Electric brake device

Abstract

As an example, a lightweight electric brake device can be obtained. [Solution] As an example, an electric brake device according to an embodiment includes a screw shaft having a male thread, a motor that drives the screw shaft to rotate around a rotation axis, a nut that has an inner surface facing the rotation axis, a female thread that is provided on the inner surface and that engages with the male thread, an outer surface that is located opposite the inner surface, and a convex portion protruding from the outer surface, and a resin case that at least partially accommodates the screw shaft, the motor, and the nut and is formed as one unit, the case having a groove that extends in the axial direction along the rotation axis and accommodates the convex portion, a limiting wall that defines the groove and supports the convex portion to limit the rotation of the nut around the rotation axis, and a rib that protrudes from the limiting wall, the limiting wall being located between the nut and the rib.

Description

[Technical Field]

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

[0002] Conventionally, electric brake devices that move brake shoes by pulling a cable have been known. The electric brake device includes, for example, a screw shaft, a motor that rotates the screw shaft, a nut that pulls the cable in response to the rotation of the screw shaft, a member that limits the rotation of the nut, and a case that houses these components (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-058092 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional configuration, the member that limits the rotation of the nut and the case are separate components that are fixed to each other, and the structure for fixing the member and the case can make the electric brake device heavy.

[0005] The present invention has been made in view of the above, and provides an electric brake device that can be made lighter. [Means for solving the problem]

[0006]

[0006] An electric brake device according to an embodiment of the present invention includes, as an example, a threaded shaft having an external thread, a motor that drives the threaded shaft to rotate around a rotation axis, a nut having an inner circumferential surface facing the rotation axis, an internal thread on the inner circumferential surface that engages with the external thread, an outer circumferential surface opposite the inner circumferential surface, and a protrusion protruding from the outer circumferential surface, and a resin case that at least partially houses the threaded shaft, the motor, and the nut and is integrally formed therewith, the case having a groove extending in an axial direction along the rotation axis and receiving the protrusion, a limiting wall that defines the groove and supports the protrusion to limit rotation of the nut around the rotation axis, and a rib protruding from the limiting wall, the limiting wall being located between the nut and the rib, and the nut moving in the axial direction as the threaded shaft rotates around the rotation axis. Therefore, as an example, the electric brake device can be made lighter than when the portion of the case that houses the threaded shaft and the nut and the limiting wall are separate members. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a side view showing an electric brake device according to one embodiment. [Figure 2] FIG. 2 is a rear view showing the electric brake device of the embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing the MGU of the above embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing the MGU of the embodiment taken along line F4-F4 in FIG. [Figure 5] FIG. 5 is a perspective view showing the upper case of the embodiment. [Figure 6] FIG. 6 is a bottom view showing a part of the nut and the upper case of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment will be described below with reference to FIGS. 1 to 6. Note that 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 side view showing an electric brake device 10 according to this embodiment. FIG. 2 is a rear view showing the electric brake device 10 according to this embodiment. As shown in FIG. 2, the electric brake device 10 is a drum brake mounted on a vehicle 1 such as an automobile. The electric brake device 10 may also be referred to as a braking device.

[0011] The electric brake device 10 is disposed inside the cylindrical peripheral wall 2a of the wheel 2. The electric brake device 10 may be disposed inside either a driving wheel or a non-driving wheel 2. However, the electric brake device 10 is not limited to this example.

[0012] As shown in Figures 1 and 2, for convenience, an X-axis, a Y-axis, and a Z-axis are defined in this specification. The X-axis, the Y-axis, and the Z-axis are perpendicular to one another. The X-axis is provided along the width of the electric braking device 10. The Y-axis is provided along the thickness of the electric braking device 10. The Z-axis is provided along the height of the electric braking device 10. The X-axis extends substantially in the front-rear direction of the vehicle 1. Furthermore, the Y-axis extends substantially in the width direction (vehicle width direction) of the vehicle 1.

[0013] Furthermore, in this specification, the X direction, Y direction, and Z direction are defined. The X direction (front-rear direction) is a direction along the X axis and includes the +X direction indicated by the X axis arrow and the -X direction opposite to the X axis arrow. The Y direction (vehicle width direction) is a direction along the Y axis and includes the +Y direction indicated by the Y axis arrow (outer side in the vehicle width direction) and the -Y direction opposite to the Y axis arrow (inner side in the vehicle width direction). The Z direction (height direction) is a direction along the Z axis and includes the +Z direction indicated by the Z axis arrow (upward) and the -Z direction opposite to the Z axis arrow (downward).

[0014] 1, the electric brake device 10 includes two brake shoes 11, a backing plate 12, an anchor 13, a wheel cylinder 14, a motor gear unit (MGU) 15, a spring 16, and a movement mechanism 17. The brake shoes 11 are an example of a braking member.

[0015] The two brake shoes 11 are spaced apart from each other in the X direction. The two brake shoes 11 extend in a substantially arc shape along the cylindrical inner circumferential surface 3a of the drum rotor 3 shown in Fig. 2. The drum rotor 3 may also be referred to as a brake drum.

[0016] The drum rotor 3 is attached to the wheel 2. The drum rotor 3 rotates integrally with the wheel 2 around a central axis Axd extending in the Y direction. The central axis Axd is the central axis of the wheel 2 and the drum rotor 3.

[0017] The backing plate 12 is formed in a substantially disk shape and disposed so as to be substantially perpendicular to the central axis Axd. The backing plate 12 is connected to the body of the vehicle 1, for example, via a part of the suspension. The backing plate 12 supports various elements of the electric brake device 10.

