Electric brake device

Abstract

Provided is an electric brake device having a structure capable of readily and forcibly releasing a braking state even if some failure occurs on the electric drive source side in a parking brake state. An electric actuator of a drum brake comprises: an electric motor; a rotary shaft of the electric motor; a rotary linear motion conversion mechanism capable of switching to a braking state or a non-braking state by converting rotation from the rotary shaft to linear motion; and a housing in which the rotary shaft is housed. The housing has a forcible brake release mechanism capable of forcibly releasing the braking state to the non-braking state. With this forcible brake release mechanism, even if some failure occurs on the electric motor side in a parking brake state, the braking state can be readily and forcibly released.

Description

Electric brake device

[0001] The present invention relates to an electric brake device such as a disc brake or a drum brake used for braking a vehicle.

[0002] For example, in a vehicle brake device described in Patent Document 1, the actuator case is configured so that a manual tool can be inserted therethrough to enable the rotation of a rotating member by manual operation from outside the actuator case. If a malfunction occurs on the electric drive source side while the parking brake is applied, the manual tool can be inserted through the actuator case to rotate the rotating member, thereby releasing the parking brake and allowing the vehicle to move.

[0003] JP 2019-48587 A

[0004] In the vehicle brake device described in the above-mentioned Patent Document 1, a retaining hole that engages with the tip of a manually operated tool, i.e., a retaining hole that is hexagonal in front view, is formed in the rotating member (pinion gear), but this structure leads to increased costs. Also, the vehicle brake device described in Patent Document 1 requires a dedicated tool to break through the portion surrounded by the indicator tube that faces the retaining hole, which also leads to increased costs.

[0005] Furthermore, in the vehicle brake device described in Patent Document 1, an access hole for a manually operated tool is formed by breaking through the portion surrounded by the indicator tube portion that faces the retaining hole, but there is a risk that the broken-through debris will cover the retaining hole, making it impossible to easily engage the manually operated tool with the retaining hole through the access hole.As a result, work such as removing the covering debris is required, which poses problems such as reduced work efficiency and leaves room for improvement.

[0006] In view of the above-mentioned problems, the present invention aims to provide an electric brake device having a structure that can easily and forcibly release the braking state even if some kind of failure occurs on the electric drive source side when the parking brake is applied.

[0007] As a means for solving the above problem, the electric brake device of the present invention comprises an electric motor, a rotating member to which rotation from the electric motor is transmitted, a rotary-to-linear motion conversion mechanism that converts the rotation from the rotating member into linear motion, thereby enabling switching between a braking state and a non-braking state, and a housing that accommodates the rotating member, wherein the housing has a brake forced release mechanism that can forcibly release the braking state to the non-braking state.

[0008] An electric brake device according to one embodiment of the present invention has a structure that allows the braking state to be easily and forcibly released even if some kind of failure occurs on the electric drive source side in the parking brake state.

[0009] 2. A front view of a drum brake according to the present embodiment. 3. A cross-sectional view of an electric actuator employed in the drum brake according to the present embodiment. 4. A perspective view of the vicinity of a protruding portion of a rotation shaft of an electric motor employed in the electric actuator of FIG. 2. 5. A perspective view of an engagement portion of a brake forced release mechanism according to a first embodiment employed in the electric actuator of FIG. 2. 6. A perspective view of an operation portion of a brake forced release mechanism according to a first embodiment employed in the electric actuator of FIG. 2. 7. A cross-sectional view showing, in stages, the operation of a brake forced release mechanism according to a second embodiment. 8. A cross-sectional view showing, in stages, the operation of a brake forced release mechanism according to a third embodiment.

[0010] This embodiment will be described in detail below with reference to Figures 1 to 8. Referring to Figure 1, a drum brake 1 as an electric brake device according to this embodiment of the present invention includes an electric actuator 2. The drum brake 1 includes a back plate 4 fixed to a non-rotating portion of an axle of a vehicle, a pair of bow-shaped first and second brake shoes 5, 6 provided on the inner surface of the back plate 4, a wheel cylinder 7 having pistons 10, 10 against which one ends of the first and second brake shoes 5, 6 abut, a return spring 8 provided between the first and second brake shoes 5, 6, and the electric actuator 2 that is driven to activate the parking brake.

[0011] 1, the back plate 4 has an axle insertion hole 12 formed in the radial center thereof, through which an axle is inserted. Mounting cylindrical portions (not shown) for mounting electric actuators 2, which will be described in detail later, are integrally formed and protrude from the back surface of the back plate 4. The mounting cylindrical portions protrude rearward or forward from the back surface of the back plate 4 and toward the inside in the vehicle width direction. The electric actuator 2 is inserted and fixed into these mounting cylindrical portions from the side of its bellows-like boot 110 (see FIG. 2).

[0012] 1 , the first and second brake shoes 5, 6 are formed in the same shape and are used by inverting them. The first and second brake shoes 5, 6 include first and second shoe webs 21, 22 arranged parallel to the back plate 4, first and second arc-shaped rims 24, 25 arranged on the outer edges of the first and second shoe webs 21, 22 in a direction perpendicular to the first and second shoe webs 21, 22, and first and second linings 27, 28 attached to the outer peripheral surfaces of the first and second rims 24, 25.

[0013] One ends (upper ends) of the first and second shoe webs 21, 22 of the first and second brake shoes 5, 6 respectively abut against a pair of pistons 10, 10 of the wheel cylinder 7. Meanwhile, the other ends (lower ends) of the first and second shoe webs 21, 22 of the first and second brake shoes 5, 6 are supported by an anchor block 30, which serves as a fulcrum when the first and second brake shoes 5, 6 expand and contract. The wheel cylinder 7 is disposed above the back plate 4. The anchor block 30 is disposed below the back plate 4. When the drum brake 1 functions as a normal hydraulic brake, operation of the wheel cylinder 7 causes the first and second brake shoes 5, 6 to expand radially outward from the back plate 4, causing the first and second linings 27, 28 on the outer periphery to slide against a brake drum 29 that rotates together with the wheel, thereby applying braking.

