Drum brake and electronic parking brake

Abstract

The present disclosure relates to a drum brake. The drum brake includes a bolt screw that rotates with driving of a first motor, a nut piston that is combined with a circumference line of the bolt screw through a bolt nut fastener and moves toward a direction in which a brake shoe is pressed against the nut piston with rotation of the bolt screw, and a press nut that is combined with a circumference line of the nut piston through the bolt nut fastener and moves together in an axial direction to abut against the bolt screw with driving of a second motor, thereby preventing the nut piston from being pushed due to a reaction force of the brake. According to the present disclosure, the number of components and the volume weight of a service brake and a parking brake can be significantly reduced, and the space utilization and the degree of freedom in layout design can be further improved.

Description

Technical Field

[0001] This disclosure relates to drum brakes and electronic parking brakes, and more particularly to a drum brake and an electronic parking brake capable of keeping a vehicle stationary using an actuator. Background Technology

[0002] Typically, service brakes are used to reduce vehicle speed or for emergency braking, while parking brakes are used to park or keep the vehicle stationary. Drum brakes slow or stop a vehicle by generating friction with a drum that rotates with the wheels. Drum brakes are mounted on a backing plate with the inner circumferential surface of the brake drum facing it. A drum brake presses a pair of brake pads coated with friction material against the brake drum, causing friction and generating braking force for both service and parking.

[0003] An electromechanical brake (EMB) is a braking device that uses force assisted by a motor, gears, and a screw. The electronic control unit (ECU) converts the pressure of the brake pedal pressed by the driver into an electrical signal. The EMB applies braking force corresponding to the electrical signal. An electronic parking brake (EPB) is an electronically operated braking device. When the vehicle is stationary, the ECU measures vehicle speed and engine speed, and detects braking operations, thereby maintaining the brakes.

[0004] To perform service braking, the vehicle must automatically disengage from the brakes after EMB (Electronic Braking System) is activated. This requires that the screw used for EMB is not self-locking. To meet this requirement, a high-lead screw, an increased lead, or a ball screw with an increased number of starts must be used. Conversely, to perform parking braking, the brakes must be maintained after EPB (Electronic Braking System) is activated. Therefore, the screw used for EPB must be self-locking. Consequently, the characteristics of the screw required for service braking differ from those required for parking braking.

[0005] Drum brakes in related technologies have a structure in which the screw for service braking and the screw for parking braking are separately arranged; and components for enhancing the screw force for service braking and components for enhancing the screw force for parking braking are also separately arranged. This results in an increase in the number of components, a more complex layout, and increased manufacturing costs.

[0006] Therefore, this problem needs to be solved.

[0007] The background technology disclosed herein is disclosed in Korean Patent No. 2288508 entitled "Electronic Parking Brake", registered on August 4, 2021. Summary of the Invention

[0008] The purpose of this disclosure is to provide a drum brake and an electronic parking brake that can employ a simple structure to allow the service brake and parking brake to share a single screw.

[0009] According to one aspect of this disclosure, a drum brake is provided, comprising: a bolt screw that rotates with the drive of a first motor; a nut piston engaged with the circumference of the bolt screw by a bolt-nut fastener and moving in a direction that causes the nut piston to press against the brake shoe as the bolt screw rotates; and a pressing nut engaged with the circumference of the nut piston by the bolt-nut fastener and moving axially with the drive of a second motor to abut against the bolt screw, thereby preventing the nut piston from being pushed by the reaction force of the brake shoe.

[0010] In this drum brake, the first motor, the bolt and screw, and the nut piston are components of the service brake, which is used to reduce vehicle speed or for emergency stopping of the vehicle. The second motor and the pressing nut are components of the parking brake, which is used to park or keep the vehicle stopped. When the nut piston is pressed against the brake shoe due to the drive of the first motor, the pressing nut and the bolt and screw are spaced apart from each other in the axial direction, and the pressing nut moves toward the bolt and screw due to the drive of the second motor, thereby abutting against the bolt and screw.

[0011] In this drum brake, the inner circumferential portion of the nut piston and the outer circumferential portion of the bolt screw have a threaded structure. According to this threaded structure, when the nut piston is pressed against the brake shoe, the nut piston will not self-lock in response to the reaction force of the brake shoe when the first motor stops being driven. Furthermore, the inner circumferential portion of the nut piston and the outer circumferential portion of the nut piston have a threaded structure. According to this threaded structure, when the nut piston is pressed against the bolt screw in the axial direction, the nut piston will self-lock in response to the reaction force of the brake shoe when the second motor stops being driven.

[0012] In this drum brake, the first motor, the bolt and screw, and the nut piston are components of the service brake, which is used to reduce vehicle speed or for emergency stopping of the vehicle. The service brake may also include a first transmission device that transmits the rotational force of the first motor to the bolt and screw. The first transmission device may include: a drive gear powered by the first motor and thus rotated; and a driven gear that meshes with the drive gear and rotates at a reduced speed, and is coaxially engaged with the bolt and screw.

[0013] In this drum brake, the bolt may include: a gear assembly portion having a polygonal cross-section, mounted to pass through a bolt engagement hole in the driven gear, and capable of sliding axially along the bolt engagement hole; and a bolt extension portion formed to be coaxially continuous with the gear assembly portion and engaged with the nut piston via the bolt-nut fastener.

[0014] In this drum brake, the diameter of the screw extension may be smaller than the diameter of the gear assembly portion, and the pressure nut may be installed on the side portion facing the first side of the gear assembly portion in the axial direction.

[0015] In this drum brake, the bolt may include: a gear assembly portion which is provided with rotational force by the first motor; a bolt extension portion which is formed to be coaxially continuous with the gear assembly portion and engaged with the nut piston by the bolt-nut fastener; and a pressing contact portion which is arranged on the gear assembly portion or the bolt extension portion with its axial surface facing the pressing nut and abutting against the pressing nut.

[0016] In this drum brake, the bolt may include: a gear assembly portion which is provided with rotational force by the first motor; a bolt extension portion which is engaged with the nut piston by the bolt-nut fastener; a fixing portion which is formed between the gear assembly portion and the bolt extension portion and is formed to be coaxially continuous with the gear assembly portion and the bolt extension portion; a pressure plate which is fixed to the fixing portion and is arranged to protrude more radially than the bolt extension portion; and a pressing contact portion which is arranged on the pressure plate and faces the pressing nut in the axial direction to abut against the pressing nut.

[0017] In this drum brake, the diameter of the gear assembly portion is smaller than the diameter of the screw extension portion, and the pressure nut is arranged on the side portion of the first side of the pressure plate in the axial direction.

[0018] In this drum brake, the fixed part has external threads, and the pressure plate is fixed by means of bolt and nut fasteners, which combine an annular member with internal threads with the fixed part.

[0019] In this drum brake, the second motor and the pressure nut are components of the parking brake, which is used to park or keep the vehicle stopped. The parking brake may also include: a second transmission device that transmits the rotational force of the second motor to the pressure nut; the second transmission device may include: a first gear connected to the second motor; and a second gear, the first side portion of which meshes with the first gear to rotate at a reduced speed, and the second side portion of which meshes with the pressure nut.

