Electric parking brake

Abstract

To obtain, as an example, an electric parking brake in which a diameter of a bearing can be configured to be larger than a diameter of a piston.SOLUTION: An electric parking brake according to an embodiment includes: a rotary member rotatable about a rotation axis; a linear motion member that moves along the rotation axis in accordance with rotation of the rotary member; a body which has a cylinder provided with a bore extending along the rotation axis, and in which the bore includes a first portion open toward an outside and a second portion communicating with the first portion, and a diameter of the first portion is smaller than a diameter of the second portion; a piston fitted into the first portion movably along the rotation axis; a drive device configured to rotate the rotary member; a lid which is attached to the cylinder and covers an end of the second portion; and a bearing which is accommodated in the second portion, interposed between the rotary member and the lid, and supports the rotary member along the rotation axis rotatably about the rotation axis.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an electric parking brake. [Background technology]

[0002] A conventional electric parking brake is known that includes a cylinder, a piston fitted in the bore of the cylinder, a linearly moving member attached to the piston, a rotating member that rotates to move the linearly moving member in a straight line, a bearing that supports the rotating member, and an electric drive device that rotates the rotating member. The bearing is located at the bottom of the bore (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2008-527258 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional designs, the bore diameter is constant or tapers off towards the bottom of the bore, which limits the bearing diameter to no greater than the piston diameter.

[0005] Therefore, the present invention has been made in view of the above, and provides an electric parking brake in which the diameter of the bearing can be set larger than the diameter of the piston. [Means for solving the problem]

[0006] As an example, an electric parking brake according to an embodiment of the present invention may include a rotating member rotatable about a rotation axis, a linearly moving member attached to the rotating member so as to move in a first axial direction along the rotation axis or in a second axial direction opposite to the first axial direction in response to rotation of the rotating member about the rotation axis, and a cylinder having a bore extending along the rotation axis, the bore accommodating at least a portion of the rotating member and the linearly moving member, the bore having a first portion that is open to the outside of the cylinder at an end in the first axial direction, and a second portion that communicates with an end of the first portion in the second axial direction; the cylinder includes a body having a diameter of the first portion smaller than a diameter of the second portion, a piston fitted in the first portion so as to be movable along the rotation axis and configured to be pushed in the first axial direction by the linear motion member moving in the first axial direction, a drive unit configured to rotate the rotating member around the rotation axis, a lid attached to the cylinder and closing an end of the second portion in the second axial direction, and a bearing housed in the second portion, interposed between the rotating member and the lid, and supporting the rotating member along the rotation axis so as to be rotatable around the rotation axis. Thus, as an example, the bearing can be set to have a diameter larger than that of the piston because it is housed in the second portion having a diameter larger than that of the first portion. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a front view schematically showing a braking device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the braking device of the first embodiment taken along line F2-F2 in FIG. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a part of the EPB of the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view schematically showing a part of the EPB according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) A first embodiment will be described below with reference to FIGS. 1 to 3. In this specification, components according to the embodiment and descriptions of the components may be described using multiple expressions. The components and their descriptions are merely examples and are not limited by the expressions in this specification. The components may also be identified by names different from those in this specification. Furthermore, the components may also be described using expressions different from those in this specification.

[0009] In the following description, "suppress" is defined as, for example, preventing an event, action, or influence from occurring, or reducing the severity of an event, action, or influence. Also, in the following description, "restrict" is defined as, for example, preventing movement or rotation, or allowing movement or rotation within a predetermined range and preventing movement or rotation beyond the predetermined range.

[0010] FIG. 1 is a front view that schematically shows a braking device 10 according to a first embodiment. FIG. 2 is a cross-sectional view that schematically shows the braking device 10 of the first embodiment along line F2-F2 in FIG. 1. The braking device 10 is a disc brake that is mounted on a vehicle 1 such as a four-wheeled automobile. However, the braking device 10 is not limited to this example. As shown in FIG. 1, the braking device 10 has a disc rotor 11 and an electric parking brake (EPB) 12.

[0011] The disc rotor 11 rotates around a central axis Axd integrally with the wheel of the vehicle 1. The central axis Axd is, for example, the central axis of an axle, the central axis of the disc rotor 11, and also the central axis of rotation of the disc rotor 11. Note that the central axis Axd is not limited to this example.

[0012] Hereinafter, the direction along the central axis Axd will be referred to as the axial direction. The axial direction is a direction that is approximately along the width of the vehicle 1, and includes the outward direction Do and the inward direction Di shown in FIG. 2. The outward direction Do is a direction that is along the central axis Axd, and is an example of a first axial direction. The inward direction Di is the opposite direction to the outward direction Do, and is an example of a second axial direction. For example, the outward direction Do is a direction toward the outside of the vehicle 1, and the inward direction Di is a direction toward the inside of the vehicle 1.

[0013] 1, the disc rotor 11 has a rotor body 11a and a hat portion 11b. The rotor body 11a is formed in a disk shape that is substantially perpendicular to the central axis Axd. The hat portion 11b is formed in a substantially cylindrical shape and is coupled to, for example, an axle of the vehicle 1.

[0014] The EPB 12 can operate as a hydraulic service brake and can also operate as an electric brake. As shown in Fig. 2, the EPB 12 of this embodiment has a caliper 21, a pair of brake pads 22, a rotary-to-linear motion conversion mechanism 23, and a drive unit 24. The drive unit 24 may also be referred to as a motor gear unit (MGU).

[0015] For example, the caliper 21 and the brake pads 22 constitute a hydraulic service brake, and the caliper 21, the brake pads 22, the rotary-to-linear motion conversion mechanism 23, and the drive unit 24 constitute an electric brake. The EPB 12 may simply be an electric brake. The EPB 12 is configured so that the braking state provided by the electric brake function is maintained during parking. The electric brake may also be activated during driving or when the vehicle is stopped.

