 12.

[0011] The piston 30 has, for example, a cylindrical shape with a bottom. The bottom surface of the piston 30 abuts against a brake pad 40. The inner peripheral surface of the piston 30 faces the outer peripheral surface of the linear motion portion 11. The outer peripheral surface of the piston 30 faces the inner peripheral surface of the cylinder 20. The brake pad 40 is an example of a friction material. The piston 30 has a first engagement portion 31 on a part of its inner circumferential surface. The piston 30 shown in FIG. 1 has two first engagement portions 31 on its inner circumferential surface. The first engagement portions 31 are, for example, through holes that penetrate between the inner circumferential surface and the outer circumferential surface of the piston 30. The opening shape of the first engagement portions 31 is, for example, a perfect circle.

[0012] The linear motion portion 11 has a second engagement portion 13 on a part of its outer circumferential surface. The second engagement portion 13 is disposed at a position facing the first engagement portion 31 of the piston 30. The linear motion portion 11 shown in FIG. 1 has two second engagement portions 13 on its outer circumferential surface. The second engagement portions 13 are, for example, recesses recessed radially from the outer circumferential surface of the linear motion portion 11. The bottom surface of the second engagement portion 13 shown in FIG. 1 is a curved surface, and the opening shape of the second engagement portion 13 is a perfect circle.

[0013] The forward direction end of the outer circumferential surface of the linear moving part 11 has a first curved surface 14 that curves toward the axis A of the cylinder 20 and is narrowed. The inner circumferential surface of the piston 30 has a tapered surface 32 at a position facing the first curved surface 14. When the first engagement part 31 of the piston 30 is at a position facing the second engagement part 13 of the linear moving part 11, the first curved surface 14 of the linear moving part 11 abuts against the tapered surface 32 of the piston 30.

[0014] The connecting member 50 connects the linear moving part 11 and the piston 30 by engaging with the first engagement part 31 of the piston 30 and the second engagement part 13 of the linear moving part 11. The connecting member 50 is, for example, a steel ball. The electric braking device 1 shown in FIG. 1 has two connecting members 50. A part of the connecting member 50 engages with the second engagement part 13 of the linear moving part 11, and another part of the connecting member 50 engages with the first engagement part 31 of the piston 30. The spherical surface of the part of the surface of the connecting member 50 that engages with the first engagement part 31 of the piston 30 is an example of a second curved surface. The diameter of the spherical connecting member 50 is smaller than the hole diameter of the first engagement part 31 of the piston 30 and larger than the depth of the second engagement part 13 of the linear moving part 11. In addition, the sum of the depths of the first engagement part 31 and the second engagement part 13 is and the diameter of the connecting member 50 is smaller than the depth of the second engaging portion 13.

[0015] 2 is a diagram illustrating an example of a method for connecting a piston of an electric braking device according to an embodiment of the present disclosure to a linear motion part. As shown in FIG. 2, the connecting member 50 is inserted from the opening of the first engagement part 31 on the outer circumferential surface side of the piston 30, and a portion of the connecting member 50 protrudes from the opening of the first engagement part 31 on the inner circumferential surface side of the piston 30 toward the second engagement part 13 of the linear motion part 11, thereby engaging with the second engagement part 13. Because the diameter of the connecting member 50 is larger than the depth of the second engagement part 13, the connecting member 50 can engage with the first engagement part 31 even when engaged with the second engagement part 13. The opening of the first engagement part 31 on the outer circumferential surface side of the piston 30 is covered by the inner circumferential surface of the cylinder 20, and the connecting member 50 is housed in a space formed by the first engagement part 31 of the piston 30 and the second engagement part 13 of the linear motion part 11.

[0016] The difference between the diameter of the connecting member 50 and the sum of the depths of the first engagement portion 31 and the second engagement portion 13 is smaller than the depth of the second engagement portion 13, so that the connecting member 50 will not come off the second engagement portion 13 even when it abuts against the inner circumferential surface of the cylinder 20. Furthermore, because the diameter of the connecting member 50 is larger than the depth of the second engagement portion 13 of the linear motion portion 11, the connecting member 50 will not come off the first engagement portion 31 even when it abuts against the bottom surface of the second engagement portion 13. Therefore, the piston 30 is connected to the linear motion portion 11, and the linear movement of the piston 30 relative to the linear motion portion 11 is restricted.