[0020] In this drum brake, the pressure nut has a diameter larger than the second gear and meshes with the second gear, and its axial length allows the pressure nut to move to abut or disengage from the bolt while maintaining engagement with the second gear.

[0021] The drum brake may further include: a housing having a communicating space in which the bolt, the nut piston, and the press nut are accommodated, wherein the housing may include: a first housing unit accommodating a portion of the service brake; a second housing unit accommodating a portion of the parking brake; and a coupling cylinder unit formed in the portion where the first housing unit and the second housing unit are combined, having a hollow cylindrical shape and accommodating the bolt, the nut piston, and the press nut.

[0022] In this drum brake, the second housing unit may include: a motor housing unit that houses the second motor; a gear housing unit that houses a second transmission device that transmits the rotational force of the second motor to the pressing nut; and a piston housing unit that is coupled to the first housing unit at one end facing the first housing unit to form the coupling cylinder unit, and the nut piston is mounted on the other part of the piston housing unit facing the brake shoe by passing through the piston housing unit, the piston housing unit being configured to communicate with the gear housing unit.

[0023] According to another aspect of this disclosure, an electronic parking brake is provided, comprising: a second motor; a pressing nut, which, via a bolt-nut fastener, engages with the circumference of a nut piston of a service brake pressed against a brake shoe, and moves axially as driven by the second motor to abut against a bolt thread engaged with the nut piston via the bolt-nut fastener, thereby preventing the nut piston from being pushed by the reaction force of the brake shoe; and a second transmission device that transmits the rotational force of the second motor to the pressing nut.

[0024] In this electronic parking brake, the pressing nut may include: a nut body arranged on the circumference of the nut piston; a threaded engagement portion formed on the inner circumference of the nut body and engaged with the nut piston by the bolt-nut fastener; a toothed portion formed on the outer circumference of the nut body and provided with rotational force by the second motor; and a screw mounting / unmounting portion formed on the end of the nut body, which abuts against the bolt screw in the axial direction when the nut body moves.

[0025] In this electronic parking brake, the screw loading / unloading portion may include: a limiting jaw formed on the axial end of the nut body, protruding inward toward the axial center and arranged facing the nut piston located inside the nut body in the axial direction; and a screw contact portion formed on the limiting jaw, protruding axially and facing the bolt screw in the axial direction to abut against it.

[0026] In this electronic parking brake, the inner circumferential portion of the limiting jaw and the screw contact portion both have a larger diameter than the bolt screw and are spaced apart from the circumference of the bolt screw. Furthermore, the power transmitted from the second motor to the nut body is used as stress and applied to the bolt screw in the axial direction through the threaded contact portion.

[0027] In this electronic parking brake, when the second motor is driven in the forward direction, the pressing nut can move axially to one side until the screw contact portion is pressed against and abuts the bolt screw. When the second motor is driven in the reverse direction, the pressing nut can move axially to the other side until the limiting jaw presses against and abuts the nut piston in the axial direction.

[0028] In this electronic parking brake, at least a portion of the second motor, together with the bolt, the nut piston and the pressing nut, is housed in the housing and is arranged on one side of the back plate, parallel to the bolt, the nut piston and the pressing nut.

[0029] In the structure of the drum brake according to this disclosure, the service brake and the parking brake are coaxially connected to each other. More specifically, according to this disclosure, in the structure of the drum brake, the bolt and nut piston of the service brake and the pressure nut of the parking brake are coaxially connected to each other by bolt and nut fasteners. In other words, the parking brake according to this disclosure has a simple structure in which the pressure nut is also connected to the circumference of the nut piston provided in the service brake by bolt and nut fasteners. That is to say, according to this disclosure, the drum brake has a simple structure in which the service brake and the parking brake share a single screw, corresponding to the bolt and nut.

[0030] Therefore, compared with the case in the related art where the service brake and parking brake are arranged independently of each other, in other words, compared with the case in the related art where the service brake and parking brake are arranged in a spaced-apart manner, the structure according to this disclosure has the following advantages: The number of components, volume, and weight of the service brake and parking brake can be significantly reduced, and space utilization and layout design freedom can be further improved. In addition, manufacturing costs can be improved and productivity can be increased.

[0031] Furthermore, the parking brake prevents the nut piston from rotating by pressing the bolt thread against the nut. Therefore, compared to existing parking brakes that directly press against the brake shoe, it requires only a very low output stress to stably apply the parking brake. Consequently, the motor, transmission, and housing can be reduced in size and weight. Attached Figure Description

[0032] Figure 1 This is a schematic perspective view of a drum brake according to a first embodiment of the present disclosure.

[0033] Figure 2 It is shown Figure 1 A three-dimensional view of the basic components of a drum brake.

[0034] Figure 3 It is shown Figure 1 Cross-sectional view of the basic components of a drum brake.

[0035] Figure 4 It is shown Figure 1 A perspective view of the other basic components of a drum brake.

[0036] Figure 5 It is shown Figure 1 An exploded perspective view of the other basic components of a drum brake.

[0037] Figure 6 This is an operational view showing the state in which the service brake is performing braking according to the first embodiment of this disclosure.

[0038] Figure 7 This is an operational view showing the state in which the parking brake is applied by the parking brake according to the first embodiment of this disclosure.

[0039] Figure 8 This is a schematic cross-sectional view showing the basic components of a drum brake according to a second embodiment of the present disclosure.

[0040] Figure 9 This is a perspective view schematically showing the basic components of a drum brake according to a second embodiment of the present disclosure.

[0041] Figure 10 This is an exploded perspective view schematically showing the basic components of a drum brake according to a second embodiment of the present disclosure.

[0042] Figure 11 This is an operational view showing the state in which the service brake is applied by the vehicle brake according to the second embodiment of this disclosure.

[0043] Figure 12 This is an operational view showing the state in which the parking brake is applied by the parking brake according to the second embodiment of this disclosure. Detailed Implementation

[0044] The following description, with reference to the accompanying drawings, will depict a drum brake and an electronic parking brake according to embodiments of the present disclosure. For clarity and convenience, the thickness of lines, the size of components, etc., may not be shown to exact scale in the drawings. Furthermore, the terminology assigned to the components according to the present disclosure is defined with respect to the function of the components and may vary depending on the user's intent, the administrator's intent, or based on practice in the art. Therefore, the terminology should be defined in the context of this specification.

[0045] Figure 1 This is a schematic perspective view of a drum brake 1 according to a first embodiment of the present disclosure. Figure 2 It is shown Figure 1 A three-dimensional view of the basic components of a drum brake. Figure 3 It is shown Figure 1 Cross-sectional view of the basic components of a drum brake.