[0016] The caliper 21 is, for example, a floating caliper. The caliper 21 is disposed so as to straddle the rotor body 11a. The caliper 21 includes a mounting 31, a caliper body 32, a cylinder cap 33, a piston 34, a piston seal 35, and a plurality of sealing members 36, 37, and 38. The caliper body 32 is an example of a body. The cylinder cap 33 is an example of a lid. The sealing members 36, 37, and 38 may also be referred to as O-rings.

[0017] The mounting 31 is fixed to a non-rotating portion of the vehicle 1. For example, the mounting 31 is attached to the body of the vehicle 1. The mounting 31 supports the brake pads 22 and the caliper body 32 so that they are axially movable.

[0018] The caliper body 32 is made of a metal such as cast iron or an aluminum alloy, and includes a cylinder 41, a pawl 42, and a bridge 43. However, the caliper body 32 is not limited to this example.

[0019] The cylinder 41 has an outer end surface 41a and an inner end surface 41b. The outer end surface 41a is provided at the end of the cylinder 41 in the outward direction Do. The inner end surface 41b is provided at the end of the cylinder 41 in the inward direction Di. The cylinder 41 is provided with a bore 45, a seal groove 46, and a flow path 47. The bore 45 may also be referred to as a hole or a through-hole.

[0020] The bore 45 extends along a central axis Axc and penetrates the cylinder 41. The central axis Axc is an example of a rotation axis. The central axis Axc is the central axis of the bore 45 that extends substantially parallel to the central axis Axd of the disc rotor 11.

[0021] Hereinafter, the direction perpendicular to the central axis Axc will be referred to as the radial direction, and the direction around the central axis Axc will be referred to as the circumferential direction. Furthermore, since the central axis Axc is substantially parallel to the central axis Axd, the outward direction Do and the inward direction Di are also directions along the central axis Axc.

[0022] The bore 45 has a small diameter portion 51 and a large diameter portion 52. The small diameter portion 51 is an example of a first portion. The large diameter portion 52 is an example of a second portion. In this embodiment, the large diameter portion 52 has an accommodating portion 55 and a fitting portion 56.

[0023] The cross sections of the small diameter portion 51 and the large diameter portion 52 (the accommodation portion 55 and the fitting portion 56) that are perpendicular to the central axis Axc are formed into concentric, approximately circular shapes. Note that the cross sections of the small diameter portion 51 and the large diameter portion 52 may partially have other shapes.

[0024] The end of the small diameter portion 51 in the outward direction Do opens to the outer end surface 41a of the cylinder 41. That is, the small diameter portion 51 opens to the outside of the cylinder 41 at the end of the small diameter portion 51 in the outward direction Do.

[0025] The accommodating portion 55 of the large diameter portion 52 communicates with the end of the small diameter portion 51 in the inward direction Di. The accommodating portion 55 is spaced apart from the outer end surface 41a and the inner end surface 41b of the cylinder 41. The fitting portion 56 of the large diameter portion 52 communicates with the end of the accommodating portion 55 in the inward direction Di. Furthermore, the end of the fitting portion 56 in the inward direction Di opens to the inner end surface 41b of the cylinder 41. That is, the large diameter portion 52 opens to the outside of the cylinder 41 at the end of the large diameter portion 52 in the inward direction Di.

[0026] The diameter of the small diameter portion 51 is smaller than the diameter of the accommodating portion 55 and smaller than the diameter of the fitting portion 56. That is, the diameter of the small diameter portion 51 is smaller than the diameter of the large diameter portion 52. The diameter of the accommodating portion 55 is smaller than the diameter of the fitting portion 56. That is, the diameter of the bore 45 expands discontinuously in the inward direction Di.

[0027] 3 is a cross-sectional view schematically illustrating a portion of the EPB 12 according to the first embodiment. As shown in FIG. 3, the cylinder 41 further includes an inner circumferential surface 51a that defines the small diameter portion 51, an inner circumferential surface 55a and a bottom surface 55b that define the accommodation portion 55, an inner circumferential surface 56a and a bottom surface 56b that define the fitting portion 56, and a protrusion 58.

[0028] The inner circumferential surfaces 51a, 55a, and 56a are generally cylindrical curved surfaces extending along the central axis Axc. The bottom surface 55b is provided between an end of the inner circumferential surface 51a in the inward direction Di and an end of the inner circumferential surface 55a in the outward direction Do, and faces the inward direction Di. The bottom surface 56b is provided between an end of the inner circumferential surface 55a in the inward direction Di and an end of the inner circumferential surface 56a in the outward direction Do, and faces the inward direction Di.

[0029] The protrusion 58 protrudes inwardly Di from the bottom surface 56b. The protrusion 58 is formed in a generally cylindrical shape extending along the central axis Axc. The protrusion 58 has an inner circumferential surface 58a, an outer circumferential surface 58b, an end surface 58c, and a female thread 58d.

[0030] The inner circumferential surface 58a and the outer circumferential surface 58b are generally cylindrical curved surfaces extending along the central axis Axc. The inner circumferential surface 58a faces the central axis Axc. The inner circumferential surface 58a is substantially continuous with, for example, the inner circumferential surface 55a that defines the housing portion 55. That is, the diameter of the inner circumferential surface 58a is generally equal to the diameter of the inner circumferential surface 55a. Note that the diameter of the inner circumferential surface 58a may be larger than the diameter of the inner circumferential surface 55a.

[0031] The outer peripheral surface 58b is located on the opposite side to the inner peripheral surface 58a. The diameter of the outer peripheral surface 58b is smaller than the diameter of the inner peripheral surface 56a that defines the fitting portion 56. Therefore, the outer peripheral surface 58b faces the inner peripheral surface 56a via a gap.