[0014] 1 , a return spring 8 is tensioned between the first brake shoe 5 and the second brake shoe 6, radially inwardly of the wheel cylinder 7. The return spring 8 constantly urges the first and second brake shoes 5, 6 in a radially contracting direction. A coil spring 32 is provided between the lower ends of the first and second shoe webs 21, 22 of the first and second brake shoes 5, 6, urging the lower ends of the first and second shoe webs 21, 22 toward the anchor block 30. An automatic brake gap adjustment device 35 (a so-called auto adjuster) is also provided on the center side of the back plate 4 of the return spring 8. The automatic brake gap adjustment device 35 regulates the radially contracted position of the first and second brake shoes 5, 6, automatically adjusting the brake gap between the brake drum 29.

[0015] The automatic brake gap adjustment device 35 is provided between the first and second shoe webs 21, 22 of the first and second brake shoes 5, 6, and is equipped with a contraction position control strut 37 that extends when an adjustment gear 41 rotates, an adjustment lever 38 that has a feed pawl 43 that engages with the adjustment gear 41 and is rotatably supported on the second shoe web 22 of the second brake shoe 6, and an adjustment spring 39 that biases the contraction position control strut 37 in the rotational direction of the adjustment gear 41 to extend it.

[0016] The retraction position restricting strut 37 restricts the retraction positions of the first and second brake shoes 5, 6. The retraction position restricting strut 37 includes a first rod 46 having a first engagement portion 46A that engages with an upper portion of the first shoe web 21 of the first brake shoe 5, a second rod 47 having a second engagement portion 47A that engages with an upper portion of the second shoe web 22 of the second brake shoe 6, and an adjustment bolt 48 having one end inserted into the first rod 46 so as to be relatively movable in the axial direction and the other end coaxially threadedly engaged with the second rod 47. The first and second rods 46, 47 are arranged coaxially. The adjustment gear 41 is arranged between the first rod 46 and the second rod 47 and on the outer periphery of the adjustment bolt 48.

[0017] A first locking recess 50 is provided in an upper portion of the first shoe web 21 of the first brake shoe 5, with which the first engaging portion 46A of the first rod 46 engages. A second locking recess 51 is provided in an upper portion of the second shoe web 22 of the second brake shoe 6, with which the second engaging portion 47A of the second rod 46 engages. The adjustment lever 38 is rotatably supported on the second shoe web 22 of the second brake shoe 6 via a support shaft 53. An adjustment spring 39 is provided between the second shoe web 22 of the second brake shoe 6 and the adjustment lever 38. The elastic force of the adjustment spring 39 is set to be smaller than the elastic force of the return spring 8.

[0018] In the automatic brake gap adjustment device 35, if the first and second brake shoes 5, 6 expand by more than a certain value due to wear on the first and second linings 27, 28 when they are expanded by operation of the wheel cylinder 7, the force of the adjustment spring 39 causes the adjustment lever 38 to rotate around the axis of the support shaft 53, and as the adjustment gear 41 rotates as a result, the effective length of the contraction position control strut 37 is increased.

[0019] The drum brake 1 is equipped with a parking brake lever 55. The parking brake lever 55 is connected to a brake cable 93 of the electric actuator 2. The parking brake lever 55 extends in the vertical direction so as to partially overlap the first shoe web 21 of the first brake shoe 5 in a front view. The upper end of the parking brake lever 55 is connected to the upper part of the first shoe web 21 of the first brake shoe 5 via a pin 56.

[0020] An upper portion of the parking brake lever 55 engages with the first engaging portion 46A of the retraction position limiting strut 37. An engaging piece 93A of the brake cable 93 of the electric actuator 2 is connected to a lower portion of the parking brake lever 55. In short, by pulling or paying out the brake cable 93 through operation of the electric actuator 2, the parking brake lever 55 can be rotated around the pin 56 in the forward direction, i.e., the braking direction, or in the reverse direction, i.e., the braking release direction.

[0021] When the parking brake of the vehicle is applied, the brake cable 93 is pulled by the operation of the electric actuator 2, and the parking brake lever 55 is rotated counterclockwise in Figure 1 around the pin 56. Then, as the parking brake lever 55 rotates, a force is first applied to the second brake shoe 6 via the contraction position limiting strut 37 in a direction that presses the second lining 28 against the inner peripheral surface of the brake drum 29.

[0022] 1, the parking brake lever 55 rotates counterclockwise about the point of engagement with the first engagement portion 46A of the contraction position limiting strut 37, causing the first brake shoe 5 to expand via the pin 56, and the first lining 27 of the first brake shoe 5 to press against the inner periphery of the brake drum 29, maintaining the braking state. In other words, the rotation of the parking brake lever 55 causes the first and second linings 27, 28 of the first and second brake shoes 5, 6 to operate in a braking position where they press against the inner periphery of the brake drum 29, and in this state the parking brake state is obtained.

[0023] On the other hand, when releasing the parking brake, the brake cable 93 is unwound by operation of the electric actuator 2, and the parking brake lever 55 is rotated clockwise in Figure 1 around the pin 56 by the force of the return spring 8, so that the first and second brake shoes 5, 6 return to their initial positions and the braking state is released.