[0046] refer to Figures 1 to 3 In the configuration of the drum brake 1 according to the first embodiment of the present disclosure, the service brake 2 for reducing vehicle speed or for emergency stopping of the vehicle and the parking brake 3 for parking or for keeping the vehicle stopped share the same screw member, corresponding to the bolt screw 23, and are arranged in a communicating space.

[0047] According to the first embodiment of this disclosure, the service brake 2 performs the following operations: Driven by the first motor 21, the bolt screw 23 rotates, moving the nut piston 24 axially, thereby pressing against and pushing the brake shoe 5. The nut piston 24 is engaged with the bolt screw 23 via a bolt-nut fastener (see...). Figure 6 ).

[0048] According to the first embodiment of this disclosure, the parking brake 3 overlaps with the pressing nut 33, and is engaged with the circumference of the nut piston 24 by a bolt and nut fastener, and performs the following operations to prevent the nut piston 24 from being pushed in the opposite direction due to the reaction force of the brake shoe 5: as the second motor 31 drives, the pressing nut 33 is moved in the axial direction, thereby pressing the pressing nut 33 in the axial direction, so that the pressing nut 33 contacts the bolt screw 23 (see...). Figure 7 ).

[0049] exist Figure 3 In this design, the bolt spur 23 is arranged in a transversely extending manner. For convenience, transverse is defined below as the axial or left-right direction. The positional and assembly relationships between the components will be described below according to this definition. Throughout this specification, the portion of the bolt spur 23 that contacts the pressing nut 33 in the axial direction is referred to as the pressing contact portion 235.

[0050] Press nut 33 is located at Figure 3 Between the left-side pressing contact portion 235 and the right-side nut piston 24. Depending on the axial position of the pressing nut 33, a portion of the left side of the pressing nut 33 is detachably connected to the pressing contact portion 235. Although the axial position of the pressing nut 33 can vary, a portion of the right side of the pressing nut 33 is always engaged with the circumference of the nut piston 24 by a bolt and nut fastener.

[0051] The pressing nut 33 moves axially while maintaining engagement with the nut piston 24. Then, when the pressing nut 33 contacts the pressing contact portion 235 of the bolt thread 23, the pressing nut 33 also applies a rightward pressure to the nut piston 24 and a leftward pressure to the bolt thread 23. Therefore, it can prevent the nut piston 24 from being pushed towards the pressing contact portion 235 due to the reaction force of the brake shoe 5.

[0052] According to the first embodiment of this disclosure, as described above, the parking brake can be activated by moving the nut 33 while the nut piston 24 is pressed against the brake shoe 5 under the drive of the first motor 21. At this time, the stress is at least sufficient to limit the rotation of the nut piston 24 (returning to...). Figure 3 In the case of the waiting position shown, it is necessary to make the pressing nut 33 contact with the pressing contact portion 235.

[0053] In related technologies, the parking brake 3 is separately installed from the service brake 2 and is configured to directly press against the brake shoe 5. Therefore, in related technologies, a second motor 31, a second transmission device 32, etc., are required to ultimately output a stress of 1200 to 1400 kg. However, according to this disclosure, the parking brake can be stably operated by outputting a very low stress of 10 to 20 kg.

[0054] Figure 4 It is shown Figure 1 A perspective view of the other basic components of a drum brake. Figure 5 It is shown Figure 1 An exploded perspective view of the other basic components of a drum brake.

[0055] refer to Figures 3 to 5 According to the first embodiment of this disclosure, the service brake 2 includes a first motor 21, a first transmission device 22, a bolt 23, and a nut piston 24.

[0056] Reference Figure 1 The bolt screw 23 and nut piston 24 are arranged in front of the back plate 6 (on one side of its surface), and the first motor 21 is arranged behind the back plate 6 (on the other side of its surface). A first transmission device 22 is arranged on the back plate 6 such that it passes through the back plate 6, and transmits the rotational force of the first motor 21 arranged behind the back plate 6 to the bolt screw 23 in front of the back plate 6. According to a first embodiment of this disclosure, the first transmission device 22 includes a drive gear 221 and a driven gear 222.

[0057] The drive gear 221 is a gear component connected to the output shaft of the first motor 21. The drive gear 221 has a worm gear structure and is powered by the first motor 21, thus rotating in its normal position. The driven gear 222 is a gear component that transmits the rotational force of the drive gear 221 to the bolt screw 23. The driven gear 222 has a gear structure, is mounted to mesh with the drive gear 221, and rotates at a reduced speed in its normal position.

[0058] The driven gear 222 has a screw engagement hole 223. The bolt 23 passes through the screw engagement hole 223 to engage with it. The bolt 23 is mounted therein by passing through the screw engagement hole 223 in an axial direction. When the first motor 21 is driven, the bolt 23 rotates with the same rotational displacement as the driven gear 222. According to the first embodiment of this disclosure, the bolt 23 includes a gear assembly portion 231, a screw extension portion 232, and a pressing contact portion 235.

[0059] The gear assembly portion 231 is part of the bolt shank 23, to which rotational force is supplied from the first motor 21 via the first transmission device 22. The gear assembly portion 231 is mounted axially through the bolt engagement hole 223 in the driven gear 222 and has a cross-section with a fixed shape relative to the axial direction. Therefore, the bolt shank 23 can slide axially while being guided by the edge portion of the bolt engagement hole 223.

[0060] Furthermore, the cross-sections of both the gear assembly portion 231 and the screw engagement hole 223 are non-circular; for example, they can be polygonal cross-sections. Therefore, when the driven gear 222 rotates, the bolt screw 23 can rotate stably with the same rotational displacement as the driven gear 222.

[0061] The screw extension 232 is part of the bolt screw 23 and is engaged with the nut piston 24 by a bolt and nut fastener. The screw extension 232 is formed coaxially and continuously with the gear assembly portion 231. The circumference of the screw extension 232 has external threads, allowing the nut piston 24 to be engaged with the screw extension 232 by the bolt and nut fastener. According to the first embodiment of this disclosure, the externally threaded screw extension 232 has a tapered screw structure.

[0062] The diameter of the screw extension 232 is smaller than the diameter of the gear assembly portion 231. The screw extension 232 has a circular cross-section, while the gear assembly portion 231 generally has a non-circular cross-section. Therefore, at the junction of the gear assembly portion 231 and the screw extension 232, the right-side side portion of the gear assembly portion 231 has a hook-jaw shape.

[0063] The gear assembly portion 231 is arranged such that, in the axial direction, its right side faces the left side of the pressing nut 33. The pressing nut 33 is engaged with the circumference of the nut piston 24 by a bolt and nut fastener. When the pressing nut 33 moves to the left, its right side surface presses against and abuts against the pressing nut 33. In other words, the right side of the gear assembly portion 231 (i.e., the portion that extends radially beyond the screw extension portion 232) is the pressing contact portion 235, to which the pressing nut 33 is detachably attached.