[0032] The end surface 58c is provided at the end of the protrusion 58 in the inward direction Di. The end surface 58c connects the ends of the inner circumferential surface 58a and the outer circumferential surface 58b in the inward direction Di. The female thread 58d is provided on the inner circumferential surface 58a.

[0033] 2, the seal groove 46 opens to an inner circumferential surface 51a that defines the small diameter portion 51. The seal groove 46 extends around the central axis Axc. The piston seal 35 is fitted in the seal groove 46.

[0034] The flow passage 47 is spaced inwardly Di from the seal groove 46 and opens, for example, at an inner circumferential surface 51a that defines the small diameter portion 51. Brake fluid is supplied to or discharged from the bore 45 through the flow passage 47.

[0035] The claws 42 are spaced apart from the cylinder 41 in the outward direction Do. In a projection view seen in the inward direction Di as in FIG. 1, the claws 42 cover the entire area of ​​the small diameter portion 51. In other words, the claws 42 cover the entire area of ​​the small diameter portion 51 in the inward direction Di. Note that the claws 42 are not limited to this example. As shown in FIG. 2, a bridge 43 connects the cylinder 41 and the claws 42.

[0036] The cylinder cap 33 is made of a metal such as cast iron or an aluminum alloy. The cylinder cap 33 is formed in a disk shape arranged approximately perpendicular to the central axis Axc. However, the cylinder cap 33 is not limited to this example. As shown in FIG. 3, the cylinder cap 33 has two side surfaces 33a and 33b and an outer peripheral surface 33c.

[0037] The side surface 33a is formed to be approximately flat and faces the outward direction Do. The side surface 33b is located opposite the side surface 33a. The side surface 33b is formed to be approximately flat and faces the inward direction Di. The outer peripheral surface 33c is a substantially cylindrical curved surface extending along the central axis Axc and connects the ends of the two side surfaces 33a, 33b on the outside in the radial direction.

[0038] The cylinder cap 33 is provided with an insertion hole 61, a fitting groove 62, and three seal grooves 63, 64, and 65. The insertion hole 61 is a substantially circular hole that penetrates the cylinder cap 33 along the central axis Axc. The insertion hole 61 opens to the two side surfaces 33a and 33b.

[0039] The fitting groove 62 is open to the side surface 33a and extends around the central axis Axc. The cylinder cap 33 further has an inner surface 62a, an outer surface 62b, and a bottom surface 62c that define the fitting groove 62.

[0040] The inner surface 62a and the outer surface 62b are substantially cylindrical curved surfaces extending along the central axis Axc. The inner surface 62a faces radially outward. The outer surface 62b faces the central axis Axc. The inner surface 62a and the outer surface 62b face each other via the fitting groove 62. The bottom surface 62c is provided at the end of the fitting groove 62 in the inward direction Di, and connects the ends of the inner surface 62a and the outer surface 62b in the inward direction Di. The cylinder cap 33 further has a male thread 62d. The male thread 62d is provided on the inner surface 62a.

[0041] The seal groove 63 opens to the side surface 33a and is spaced apart from the side surface 33b. The seal groove 63 extends around the central axis Axc and communicates with the insertion hole 61. The seal member 36 is fitted into the seal groove 63. The cylinder cap 33 restricts the seal member 36 from moving in the inward direction Di.

[0042] The seal groove 64 opens to the outer surface 62b that defines the fitting groove 62. Therefore, the seal groove 64 communicates with the fitting groove 62. The seal groove 64 extends around the central axis Axc. The seal member 37 is fitted into the seal groove 64. The seal groove 65 opens to the outer peripheral surface 33c. The seal groove 65 extends around the central axis Axc. The seal member 38 is fitted into the seal groove 65.

[0043] The cylinder cap 33 is fitted into the fitting portion 56 of the bore 45. That is, the cylinder cap 33 closes the end of the large diameter portion 52 in the inward direction Di. Therefore, the side surface 33a of the cylinder cap 33 is provided at the bottom of the bore 45. A portion of the cylinder cap 33 protrudes in the inward direction Di from the inner end surface 41b of the cylinder 41. The seal member 38 and the seal groove 65 are located outside the large diameter portion 52.

[0044] In this embodiment, the cylinder cap 33 is located at the end of the bore 45 in the inward direction Di. However, the cylinder cap 33 may be spaced apart in the outward direction Do from the end of the bore 45 in the inward direction Di. In this case, the bore 45 further has a portion that can be distinguished from the large diameter portion 52 between the cylinder cap 33 and the end of the bore 45 in the inward direction Di. The cylinder cap 33 may also be located outside the bore 45. For example, the cylinder cap 33 may be supported on the inner end surface 41b of the cylinder 41.

[0045] The cylinder cap 33 is attached to the cylinder 41. In this embodiment, the protrusion 58 is fitted into the fitting groove 62. The female thread 58d provided on the protrusion 58 and the male thread 62d provided in the fitting groove 62 are fitted together, thereby attaching the cylinder cap 33 to the cylinder 41. In other words, the cylinder cap 33 is attached to the cylinder 41 by screwing. However, the cylinder cap 33 may be attached to the cylinder 41 by other methods. Alternatively, the cylinder 41 may have a male thread and the cylinder cap 33 may have a female thread.

[0046] When the protrusion 58 is fitted into the fitting groove 62, an end surface 58c of the protrusion 58 abuts against a bottom surface 62c of the fitting groove 62. The side surface 33a of the cylinder cap 33 may abut against the bottom surface 56b of the fitting portion 56.

[0047] The seal member 37 fitted in the seal groove 64 comes into contact with the outer peripheral surface 58b of the protrusion 58. As a result, the seal member 37 seals the gap between the cylinder cap 33 and the cylinder 41 in a watertight manner.