[0017] As shown in FIG. 1 , in the linear motion conversion mechanism 10, when rotational motion is transmitted from an electric motor (not shown), the rotating part 12 rotates. The rotation of the rotating part 12 is transmitted to the linear motion part 11, the inner circumferential surface of which is threadedly engaged with the rotating part 12. The relative rotation of the linear motion part 11 with respect to the cylinder 20 is restricted by frictional force. For example, the brake pad 40 and the piston 30 may be engaged by frictional force generated at the contact portion where the brake pad 40 and the bottom surface of the piston 30 come into contact, thereby restricting the relative rotation of the linear motion part 11 and the piston 30 with respect to the cylinder 20. This allows the linear motion part 11 to efficiently convert the rotation of the rotating part 12 into linear motion. The relative rotation of the linear motion portion 11 with respect to the cylinder 20 is also restricted by the frictional force generated at the contact portion between the tapered surface 32 of the piston 30 and the first curved surface 14 of the linear motion portion 11 .

[0018] If a waterproof and dustproof mechanism using an O-ring or the like is provided between the inner peripheral surface of the cylinder 20 and the outer peripheral surface of the piston 30, the relative rotation of the linearly moving part 11 with respect to the cylinder 20 is also restricted by the frictional force between the outer peripheral surface of the piston 30 and the waterproof and dustproof mechanism.

[0019] When the linearly moving part 11 moves linearly in the forward direction, the first curved surface 14 of the linearly moving part 11 serves as a pressing surface that presses the piston 30, and the tapered surface 32 of the piston 30 serves as a pressed surface. The piston 30 moves in the forward direction in accordance with the linear movement of the linearly moving part 11 in the forward direction. The movement of the piston 30 in the forward direction presses the brake pads 40, and the brake pads 40 are pressed against a rotating body such as a disc rotor that rotates together with the wheel, applying a braking force to the wheel.

[0020] The position at which the connecting member 50 contacts the first engagement portion 31 and the second engagement portion 13 changes depending on the rotation direction of the rotating portion 12. The linear axis of the piston 30 tilts with respect to the axis A of the cylinder 20 depending on the position at which the connecting member 50 contacts the inner wall surface of the first engagement portion 31. The axial direction of the piston 30 can swing within, for example, a range R shown in FIG. 1. The range R passes through the contact point where the first curved surface 14 of the linear motion portion 11 and the tapered surface 32 of the piston 30 contact each other, and has a spherical crown shape that is convex in the forward movement direction. In the cross-sectional view of FIG. 1, the range R is illustrated as a circular arc.

[0021] The load applied in the direction of tilting the linear axis of the piston 30 relative to the axis A of the cylinder 20 is absorbed by the spherical surface (second curved surface) in the range where the connecting member 50 engages with the first engaging portion 31, and the cylinder The pressure is transmitted to the inner peripheral surface of the cylinder 20.

[0022] [Modification] In the above embodiment, the connecting member 50 is a steel ball, but is not limited to this. The connecting member 50 may be formed of a material other than steel as long as it has sufficient rigidity to avoid deformation due to the load applied in accordance with the rotational movement of the electric motor. Furthermore, the connecting member 50 has a surface that becomes the second curved surface at least in the area where it engages with the first engagement portion 31, and may have a shape other than a sphere as long as the shape does not impair the function of connecting the piston 30 to the linear motion portion 11. For example, the connecting member 50 may be hemispherical, oval, or semi-oval.

[0023] In the above embodiment, the first engagement portion 31 has an opening shape that is a perfect circle and is a through-hole that penetrates between the inner and outer circumferential surfaces of the piston 30. However, this is not limiting. The shape of the first engagement portion 31 may be any shape that has an opening at least on the inner circumferential surface side of the piston 30 and is capable of engaging with the connecting member 50. For example, the first engagement portion 31 may be a recess or a hole that does not penetrate between the inner and outer circumferential surfaces of the piston 30. The opening shape of the first engagement portion 31 may be, for example, an elongated hole extending in the direction of the linear axis of the piston 30. By forming the first engagement portion 31 as an elongated hole extending in the direction of the linear axis of the piston 30, it is possible to prevent the piston 30 from colliding with the connecting member 50 due to swinging in a direction that tilts the linear axis.

[0024] In the above embodiment, the first engagement portion 31 is illustrated on the forward direction side of the piston 30. However, the first engagement portion 31 may be arranged at a position on the rearward direction side of the piston 30. By arranging the first engagement portion 31 at a position on the rearward direction side of the piston 30, it is possible to prevent contact with a seal member (not shown) provided between the piston 30 and the cylinder 20.