[0064] The nut piston 24 is engaged with the circumference of the bolt shank 23 via a bolt nut fastener, and moves axially (to the right) as the bolt shank 23 rotates, thereby pressing against and pushing the brake shoe 5. The threaded structure of the nut piston 24 ensures that when the first motor 21 stops being driven while the nut piston 24 is pressed against the brake shoe 5, the nut piston 24 does not self-lock in response to the reaction force of the brake shoe 5. The end of the nut piston 24 that contacts the brake shoe 5 has a clamping shape, so that its end faces the front and rear surfaces of the brake shoe 5 before contacting it. Therefore, the nut piston 24 only displaces in the axial direction and does not rotate.

[0065] In this specification, when the nut piston 24 is described as non-self-locking, it means the following: When the bolt screw 23 is rotated and advanced by the drive of the first motor 21, the nut piston 24 moves to the right, thereby pressing against and pushing the brake shoe 5. At this time, the first motor 21 stops being driven, that is, it no longer performs the vehicle's service brake. Due to the reaction force of the brake shoe 5 applied to the nut piston 24, the nut piston 24 is pushed to the left by itself. At this time, the nut piston 24 only has linear displacement in the axial direction, so the bolt screw 23 rotates in the opposite direction.

[0066] When implementing a non-self-locking threaded structure for the nut piston 24 in this way, various factors can be considered, such as the lead angle, lead, number of thread starts, thread type, material, and surface roughness of the thread surface. For example, the larger the lead angle of the thread surface, the smaller the rotational force generated relative to the stress in the axial direction. In other words, the larger the lead angle, the easier it is for the nut piston 24 to be pushed by the reaction force of the brake shoe 5. Therefore, a non-self-locking structure for the nut piston 24 can be easily implemented.

[0067] The foregoing description of a service brake 2 according to a first embodiment of the present disclosure is solely for the purpose of disclosing a service brake 2 according to a preferred embodiment of the present disclosure and is not intended to specifically limit the structure of the service brake 2 according to the present disclosure. The service brake 2 according to the present disclosure is not limited to specific structures and shapes included in the related art, but only requires that in its configuration, with the drive of the first motor 21, the bolt screw 23 rotates and the nut piston 24 moves in the axial direction.

[0068] refer to Figures 3 to 5 According to the first embodiment of this disclosure, the parking brake 3 includes a second motor 31, a second transmission device 32, and a pressing nut 33.

[0069] The second motor 31 can be installed separately from the first motor 21 and mounted on the front of the back plate 6 (on one side of the plate surface) in a manner parallel to the bolt screw 23 and nut piston 24. The second motor 31 can also be arranged together with the first motor 21 at the rear of the back plate 6. However, the smaller the second motor 31 is, the easier it is to arrange it together with the second transmission device 32 at the front of the back plate 6.

[0070] When the second motor 31 is to be mounted on the front of the backplate 6, it is arranged such that it is partially or entirely housed in a housing 40 having a communicating space that houses the bolt 23, the nut piston 24, and the press-fit nut 33. The second motor 31 can be arranged in a second housing unit 42 (described below) of the housing 40, and thus can be arranged parallel to the bolt 23, the nut piston 24, and the press-fit nut 33 on the front of the backplate 6.

[0071] When the second motor 31 is positioned in front of the back plate 6, there is no need to form a through hole in the back plate 6 to transmit the output of the second motor 31 to the pressure nut 33. Therefore, the overall structural rigidity of the device including the back plate 6 can be more reliably ensured. In addition, because the second motor 31 is positioned closer to the pressure nut 33, the transmission is more efficient, and the second transmission device 32 can also be miniaturized.

[0072] The second transmission device 32 transmits the rotational force of the second motor 31 to the pressing nut 33. According to the first embodiment of this disclosure, the second transmission device 32 includes a first gear 321 and a second gear 322.

[0073] The first gear 321 is a gear component connected to the output shaft of the second motor 31. The second gear 322 is a reduction gear component that transmits the rotational force of the first gear 321 to the pressing nut 33. The diameter of the second gear 322 is larger than the diameter of the first gear 321, and the second gear 322 meshes with the first gear 321. A first side portion of the second gear 322 with teeth formed on its circumference meshes with the first gear 321, and a second side portion meshes with the outer circumference portion of the pressing nut 33, more specifically, with the toothed portion 333 of the pressing nut 33 (described below).

[0074] The diameter of the clamping nut 33 is larger than the diameter of the second gear 322. The clamping nut 33 is engaged with the circumference of the nut piston 24 via a bolt and nut fastener and meshes with the second gear 322. The diameter of the screw extension 232 of the bolt screw 23 is smaller than the diameter of the gear assembly portion 231. The clamping nut 33 moves axially as driven by the second motor 31, thereby abutting or disengaging from the bolt screw 23 in the axial direction.

[0075] More specifically, the clamping nut 33 and the screw extension 232 are arranged on the same axis, but the clamping nut 33 is positioned as a side portion facing the first side of the gear assembly portion 231 in the axial direction. When in contact with the bolt screw 23 in the axial direction, the clamping nut 33 prevents the nut piston 24 from being pushed by the reaction force of the brake shoe 5. According to the first embodiment of this disclosure, the clamping nut 33 includes a nut body 331, a threaded engagement portion 332, a gear tooth portion 333, and a screw mounting / unmounting portion 334.

[0076] The nut body 331 is the portion that forms the main body of the pressing nut 33, which is attached to the pressing nut 33. The nut body 331 has the shape of a short tube, a long tube, or a ring, and has an inner circumferential portion and an outer circumferential portion, and is arranged on the circumference of the nut piston 24. The nut body 331 is held in the following state: the threaded engagement portion 332 is engaged with the nut piston 24 by a bolt and nut fastener, and the gear tooth portion 333 meshes with the second gear 322; the axial length of the nut body 331 allows the screw loading and unloading portion 334 to move in a manner that abuts against or moves away from the bolt screw 23.

[0077] The threaded engagement portion 332 is part of the nut 33 and engages with the circumference of the nut piston 24 via a bolt-nut fastener. The threaded engagement portion 332 is formed on the inner circumference of the nut body 331 with an internally threaded portion. At this time, the threaded engagement portion 332 has a threaded structure, wherein the nut piston 24 self-locks in response to the reaction force of the brake shoe 5.

[0078] When the vehicle speed decreases or the brake shoe 5 is pressed against the brake for emergency braking (i.e., during service braking), the nut piston 24 is structured such that when the first motor 21 stops being driven, the nut piston 24 will not self-lock due to the reaction force of the brake shoe 5. For example, the nut piston 24 has a high lead angle that prevents it from self-locking. Using this structure, the nut piston 24 is connected to the bolt shank 23 via a bolt-nut fastener.

[0079] Conversely, in the state where the vehicle is stopped or held stationary by pressing against the abutment bolt 23 in the axial direction, i.e., in the parking brake state, the structure of the pressing nut 33 is such that when the second motor 31 stops being driven, the nut piston 24 self-locks in response to the reaction force of the brake shoe 5. In this structure, the pressing nut 33 is engaged with the nut piston 24 by a bolt and nut fastener.