[0048] 2, the piston 34 is formed in a generally cylindrical shape that is open inwardly Di. The piston 34 has an outer peripheral surface 34a. The outer peripheral surface 34a is a generally cylindrical curved surface that extends along the central axis Axc and faces radially outward.

[0049] The piston 34 is fitted into the small diameter portion 51 so as to be movable along the central axis Axc. A portion of the piston 34 may be located outside the small diameter portion 51. The diameter of the outer circumferential surface 34a of the piston 34 is slightly smaller than the diameter of the inner circumferential surface 51a that defines the small diameter portion 51.

[0050] When the piston 34 is fitted into the small diameter portion 51, the piston seal 35 fitted into the seal groove 46 comes into contact with the outer circumferential surface 34a of the piston 34. As a result, the piston seal 35 seals the gap between the piston 34 and the cylinder 41 watertightly.

[0051] The cylinder cap 33, the piston 34, and the cylinder 41 define a pressure chamber R that is part of the bore 45. The pressure chamber R communicates with a flow path 47. The piston seal 35 and the sealing member 36 seal the pressure chamber R from the outside.

[0052] The pair of brake pads 22 are positioned between the cylinder 41 and the pawls 42. The pair of brake pads 22 are spaced apart from each other along the central axis Axc. The rotor body 11a of the disc rotor 11 is disposed between the pair of brake pads 22.

[0053] Brake fluid fills the pressure chamber R. For example, a master cylinder or pump of the braking device 10 increases the pressure in the pressure chamber R through the flow path 47 in response to brake pedal operation or control by an ECU. The increase in pressure in the pressure chamber R moves the piston 34 outward Do, pressing one brake pad 22 against the rotor body 11a.

[0054] When one brake pad 22 is pressed against the rotor body 11a, the caliper body 32 moves inward in reaction to the force Di. This causes the claws 42 of the caliper body 32 to press the other brake pad 22 inward in the direction Di. This causes the pair of brake pads 22 to be pressed against the rotor body 11a.

[0055] The pair of brake pads 22 receive a force from the disc rotor 11 about the central axis Axd due to friction between the brake pads 22 and the rotor body 11a. The mounting 31 receives the braking force (braking torque) transmitted via the pair of brake pads 22 and transmits it to the body of the vehicle 1. In this way, the braking device 10 brakes the disc rotor 11 as a service brake.

[0056] The piston seal 35 has a retraction function that, as the pressure in the pressure chamber R decreases, retracts the piston 34 in the inward direction Di toward the pressure chamber R, separating the piston 34 from the brake pad 22. In other words, as the pressure in the pressure chamber R decreases, the piston 34 is released from pressing the brake pad 22, and the piston 34 releases the brake pad 22 from pressing against the rotor body 11a. This causes the braking device 10 to enter a brake release state in the service brake.

[0057] The rotary-linear motion conversion mechanism 23 includes a rotary member 71, a linear motion member 72, and a bearing 73. The rotary member 71 may also be referred to as a bolt. The linear motion member 72 may also be referred to as a nut. The caliper body 32 accommodates at least a portion of the rotary member 71, at least a portion of the linear motion member 72, and the bearing 73 in the bore 45.

[0058] The rotating member 71 is rotatably supported on the cylinder 41 via, for example, a cylinder cap 33 around the central axis Axc. As shown in FIG.

[0059] The flange 81 is formed in a disk shape that is substantially perpendicular to the central axis Axc. The flange 81 is located between the coupling shaft 82 and the screw shaft 83. The flange 81 has two side surfaces 81a and 81b and an outer peripheral surface 81c.

[0060] The side surface 81a is formed to be approximately flat and faces the outward direction Do. The side surface 81a faces the piston 34 via a gap. The side surface 81b is located opposite the side surface 81a. The side surface 81b is formed to be approximately flat and faces the inward direction Di. The outer peripheral surface 81c is the end face of the flange 81 on the radially outer side. The outer peripheral surface 81c is formed to be approximately cylindrical and faces the radially outer side. The outer peripheral surface 81c connects the ends of the two side surfaces 81a, 81b on the radially outer side.

[0061] The flange 81 is disposed in the housing portion 55 of the large diameter portion 52 of the bore 45. The diameter of the outer peripheral surface 81c of the flange 81 is larger than the diameter of the outer peripheral surface 34a of the piston 34 and larger than the diameter of the small diameter portion 51. On the other hand, the diameter of the outer peripheral surface 81c of the flange 81 is smaller than the diameter of the housing portion 55. The diameter of the outer peripheral surface 81c may be smaller than the diameters of the outer peripheral surface 34a and the small diameter portion 51.

[0062] The side surface 81a faces the bottom surface 55b of the storage portion 55 via a gap. The side surface 81b faces the side surface 33a of the cylinder cap 33 via a gap. That is, the flange 81 is spaced outwardly Do from the cylinder cap 33. The outer peripheral surface 81c faces the inner peripheral surface 55a of the storage portion 55 via a gap.

[0063] The connecting shaft 82 and the screw shaft 83 are each formed in a generally cylindrical shape extending along the central axis Axc. In this embodiment, the central axis Axc also serves as the central axis of the flange 81, the connecting shaft 82, and the screw shaft 83.

[0064] The connecting shaft 82 extends inwardly Di from the side surface 81b of the flange 81 and is fitted into the insertion hole 61 of the cylinder cap 33. The seal member 36 fitted into the seal groove 63 comes into contact with the connecting shaft 82. As a result, the seal member 36 watertightly seals the gap between the cylinder cap 33 and the connecting shaft 82.