[0018] The anchor 13 is attached to the backing plate 12 near the end of the backing plate 12 in the -Z direction. The wheel cylinder 14 is attached to the backing plate 12 near the end of the backing plate 12 in the +Z direction. The two brake shoes 11, the anchor 13, the wheel cylinder 14, the spring 16, and the movement mechanism 17 are located outside the backing plate 12 in the vehicle width direction. On the other hand, the MGU 15 is attached to the backing plate 12 so as to protrude inward from the backing plate 12 in the vehicle width direction.

[0019] An end 11a of the brake shoe 11 in the -Z direction is supported by the anchor 13 so as to be rotatable around the end 11a. As a result, the brake shoe 11 is supported by the backing plate 12 via the anchor 13. Furthermore, an end 11b of the brake shoe 11 in the +Z direction is supported by a movable part of the wheel cylinder 14.

[0020] Each of the two brake shoes 11 has a strip-shaped lining 11c. The electric brake device 10 moves the two brake shoes 11 so as to press the lining 11c against the inner circumferential surface 3a of the drum rotor 3. The brake shoes 11 come into contact with the drum rotor 3, which rotates integrally with the wheel 2, and brake the wheel 2 due to friction between the lining 11c and the inner circumferential surface 3a of the drum rotor 3.

[0021] For example, the electric brake device 10 moves the brake shoes 11 using hydraulic pressure in the wheel cylinders 14 while the vehicle 1 is traveling. On the other hand, when the vehicle 1 is parking, the electric brake device 10 moves the brake shoes 11 using the MGU 15. In other words, the electric brake device 10 is a so-called electric parking brake. Note that the MGU 15 may move the brake shoes 11 while the vehicle 1 is traveling.

[0022] The wheel cylinder 14 presses the end portions 11b of the brake shoes 11 in response to the hydraulic pressure. This causes the two brake shoes 11 to rotate around the end portions 11a, and the end portions 11b of the two brake shoes 11 to move away from each other in the X direction. This causes the two brake shoes 11 to move toward the inner circumferential surface 3a of the drum rotor 3, and the linings 11c are pressed against the inner circumferential surface 3a of the drum rotor 3.

[0023] The spring 16 pulls the two brake shoes 11 toward each other. When the wheel cylinder 14 stops pressing the brake shoes 11, the spring 16 moves the two brake shoes 11 away from the inner peripheral surface 3a of the drum rotor 3.

[0024] The MGU 15 moves the two brake shoes 11 via a movement mechanism 17. The movement mechanism 17 has a lever 21, a pin 22, a cable 23, and a strut 24. Note that the components included in the movement mechanism 17 are not limited to this example.

[0025] The lever 21, one brake shoe 11 (11L), and backing plate 12 are aligned in a direction along the central axis Axd. A pin 22 attaches an end 21a of the lever 21 in the +Z direction to the brake shoe 11L near the end 11b. The lever 21 and the brake shoe 11L are attached to each other so as to be rotatable relative to each other around the pin 22.

[0026] The cable 23 passes through the backing plate 12 and extends between the MGU 15 and the lever 21. One end 23a of the cable 23 is attached to the end 21b of the lever 21 in the -Z direction. The MGU 15 can pull the lever 21 via the cable 23 so that the end 21b of the lever 21 approaches the central axis Axd.

[0027] The strut 24 is interposed between the lever 21 attached to one brake shoe 11L and the other brake shoe 11 (11R). The strut 24 abuts against the lever 21 between the two ends 21a, 21b of the lever 21.

[0028] 3 is a cross-sectional view showing the MGU 15 of this embodiment. As shown in Fig. 3, the MGU 15 has a housing 31, a motor 32, a speed reduction mechanism 33, a motion conversion mechanism 34, a bearing 35, and a cable end 36.

[0029] The housing 31 accommodates the other end 23b of the cable 23, the motor 32, the speed reduction mechanism 33, the motion conversion mechanism 34, the bearings 35, and the cable end 36. The housing 31 is attached to the backing plate 12, for example, by bolts.

[0030] The motor 32 has an output shaft 41. The motor 32 is controlled by a control device such as an ECU to rotate the output shaft 41. The motor 32 may also be referred to as an actuator.

[0031] The reduction mechanism 33 has a plurality of gears 45, 46, and 47 rotatably supported on the housing 31, and a support shaft 48. The gear 45 is attached to the output shaft 41 of the motor 32. The gear 46 is supported on the support shaft 48. The gears 45 and 46 mesh with each other, and the gears 46 and 47 mesh with each other. The reduction mechanism 33 reduces the rotation of the output shaft 41 and transmits it to the motion conversion mechanism 34.

[0032] The motion conversion mechanism 34 has a threaded shaft 51 and a nut 52. The threaded shaft 51 may also be referred to as a rotating member. The nut 52 may also be referred to as a linear motion member. The threaded shaft 51 and the nut 52 are made of a metal such as iron. However, the threaded shaft 51 and the nut 52 may also be made of other materials.

[0033] The screw shaft 51 and the nut 52 are each formed in a substantially cylindrical shape extending along a central axis Axc. The central axis Axc is an example of a rotation axis, and is, for example, the central axis of the screw shaft 51 and the nut 52. Note that the screw shaft 51 and the nut 52 may be formed in other shapes.