[0025] In the above embodiment, the second engagement portion 13 has a recessed portion with a curved bottom surface, but this is not limited thereto. The second engagement portion 13 may have any shape as long as it is recessed from the outer circumferential surface of the linear motion portion 11 and can engage with the connecting member 50. For example, the bottom surface of the second engagement portion 13 may be flat, and the opening shape of the second engagement portion 13 may be polygonal. The bottom surface of the second engagement portion 13 may also be a curved surface, for example, an arc shape having the same center as the range R. By having the bottom surface of the second engagement portion 13 have an arc shape having the same center as the range R, it is possible to suppress an unbalanced load generated in the linear motion portion 11 due to the pivoting of the connecting member 50 in a direction that tilts the linear motion axis of the piston 30.

[0026] In the above embodiment, the electric braking device 1 is illustrated as having two each of the connecting members 50, the first engagement portions 31, and the second engagement portions 13. However, the electric braking device 1 may be provided with at least one each of the connecting members 50, the first engagement portions 31, and the second engagement portions 13.

[0027] In the above embodiment, the pressing surface of the linear moving part 11 that presses the piston 30 is the first curved surface 14, and the pressed surface of the piston 30 that is pressed by the linear moving part 11 is the tapered surface 32. However, it is sufficient if at least one of the pressing surface of the linear moving part 11 and the pressed surface of the piston 30 forms the first curved surface. When the pressed surface of the piston 30 is a curved surface, the pressing surface of the linear moving part 11 may be a tapered surface.

[0028] In the above embodiment, the piston 30 is engaged by the frictional force generated at the contact portion where the brake pad 40 and the bottom surface of the piston 30 come into contact. However, the engagement between the brake pad 40 and the bottom surface of the piston 30 is not limited to the frictional force generated at these contact portions. For example, the piston 30 and the brake pad 40 may be provided with fitting portions that fit together, and the piston 30 may be fitted into the brake pad 40, thereby engaging the brake pad 40 with the bottom surface of the piston 30. The relative rotation of the linearly moving portion 11 and the piston 30 with respect to the cylinder 20 may be controlled regardless of the force with which the piston 30 presses the brake pad 40. can be regulated.

[0029] In the above embodiment, the piston 30 has a cylindrical shape with a bottom, but is not limited to this. For example, the bottom shape of the piston 30 may be a regular polygon. The piston 30 only needs to be restricted in rotation relative to the cylinder 20, and the piston 30 may have a fitting portion on its side that fits with the cylinder 20 or the brake pad 40. Furthermore, the bottom shape of the piston 30 may be annular, and may have a fitting portion that fits with the bottom of the piston 30 and the brake pad.

[0030] The dimensions of the linear motion conversion mechanism 10, the cylinder 20, the piston 30, and the connecting member 50 are not limited to those shown in Figures 1 and 2, but are determined according to the required strength determined at the design stage of the electric braking device 1.

[0031] 〔summary〕 An electric braking device according to one embodiment of the present disclosure converts the rotational motion of an electric motor into linear motion of a linear motion part of a linear motion conversion mechanism, and uses the linear motion to drive a piston that is in contact with the inner circumference of a cylinder, thereby pressing a friction material against a rotating body that rotates together with the wheel of a vehicle, thereby applying a braking force to the wheel.The piston has a first engagement portion with which a connecting member engages on its inner surface, and a second engagement portion with which the connecting member engages on the outer surface of the linear motion part that faces the inner surface of the piston, the connecting member engages with both the first engagement portion and the second engagement portion, a pressing surface of the linear motion part that presses the piston contacts a pressed surface of the piston that is pressed by the linear motion part, at least one of the pressing surface and the pressed surface has a first curved surface, and the connecting member has a second curved surface in the range engaged with the first engagement portion so that the piston oscillates so that the linear motion axis of the linear motion is tilted. When the piston rotates so that the linear axis of the linear moving part is tilted relative to the axial direction of the cylinder, the piston may come into contact with the linear moving part, potentially causing an unbalanced load on the linear moving part. In the present disclosure, the pressing surface where the linear moving part presses the piston and the pressed surface where the piston is pressed by the linear moving part are in swingable contact, thereby reducing the force applied to the linear moving part when the piston rotates so that the linear moving axis is tilted, and suppressing the unbalanced load generated between the pressing surface and the pressed surface. Furthermore, because the connecting member has a second curved surface in the range where it engages with the first engaging part, the force generated when the piston rotates so that the linear moving axis is tilted is not transmitted to the linear moving part via the connecting member, but is transmitted to the contact part between the piston and the inner circumferential surface of the cylinder. This reduces the force applied to the linear moving part, thereby suppressing the unbalanced load generated between the first engaging part and the connecting member.

[0032] In the electric braking device according to one aspect of the present disclosure, the first engagement portion has a through-hole that penetrates between an inner circumferential surface and an outer circumferential surface of the piston. The first engagement portion has a through hole that passes through the piston between its inner and outer circumferential surfaces, which allows for easy assembly by inserting the connecting member through the through hole.