[0024] Next, the electric actuator 2 will be described in detail with reference to Figures 2 to 8. In the detailed description of the electric actuator 2 below, for convenience, the right side of Figure 2 will be referred to as one end side, and the left side of Figure 2 will be referred to as the other end side. In other figures, the directions of the one end side and the other end side will also be described as shown in the figures, as appropriate. The electric actuator 2 is used to operate a parking brake. Referring to Figure 2, the electric actuator 2 includes an electric motor 60, a reduction gear mechanism 61, a rotary-to-linear motion conversion mechanism 62, and a housing 63 that accommodates the electric motor 60, the reduction gear mechanism 61, and the rotary-to-linear motion conversion mechanism 62.

[0025] Referring to FIG. 2 , the electric motor 60 includes a cylindrical main body 65 and a rotating shaft 66 extending from the main body 65 to one end and the other end. The rotating shaft 66 corresponds to the rotating member. A cylindrical first bearing 70 that rotatably supports the rotating shaft 66 is provided to protrude from one end of a motor case 68 of the electric motor 60. One end of the rotating shaft 66 passes through the first bearing 70 and protrudes from one end of the motor case 68. Meanwhile, a cylindrical second bearing 71 with a bottom is provided to protrude from the other end of the motor case 68 and rotatably supports the other end of the rotating shaft 66. The main body 65 of the electric motor 60 is accommodated in a motor accommodating main body 113 of the housing 63. Note that the reference numeral 73 in FIG. 3 denotes a terminal portion.

[0026] The motor housing main body 113 includes a cylindrical motor housing portion 118 with a bottom, and a lid member 119 that closes the open portion on the other end side of the motor housing portion 118. An insertion hole 121 is formed in the bottom wall portion of the motor housing portion 118, and one end of the rotating shaft 66 is inserted therethrough. One end of the rotating shaft 66 is rotatably supported in the insertion hole 121 via a first bearing portion 70. One end of the rotating shaft 66 is located closer to the one end side than the motor housing portion 118. A second bearing portion 71 is supported in the radial center of the lid member 119. A wave washer 123 is disposed between the second bearing portion 71 and the lid member 119.

[0027] The reduction gear mechanism 61 includes a first reduction gear 75 press-fitted and fixed to the rotating shaft 66 of the electric motor 60, and a second reduction gear 76 meshing with the first reduction gear 75. The first reduction gear 75 is a spur gear. With reference to FIGS. 2 and 3, the rotating shaft 66 of the electric motor 60 protrudes from the first reduction gear 75 toward one end. The protruding portion 66A is D-shaped when viewed from the front. With reference to FIG. 2, the second reduction gear 76 is a two-stage reduction gear. That is, the second reduction gear 76 includes a large gear 81 disposed at one end and a small gear 82 disposed at the other end, which is integrally connected concentrically with the large gear 81.

[0028] The large gear 81 of the second reduction gear 76 meshes with the first reduction gear 75. The small gear 82 of the second reduction gear 76 meshes with a large diameter gear portion 94 of a nut member 86 of the rotary-to-linear motion conversion mechanism 62, which will be described later. The second reduction gear 76 is rotatably supported by a shaft member 79 provided between the motor housing main body 113 and the cover member 115. Rotation from the rotary shaft 66 of the electric motor 60 is transmitted to the nut member 86 of the rotary-to-linear motion conversion mechanism 62 via the first reduction gear 75 and the second reduction gear 76 of the reduction gear mechanism 61. Note that although the reduction gear mechanism 61 is used as the rotation transmission mechanism in this embodiment, other transmission mechanisms, such as a belt / pulley mechanism, may also be used.

[0029] Referring to FIG. 2 , the rotary-to-linear motion conversion mechanism 62 is a screw mechanism. The rotary-to-linear motion conversion mechanism 62 includes a slide rod 85 and a nut member 86 threadedly engaged with the slide rod 85. The slide rod 85 includes a head 88 formed in a substantially rectangular parallelepiped shape, an externally threaded portion 89 extending continuously from the head 88 to the other end, and a distal rod portion 90 extending continuously from the externally threaded portion 89 to the other end. The head 88 of the slide rod 85 is disposed within a rotation-preventing tubular portion 127, which is integrally formed with a cover member 115 (described in detail below) and has an internal space with a substantially rectangular cross section (a cross section perpendicular to the axial direction). This supports the slide rod 85 relative to the housing 63, allowing it to move axially and preventing it from rotating about its axis. A receiving recess 92 is formed in the distal end surface of the distal rod portion 90 of the slide rod 85, extending axially. A brake cable 93 is connected to the receiving recess 92. The brake cable 93 has an engagement piece 93A at its tip.

[0030] The nut member 86 includes a large-diameter gear portion 94 disposed at one end, a large-diameter cylindrical portion 95 disposed at the other end concentrically with the large-diameter gear portion 94, a small-diameter nut portion 96 disposed at the other end concentrically with the large-diameter cylindrical portion 95, and an annular plate portion 97 connecting the other end of the large-diameter cylindrical portion 95 and one end of the small-diameter nut portion 96. The large-diameter gear portion 94 of the nut member 86 meshes with the second reduction gear 76 (pinion gear 82) of the reduction gear mechanism 61. A female thread portion 100 is formed on the inner circumferential surface of the small-diameter nut portion 96. The male thread portion 89 of the slide rod 85 is threadedly engaged with the female thread portion 100 of the small-diameter nut portion 96 of the nut member 86. The small-diameter nut portion 96 of the nut member 86 is rotatably supported within a conversion mechanism accommodating main body 114 of the housing 63, which will be described in detail later, via a bearing 102.