[0034] For convenience, the terms axial, radial, and circumferential are defined herein. The axial direction is the direction along the central axis Axc. The axial direction includes a first axial direction Dx1 that is one direction along the central axis Axc and a second axial direction Dx2 that is opposite to the first axial direction Dx1. The radial direction is the direction perpendicular to the central axis Axc. The circumferential direction is the direction around the central axis Axc.

[0035] The screw shaft 51 has a cylindrical wall 55 and a flange 56. The cylindrical wall 55 is formed in a generally cylindrical shape extending along the central axis Axc. The flange 56 is formed in a generally disk shape protruding radially outward from the cylindrical wall 55. The gear 47 of the reduction mechanism 33 is provided at the end of the flange 56 on the radially outer side.

[0036] The gear 47 provided on the flange 56 can transmit rotation between the output shaft 41 and the gear 47 via other gears 45, 46 included in the reduction gear mechanism 33. Therefore, the motor 32 drives the screw shaft 51 via the reduction gear mechanism 33 to rotate around the central axis Axc.

[0037] The cylindrical wall 55 has a first outer peripheral surface 55a, a second outer peripheral surface 55b, and a male thread (external thread / bolt thread) 55c. The first outer peripheral surface 55a and the second outer peripheral surface 55b are substantially cylindrical curved surfaces extending along the central axis Axc and facing radially outward.

[0038] The first outer peripheral surface 55a extends in the first axial direction Dx1 from the flange 56. The second outer peripheral surface 55b extends in the second axial direction Dx2 from the flange 56. A male thread 55c is provided on the first outer peripheral surface 55a.

[0039] The cable 23 extends in the axial direction, passing through the inside of the substantially cylindrical tube wall 55. Inside the housing 31, the cable 23 extends, for example, along the central axis Axc. That is, the central axis Axc is also the central axis of the cable 23 inside the housing 31. However, the central axis Axc is not limited to this example.

[0040] The nut 52 is spaced apart from the flange 56 in the first axial direction Dx1 and surrounds a first outer peripheral surface 55a of the cylindrical wall 55. The nut 52 has an end face 52a, an inner peripheral surface 52b, an internal thread / nut thread 52c, and an outer peripheral surface 52d.

[0041] The end surface 52a is provided at an end of the nut 52 in the first axial direction Dx1. The inner circumferential surface 52b is a generally cylindrical curved surface extending along the central axis Axc and facing radially inward. In other words, the inner circumferential surface 52b faces the central axis Axc.

[0042] The female thread 52c is provided on the inner circumferential surface 52b. The female thread 52c and the male thread 55c mesh with each other, thereby attaching the nut 52 to the screw shaft 51. The outer circumferential surface 52d is located on the opposite side of the inner circumferential surface 52b. The outer circumferential surface 52d is a substantially cylindrical curved surface that extends along the central axis Axc and faces radially outward.

[0043] Figure 4 is a cross-sectional view of the MGU 15 of this embodiment taken along line F4-F4 in Figure 3. As shown in Figure 4, the nut 52 further has two protrusions 58. Note that the number of protrusions 58 is not limited to this example. The two protrusions 58 protrude, for example, radially outward from the outer circumferential surface 52d.

[0044] The bearing 35 is, for example, a ball bearing. However, the bearing 35 may be another type of bearing such as a roller bearing or a bushing, or may be a thrust bearing. An inner race of the bearing 35 is attached to the second outer peripheral surface 55b of the cylindrical wall 55.

[0045] The cable end 36 is attached to the end 23b of the cable 23. The cable end 36 is spaced apart in the first axial direction Dx1 from the screw shaft 51. An end face 52a of the nut 52 faces the cable end 36.

[0046] 3, the housing 31 has a lower case 61, an upper case 62, a plurality of fasteners 63 such as screws, and a motor bracket 64. The upper case 62 is an example of a case. The lower case 61 and the upper case 62 are each made of synthetic resin.

[0047] The lower case 61 may be made of other materials. Furthermore, the resin lower case 61 and upper case 62 may be joined to metal parts by, for example, insert molding. However, in this embodiment, the lower case 61 and upper case 62 are each integrally formed resin parts. In other words, the lower case 61 and upper case 62 do not include multiple parts that are assembled disassemblably by screwing or fitting, but are each a single part made entirely of resin.

[0048] The lower case 61 has two end faces 61a and 61b. The end face 61a is provided at an end of the lower case 61 in the first axial direction Dx1. The end face 61a is formed to be substantially flat and faces the first axial direction Dx1. The end face 61b is provided at an end of the lower case 61 in the second axial direction Dx2. The end face 61b is supported by the backing plate 12 directly or via a member such as a gasket.

[0049] The lower case 61 is provided with a through space 71, a recess 72, and a plurality of screw holes 73. The through space 71 is a hole that passes through the lower case 61 along the central axis Axc. The through space 71 opens to two end faces 61a, 61b.

[0050] The through space 71 has a plurality of portions that communicate with each other in the axial direction and that differ in size and shape. That is, the diameter of the through space 71 is not constant. A portion of the cable 23, the bearing 35, a portion of the nut 52, a portion of the cylindrical wall 55, and the flange 56 are arranged in the through space 71. Note that the bearing 35, the nut 52, the cylindrical wall, and the flange 56 may be located outside the through space 71.

[0051] The lower case 61 further has an inner circumferential surface 71a and a support surface 71b that define a portion of the through-space 71. The inner circumferential surface 71a is a substantially cylindrical curved surface extending along the central axis Axc. The support surface 71b is a substantially annular flat surface that extends in the circumferential direction and faces the first axial direction Dx1. The support surface 71b is connected to an end of the inner circumferential surface 71a in the second axial direction Dx2.