[0080] In other words, the threaded engagement portion 332 of the pressing nut 33 is engaged with the nut piston 24 by a bolt and nut fastener. In the threaded structure, when rotating, the pressing nut 33 moves axially along the nut piston 24, but when the nut piston 24 presses against it in the axial direction, the pressing nut 33 can remain stationary. For example, a small lead angle can make the nut piston 24 self-locking.

[0081] The gear tooth portion 333 is part of the pressing nut 33 and is powered by the second motor 31. The gear tooth portion 333 is formed on the outer circumferential portion of the nut body 331. When the first gear 321 and the second gear 322 have a spur gear structure, the gear tooth portion 333 can have a corresponding spur gear structure. There are no particular restrictions on the structure and type of this gear. Besides a spur gear structure, any structure capable of transmitting rotational force can also be used.

[0082] The screw mounting / unmounting portion 334 is formed at the axial end of the nut body 331. Figure 3 (Left end). When the nut body 331 moves to the left, the screw loading / unloading portion 334 contacts the bolt screw 23 in the axial direction. According to the first embodiment of this disclosure, the screw loading / unloading portion 334 includes a limiting jaw 335 and a screw contact portion 336.

[0083] The limiting jaw 335 is formed at the axial end of the nut body 331. Figure 3 The left end of the jaw protrudes inward toward the axis. The limiting jaw 335 is arranged such that, facing the left end of the nut piston 24, it is located inside the nut body 331 and positioned axially. Figure 3 (in the left and right directions), and the jaw 335 sets the limit for the rightward movement of the pressing nut 33 relative to the nut piston 24.

[0084] The limiting jaw 335 is formed by protruding inward in the axial direction, but its protruding tip is still spaced from the bolt shank 23, and therefore will not make contact. In other words, when the limiting jaw 335 is generally circular, the diameter (width) of the inner circumference of the limiting jaw 335 is larger than the diameter of the thread extension 232 of the bolt shank 23. That is to say, the limiting jaw 335 maintains a distance from the circumference of the bolt shank 23.

[0085] The screw contact portion 336 is formed on the limiting jaw 335 and protrudes in the axial direction, more specifically, toward the gear assembly portion 231 and the pressing contact portion 235 (towards). Figure 3 (Left side) Protruding. The screw contact portion 336 is formed on the upper surface of the limiting jaw 335 facing the pressure contact portion 235 and protrudes from there. The inner circumferential portion of the screw contact portion 336 is spaced apart from the circumferential line of the bolt screw 23.

[0086] More specifically, the pressing contact portion 235 is formed in such a ring-shaped manner that its radial width corresponds to the diameter difference between the gear assembly portion 231 and the screw extension portion 232, and the screw contact portion 336 has an annular cross-section facing the pressing contact portion 235. Therefore, when the pressing nut 33 moves to the left, it can precisely press against and abut against the pressing contact portion 235 via the screw contact portion 336. The power transmitted from the second motor 31 to the pressing nut 33 ultimately serves as stress axially applied to the pressing contact portion 235 of the bolt screw 23 via the screw contact portion 336.

[0087] When the second motor 31 is driven in the forward direction, the maximum leftward movement of the pressing nut 33 is the position where the screw contact portion 336 presses against and abuts against the bolt screw 23 axially upward. When the second motor 31 is driven in the reverse direction, the maximum rightward movement of the pressing nut 33 is the position where the limiting jaw 335 abuts against the nut piston 24 axially upward.

[0088] In the configuration of the drum brake 1 according to the first embodiment of this disclosure, the service brake 2 and the parking brake 3 share a single screw member, corresponding to the bolt screw 23, and are arranged within a communicating space. (Refer to...) Figures 1 to 3 According to the first embodiment of the present disclosure, the drum brake 1 may include a housing 40 as a component of the communicating space.

[0089] In the structure of the housing 40, the bolt 23, the nut piston 24, and the press nut 33 can be accommodated in a communicating space. The housing 40 according to a first embodiment of this disclosure includes a first housing unit 41, a second housing unit 42, and a combined cylinder unit 43.

[0090] The first housing unit 41 houses the service brake 2. The second housing unit 42 houses the parking brake 3. The combined cylinder unit 43 is part of the housing 40 and houses the bolt 23, nut piston 24, and press nut 33. The combined cylinder unit 43 is formed in the shape of a hollow cylinder and is located in the part where the first housing unit 41 and the second housing unit 42 are combined.

[0091] In addition to the portion (one or all) housed in the combined cylinder unit 43, the service brake 2 may also be partially housed in the first housing unit 41. In addition to the portion housed in the combined cylinder unit 43, the parking brake 3 may also be partially housed in the second housing unit 42. The second housing unit 42 according to a first embodiment of this disclosure includes a motor housing unit 421, a gear housing unit 422, and a piston housing unit 423.

[0092] The shape of the motor housing unit 421 can accommodate part or all of the second motor 31. The shape of the gear housing unit 422 can accommodate the second transmission device 32. The shape of the piston housing unit 423 can be combined with the first housing unit 41 to form a combined cylinder unit 43.

[0093] Piston receiving unit 423 faces one end of the first housing unit 41. Figure 3 The left end of the piston receiving unit 423 is combined with the first housing unit 41, and the piston receiving unit 423 forms the combined cylinder unit 43. The nut piston 24 is arranged at the other end of the piston receiving unit 423 facing the brake shoe 5. Figure 3 (The right end of the middle), passing through the combined cylinder unit 43 from the inside out.

[0094] Figure 6 This is an operational view showing the state in which the service brake 2 performs braking according to the first embodiment of this disclosure. Figure 7 This is an operational view showing the state in which the parking brake 3 performs braking according to the first embodiment of this disclosure.

[0095] refer to Figure 6 According to the first embodiment of this disclosure, the service brake 2 performs the operation of pressing and pushing the brake shoe 5 by rotating the bolt screw 23 as driven by the first motor 21, causing the nut piston 24, which is engaged with the circumference of the bolt screw 23 by the bolt and nut fastener, to move in the axial direction.

[0096] refer to Figure 7 According to the first embodiment of this disclosure, the parking brake 3 overlaps with the clamping nut 33, and is connected to the circumference of the nut piston 24 by the bolt and nut fastener, and performs the following operations to prevent the nut piston 24 from being pushed in the opposite direction due to the reaction force of the brake shoe 5: as the second motor 31 drives, the clamping nut 33 is moved in the axial direction, thereby pressing the clamping nut 33 in the axial direction, so that the clamping nut 33 contacts the gear assembly portion 231 of the bolt screw 23.

[0097] exist Figure 3 In the initial state shown, the first motor 21 is driven in the forward direction, and the nut piston 24 (as shown) Figure 6 (As shown) Move to the right, push the right brake shoe 5 of the pair of brake shoes 5 to the right, and press against the right brake shoe 5. Through this operation, the service brake is applied. At this time, the gear assembly portion 231 pressing against the nut 33 and the bolt screw 23 is spaced apart from each other in the axial direction.