[0031] An accommodating recess 106 is provided inside the large-diameter cylindrical portion 95 of the nut member 86. The accommodating recess 106 accommodates a plurality of disc springs 107, 107, and an annular retainer 108 that sandwiches each disc spring 107 between the disc springs 107 and the annular plate portion 97 of the nut member 86. A holding member 109 that prevents each disc spring 107 and the retainer 108 from coming out of the accommodating recess 106 is attached to the open end of the accommodating recess 106. A bellows-like boot 110 is provided to cover a portion of the slide rod 85 that protrudes from the nut member 86 to the other end. One end of the bellows-like boot 110 is connected to the other end of the conversion mechanism accommodating main body 114 of the housing 63. In the rotary-to-linear motion conversion mechanism 62, rotation from the rotary shaft 66 of the electric motor 60 is transmitted to the nut member 86 via the reduction gear mechanism 61, causing the slide rod 85 to move forward or backward, thereby pulling or paying out the brake cable 93. By pulling or paying out the brake cable 93 through the action of the rotary-to-linear motion conversion mechanism 62 in conjunction with the operation of the electric actuator 2, the drum brake 1 can be switched between its braking state and its non-braking state.

[0032] 2, the housing 63 includes a motor housing main body 113 that houses the electric motor 60, a conversion mechanism housing main body 114 that is continuous with the motor housing portion 118 of the motor housing main body 113 and houses the rotary-to-linear conversion mechanism 62, and a cover member 115 that is formed on one end side of the motor housing main body 113 to have a space for housing the reduction gear mechanism 61 and that closes the open portion on one end side of the conversion mechanism housing main body 114. The motor housing main body 113 and the conversion mechanism housing main body 114 are arranged side by side in the radial direction. Since the motor housing main body 113 has been described above, detailed description thereof will be omitted here. The conversion mechanism housing main body 114 is formed in a cylindrical shape with a bottom in cooperation with the motor housing portion 118 of the motor housing main body 113.

[0033] The nut member 86 of the rotary-to-linear motion conversion mechanism 62 is rotatably supported within the conversion mechanism housing main body 114 via a bearing 102. An insertion hole 125 is formed in the bottom of the conversion mechanism housing main body 114, through which the other end of the small-diameter nut portion 96 of the nut member 86 is inserted. The slide rod 85 protrudes from this insertion hole 125 toward the other end. A rotation-preventing tubular portion 127 is protruded from one end of the cover member 115, concentrically positioned opposite the slide rod 85 along the axial direction. The rotation-preventing tubular portion 127 has an internal space with a cross section (a cross section perpendicular to the axial direction) that is substantially rectangular. As described above, the head 88 of the slide rod 85 is disposed within the rotation-preventing tubular portion 127, thereby supporting the slide rod 85 relative to the housing 63 so as to be movable along the axial direction and non-rotatable about its axis. The cover member 115 is also provided with a brake forced release mechanism 130A according to the first embodiment at a position facing one end surface of the rotary shaft 66 of the electric motor 60 .

[0034] First, a brake forcible release mechanism 130A according to the first embodiment will be described in detail with reference to Figures 4 to 6, with appropriate reference to Figures 2 and 3. The brake forcible release mechanism 130A is integrally molded from synthetic resin together with the cover member 115. Referring to Figure 6, a cylindrical portion 135 that protrudes outward is provided on the cover member 115 at a location facing one end face of the rotary shaft 66 (protruding portion 66A) of the electric motor 60. The brake forcible release mechanism 130A is integrally connected to the cover member 115 via a thin-walled portion 137 so as to close the opening at one end of the cylindrical portion 135.

[0035] Referring to FIG. 6 , the brake forced release mechanism 130A includes a cylindrical engaging portion 140 that protrudes toward the interior of the cylindrical portion 135 of the cover member 115, and a cylindrical operating portion 141 that protrudes outward from the cylindrical portion 135 of the cover member 115. Referring also to FIGS. 3 and 4 , the engaging portion 140 protrudes toward the interior of the cylindrical portion 135 from a position slightly inside one end of the cylindrical portion 135 of the cover member 115. The engaging portion 140 has an engaging recess 143 that is D-shaped in front view and is provided on the other end surface. The engaging recess 143 is disposed concentrically with the rotating shaft 66 of the electric motor 60. The protruding portion 66A of the rotating shaft 66 of the electric motor 60 is engaged with the engaging recess 143 so as to be non-rotatable relative to the rotating shaft 66. The depth of the engaging recess 143 is set to be smaller than the axial length of the protruding portion 66A of the rotating shaft 66.

[0036] In this embodiment, the protruding portion 66A of the rotating shaft 66 and the engaging recess 143 are both formed in a D-shape when viewed from the front and are engaged with each other so as to be non-rotatable relative to each other, but it is sufficient that the protruding portion 66A of the rotating shaft 66 and the engaging recess 143 are engaged with each other so as to be non-rotatable relative to each other, and for example, the protruding portion 66A of the rotating shaft 66 and the engaging recess 143 may be spline-engaged. In another embodiment, the protruding portion 66A may not be formed on the rotating shaft 66, but the first reduction gear 75 may be slightly protruded from one end, and the engaging recess 143 may be directly engaged with (mesh with) the gear portion of the first reduction gear 75 so as to be non-rotatable relative to each other.

[0037] 2, 5, and 6, the operating portion 141 can be operated to rotate the rotary shaft 66, which is non-rotatably engaged with the engagement recess 143. The operating portion 141 protrudes outward from a position slightly inside one end of the cylindrical portion 135 of the cover member 115. The operating portion 141 has an engagement recess 145, which is hexagonal in front view and is provided on one end surface, and can be engaged with a general tool such as a hexagonal wrench or hexagonal driver (not shown). The engagement recess 145 of the operating portion 141 and the engagement recess 143 of the engaging portion 140 are positioned concentrically. Note that in this embodiment, the engaging portion 140 and the operating portion 141 are integrally molded with the cover member 115 using synthetic resin; however, at least one or both of the engaging portion 140 and the operating portion 141 may be made of ceramic or metal.