[0065] The screw shaft 83 extends in the outward direction Do from the side surface 81a of the flange 81. The screw shaft 83 has an outer peripheral surface 83a and a male thread 83b. The outer peripheral surface 83a is formed in a substantially cylindrical shape extending along the central axis Axc and faces radially outward. The outer peripheral surface 83a faces the inner peripheral surface 51a of the small diameter portion 51 via a gap. The male thread 83b is provided on the outer peripheral surface 83a.

[0066] As shown in Fig. 2, the linear motion member 72 is attached to the rotating member 71 so as to move in an outward direction Do or an inward direction Di in response to the rotation of the rotating member 71. The linear motion member 72 is formed in a substantially cylindrical shape extending along the central axis Axc. As shown in Fig. 3, the linear motion member 72 has an inner circumferential surface 72a and a female thread 72b.

[0067] The inner circumferential surface 72a is a substantially cylindrical curved surface extending along the central axis Axc and facing the central axis Axc. The female thread 72b is provided on the inner circumferential surface 72a. The screw shaft 83 of the rotating member 71 is fitted into the inside of the linear motion member 72, and the female thread 72b and the male thread 83b fit together. In this way, the linear motion member 72 is attached to the screw shaft 83. The side surface 81a of the flange 81 faces the linear motion member 72.

[0068] The linear motion member 72 and at least a portion of the screw shaft 83 are housed inside the piston 34. The linear motion member 72 is attached to the piston 34, for example, with its rotation around the central axis Axc restricted. Meanwhile, the linear motion member 72 can move away from the piston 34 in the inward direction Di.

[0069] The bearing 73 is, for example, a thrust roller bearing. However, the bearing 73 may be another type of bearing. The bearing 73 is housed in the housing portion 55 of the bore 45 and is interposed between the cylinder cap 33 and the flange 81 of the rotating member 71. The bearing 73 has a raceway 91 and a plurality of rolling elements 92.

[0070] The bearing ring 91 is a substantially annular metal plate extending around the central axis Axc. The bearing ring 91 is supported on the side surface 81b of the flange 81. Each of the plurality of rolling elements 92 is formed in a substantially cylindrical shape extending in a substantially radial direction. Note that the rolling elements 92 may be other rolling elements such as balls. The plurality of rolling elements 92 are arranged around the central axis Axc. That is, the plurality of rolling elements 92 are arranged in a substantially radial pattern.

[0071] The rolling elements 92 are interposed between the raceway 91 and the side surface 33a of the cylinder cap 33. The side surface 33a of the cylinder cap 33 supports the rolling elements 92 so that they can roll around the central axis Axc. In other words, the cylinder cap 33 is used as one raceway in the thrust roller bearing. Note that the bearing 73 may further include another raceway supported on the side surface 33a of the cylinder cap 33.

[0072] The bearing 73 is supported by the cylinder cap 33 along the central axis Axc and also supports the flange 81 of the rotating member 71. That is, the bearing 73 receives a thrust load along the central axis Axc. The rotating member 71 is supported by the bearing 73 so as to be able to rotate smoothly around the central axis Axc.

[0073] The diameter (outer diameter) of the bearing 73 is larger than the diameter of the outer peripheral surface 34a of the piston 34 and larger than the diameter of the small diameter portion 51. On the other hand, the diameter of the bearing 73 is smaller than the diameter of the accommodating portion 55. The diameter of the bearing 73 may be smaller than the diameters of the outer peripheral surface 34a and the small diameter portion 51.

[0074] The driving device 24 is driven by driving power based on a control signal. As shown in Fig. 2, the driving device 24 has a case 101, a stator 102, a rotor 103, and a reducer 104. However, the driving device 24 is not limited to this example.

[0075] 3, the case 101 is attached to, for example, the inner end surface 41b of the cylinder 41. A housing chamber 105 is provided inside the case 101. The housing chamber 105 is, for example, a substantially cylindrical space extending along the central axis Axc and is open in the outward direction Do.

[0076] 2, the case 101 accommodates the stator 102, the rotor 103, and at least a part of the reducer 104 in the accommodation chamber 105. Furthermore, a part of the cylinder cap 33 is accommodated in the accommodation chamber 105.

[0077] 3, the case 101 has an inner circumferential surface 105a that defines the housing chamber 105. The inner circumferential surface 105a is a substantially cylindrical curved surface that extends along the central axis Axc and faces the central axis Axc.

[0078] When a portion of the cylinder cap 33 is accommodated in the accommodation chamber 105, the seal member 38 fitted in the seal groove 65 comes into contact with the inner circumferential surface 105a of the accommodation chamber 105. As a result, the seal member 38 watertightly seals the gap between the cylinder cap 33 and the case 101. The seal member 38 can prevent grease or lubricating oil from leaking out of the drive unit 24.

[0079] The stator 102 is fixed to the case 101. The rotor 103 is disposed inside the stator 102 and is rotatable around a central axis Axc. The reducer 104 is, for example, a planetary gear mechanism. A sun gear of the reducer 104 is coupled to the rotor 103, and a planetary carrier of the reducer 104 is coupled to the coupling shaft 82 of the rotating member 71. However, the reducer 104 is not limited to this example.

[0080] When the driving device 24 is driven, the rotor 103 rotates around the central axis Axc. The rotation of the rotor 103 is reduced in speed by the reducer 104 and transmitted to the rotating member 71. As a result, the driving device 24 rotates the rotating member 71 around the central axis Axc.

[0081] When the driving device 24 rotates the rotating member 71 in one direction around the central axis Axc, the linearly-acting member 72 moves linearly in the outward direction Do. The piston 34 is pushed in the outward direction Do by the linearly-acting member 72 moving in the outward direction Do, and presses the brake pad 22 against the rotor body 11a. As a result, the braking device 10 attains a braking state by the electric brake, in which the wheel of the vehicle 1, which rotates integrally with the disc rotor 11, is braked.