[0098] Subsequently, when the second motor 31 is driven in the forward direction, it presses against the nut 33 (such as...). Figure 7(As shown) It moves towards the gear assembly portion 231 and abuts against the pressing contact portion 235 of the bolt screw 23. At this time, with the first side portion of the pressing nut 33 being held against the nut piston 24, the second side portion of the pressing nut 33 abuts against the bolt screw 23 in the axial direction, thereby performing the parking brake. Then, even if the second motor 31 stops being driven, this parking brake state will be maintained due to the self-locking structure.

[0099] like Figure 6 As shown, when the nut 33 is not in contact with the bolt screw 23, and the first motor 21 stops being driven (i.e., when only the service brake is applied and not the parking brake), the nut piston 24 is pushed by the reaction force of the brake shoe 5, causing the bolt screw 23 to rotate in the opposite direction. Figure 3 As shown, it returns to its initial state.

[0100] With the parking brake released, the following process can be executed continuously. The first motor 21 is driven in the forward direction. Consequently, the nut piston 24 is pushed further towards the brake shoe 5, separating the pressing contact portion 235 between the pressing nut 33 and the bolt shank 23. Subsequently, the second motor 31 is driven in the reverse direction. By performing this operation to release the parking brake, the bolt shank 23, the nut piston 24, and the pressing nut 33 can each return to their initial state, as... Figure 3 As shown.

[0101] Figure 8 This is a schematic cross-sectional view showing the basic components of a drum brake 1 according to a second embodiment of the present disclosure. Figure 9 This is a perspective view schematically showing the basic components of a drum brake 1 according to a second embodiment of the present disclosure. Figure 10 This is an exploded perspective view schematically showing the basic components of a drum brake 1 according to a second embodiment of the present disclosure.

[0102] Reference Figures 8 to 10 According to the second embodiment of the present disclosure, the drum brake 1 and Figures 1 to 7 The difference between the drum brake 1 shown according to the first embodiment of the present disclosure and the drum brake 1 according to the second embodiment is that the diameter of the gear assembly portion 231 of the bolt screw 23 is smaller than the diameter of the screw extension portion 232, and the bolt screw 23 also includes a fixing portion 233 and a pressure plate 234.

[0103] In the components of the drum brake 1 according to the second embodiment of this disclosure, all those that are related to... Figures 1 to 7 The components of the drum brake 1 shown according to the first embodiment of this disclosure are the same, similar or corresponding, and will not be described again below.

[0104] refer to Figures 8 to 10According to the second embodiment of this disclosure, the bolt 23 includes a gear assembly portion 231, a bolt extension portion 232, a fixing portion 233, a pressure plate 234, and a pressing contact portion 235.

[0105] The gear assembly portion 231 is part of the bolt shank 23, to which rotational force is supplied from the first motor 21 via the first transmission device 22. The gear assembly portion 231 is mounted such that it passes axially through a screw engagement hole 223 in the driven gear 222, and its cross-section has a fixed shape relative to the axial direction. Therefore, the bolt shank 23 can slide axially while being guided by the edge portion of the screw engagement hole 223.

[0106] Furthermore, both the gear assembly portion 231 and the screw engagement hole 223 have non-circular cross-sections, for example, polygonal cross-sections. Therefore, when the driven gear 222 is driven, the bolt screw 23 can rotate stably with the same rotational displacement as the driven gear 222.

[0107] The screw extension 232 is part of the bolt screw 23 and is engaged with the nut piston 24 by a bolt and nut fastener. The screw extension 232 is formed on the same axis as the gear assembly portion 231. The screw extension 232 has external threads on its circumference, allowing the nut piston 24 to be engaged with the screw extension 232 by a bolt and nut fastener. According to the second embodiment of this disclosure, the screw extension 232 has external threads and a ball screw structure.

[0108] Typically, as described in the first embodiment of this disclosure, when the circumference of the end of a strip member has internal threads, the middle portion of the strip member in the longitudinal direction is pre-machined, depending on the ease of machining the strip member, and then its tail end portion is machined. Therefore, the diameter of the internally threaded end is relatively smaller than that of the middle portion. This can be applied to the bolt shank 23 according to the first embodiment of this disclosure.

[0109] However, unlike the case where the circumference of the end of the strip member is internally threaded, typically, in the case of the second embodiment of this disclosure, the ball screw is formed on the circumference of the end of the strip member. Depending on the ease of machining the strip member, the longitudinal ends of the strip member are pre-machined first, followed by the middle portion. Therefore, the end with the ball screw has a relatively larger diameter than the middle portion. This applies to the bolt screw 23 according to the second embodiment of this disclosure.

[0110] According to the first embodiment of this disclosure, the external threaded extension 232 of the bolt screw 23 has a self-tapping screw structure. Conversely, according to the second embodiment of this disclosure, the extension 232 of the bolt screw 23 has a ball screw structure. In this way, taking into account various conditions such as processing conditions, component specifications, and the layout relationship between the bolt screw 23 and each adjacent other component, both the diameter and cross-section of the bolt screw 23 according to this disclosure vary with its position in the length direction.

[0111] The fixing portion 233 is the part on the bolt screw 23 that fixes the pressure plate 234. The fixing portion 233 is formed between the gear assembly portion 231 and the screw extension portion 232, and is formed in a manner that is coaxial and continuous with the gear assembly portion 231 and the screw extension portion 232. According to the second embodiment of this disclosure, the fixing portion 233 has a smaller diameter than the screw extension portion 232 and a larger diameter than the gear assembly portion 231.

[0112] Therefore, the annular pressure plate 234 can pass through the circumference of the gear assembly portion 231 and can move smoothly to the fixed portion 233. When the pressure plate 234 reaches the fixed portion 233, it is engaged at the boundary between the fixed portion 233 and the jaw-shaped screw extension portion 232, thereby reliably preventing the pressure plate 234 from moving towards the screw extension portion 232. Thus, the pressure plate 234 can be securely held in a set position where it abuts against the screw extension portion 232.

[0113] The pressure plate 234 is fixed to the fixing portion 233 and is arranged to protrude radially more than the screw extension portion 232. Therefore, the side portion of the pressure plate 234 that contacts or faces the right side of the screw extension portion 232 has a hook-jaw shape.

[0114] The pressure plate 234 is arranged such that, axially, its right side portion faces the left side portion of the pressing nut 33, which is engaged with the circumference of the nut piston 24 by a bolt and nut fastener. When the pressing nut 33 moves to the left, the right side portion of the pressure plate 234 presses against and abuts against the pressing nut 33. In other words, the portion on the right side portion of the pressure plate 234 that is formed to protrude radially more than the screw extension 232 is the pressing contact portion 235, to which the pressing nut 33 is detachably attached.

[0115] According to the second embodiment of this disclosure, the pressure plate 234 is annular. The right-side portion of the pressure plate 234 facing the screw extension 232 may have a larger diameter than its left-side portion. Considering that the left-side end is to mate with the tooling, the left-side end may have a polygonal cross-section. This shape is disclosed as a preferred example of the pressure plate 234 according to this disclosure and is not intended to impose any limitation on the pressure plate 234.