[0038] The outer periphery between the operating portion 141 and the engaging portion 140 is integrally molded via an annular thin-walled portion 137 at a position slightly inside one end of the cylindrical portion 135 of the cover member 115. The annular thin-walled portion 137 is configured by forming, for example, a V-shaped annular groove 148 on a wall surface connecting the inner periphery slightly inside one end of the cylindrical portion 135 of the cover member 115 to the outer periphery between the operating portion 141 and the engaging portion 140. The annular groove 148 is provided close to the inner periphery of the cylindrical portion 135 of the cover member 115. Referring to FIG. 5 , an arrow indicating the operating direction of the operating portion 141, i.e., the rotation direction of the tool, is marked on the wall surface around the operating portion 141 of the cover member 115, i.e., on one end surface of the cylindrical portion 135. This arrow indicates the direction in which the parking brake is released. 6, a gap is provided between one end face of the rotary shaft 66 (protruding portion 66A) of the electric motor 60, i.e., the end face on the cover member 115 side of the housing 63, and the other end face of the engaging portion 140, i.e., the end face on the rotary shaft 66 side. The length L1 of the gap is set to be larger than the protruding length L2 of the operating portion 141.

[0039] Next, a procedure for forcibly releasing the brake state using the brake forced release mechanism 130A when some kind of failure occurs on the electric motor 60 side while the parking brake is applied will be described. First, an operator strikes the top surface of the operating portion 141 with a hammer or other general-purpose tool so as to push the brake forced release mechanism 130A (the engaging portion 140 and the operating portion 141) into the cylindrical portion 135 of the cover member 115 from the state shown in Figure 6(a). This cuts the thin-walled portion 137, and the brake forced release mechanism 130A (the engaging portion 140 and the operating portion 141) becomes slightly pushed into the cylindrical portion 135 of the cover member 115.

[0040] 6(b), when the brake forcible release mechanism 130A (the engagement portion 140 and the operation portion 141) is slightly pressed into the cylindrical portion 135 of the cover member 115, an annular cut piece 149 that protrudes radially outward between the engagement portion 140 and the operation portion 141 of the brake forcible release mechanism 130A fits along the inner circumferential surface of the cylindrical portion 135, thereby restricting radial movement of the brake forcible release mechanism 130A. As a result, the engagement recess 143 of the engagement portion 140 is positioned approximately concentrically with the protruding portion 66A of the rotation shaft 66, making it easy for them to engage with each other. Furthermore, the length L1 of the gap between one end face of the rotating shaft 66 (protruding portion 66A) and the other end face of the engaging portion 140 is set to be larger than the protruding length L2 of the operating portion 141. Therefore, even if the top surface of the operating portion 141 is struck with a hammer or the like and the brake forced release mechanism 130A (engaging portion 140 and operating portion 141) is pushed into the cylindrical portion 135 of the cover member 115, a gap still occurs between the other end face of the engaging portion 140 and one end face of the protruding portion 66A of the rotating shaft 66, thereby preventing the other end face of the engaging portion 140 from severely interfering with the one end face of the protruding portion 66A of the rotating shaft 66.

[0041] 6(b), an operator engages the tip of a general tool such as a hex wrench or hex driver with the engaging recess 145 of the operating unit 141, and rotates the tool in the forward or reverse direction while making fine adjustments, until the engaging recess 143, which is D-shaped in front view and provided on the engaging unit 140, engages with the protruding portion 66A, which is D-shaped in front view, of the rotating shaft 66 (engages so as not to rotate relative to the rotating shaft 66), and moves the engaging unit 140 forward toward the other end until the bottom surface of the engaging recess 143 of the engaging unit 140 comes into contact with one end surface of the rotating shaft 66. At this time, the entire axial length of the brake forced release mechanism 130A (the engaging unit 140 and the operating unit 141) is disposed within the cylindrical portion 135 of the cover member 115. Finally, when the tool is rotated in the brake release direction, i.e., in the direction of the arrow indicated on one end face of the cylindrical portion 135 of the cover member 115 as shown in Figure 5, as the tool rotates, the rotating shaft 66 of the electric motor 60 rotates in the brake release direction via this brake forced release mechanism 130A (operating portion 141 and engaging portion 140), and the parking brake is released.

[0042] In the electric actuator 2 of the drum brake 1 according to the present embodiment described above, the cover member 115 (housing 63) that constitutes the electric actuator 2 has the brake forced release mechanism 130A according to the first embodiment, which can forcibly release the braking state to a non-braking state when the parking brake is applied, and the brake forced release mechanism 130A is integrally molded with the cover member 115 (housing 63) from synthetic resin. This brake forced release mechanism 130A according to the first embodiment makes it possible to easily forcibly release the braking state when the electric motor 60 is in the parking brake state. Specifically, the brake forced release mechanism 130A according to the first embodiment can suppress an increase in the cost of its structure compared to a conventional brake forced release mechanism (disclosed in JP 2019-48587 A). Furthermore, the brake forced release mechanism 130A according to the first embodiment does not require any special tools, and the parking brake state can be forcibly released using general tools such as a hammer, hex wrench, or hex driver. This also helps to reduce costs compared to the prior art (disclosed in JP 2019-48587 A).

[0043] Furthermore, the brake forced release mechanism 130A according to the first embodiment includes an engagement portion 140 that engages with the protruding portion 66A of the rotary shaft 66 of the electric motor 60 so as not to rotate relative to the protruding portion 66A, and an operation portion 141 that can be operated to rotate the rotary shaft 66. After the worker separates the brake forced release mechanism 130A from the cover member 115 with a hammer or the like, the separated member includes the engagement portion 140 and the operation portion 141. Therefore, unlike the conventional mechanism (disclosed in JP 2019-48587 A), no inconvenience occurs due to broken-in debris, and work efficiency can be improved.