[0052] The outer race of the bearing 35 is attached to the inner circumferential surface 71a and is supported in the axial direction by the support surface 71b. As a result, the screw shaft 51 is supported by the housing 31 via the bearing 35 so as to be rotatable around the central axis Axc.

[0053] The recess 72 is recessed from the end face 61a. In other words, the recess 72 opens to the end face 61a. Furthermore, the recess 72 communicates with the through-space 71 in the radial direction. The gears 45, 46 and the support shaft 48 are housed in the recess 72. The end of the support shaft 48 in the second axial direction Dx2 is held by the lower case 61 in the recess 72.

[0054] The plurality of screw holes 73 are spaced apart from the through space 71 and the recess 72 and open to the end face 61a. For example, a metal cylinder may be joined to the inside of the screw hole 73 by insert molding.

[0055] Fig. 5 is a perspective view showing the upper case 62 of this embodiment. As shown in Fig. 5, the upper case 62 has a flange 81, a motor cover 82, and a mechanism cover 83. However, the upper case 62 is not limited to this example.

[0056] The flange 81 has an end surface 81a. The end surface 81a is provided at an end of the flange 81 in the second axial direction Dx2. The end surface 81a is formed to be substantially flat and faces the second axial direction Dx2.

[0057] 3, an end surface 81a of the flange 81 faces an end surface 61a of the lower case 61. The flange 81 is supported on the end surface 61a of the lower case 61 directly or via a member such as a gasket.

[0058] A plurality of insertion holes 85 are provided in the flange 81. The insertion holes 85 pass through the flange 81 and open to an end face 81a. A metal cylinder may be joined to the inside of the insertion holes 85 by, for example, insert molding.

[0059] The insertion holes 85 of the flange 81 communicate with the screw holes 73 of the lower case 61. The multiple fasteners 63 pass through the insertion holes 85 and are fitted into the screw holes 73. In this way, the fasteners 63 attach the upper case 62 to the lower case 61.

[0060] The motor cover 82 protrudes from the flange 81 in the first axial direction Dx1. The motor cover 82 defines a motor chamber 87. The motor chamber 87 is recessed from the end surface 81a of the flange 81 in the first axial direction Dx1. The motor 32 is disposed in the motor chamber 87. That is, the upper case 62 at least partially accommodates the motor 32.

[0061] The motor bracket 64 is attached to the motor cover 82 so as to cover the motor chamber 87. The motor bracket 64 holds the motor 32 in the motor chamber 87. The motor bracket 64 also holds the end of the support shaft 48 in the first axial direction Dx1.

[0062] 4, the mechanism cover 83 has an outer wall 91, an intermediate wall 92, and an end cover 93. The outer wall 91 protrudes from the flange 81 in the first axial direction Dx1. The outer wall 91 is formed, for example, in a generally cylindrical shape extending along the central axis Axc, or in a generally truncated cone shape tapering toward the first axial direction Dx1.

[0063] The outer wall 91 surrounds a part of the cable 23, a part of the nut 52, and a part of the cylindrical wall 55. That is, the upper case 62 at least partially accommodates the screw shaft 51 and the nut 52.

[0064] The intermediate wall 92 is connected to an end of the outer wall 91 in the first axial direction Dx1. The end cover 93 protrudes in the first axial direction Dx1 from the intermediate wall 92. The end cover 93 defines a cable end chamber 94.

[0065] The cable end chamber 94 is recessed from the intermediate wall 92 in the first axial direction Dx1. The end portion 23b of the cable 23 and the cable end 36 are disposed in the cable end chamber 94. The cable end chamber 94 is longer in the axial direction than the cable end 36. In the cable end chamber 94, the cable end 36 can move in the axial direction.

[0066] As shown in Fig. 5, the upper case 62 further has a limiting wall 95 and a plurality of ribs 96. Note that the number of ribs 96 is not limited to this example. As shown in Fig. 4, the limiting wall 95 and the ribs 96 extend from the intermediate wall 92 in the second axial direction Dx2 (axial direction). The outer wall 91 surrounds the limiting wall 95 and the ribs 96.

[0067] The limiting wall 95 surrounds the screw shaft 51 and the nut 52. Therefore, the limiting wall 95 is located between the nut 52 and the outer wall 91. As shown in Fig. 5, the limiting wall 95 has two groove walls 101 and a connecting wall 102. Note that the limiting wall 95 is not limited to this example.

[0068] Fig. 6 is a bottom view showing a portion of the nut 52 and the upper case 62 of this embodiment. As shown in Fig. 6, the two groove walls 101 are formed, for example, in a substantially mirror-symmetrical manner. Each of the two groove walls 101 is formed, for example, in a substantially U-shape and has a first wall 111 and two second walls 112.

[0069] The first wall 111 is formed in a plate shape that is approximately perpendicular to the radial direction. The first wall 111 has two flat surfaces 111a and 111b. The flat surface 111a faces the central axis Axc. The flat surface 111b is located on the opposite side to the flat surface 111a.

[0070] The two second walls 112 extend inward in a roughly radial direction from both ends of the first wall 111 in the circumferential direction. In other words, the second walls 112 are connected to the ends of the first wall 111 in the circumferential direction.