[0033] In the electric braking device according to one aspect of the present disclosure, the connecting member is a ball. If the connecting member has a complex shape, the processing, manufacturing, and assembly costs for shaping and assembling the connecting member will be high. For example, if the connecting member is processed so that it makes surface contact with the second engagement portion of the linear motion portion, the processing costs will be high. In this disclosure, by making the connecting member spherical, it is possible to use material that has been pre-processed into a spherical shape as is without additional processing, and processing, manufacturing, and assembly can be done inexpensively.

[0034] In the electric braking device according to one aspect of the present disclosure, relative rotation of the piston and the linearly moving portion with respect to the cylinder is restricted by a frictional force generated at a contact point between the piston and the friction portion. By restricting the relative rotation of the piston and linear motion part with respect to the cylinder by the friction force generated at the point where the piston and friction part come into contact, it is possible to reduce the costs of processing, manufacturing, and assembling the anti-rotation member used to restrict relative rotation and the groove into which the anti-rotation member is inserted, thereby reducing the manufacturing costs of the electric braking device.

[0035] An electric braking device according to one aspect of the present disclosure converts the rotational motion of an electric motor into linear motion of a linear motion part of a linear motion conversion mechanism, drives a piston, and applies a braking force to a vehicle wheel by pressing a friction material against a rotating body that rotates together with the wheel. The piston has a cylindrical shape with a bottom, is engaged with the friction material, and has an outer peripheral surface abutting a cylinder. The linear motion part has a cylindrical shape, an outer peripheral surface facing the inner peripheral surface of the piston, and has a pressing surface that abuts a predetermined pressed surface of the piston when it moves linearly in accordance with the rotational motion of the electric motor. A connecting member is provided that connects the piston to the linear motion part by engaging with the inner peripheral surface of the piston and the outer peripheral surface of the linear motion part. At least one of the pressing surface and the pressed surface has a first curved surface so that the axial direction of the piston can oscillate so as to be inclined with respect to the axial direction of the cylinder, and a second curved surface is provided on the surface of the connecting member in a range that engages with the inner peripheral surface of the piston.

[0036] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0037] 1 Electric braking device 10. Linear motion conversion mechanism 11 Linear motion section 12 Rotating part 13 Second engagement portion 14 First curved surface 20 cylinders 30 pistons 31 first engagement portion 32 Tapered surface 40 brake pads 50 Connecting member

Claims

1. An electric braking device that converts the rotational motion of an electric motor into linear motion of a linear motion conversion mechanism, drives a piston that is in contact with the inner periphery of a cylinder by the linear motion, and presses a friction material against a rotating body that rotates together with the wheel of a vehicle, thereby applying a braking force to the wheel, the piston has a first engagement portion on an inner circumferential surface with which a connecting member is engaged, a second engaging portion that engages with the connecting member on an outer peripheral surface of the linear motion portion that faces an inner peripheral surface of the piston; the connecting member engages with both the first engaging portion and the second engaging portion, a pressing surface of the linear motion portion that presses the piston and a pressed surface of the piston that is pressed by the linear motion portion are in contact with each other, and at least one of the pressing surface and the pressed surface has a first curved surface, The electric braking device according to claim 1, wherein the connecting member has a second curved surface in a range where the connecting member is engaged with the first engaging portion, so that the piston swings so that the linear motion axis of the linear motion is tilted.

2. 2. The electric braking device according to claim 1, wherein the first engagement portion has a through-hole that penetrates between an inner peripheral surface and an outer peripheral surface of the piston.

3. The electric braking device according to claim 1 or 2, wherein the connecting member is a ball.

4. An electric braking device that applies braking force to a vehicle wheel by converting the rotational motion of an electric motor into linear motion of a linear motion part of a linear motion conversion mechanism, driving a piston, and pressing a friction material against a rotating body that rotates together with the wheel, The piston has a cylindrical shape with a bottom, is engaged with the friction material, and has an outer circumferential surface that abuts against a cylinder. the linear motion portion has a cylindrical shape, an outer peripheral surface of which faces an inner peripheral surface of the piston, and a pressing surface that comes into contact with a predetermined pressed surface of the piston when the linear motion is linearly caused in response to the rotational motion of the electric motor, a connecting member that connects the piston to the linear motion portion by engaging with an inner peripheral surface of the piston and an outer peripheral surface of the linear motion portion, an electric braking device, characterized in that at least one of the pressing surface and the pressed surface has a first curved surface, and the connecting member has a second curved surface in a range that engages with the inner peripheral surface of the piston, so that the axial direction of the piston swings so as to be inclined with respect to the axial direction of the cylinder.

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