[0044] Furthermore, in the brake forced release mechanism 130A according to the first embodiment, a thin-walled portion 137 is formed around the periphery, so that an operator can easily, in other words, with little force, separate the brake forced release mechanism 130A from the cover member 115.

[0045] Furthermore, in the brake forced release mechanism 130A according to the first embodiment, the operating part 141 protrudes outward from the cover member 115, so that an operator can easily visually determine the position of the operating part 141. Moreover, the operating direction of the operating part 141 is indicated by an arrow on the surface of the wall of the cover member 115 around the operating part 141 (one end face of the cylindrical part 135), so that an operator can easily determine the rotation direction by visually checking this arrow, thereby improving work efficiency.

[0046] Furthermore, in the brake forced release mechanism 130A according to the first embodiment, the length L1 of the gap between one end face of the rotary shaft 66 (protruding portion 66A) of the electric motor 60 and the other end face of the engaging part 140 is set to be greater than the protruding length L2 of the operating part 141. This prevents the other end face of the engaging part 140 from severely interfering with the one end face of the rotary shaft 66 even if an operator strikes the top face of the operating part 141 with a general-purpose hammer or the like, thereby preventing damage to the engaging part 140.

[0047] Furthermore, in the brake forced release mechanism 130A according to the first embodiment, the engagement portion 140 and the operating portion 141 are molded from synthetic resin, or, if necessary, either or both of the engagement portion 140 and the operating portion 141 are made from ceramic or metal, thereby ensuring that rotation from the tool can be transmitted reliably to the rotating shaft 66 of the electric motor 60.

[0048] Next, a brake forced release mechanism 130B according to a second embodiment of the electric actuator 2 will be described in detail based on FIG. 7 with reference to FIGS. 2 and 3. The brake forced release mechanism 130B according to the second embodiment is provided on the cover member 115 at a location facing one end surface of the rotary shaft 66 (protruding portion 66A) of the electric motor 60. A multi-step cylindrical portion 151 protruding outward is formed on the cover member 115 at a location facing one end surface of the rotary shaft 66 (protruding portion 66A) of the electric motor 60. The multi-step cylindrical portion 151 is configured with a small-diameter cylindrical portion 152 and a large-diameter cylindrical portion 153 extending from one end to the other. A female thread portion 155 is formed within a predetermined axial range on the inner circumferential surface of one end of the small-diameter cylindrical portion 152. An annular tapered surface 156, which increases in diameter toward the other end, is formed on the inner circumferential surface at the boundary between the small-diameter cylindrical portion 152 and the large-diameter cylindrical portion 153. A columnar body member 160 is disposed within the multi-stage cylindrical portion 151 so as to be slidable along the axial direction and rotatable about the axis. The body member 160 corresponds to the brake forced release mechanism 130B according to the second embodiment.

[0049] The body member 160 may be made of synthetic resin, ceramic, or metal. The body member 160 includes an engaging portion 140 located at the other end and an operating portion 141 located at one end and integrally connected to the engaging portion 140. Either the engaging portion 140 or the operating portion 141 may be made of ceramic or metal. The engaging portion 140 includes a circular recess 161 that is circular in front view and provided on the other end surface, and an engaging recess 143 that is D-shaped in front view and provided on the bottom surface of the circular recess 161. The circular recess 161 acts as a guide that guides the protruding portion 66A of the rotating shaft 66 and the engaging recess 143 of the engaging portion 140 to positions where they can engage with each other. The protruding portion 66A of the rotating shaft 66 of the electric motor 60 is engaged with the engaging recess 143 so as not to rotate relative to each other. The depth from the other end face of the engaging portion 140 to the bottom face of the engaging recess 143 is approximately the same as the axial length of the protruding portion 66A of the rotating shaft 66. The operating portion 141 has an engaging recess 145 that is hexagonal in front view and provided on one end face, and can be engaged with a general tool such as a hexagonal wrench or hexagonal driver.

[0050] An external thread portion 163 is formed in a predetermined axial range on the outer peripheral surface of one end of the body member 160, i.e., the operating portion 141. An annular groove portion 165 is formed on the outer peripheral surface of the other end closer to the external thread portion 163. A seal member 166 is fitted into the annular groove portion 165. An annular flange portion 168 that protrudes radially outward is provided on the outer peripheral surface of the other end of the body member 160, i.e., the engaging portion 140. The outer diameter of the annular flange portion 168 is set to be larger than the inner diameter of the small-diameter cylindrical portion 152 and smaller than the inner diameter of the large-diameter cylindrical portion 153. The annular flange portion 168 is formed with a triangular cross section. One end face of the annular flange portion 168 is formed with an annular tapered surface 170 that tapers in diameter toward the one end.

[0051] 7A, under normal circumstances, the male thread portion 163 of the body member 160 is threadedly engaged with the female thread portion 155 of the small-diameter cylindrical portion 152 of the multi-stepped cylindrical portion 151, so that one end surface of the small-diameter cylindrical portion 152 coincides with one end surface of the body member 160 (operating portion 141). At this time, the annular tapered surface 170 of the annular flange 168 of the body member 160 abuts against the annular tapered surface 156 provided on the inner circumferential surface between the small-diameter cylindrical portion 152 and the large-diameter cylindrical portion 153 of the multi-stepped cylindrical portion 151, thereby restricting movement of the body member 160 toward the one end relative to the multi-stepped cylindrical portion 151. Furthermore, the outer circumferential surface of the body member 160 and the inner circumferential surface of the small-diameter cylindrical portion 152 (the other end side of the female thread portion 155) are tightly fitted together via the seal member 166. As a result, the interior of the housing 63 (see FIG. 2) is maintained airtight.