[0071] Each of the two second walls 112 has two flat surfaces 112a and 112b. The flat surface 112a of one second wall 112 faces the flat surface 112a of the other second wall 112. The flat surface 112b is located on the opposite side of the flat surface 112a.

[0072] The groove wall 101 has a concave surface 101a and an outer surface 101b. The concave surface 101a has a flat surface 111a of the first wall 111 and flat surfaces 112a of the two second walls 112. The outer surface 101b is located on the opposite side of the concave surface 101a. The outer surface 101b has a flat surface 111b of the first wall 111 and flat surfaces 112b of the two second walls 112.

[0073] The concave surface 101a of the groove wall 101 defines a groove 115. That is, two grooves 115 are provided in the upper case 62. Note that the number of grooves 115 is not limited to this example. The groove 115 may also be referred to as a recess. The groove 115 is recessed from the end of the groove wall 101 on the radially inner side to the radially outer side. The groove 115 extends in the axial direction.

[0074] The two protrusions 58 of the nut 52 are housed in the two grooves 115. The protrusions 58 are shorter than the grooves 115 in the axial and circumferential directions. The protrusions 58 are movable along the grooves 115 in the axial direction.

[0075] In the circumferential direction, the protrusion 58 is located between two second walls 112 of the groove wall 101. The second walls 112 support the protrusion 58, thereby restricting the rotation of the nut 52 around the central axis Axc. Note that the first wall 111 or another portion of the restricting wall 95 may support the protrusion 58.

[0076] The groove wall 101 has two ends 101c and 101d in the circumferential direction. The end 101c of one groove wall 101 and the end 101c of the other groove wall 101 face each other in the circumferential direction. Furthermore, the end 101d of one groove wall 101 and the end 101d of the other groove wall 101 face each other in the circumferential direction. The end 101d is closer to the motor 32 than the end 101c.

[0077] The connecting wall 102 extends in a substantially circumferential direction between an end 101c of one groove wall 101 and an end 101c of the other groove wall 101. A notch 116 is provided in the connecting wall 102. As shown in FIG. 5 , the notch 116 extends from an end of the connecting wall 102 in the second axial direction Dx2 to the first axial direction Dx1.

[0078] The end 101d of one groove wall 101 and the end 101d of the other groove wall 101 are spaced apart from each other. That is, a gap 117 is provided between the end 101d of one groove wall 101 and the end 101d of the other groove wall 101. The gap 117, for example, connects the space inside the limiting wall 95 and the motor chamber 87.

[0079] 6, each of the multiple ribs 96 extends between the outer wall 91 and the limiting wall 95. That is, the ribs 96 protrude radially outward from the limiting wall 95 and are connected to the outer wall 91. Therefore, the limiting wall 95 is located between the nut 52 and the ribs 96.

[0080] The plurality of ribs 96 include two pairs of ribs 96A, a pair of ribs 96B, a pair of ribs 96C, and one rib 96D. Note that a description common to the ribs 96A, 96B, 96C, and 96D will be described as a description of the rib 96.

[0081] Each of the two pairs of ribs 96A protrudes radially outward from the corner between the first wall 111 and the second wall 112. Therefore, each of the two pairs of ribs 96A is connected to the flat surface 111b of the first wall 111 and the flat surface 112b of the second wall 112.

[0082] Each of the pair of ribs 96B protrudes radially outward from the flat surface 111b of the first wall 111. That is, the rib 96B is located between the two ribs 96A. In the circumferential direction, the width of the rib 96B is approximately equal to the width of the rib 96A.

[0083] The pair of ribs 96C, 96D each protrude radially outward from the connecting wall 102. The rib 96D is located between the pair of ribs 96C in the circumferential direction. The rib 96D and the notch 116 are aligned in the axial direction. The rib 96D extends axially from the intermediate wall 92 to the notch 116.

[0084] Each rib 96C has a cylinder 121 and two connection portions 122, 123. The cylinder 121 extends from the intermediate wall 92 in the second axial direction Dx2. The cylinder 121 has a receiving surface 121a. The receiving surface 121a is an example of a flat surface.

[0085] The receiving surface 121a is provided at the end of the rib 96C in the second axial direction Dx2. The receiving surface 121a is a circular flat surface. The diameter of the receiving surface 121a is approximately equal to the width of the ribs 96A and 96B. Note that the diameter of the receiving surface 121a is not limited to this example.

[0086] The connecting portion 122 connects the connecting wall 102 and the cylinder 121. The connecting portion 123 connects the outer wall 91 and the cylinder 121. The width of each of the connecting portions 122 and 123 in the circumferential direction is smaller than the diameter of the receiving surface 121a. Furthermore, the width of each of the connecting portions 122 and 123 in the circumferential direction is approximately equal to the width of the rib 96D.

[0087] 5, the limiting wall 95 and the ribs 96A, 96B, and 96C are each longer in the axial direction than the outer wall 91. Therefore, the limiting wall 95 and the ribs 96A, 96B, and 96C extend in the second axial direction Dx2 beyond the end face 81a of the flange 81. The limiting wall 95 and the ribs 96A, 96B, and 96C are housed in the through-space 71 of the lower case 61.

[0088] The ends of the limiting wall 95 and the rib 96 in the second axial direction Dx2 are located at the end of the entire upper case 62 in the second axial direction Dx2. Therefore, the receiving surface 121a is located at the end of the upper case 62 in the second axial direction Dx2.

[0089] 6, the ribs 96 are spaced apart from one another in the circumferential direction. The outer wall 91 and the limiting wall 95 are also spaced apart from one another in the radial direction. Therefore, the upper case 62 has a plurality of cavities 125.