[0116] Any pressure plate 234 that can be formed in this way can have various shapes, including annular, and can be arranged on the fixing part 233. The pressure plate 234 can be fixed to the fixing part 233 by various methods, such as bolt and nut fasteners, press-fit (plastic deformation), and key.

[0117] Structurally, according to the second embodiment of this disclosure, the inner circumferential portion of the pressure plate 234 has an internal thread and is fixed to the externally threaded fixing portion 233 by bolts and nuts. In this way, with the pressure plate 234 fixed to the fixing portion 233 by bolts and nuts, the pressure plate 234 is pressed against the fixing portion 233 and undergoes plastic deformation. Therefore, for example, the internally threaded portion of the pressure plate 234 can be pressed very firmly against the externally threaded portion of the fixing portion 233, and compressed to permanently prevent them from separating from each other.

[0118] A pressing contact portion 235 is formed on the right side of the pressure plate 234, facing the end of the pressing nut 33 in the axial direction. As the pressing nut 33 moves in the axial direction, the pressing contact portion 235 approaches or moves away from the left end of the pressing nut 33. More specifically, the pressing contact portion 235 may be annular, the width of which corresponds in the radial direction to the diameter difference between the pressure plate 234 and the screw extension 232.

[0119] The cross-section of the screw contact portion 336 facing the pressing contact portion 235 is annular. Therefore, when the pressing nut 33 moves to the left, it is precisely pressed against and abuts against the pressing contact portion 235 through the screw contact portion 336. The power transmitted from the second motor 31 to the pressing nut 33 ultimately becomes the stress applied axially to the pressing contact portion 235 of the bolt screw 23 through the screw contact portion 336.

[0120] Figure 11 This is an operational view showing the state in which the service brake 2 performs braking according to the second embodiment of this disclosure. Figure 12 This is an operational view showing the state in which the parking brake 3 performs braking according to the second embodiment of this disclosure.

[0121] Reference Figure 11According to the second embodiment of this disclosure, the service brake 2 performs the operation of pressing and pushing the brake shoe 5 by driving the first motor 21 to rotate the bolt screw 23, causing the nut piston 24, which is engaged with the circumference of the bolt screw 23 by the bolt and nut fastener, to move in the axial direction.

[0122] refer to Figure 12 According to the first embodiment of this disclosure, the parking brake 3 overlaps with the pressing nut 33 and is combined with the circumference of the nut piston 24 by bolt and nut fasteners, and performs the following operations to prevent the nut piston 24 from being pushed in the opposite direction by the reaction force of the brake shoe 5: as the second motor 31 drives, the pressing nut 33 moves in the axial direction, thereby pressing the pressing nut 33 in the axial direction, so that the pressing nut 33 contacts the pressure plate 234 of the bolt screw 23.

[0123] exist Figure 8 In the initial state shown, when the first motor 21 is driven in the forward direction, the nut piston 24 (as shown) Figure 11 (As shown) Move to the right, push the right brake shoe 5 of the pair of brake shoes 5 to the right, and press against the right brake shoe 5. Through this operation, the service brake is applied. At this time, the pressure plates 234 pressing against the nut 33 and the bolt screw 23 are spaced apart from each other in the axial direction.

[0124] Subsequently, when the second motor 31 is driven in the forward direction, as Figure 12 As shown, the pressing nut 33 moves towards the pressure plate 234 and abuts against the pressing contact portion 235 of the bolt screw 23. At this time, with the first side portion of the pressing nut 33 pressed against the nut piston 24, the second side portion of the pressing nut 33 abuts against the bolt screw 23 in the axial direction, thereby performing the parking brake. Then, even if the second motor 31 stops being driven, this parking brake state will be maintained due to the self-locking structure.

[0125] like Figure 11 As shown, when the nut 33 is not in contact with the bolt screw 23, and the first motor 21 stops being driven (i.e., when only the service brake is applied and not the parking brake), the nut piston 24 is pushed by the reaction force of the brake shoe 5, causing the bolt screw 23 to rotate in the opposite direction. Figure 8 As shown, it returns to its initial state.

[0126] With the parking brake released, the following process can be executed continuously. The first motor 21 is driven in the forward direction. Consequently, the nut piston 24 is pushed further towards the brake shoe 5, separating the pressing contact portion 235 between the pressing nut 33 and the bolt shank 23. Subsequently, the second motor 31 is driven in the reverse direction. By performing this parking brake release operation, the bolt shank 23, the nut piston 24, and the pressing nut 33 can each return to their initial state, as... Figure 8 As shown.

[0127] The drum brake 1 according to this disclosure has the following structure: the service brake 2 and the parking brake 3 are coaxially connected to each other. More specifically, according to this disclosure, the drum brake 1 has the following structure: the bolt thread 23 and nut piston 24 of the service brake 2 and the pressure nut 33 of the parking brake 3 are coaxially connected to each other by bolt and nut fasteners. In other words, the parking brake 3 according to this disclosure has a simple structure, wherein the pressure nut 33 is also connected to the circumference of the nut piston 24 provided in the service brake 2 by bolt and nut fasteners. In other words, according to this disclosure, the drum brake 1 has a simple structure, wherein the service brake 2 and the parking brake 3 share a single thread corresponding to the bolt thread 23.

[0128] Therefore, compared with the case in the related art where the service brake 2 and parking brake 3 are arranged independently of each other, in other words, compared with the case in the related art where the service brake 2 and parking brake 3 are arranged separately from each other, the structure according to this disclosure has the following advantages: The number of components, volume, and weight of the service brake 2 and parking brake 3 can be significantly reduced, and space utilization and layout design freedom can be further improved. In addition, manufacturing costs can be improved and productivity increased.

[0129] Furthermore, according to this disclosure, parking brakes can be applied simply by applying sufficiently high stress to restrict the rotation of the nut piston 24, causing the pressing nut 33 to contact the pressing contact portion 235. Therefore, compared to the prior art parking brake 3 that directly presses against the brake shoe 5, parking brakes can be stably performed by outputting very low stress. Consequently, the size and weight of the motor corresponding to the second motor 31, the transmission device corresponding to the second transmission device 32, and the housing housing them can be reduced.

[0130] The foregoing primarily describes embodiments of this disclosure. Those skilled in the art will understand that this disclosure can be implemented in modified forms without departing from its essence and spirit. Therefore, the disclosed embodiments should be considered from an illustrative perspective rather than a restrictive one.

Claims

1. A drum brake, comprising: The bolt screw rotates as driven by the first motor; A nut piston, which is engaged with the circumference of the bolt shank by a bolt nut fastener, and moves in the direction that presses the nut piston against the brake shoe as the bolt shank rotates; and The nut, via the bolt and nut fastener, engages with the circumference of the nut piston and moves axially with the drive of the second motor to abut against the bolt thread, thereby preventing the nut piston from being pushed by the reaction force of the brake shoe. The first motor, the bolt, and the nut piston are components of the service brake, which is used to reduce vehicle speed or for emergency braking. The second motor and the pressure nut are components of the parking brake, which is used to park or keep the vehicle stationary. In the case where the nut piston is pressed against the brake shoe due to the drive of the first motor, the pressing nut and the bolt are spaced apart from each other in the axial direction, and the pressing nut moves toward the bolt due to the drive of the second motor, thereby abutting against the bolt.