[0082] When the driving device 24 rotates the rotating member 71 in the reverse direction around the central axis Axc, the linear motion member 72 moves linearly in the inward direction Di. The piston 34 moves in the inward direction Di due to the retraction function of the piston seal 35. The pressing force of the piston 34 on the brake pad 22 decreases, and the piston 34 releases the brake pad 22 from pressing against the rotor body 11a. This causes the braking device 10 to enter a released state (non-braking state) in which braking by the electric brake is released.

[0083] When the braking device 10 functions as an electric brake to brake the disc rotor 11, the bearing 73 receives a large thrust load in the inward direction Di. However, the bearing 73 of this embodiment has a large diameter and a high load-bearing capacity. Therefore, the bearing 73 can stably support the rotating member 71.

[0084] The cylinder cap 33 also receives a large thrust load in the inward direction Di via the bearing 73. However, the cylinder cap 33 of this embodiment has a high load-bearing capacity because it is attached to the cylinder 41 by screws. Therefore, the cylinder cap 33 can stably support the bearing 73 and the rotating member 71.

[0085] On the other hand, the diameter of the outer peripheral surface 34a of the piston 34 is smaller than the diameter of the bearing 73. Therefore, the braking device 10 can move the piston 34 with a relatively small force. Therefore, the braking device 10 can reduce power consumption as an electric brake and can improve the braking feeling as a service brake.

[0086] The EPB 12 is manufactured, for example, as follows. Note that the manufacturing method of the EPB 12 is not limited to the following method, and other methods may also be used. First, the caliper body 32 is manufactured by casting. Next, a drill is inserted from the inner end surface 41b of the cylinder 41 into a through hole formed in the cylinder 41 by casting, to form the bore 45. Note that various other tools, such as a milling cutter, may also be used to form the bore 45. The protrusion 58 having the female thread 58d is also formed by the tool.

[0087] Furthermore, the cylinder cap 33 is formed by various processes such as press work, drill work, and cutting work. The cylinder cap 33 is manufactured separately from the caliper body 32. Therefore, the cylinder cap 33 can be manufactured with high precision.

[0088] Next, the bearing 73 is attached to the flange 81, and the connecting shaft 82 is inserted into the insertion hole 61 of the cylinder cap 33. As a result, the bearing 73 is disposed between the flange 81 and the cylinder cap 33. Furthermore, the linear motion member 72 is attached to the screw shaft 83.

[0089] Next, the piston 34 is fitted into the small diameter portion 51. Furthermore, the rotary-to-linear motion conversion mechanism 23 and the cylinder cap 33, which are assembled together, are inserted into the bore 45 from the inner end surface 41b of the cylinder 41. The piston 34 may be fitted into the small diameter portion 51 after the rotary-to-linear motion conversion mechanism 23 and the cylinder cap 33 are inserted into the bore 45.

[0090] Next, the cylinder cap 33 is attached to the cylinder 41. Furthermore, the drive unit 24 is attached to the cylinder 41, and the planetary carrier of the reducer 104 is connected to the connecting shaft 82 of the rotating member 71. At some point, the brake pads 22 and the caliper body 32 are attached to the mounting 31. This completes the manufacture of the EPB 12.

[0091] As described above, the cylinder cap 33 is manufactured separately from the caliper body 32. Therefore, the side surface 33a of the cylinder cap 33 can be set to have high flatness and parallelism, and can be used as a raceway of the bearing 73. Also, there is no need to insert a drill into the through-hole from the outer end surface 41a of the cylinder 41. Therefore, the claws 42 do not need holes or notches to avoid the drill.

[0092] In the brake device 10 according to the first embodiment described above, the bore 45 has a small diameter portion 51 and a large diameter portion 52. The end of the small diameter portion 51 in the outward direction Do is open to the outside of the cylinder 41. The large diameter portion 52 communicates with the end of the small diameter portion 51 in the inward direction Di. The diameter of the small diameter portion 51 is smaller than the diameter of the large diameter portion 52. The cylinder cap 33 is attached to the cylinder 41 and closes the end of the large diameter portion 52 in the inward direction Di. The bearing 73 is housed in the large diameter portion 52 and is interposed between the rotating member 71 and the cylinder cap 33. The bearing 73 supports the rotating member 71 along the central axis Axc so that the rotating member 71 can rotate around the central axis Axc. Because the bearing 73 is housed in the large diameter portion 52, which has a diameter larger than the small diameter portion 51, the bearing 73 can be set to have a diameter larger than that of the piston 34. This improves the durability of the bearing 73 in the axial direction along the central axis Axc. Furthermore, the EPB 12 can prevent the piston 34 from becoming larger, thereby reducing the power consumption of the drive device 24 for moving the piston 34 and improving the operability of the EPB 12 when it functions as a service brake to move the piston 34. The large diameter portion 52 is formed, for example, by closing the end of the bore 45 in the inward direction Di that is open to the outside of the cylinder 41 with the cylinder cap 33. Therefore, the EPB 12 can form the large diameter portion 52 without, for example, complex cutting work.

[0093] The bearing 73 has a plurality of rolling elements 92 arranged around the central axis Axc. The cylinder cap 33 supports the plurality of rolling elements 92 so that they can roll. In other words, the cylinder cap 33 serves as one of the raceways of the bearing 73. Therefore, the EPB 12 can reduce the number of parts, thereby reducing costs.

[0094] The cylinder 41 has a female thread 58d. The cylinder cap 33 has a male thread 62d, and is attached to the cylinder 41 by fitting the male thread 62d and the female thread 58d together. This allows the cylinder cap 33 to be easily attached to the cylinder 41, and also improves durability in the axial direction along the central axis Axc.