[0090] In the radial direction, each of the multiple cavities 125 is provided between the outer wall 91 and the limiting wall 95. In addition, in the circumferential direction, each of the multiple cavities 125 is provided between two adjacent ones of the multiple ribs 96. The cavities 125 are recessed from the flange 81 in the first axial direction Dx1. The intermediate wall 92 is located at the bottom of the cavities 125 in the first axial direction Dx1.

[0091] The MGU 15 moves the brake shoe 11 via the movement mechanism 17, for example, as follows: For example, in a released state in which the MGU 15 is not moving the brake shoe 11, the nut 52 is spaced apart from the cable end 36 in the second axial direction Dx2.

[0092] In the released state, the nut 52 does not apply tension to the cable 23, and the cable 23 is loose. In other words, the MGU 15 does not pull the cable 23. As a result, the spring 16 separates the brake shoe 11 from the drum rotor 3. Note that in the released state, the nut 52 may be in contact with the cable end 36, and the cable 23 may be under tension.

[0093] When the motor 32 drives the screw shaft 51 to rotate around the central axis Axc, the nut 52 attached to the screw shaft 51 is also driven around the central axis Axc. However, the limiting wall 95 supports the protrusion 58 of the nut 52, thereby limiting the rotation of the nut 52.

[0094] A notch 116 and a gap 117 are provided between the two groove walls 101. The protrusion 58 pushes the two groove walls 101 in a direction that expands the notch 116 and the gap 117. However, the rib 96 reinforces the limiting wall 95, and can prevent the limiting wall 95 from being deformed in such a way as to expand the notch 116 and the gap 117.

[0095] The male thread 55c of the rotating screw shaft 51 presses the female thread 52c of the nut 52, whose rotation is restricted, in the axial direction. Therefore, when the screw shaft 51 rotates around the central axis Axc, the nut 52 moves in the axial direction in response to the rotation of the screw shaft 51. In other words, the nut 52 is supported by the housing 31 so that its rotation around the central axis Axc is restricted and it is movable in the axial direction.

[0096] For example, when the motor 32 rotates the screw shaft 51 in one direction around the central axis Axc, the screw shaft 51 moves the nut 52 in the first axial direction Dx1. When the nut 52 moves in the first axial direction Dx1, the end face 52a of the nut 52 comes into contact with the cable end 36.

[0097] The cable end 36 is supported by the end surface 52a of the nut 52. That is, the cable 23 is supported by the nut 52 via the cable end 36. The nut 52 moves in the first axial direction Dx1, thereby moving the cable 23 in the first axial direction Dx1 via the cable end 36. In other words, the nut 52 pulls the cable 23 in the first axial direction Dx1.

[0098] The cable 23, pulled by the nut 52, pulls the lever 21. When the lever 21 is pulled by the cable 23, it pushes the brake shoe 11R via the strut 24. This causes the brake shoe 11R to rotate around the end 11a and press the lining 11c against the inner circumferential surface 3a of the drum rotor 3.

[0099] Furthermore, when the lever 21 rotates around the strut 24 as a fulcrum, the lever 21 presses the brake shoe 11L via the pin 22. As a result, the brake shoe 11L rotates around the end 11a and presses the lining 11c against the inner peripheral surface 3a of the drum rotor 3.

[0100] As described above, the movement mechanism 17 is moved by the tension of the cable 23 pulled by the nut 52, thereby bringing the brake shoes 11R, 11L into contact with the drum rotor 3. In the apply state in which the MGU 15 moves the brake shoes 11 using the movement mechanism 17, the brake shoes 11R, 11L press the linings 11c against the inner circumferential surface 3a of the drum rotor 3. As a result, the brake shoes 11R, 11L apply the brakes to the drum rotor 3 and the wheel 2.

[0101] When the motor 32 rotates the screw shaft 51 in the reverse direction around the central axis Axc, the screw shaft 51 moves the nut 52 in the second axial direction Dx2. When the nut 52 moves in the second axial direction Dx2, for example, a spring pulling the cable 23 moves the cable 23 in the second axial direction Dx2. In other words, the nut 52 sends out the cable 23 in the second axial direction Dx2 while remaining in contact with the cable 23.

[0102] As the nut 52 feeds out the cable 23, the tension on the cable 23 decreases and is eventually released, i.e., the cable 23 returns to a relaxed, released state, and the spring 16 moves the brake shoe 11 away from the drum rotor 3.

[0103] As described above, the nut 52 moves in the axial direction in response to the rotation of the screw shaft 51. When the nut 52 is located at a predetermined apply position in the axial direction, the tension in the cable 23 is a tension that causes the movement mechanism 17 to bring the brake shoe 11 into contact with the drum rotor 3. On the other hand, when the nut 52 is located at a predetermined release position in the axial direction, the tension in the cable 23 is a tension that causes the movement mechanism 17 to separate the brake shoe 11 from the drum rotor 3. When the nut 52 is located at the release position, the tension in the cable 23 may be zero.

[0104] The apply position and the release position may be defined differently. For example, the apply position may be the position of the nut 52 when the load current supplied to the motor 32 is equal to or greater than a threshold. The release position may be the position of the nut 52 when the load current supplied to the motor 32 is equal to or less than a threshold, or the position of the nut 52 after a predetermined distance or time has passed since the load current supplied to the motor 32 became equal to or less than the threshold.