[0052] Furthermore, in this state, the length L3 of the gap between one end face of the rotating shaft 66 (protruding portion 66A) of the electric motor 60, i.e., the end face of the housing 63 facing the cover member 115, and the bottom surface of the circular recess 161 of the engaging portion 140 of the body member 160, is greater than the length L4 (axial length) of engagement between the female threaded portion 155 of the cover member 115 and the male threaded portion 163 of the body member 160. Furthermore, in this state, the length L5 of the gap between one end face of the rotating shaft 66 (protruding portion 66A) of the electric motor 60, i.e., the end face of the housing 63 facing the cover member 115, and the bottom surface of the engaging recess 143 of the body member 160, is naturally greater than the length L4 (axial length) of engagement between the male threaded portion 163 of the body member 160 and the female threaded portion 155 of the small-diameter cylindrical portion 152 of the multi-step cylindrical portion 151.

[0053] Next, a procedure for forcibly releasing the brake state using the brake forced release mechanism 130B when some kind of failure occurs on the electric motor 60 side while the parking brake is applied will be described. First, referring to FIG. 7B , an operator engages the tip of a general tool such as a hex wrench or hex driver with the engaging recess 145 of the operating portion 141 of the body member 160 constituting the brake forced release mechanism 130B and rotates the tool in a direction that moves the body member 160 forward toward the other end. As the body member 160 advances toward the other end relative to the multi-step cylindrical portion 151, the male threaded portion 163 of the body member 160 disengages from the female threaded portion 155 of the small-diameter cylindrical portion 152. The circular recess 161 of the engaging portion 140 guides the engaging recess 143 of the body member 160 (engaging portion 140) and the protruding portion 66A of the rotating shaft 66 of the electric motor 60 to positions where they can engage with each other, i.e., so that they are substantially concentric.

[0054] At this time, there is still a gap between the bottom surface of the circular recess 161 of the body member 160 (engagement portion 140) and one end surface of the rotary shaft 66 (protruding portion 66A) of the electric motor 60, and the body member 160 is rotatably supported within the small-diameter cylindrical portion 152 of the multi-step cylindrical portion 151, so the tool is rotated in the forward or reverse direction while making fine adjustments, and as shown in Figure 7(c), the engagement recess 143 of the body member 160 (engagement portion 140) is engaged with the protruding portion 66A of the rotary shaft 66. Thereafter, the tool is slightly pushed in to advance the body member 160 toward the other end, so that the bottom surface of the engagement recess 143 of the engagement portion 140 comes into contact with one end surface of the rotary shaft 66.

[0055] At this time, the other end surface of the body member 160 (engagement portion 140) abuts against one end surface of the first reduction gear 75. Also, one end of the male thread portion 163 of the body member 160 (operation portion 141) is located within the axial range of the small-diameter cylindrical portion 152 of the multi-stage cylindrical portion 151. Finally, in the state of Figure 7(c), when the tool is rotated in the brake release direction (the direction of the arrow indicated on one end surface of the cylindrical portion 135 of the cover member 115 shown in Figure 5), the rotation of the tool rotates the rotary shaft 66 of the electric motor 60 in the brake release direction via the body member 160, and the parking brake is released.

[0056] Next, a brake forced release mechanism 130C according to a third embodiment of the electric actuator 2 will be described in detail with reference to FIG. 8 . When describing the brake forced release mechanism 130C according to the third embodiment, only the differences from the brake forced release mechanism 130B according to the second embodiment will be described. The body member 160 corresponding to the brake forced release mechanism 130C according to the third embodiment does not have the annular flange 168 of the body member 160 corresponding to the brake forced release mechanism 130B according to the second embodiment, but has a circular plate-shaped sealing flange 172 that protrudes radially outward at the other end of the engagement portion 140. An annular groove 165 is formed on one end surface of the sealing flange 172. A seal member 166 is fitted into the annular groove 165.

[0057] The sealing flange 172 of the body member 160 then comes into tight contact with the step 154 ​​between the small-diameter cylindrical portion 152 and the large-diameter cylindrical portion 153 of the multi-stepped cylindrical portion 151 via the seal member 166. As a result, the airtightness inside the housing 63 (see FIG. 2) is maintained. Furthermore, the sealing flange 172 comes into contact with the step 154, thereby restricting movement of the one end of the body member 160 relative to the multi-stepped cylindrical portion 151. Note that the other structure and operation of the brake forced release mechanism 130C according to the third embodiment are the same as those of the brake forced release mechanism 130B according to the second embodiment, and therefore description thereof will be omitted.

[0058] As described above, the brake forced release mechanisms 130B, 130C according to the second and third embodiments are configured with the body member 160 that is separate from the cover member 115, and therefore the body member 160 is detachable from the cover member 115, in other words, it is detachable from the cover member 115. As a result, if some kind of failure occurs on the electric motor 60 side while the parking brake is applied and the braking state needs to be forcibly released, there is no need to damage a part of the cover member 115, and therefore after the failed part on the electric motor 60 side is repaired, the same cover member 115 can be used again, thereby reducing repair costs.

[0059] Furthermore, in the brake forced release mechanisms 130B and 130C according to the second and third embodiments, a circular recess 161 is provided as a guide portion on one end face of the engaging portion 140 of the body member 160. Therefore, when the engaging recess 143 of the body member 160 (engaging portion 140) and the protruding portion 66A of the rotating shaft 66 of the electric motor 60 approach each other along the axial direction, the engaging recess 143 and the protruding portion 66A can be easily guided to a position where they can engage with each other.