2. The drum brake according to claim 1, wherein, The inner circumference of the nut piston and the outer circumference of the bolt have threaded structures. According to these threaded structures, when the nut piston is pressed against the brake shoe, and the first motor stops being driven, the nut piston will not self-lock in response to the reaction force of the brake shoe. The inner circumference of the pressing nut and the outer circumference of the nut piston have a threaded structure. According to the threaded structure, when the pressing nut abuts against the bolt in the axial direction, the nut piston self-locks in response to the reaction force of the brake shoe when the second motor stops being driven.

3. The drum brake according to claim 1, wherein, The first motor, the bolt, and the nut piston are components of a service brake, which is used to reduce vehicle speed or for emergency braking. The service brake further includes: The first transmission device transmits the rotational force of the first motor to the bolt screw. The first transmission device includes: The drive gear, powered by the first motor, is rotated; and The driven gear meshes with the driving gear, thereby rotating at a reduced speed, and is coaxially engaged with the bolt screw.

4. The drum brake according to claim 3, wherein, The bolt includes: A gear assembly portion, having a polygonal cross-section, is mounted to pass through a screw engagement hole in the driven gear and is capable of sliding axially along the screw engagement hole; and The screw extension is formed to be coaxially continuous with the gear assembly portion and is engaged with the nut piston via the bolt and nut fastener.

5. The drum brake according to claim 1, wherein, The bolt includes: The gear assembly is powered by the first motor. The screw extension, which is formed to be coaxially continuous with the gear assembly portion, and engages with the nut piston via the bolt-nut fastener; and The pressing contact portion is arranged on the gear assembly portion or the screw extension portion with its axial surface facing the pressing nut and abutting against the pressing nut.

6. The drum brake according to claim 5, wherein, The diameter of the screw extension is smaller than the diameter of the gear assembly portion, and, The pressing nut is arranged in the axial direction, facing the first side of the gear assembly portion.

7. The drum brake according to claim 1, wherein, The bolt includes: The gear assembly is powered by the first motor. The screw extension portion is engaged with the nut piston via the bolt and nut fastener; A fixed portion is formed between the gear assembly portion and the screw extension portion, and is formed to be coaxially continuous with the gear assembly portion and the screw extension portion; A pressure plate, which is fixed to the fixing portion and arranged to protrude radially beyond the screw extension; and The pressing contact portion is arranged on the pressure plate, facing the pressing nut in the axial direction to abut against the pressing nut.

8. The drum brake according to claim 7, wherein, The diameter of the gear assembly portion is smaller than the diameter of the screw extension portion, and, The pressing nut is arranged on the side portion facing the first side of the pressure plate in the axial direction.

9. The drum brake according to claim 7, wherein, The fixing part has external threads, and, The pressure plate is fixed by means of bolts and nuts, which combine the annular member with internal threads with the fixing part.

10. The drum brake according to claim 1, wherein, The second motor and the pressure nut are components of the parking brake, which is used to park or keep the vehicle stationary. The parking brake also includes: The second transmission device transmits the rotational force of the second motor to the pressing nut, and The second transmission device includes: A first gear, which is connected to the second motor; and The second gear has a first side portion that meshes with the first gear, thereby rotating at a reduced speed, and its second side portion that meshes with the pressing nut.

11. The drum brake according to claim 10, wherein, The pressing nut has a diameter larger than the second gear and meshes with the second gear, and its axial length allows the pressing nut to move to abut or disengage from the bolt thread while maintaining engagement with the second gear.

12. The drum brake according to claim 1, further comprising: The housing has a communicating space in which the bolt, the nut piston, and the press-fit nut are accommodated. The housing includes: First housing unit, which houses a portion of the service brake; The second housing unit, which houses a portion of the parking brake; and The combined cylinder unit is formed in the shape of a hollow cylinder in the portion where the first housing unit and the second housing unit are combined with each other, and houses the bolt, the nut piston and the press nut.

13. The drum brake according to claim 12, wherein, The second housing unit includes: A motor housing unit that houses the second motor; A gear receiving unit, which houses a second transmission device for transmitting the rotational force of the second motor to the pressing nut; and A piston receiving unit, having one end facing the first housing unit, is coupled to the first housing unit to form the coupling cylinder unit, and the nut piston is mounted on another portion of the piston receiving unit facing the brake shoe by passing through the piston receiving unit, the piston receiving unit being configured to communicate with the gear receiving unit.

14. An electronic parking brake, comprising: Second motor; The pressure nut, fastened by a bolt and nut fastener, engages with the circumference of the service brake nut piston pressed against the brake shoe. Driven axially by the second motor, it abuts against the bolt thread connected to the nut piston via the bolt and nut fastener, thereby preventing the nut piston from being pushed by the reaction force of the brake shoe; and The second transmission device transmits the rotational force of the second motor to the pressing nut.

15. The electronic parking brake according to claim 14, wherein, The pressing nut includes: The nut body is arranged on the circumference of the nut piston; A threaded engagement portion is formed on the inner circumferential portion of the nut body and engages with the nut piston via the bolt-nut fastener; The gear teeth are formed on the outer circumference of the nut body and are provided with rotational force by the second motor; and A screw-on / off portion is formed on the end of the nut body, and when the nut body moves, the screw-on / off portion abuts against the bolt screw in the axial direction.

16. The electronic parking brake according to claim 15, wherein, The screw loading and unloading section includes: A limiting jaw, formed on the axial end of the nut body, protruding inward toward the axial center, and arranged axially toward the nut piston located inside the nut body; and The screw contact portion, which is formed on the limiting jaw, protrudes axially and faces the bolt screw in the axial direction to abut against it.

17. The electronic parking brake according to claim 16, wherein, The inner circumferential portion of the limiting jaw and the screw contact portion both have a larger diameter than the bolt screw, and are spaced apart from the circumference of the bolt screw. The power transmitted from the second motor to the nut body is used as stress and applied to the bolt thread in the axial direction through the threaded contact portion.

18. The electronic parking brake according to claim 16, wherein, When the second motor is driven in the forward direction, the pressing nut can move axially to one side until the screw contact portion is pressed against and abuts the bolt screw in the axial direction, and When the second motor is driven in reverse, the pressing nut can move axially to the other side until the limiting jaw presses against and abuts the nut piston in the axial direction.

19. The electronic parking brake according to claim 14, wherein, At least a portion of the second motor, together with the bolt, the nut piston and the pressing nut, is housed in a housing and is arranged on one side of the back plate of the electronic parking brake, parallel to the bolt, the nut piston and the pressing nut.

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