[0105] Each of the multiple ribs 96 extends in the axial direction at least between the apply position and the release position. In this embodiment, the axial length of the ribs 96 is longer than the distance between the apply position and the release position. Therefore, the limiting wall 95 is reinforced by the ribs 96 in the section that receives the load from the protrusion 58 of the nut 52 that moves between the apply position and the release position.

[0106] The apply position and the release position change depending on, for example, wear of the lining 11c. The rib 96 extends between the apply position and the release position both when the lining 11c is not worn and when the lining 11c has worn down to its service limit. However, the rib 96 is not limited to this example.

[0107] As described above, the upper case 62 at least partially accommodates the motor 32, the screw shaft 51, and the nut 52, and limits the rotation of the nut 52. The upper case 62 is integrally formed, for example, by injection molding. That is, the flange 81, the motor cover 82, the outer wall 91, the intermediate wall 92, the end cover 93, the limiting wall 95, and the plurality of ribs 96 are integrally formed.

[0108] For example, the upper case 62 is released from the mold by the ejector pin pressing the receiving surface 121a of the cylinder 121. Since the receiving surface 121a is located at the end of the upper case 62 in the second axial direction Dx2, the ejector pin can be easily arranged in the mold.

[0109] In the electric brake device 10 according to the present embodiment described above, the resin upper case 62 at least partially houses the screw shaft 51, the motor 32, and the nut 52 and is formed as a single unit. The upper case 62 is provided with a groove 115 that extends in the axial direction along the central axis Axc and that houses the protrusion 58. The upper case 62 has a limiting wall 95 and a rib 96. The limiting wall 95 defines the groove 115 and supports the protrusion 58, thereby limiting rotation of the nut 52 around the central axis Axc. The rib 96 protrudes from the limiting wall 95. The limiting wall 95 is located between the nut 52 and the rib 96. The nut 52 is configured to move axially when the screw shaft 51 rotates around the central axis Axc.

[0110] Therefore, as an example, compared to when the portion of the upper case 62 that houses the screw shaft 51 and the nut 52 (the flange 81, the motor cover 82, and the mechanism cover 83) and the limiting wall 95 are separate members, the electric brake device 10 can reduce the weight of the upper case 62 and suppress an increase in the number of steps during assembly. Furthermore, the rib 96 improves the rigidity of the resin limiting wall 95. Therefore, by integrally forming the upper case 62 including the limiting wall 95 from resin, the electric brake device 10 can reduce the weight and suppress deformation of the resin limiting wall 95 due to the load received from the nut 52.

[0111] The brake shoe 11 is configured to brake the wheel 2 by contacting the drum rotor 3 that rotates integrally with the wheel 2. The moving mechanism 17 has a cable 23 supported by a nut 52. The moving mechanism 17 is configured to be moved by the tension of the cable 23 pulled by the nut 52, thereby bringing the brake shoe 11 into contact with the drum rotor 3. The rib 96 extends in the axial direction at least between a position of the nut 52 when the tension in the cable 23 is such that the moving mechanism 17 brings the brake shoe 11 into contact with the drum rotor 3 (apply position), and a position of the nut 52 when the tension in the cable 23 is such that the moving mechanism 17 moves the brake shoe 11 away from the drum rotor 3 (release position).

[0112] Therefore, as an example, the nut 52 moves in the axial direction to tension or loosen the cable 23. The rib 96 improves the rigidity of the limiting wall 95 over the entire area between the apply position where the nut 52 tensions the cable 23 so that the brake shoe 11 contacts the drum rotor 3, and the release position where the nut 52 loosens the cable 23 so that the brake shoe 11 moves away from the drum rotor 3. Therefore, the rib 96 can prevent the resin limiting wall 95 from being deformed by the load received from the nut 52.

[0113] The limiting wall 95 has a first wall 111 and a second wall 112 connected to one end of the first wall 111 around the central axis Axc. The rib 96 protrudes from a corner between the first wall 111 and the second wall 112.

[0114] Therefore, for example, the rib 96 can reinforce the corners where stress concentration is likely to occur, and therefore the rib 96 can prevent the resin limiting wall 95 from being deformed by the load received from the nut 52.

[0115] The upper case 62 has an outer wall 91 that surrounds the limiting wall 95 and is connected to the rib 96. A cavity 125 is provided between the outer wall 91 and the limiting wall 95.

[0116] Therefore, as an example, the rib 96 is provided between the limiting wall 95 and the outer wall 91 and supports the limiting wall 95. Therefore, the upper case 62 can prevent the resin limiting wall 95 from being deformed by the load received from the nut 52. Furthermore, the upper case 62 can be made lighter by providing the cavity 125, and can also prevent the occurrence of sink marks during molding.

[0117] The rib 96C has a receiving surface 121a provided at one end of the rib 96C in the axial direction. The receiving surface 121a is a circular flat surface. The rib 96C extends in the axial direction.

[0118] Therefore, for example, when the resin upper case 62 is removed from the mold, the ejector pin can push the receiving surface 121a in the axial direction. Because the rib 96C extends in the axial direction, it has high axial rigidity. Therefore, the rib 96C can be prevented from being deformed by the load from the ejector pin.