[0095] The caliper body 32 has a pawl 42 spaced from the cylinder 41 in the outward direction Do. The pawl 42 covers the entire small diameter portion 51 in the inward direction Di. Therefore, the EPB 12 can prevent the bore 45 and the piston 34 from being visible from the outside, improving the appearance. Furthermore, as described above, the end of the bore 45 in the inward direction Di can be open to the outside of the cylinder 41. Therefore, the bore 45 can be formed from the end of the bore 45 in the inward direction Di, for example, by drilling. The EPB 12 does not require, for example, holes or notches in the pawl 42 to avoid drilling, thereby improving the strength of the pawl 42. Furthermore, the EPB 12 improves the design freedom of the pawl 42, which in turn allows the pawl 42 to effectively press the brake pad 22 and suppresses vibration and noise caused by the natural frequency of the pawl 42.

[0096] (Second embodiment) The second embodiment will be described below with reference to Fig. 4. In the following description of the embodiment, components having the same functions as components already described are given the same reference numerals as the components already described, and further description may be omitted. Furthermore, multiple components given the same reference numerals do not necessarily have all the same functions and properties, and may have different functions and properties according to each embodiment.

[0097] 4 is a cross-sectional view schematically illustrating a portion of the EPB 12 according to the second embodiment. As shown in FIG. 4, the caliper body 32 of the second embodiment has a cylinder 201 instead of the cylinder 41. The cylinder 201 is substantially the same as the cylinder 41, except for the points described below.

[0098] The cylinder 201 has an inner end surface 201a and an outer peripheral surface 201b instead of the inner end surface 41b. The inner end surface 201a is provided at the end of the cylinder 41 in the inward direction Di. The outer peripheral surface 201b is a substantially cylindrical curved surface that extends from the inner end surface 201a in the outward direction Do along the central axis Axc.

[0099] A seal groove 205 is provided in the cylinder 201. The seal groove 205 opens to the outer circumferential surface 201b and extends around the central axis Axc. The caliper 21 further has a seal member 206 fitted in the seal groove 205.

[0100] The large diameter portion 52 of the second embodiment has a fitting portion 211 instead of the fitting portion 56. The cylinder 201 also has an inner circumferential surface 211a and a bottom surface 211b that define the fitting portion 211. The fitting portion 211, the inner circumferential surface 211a, and the bottom surface 211b are substantially identical to the fitting portion 56, the inner circumferential surface 56a, and the bottom surface 56b, except for the points described below. The end of the fitting portion 211 in the inward direction Di opens to the inner end surface 201a of the cylinder 41. No protrusion 58 is provided on the bottom surface 211b.

[0101] The caliper 21 of the second embodiment has a cylinder cap 221 instead of the cylinder cap 33. The cylinder cap 221 is substantially the same as the cylinder cap 33 except as described below.

[0102] Cylinder cap 221 has two side surfaces 221a and 221b and an outer peripheral surface 221c. Cylinder cap 221 is also provided with insertion hole 61 and seal groove 63. However, cylinder cap 221 is not provided with fitting groove 62 and seal grooves 64 and 65. Therefore, seal members 37 and 38 are also omitted.

[0103] The side surface 221a is formed to be substantially flat and faces the outward direction Do. The side surface 221a is supported by the bottom surface 211b of the fitting portion 211. Furthermore, the side surface 221a supports the plurality of rolling elements 92 of the bearing 73.

[0104] The side surface 221b is located on the opposite side to the side surface 221a. The side surface 221b is formed to be substantially flat and faces the inward direction Di. The side surface 221b and the inner end surface 201a of the cylinder 41 are disposed on substantially the same plane.

[0105] The outer peripheral surface 221c is a substantially cylindrical curved surface extending along the central axis Axc, and connects the ends of the two side surfaces 221a and 221b on the outside in the radial direction. The outer peripheral surface 221c faces the inner peripheral surface 211a of the fitting portion 211.

[0106] In the second embodiment, the cylinder 201 and the cylinder cap 221 are made of an aluminum alloy. The cylinder cap 221 is attached to the cylinder 201 by friction stir welding. Note that the cylinder cap 221 may also be attached to the cylinder 201 by other methods such as welding.

[0107] For example, a joint 225 is provided across the inner circumferential surface 211a of the fitting portion 211 and the outer circumferential surface 221c of the cylinder cap 221. The joint 225 is a portion where the cylinder 201 and the cylinder cap 221 are integrated by friction stir welding.

[0108] In this embodiment, the joint portion 225 is spaced in the inward direction Di from the bottom surface 211b of the fitting portion 211 and the side surface 221a of the cylinder cap 221. This makes it possible for the joint portion 225 to prevent deformation of the side surface 221a of the cylinder cap 221. Note that the joint portion 225 may be provided from the inner end surface 201a to the bottom surface 211b and from the side surface 221a to the side surface 221b.

[0109] The joint portion 225 may protrude from the inner end surface 201a of the cylinder 201 and the side surface 221b of the cylinder cap 221. For example, the protruding joint portion 225 may be cut, and the inner end surface 201a of the cylinder 201 and the side surface 221b of the cylinder cap 221 may be smoothed.

[0110] The cylinder 201 and a portion of the cylinder cap 221 are housed in the housing chamber 105 of the case 101. The seal member 206 fitted in the seal groove 205 contacts the inner circumferential surface 105a of the housing chamber 105. In this way, the seal member 206 seals the gap between the cylinder 201 and the case 101 in a watertight manner.

[0111] In the braking device 10 of the second embodiment described above, the cylinder cap 221 is friction stir welded to the cylinder 201. This allows the EPB 12 to prevent brake fluid from leaking from the pressure chamber R through a gap between the cylinder cap 221 and the cylinder 201 without, for example, a seal member 37. Furthermore, since the cylinder cap 221 and the cylinder 201 are integrated, the appearance of the EPB 12 can be improved.