[0060] Furthermore, the brake forced release mechanisms 130B and 130C according to the second and third embodiments employ a rotary-linear conversion mechanism (screw mechanism) in which the female threaded portion 155 of the small-diameter cylindrical portion 152 of the cover member 115 and the male threaded portion 163 of the body member 160 are threadedly engaged, thereby simplifying the structure.

[0061] Furthermore, in the brake forced release mechanisms 130B, 130C according to the second and third embodiments, in a normal state, the length L5 of the gap between one end face of the rotary shaft 66 (protruding portion 66A) of the electric motor 60 and the bottom surface of the engagement recess 143 of the body member 160 is set to be larger than the length L4 of engagement between the female threaded portion 155 of the cover member 115 and the male threaded portion 163 of the body member 160. As a result, when the parking brake is forcibly released, the body member 160 is rotated and advanced toward the other end relative to the multi-step cylindrical portion 151. Before the male threaded portion 163 of the body member 160 is disengaged from the female threaded portion 155 of the small-diameter cylindrical portion 152, that is, while the body member 160 is advancing toward the other end, the bottom surface of the engagement recess 143 of the body member 160 does not interfere with the one end face of the rotary shaft 66 of the electric motor 60, and therefore the engagement recess 143 of the body member 160 is not damaged.

[0062] Furthermore, in a normal state, the length L3 of the gap between one end face of the rotary shaft 66 (protruding portion 66A) of the electric motor 60 and the bottom surface of the circular recess 161 of the body member 160 is set to be larger than the length L4 of engagement between the female thread portion 155 of the cover member 115 and the male thread portion 163 of the body member 160. As a result, when the parking brake is forcibly released, the body member 160 is rotated and advanced toward the other end of the multi-step cylindrical portion 151, and the male thread portion 163 of the body member 160 is disengaged from the female thread portion 155 of the small-diameter cylindrical portion 152. At this point, the protruding portion 66A of the rotary shaft 66 is not yet engaged in the engaging recess 143 of the body member 160. Therefore, by rotating the tool in the forward or reverse direction while making fine adjustments, the engaging recess 143 of the body member 160 can easily be engaged with the protruding portion 66A of the rotary shaft 66, improving work efficiency.

[0063] In this embodiment, the electric actuator 2 is directly attached to the back plate 4 of the drum brake 1, but it may also be attached via a bracket or the like to a vehicle body structure located near the drum brake 1.

[0064] Furthermore, in the above-described embodiment, the electric actuator 2 is employed in the drum brake 1 as the electric braking device, but it may also be employed in a disc brake.

[0065] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0066] This application claims priority to Japanese Patent Application No. 2023-124478, filed July 31, 2023. The entire disclosure of Japanese Patent Application No. 2023-124478, filed July 31, 2023, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0067] 1 Drum brake (electric brake device), 2 Electric actuator, 60 Electric motor, 62 Rotation-to-linear motion conversion mechanism, 65 Main body, 66 Rotation shaft (rotation member), 63 Housing, 115 Cover member (housing), 130A to 130C Brake forced release mechanism according to first to third embodiments, 137 Thin-walled portion, 140 Engagement portion, 141 Operation portion, 143 Engagement recess, 155 Female thread portion, 160 Body member, 161 Circular recess (guiding portion), 163 Male thread portion

Claims

1. An electric brake device comprising: an electric motor; a rotating member to which rotation from the electric motor is transmitted; a rotary-to-linear motion conversion mechanism that converts the rotation from the rotating member into linear motion, thereby enabling switching between a braking state and a non-braking state; and a housing that accommodates the rotating member, wherein the housing has a brake forced release mechanism that is capable of forcibly releasing the braking state to the non-braking state.

2. An electric brake device according to claim 1, wherein the brake release mechanism is integrally formed with the housing.

3. An electric brake device as described in claim 1, wherein the brake forced release mechanism comprises an engagement portion that engages with the rotating member so as not to rotate relative to the rotating member, and an operating portion that can be operated to rotate the rotating member.

4. An electric brake device according to claim 1, characterized in that the brake release mechanism is provided so as to be removable from the housing.

5. An electric brake device according to claim 3, characterized in that the engaging portion is provided with a guide portion for guiding the engaging recess of the engaging portion and the rotating member to a position where they can engage with each other.

6. An electric brake device according to claim 3, wherein the operating portion is adapted to engage with a tool.

7. An electric brake device according to claim 1, characterized in that the rotating member is a rotating shaft of the electric motor.

8. An electric brake device according to claim 3, wherein the engaging portion and the operating portion are both made of synthetic resin, or either or both of the engaging portion and the operating portion are made of ceramic or metal.

9. An electric brake device according to claim 3, wherein the housing indicates the operating direction of the operating part.

10. An electric brake device as claimed in claim 1, characterized in that the housing and the brake compulsory release mechanism are integrally molded from resin, and a thin-walled portion is formed between the housing and the brake compulsory release mechanism.

11. An electric brake device according to claim 3, wherein the operating portion is provided so as to protrude outward from the housing.

12. An electric brake device as claimed in claim 11, characterized in that there is a gap between the end face of the rotating member on the housing side and the end face of the engaging portion on the rotating member side, and the length of the gap is set to be longer than the protruding length of the operating portion.

13. An electric brake device according to claim 1, characterized in that the brake forced release mechanism is configured separately from the housing.

14. An electric brake device according to claim 1, wherein the housing and the brake release mechanism are engaged with each other by their respective threads.

15. An electric brake device as claimed in claim 14, characterized in that there is a gap between the end face of the rotating member on the housing side and a bottom surface of an engagement recess provided in the engagement portion which engages with the rotating member, and the length of the gap is set to be greater than the axial length of the threaded portion.