[0119]

[0013] As an example, the electric brake device according to at least one embodiment described above includes: a threaded shaft having a male thread; a motor that drives the threaded shaft to rotate about a rotation axis; a nut that has an inner circumferential surface facing the rotation axis, a female thread that is provided on the inner circumferential surface and that engages with the male thread, an outer circumferential surface that is located opposite the inner circumferential surface, and a convex portion that protrudes from the outer circumferential surface; and a resin case that at least partially houses the threaded shaft, the motor, and the nut and is formed as one unit, the case having a groove that extends in the axial direction along the rotation axis and that houses the convex portion, and a limiting wall that defines the groove and supports the convex portion to limit rotation of the nut about the rotation axis, and a rib that protrudes from the limiting wall, the limiting wall being located between the nut and the rib, and the nut being configured to move in the axial direction as the threaded shaft rotates about the rotation axis. Therefore, as an example, compared to when the portion of the case that accommodates the screw shaft and the nut and the limiting wall are separate members, the electric brake device can reduce the weight of the case and suppress an increase in the number of steps required for assembly. Furthermore, the rib improves the rigidity of the resin limiting wall. Therefore, by integrally forming the case including the limiting wall from resin, the electric brake device can reduce its weight and suppress deformation of the resin limiting wall due to the load applied by the nut.

[0120] As an example, the electric brake device further includes a brake member configured to brake the wheel by contacting a drum rotor that rotates integrally with the wheel, and a movement mechanism having a cable supported by the nut and configured to contact the brake member with the drum rotor by being moved by the tension of the cable pulled by the nut. The rib extends in the axial direction at least between a position of the nut when the tension of the cable is sufficient to cause the movement mechanism to contact the brake member with the drum rotor and a position of the nut when the tension of the cable is sufficient to cause the movement mechanism to separate the brake member from the drum rotor. Thus, as an example, the nut moves in the axial direction to tension or loosen the cable. The rib improves the rigidity of the limiting wall throughout the entire range between a position where the nut pulls the cable so that the brake member contacts the drum rotor and a position where the nut loosens the cable so that the brake member separates from the drum rotor. Therefore, the rib can prevent the resin limiting wall from being deformed by the load applied by the nut.

[0121] In the electric brake device, as one example, the limiting wall includes a first wall and a second wall connected to one end of the first wall around the rotation axis, and the rib protrudes from a corner between the first wall and the second wall. Therefore, as one example, the rib can reinforce the corner where stress concentration is likely to occur. Therefore, the rib can prevent the resin limiting wall from being deformed by the load received from the nut.

[0122] In the electric brake device, for example, the case has an outer wall that surrounds the limiting wall and is connected to the rib, and a cavity is provided between the outer wall and the limiting wall. Therefore, for example, the rib is provided between the limiting wall and the outer wall and supports the limiting wall. Therefore, the case can prevent the resin limiting wall from being deformed by the load applied from the nut. Furthermore, the cavity in the case can reduce the weight and prevent sink marks from occurring during molding.

[0123] In the electric brake device, for example, the rib has a circular flat surface provided at one end of the rib in the axial direction and extends in the axial direction. Therefore, for example, when the resin case is removed from the mold, an ejector pin can push the flat surface in the axial direction. Because the rib extends in the axial direction, it has high rigidity in the axial direction. Therefore, the rib can be prevented from being deformed by the load received from the ejector pin.

[0124] 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]

[0125] 2...wheel, 3...drum rotor, 10...electric brake device, 11, 11L, 11R...brake shoes (braking members), 17...movement mechanism, 23...cable, 32...motor, 51...screw shaft, 52...nut, 52b...inner surface, 52c...female thread, 52d...outer surface, 55c...male thread, 58...convex portion, 62...upper case (case), 91...outer wall, 95...limiting wall, 96, 96A, 96B, 96C, 96D...rib, 111...first wall, 112...second wall, 115...groove, 121a...receiving surface (flat surface), Axc...central axis (rotation axis).

Claims

1. a screw shaft having a male thread; a motor that drives the screw shaft to rotate around a rotation axis; a nut having an inner circumferential surface facing the rotation shaft, a female thread provided on the inner circumferential surface and engaging with the male thread, an outer circumferential surface located on the opposite side of the inner circumferential surface, and a protrusion protruding from the outer circumferential surface; a resin case that at least partially accommodates the screw shaft, the motor, and the nut and is formed integrally with the screw shaft, the motor, and the nut; Equipped with The case has a groove extending in an axial direction along the rotation shaft and accommodating the protrusion, and the case has a limiting wall that defines the groove and supports the protrusion to limit rotation of the nut around the rotation shaft, and a rib that protrudes from the limiting wall, the limiting wall is located between the nut and the rib, The nut is configured to move in the axial direction by rotating the screw shaft around the rotation axis. Electric braking device.

2. a braking member configured to brake the wheel by contacting a drum rotor that rotates integrally with the wheel; a moving mechanism having a cable supported by the nut, the moving mechanism being configured to be moved by tension of the cable pulled by the nut to bring the braking member into contact with the drum rotor; Further comprising: The rib extends in the axial direction at least between a position of the nut when tension in the cable is such that the moving mechanism brings the braking member into contact with the drum rotor, and a position of the nut when tension in the cable is such that the moving mechanism moves the braking member away from the drum rotor. The electric brake device according to claim 1.

3. the limiting wall includes a first wall and a second wall connected to one end of the first wall around the rotation axis, The rib projects from a corner between the first wall and the second wall. The electric brake device according to claim 1.

4. The case has an outer wall that surrounds the limiting wall and is connected to the rib, and a cavity is provided between the outer wall and the limiting wall. The electric brake device according to claim 1.

5. The rib has a circular flat surface provided at one end of the rib in the axial direction and extends in the axial direction. The electric brake device according to claim 1.

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