[0112] As an example, the electric parking brake according to at least one embodiment described above may include a rotary member rotatable about a rotary axis, a linearly moving member attached to the rotary member so as to move in a first axial direction along the rotary axis or a second axial direction opposite to the first axial direction in response to rotation of the rotary member about the rotary axis, and a cylinder having a bore extending along the rotary axis, the bore accommodating at least a portion of the rotary member and the linearly moving member, the bore having a first portion that is open to the outside of the cylinder at an end in the first axial direction and a second portion that is in communication with an end of the first portion in the second axial direction. The electric parking brake includes a body having a first portion and a second portion, the diameter of the first portion being smaller than the diameter of the second portion; a piston fitted in the first portion so as to be movable along the rotation axis and configured to be pushed in the first axial direction by the linear motion member moving in the first axial direction; a drive unit configured to rotate the rotating member around the rotation axis; a cover attached to the cylinder and closing an end of the second portion in the second axial direction; and a bearing housed in the second portion, interposed between the rotating member and the cover, and supporting the rotating member along the rotation axis so as to be rotatable around the rotation axis. Therefore, as an example, the bearing is housed in the second portion, which has a diameter larger than the first portion, and can be set to have a larger diameter than the piston. This improves the durability of the bearing in the axial direction along the rotation axis. Furthermore, the electric parking brake can suppress an increase in the size of the piston, thereby reducing the power consumption of the drive unit for moving the piston and improving the operability when the electric parking brake moves the piston as a service brake. The second portion is formed by, for example, closing the end of the bore in the second axial direction that is open to the outside of the cylinder with a cover. Therefore, the electric parking brake can form the second portion with a large diameter without, for example, complex cutting work.

[0113] In the electric parking brake, for example, the bearing has a plurality of rolling elements arranged around the rotation shaft, and the cover supports the plurality of rolling elements so that they can roll. Therefore, for example, the cover serves as one of the raceways of the bearing. Therefore, the electric parking brake can reduce the number of parts, and ultimately the cost.

[0114] In the electric parking brake, as one example, the cylinder has one of a male thread and a female thread, and the lid has the other of the male thread and the female thread, and is attached to the cylinder by fitting the male thread and the female thread together. Thus, as one example, the lid can be easily attached to the cylinder and can improve durability in the axial direction along the rotation axis.

[0115] In the electric parking brake, for example, the cover is friction stir welded to the cylinder. Therefore, for example, the electric parking brake can prevent brake fluid from leaking from the bore through a gap between the cover and the cylinder without adding a seal such as an O-ring. Furthermore, the electric parking brake can improve its appearance.

[0116] In the above-described electric parking brake, for example, the body has a pawl spaced from the cylinder in the first axial direction, and the pawl covers the entire first portion in the second axial direction. Therefore, for example, the electric parking brake can prevent the bore and piston from being visible from the outside, improving its appearance. Furthermore, as described above, the end of the bore in the second axial direction can be open to the outside of the cylinder. Therefore, the bore can be formed from the end of the bore in the second axial direction, for example, by drilling. The electric parking brake does not require, for example, holes or notches in the pawl to avoid drilling, improving the strength of the pawl. Furthermore, the electric parking brake can improve the degree of freedom in designing the pawl, which in turn allows the pawl to effectively press the braking member and suppresses vibration and noise caused by the natural frequency of the pawl.

[0117] While the embodiments of the present invention have been described above, the above-described embodiments and modifications are merely examples and are not intended to limit the scope of the invention. The above-described embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, the configurations and shapes of each embodiment and each modification can be partially interchanged. [Explanation of symbols]

[0118] 12...electric parking brake, 24...drive unit, 32...caliper body (body), 33,221...cylinder cap (lid), 34...piston, 41,201...cylinder, 42...pawl, 45...bore, 51...small diameter portion (first part), 52...large diameter portion (second part), 58d...female thread, 62d...male thread, 71...rotating member, 72...linear member, 73...bearing, 92...rolling element, Axc...central axis (rotating axis), Do...outward direction (first axial direction), Di...inward direction (second axial direction).

Claims

1. a rotating member that is rotatable around a rotation axis; a linear motion member attached to the rotating member so as to move in a first axial direction along the rotation axis or a second axial direction opposite to the first axial direction in response to rotation of the rotating member about the rotation axis; a body including a cylinder having a bore extending along the rotation axis, the bore accommodating at least a portion of the rotary member and the linearly moving member, the bore having a first portion that is open to the outside of the cylinder at an end in the first axial direction and a second portion that communicates with an end of the first portion in the second axial direction, the first portion having a diameter smaller than a diameter of the second portion; a piston fitted in the first part so as to be movable along the rotation axis and configured to be pushed in the first axial direction by the linear moving member moving in the first axial direction; a drive device configured to rotate the rotary member about the rotation axis; a cover attached to the cylinder and closing an end of the second portion in the second axial direction; a bearing housed in the second portion, interposed between the rotating member and the lid, and supporting the rotating member along the rotation axis so as to be rotatable about the rotation axis; An electric parking brake equipped with:

2. the bearing has a plurality of rolling elements arranged around the rotation shaft, The lid supports the plurality of rolling elements so that they can roll.

2. The electric parking brake of claim 1.

3. the cylinder has one of a male thread and a female thread; The lid has the other of the male screw and the female screw, and is attached to the cylinder by fitting the male screw and the female screw together.

2. The electric parking brake of claim 1.

4. The lid is friction stir welded to the cylinder.

2. The electric parking brake of claim 1.

5. the body has a pawl spaced from the cylinder in the first axial direction; The claw covers the entire area of ​​the first portion in the second axial direction.

2. The electric parking brake of claim 1.

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