Drum brake and electronic parking brake

Abstract

drum brake (1), comprising: a bolt screw (23) which is turned in conjunction with a drive of a first motor (21); a mother piston (24) which is connected to a circumference of the bolt screw (23) by a bolt-nut fastening and is moved in a direction in conjunction with the rotation of the bolt screw (23) in which the mother piston (24) presses against a jaw (5); and a pressure nut (33), which is connected to a circumference of the nut piston (24) by the bolt-nut fastening, is moved in an axial direction in conjunction with a drive of a second motor, is brought into contact with the bolt screw (23) and thus prevents the nut piston (24) from being pressed due to a reaction force of the jaw (5), wherein the first motor, the bolt (23) and the piston nut are components of a service brake (2) for reducing the speed of a vehicle or for bringing the vehicle to a sudden stop, the service brake (2) further comprises: a first drive force transmission device (22) which transmits a rotational force of the first motor (21) to the bolt screw (23), wherein the first drive force transmission device (22) comprises: a drive gear which is supplied with driving force by the first motor (21) and is thereby rotated; and a driven gear which engages with the drive gear, is thereby rotated at a reduced speed and is combined coaxially with the bolt (23), wherein the bolt (23) has: a gear assembly section with a polygonal cross-section, installed in such a way that it passes through a screw connection hole in the driven gear and is moved axially along the screw connection hole; and a screw extension section shaped in such a way that it is coaxially continuous with the gear assembly section and is connected to the nut piston (24) by the screw and nut fastening.

Description

BACKGROUND

[0001] The present disclosure relates to a drum brake and an electronic parking brake, and in particular to a drum brake and an electronic parking brake which are capable of holding a vehicle at a standstill by means of an actuator. BACKGROUND DISCUSSION

[0002] A service brake is typically used to reduce a vehicle's speed or bring it to a sudden stop, while a parking brake is used to park the vehicle or hold it stationary. A drum brake is a device that slows down or stops a vehicle by generating friction with a drum that rotates with a wheel. The drum brake is mounted on a backplate facing an inner circumferential surface of the drum. The drum brake presses against a pair of shoes, to which a friction material is attached, in the direction of the drum, thus causing friction with the drum and generating a braking force for service braking and parking.

[0003] An electromechanical brake (hereinafter referred to as "EMB") is a braking device that utilizes a force amplified by a motor, a gearbox, and a screw. An electronic control unit (hereinafter referred to as "ECU") converts the pressure of a driver's brake pedal into an electrical signal. The EMB then applies a braking force corresponding to this electrical signal. An electronic parking brake (hereinafter referred to as "EPB") is a braking device that operates electronically. When the vehicle comes to a standstill, the ECU measures the vehicle speed and engine rotation, detects a braking action or similar event, and thus initiates a holding action by applying the brakes.

[0004] To perform a service parking maneuver, the vehicle must be automatically held out of a braking state after the EMB (Electronic Brakeforce Unit) is activated. A screw used for the EMB must not be self-locking. To meet the requirement that the screw must not be self-locking, a screw with a high pitch or a ball screw with a larger pitch or a greater number of leads must be used. Conversely, to perform the braking maneuver for parking, the braking state must be maintained after the EPB (Electronic Brakeforce Unit) is engaged. Therefore, a screw used for the EPB must be self-locking. Thus, the characteristics of the screw required for service braking differ from those required for braking for parking.

[0005] A drum brake in the related prior art has a structure in which a screw for service braking and a screw for parking braking are provided separately, and a structure in which a component for amplifying the force of the screw for service braking and a component for amplifying the force of the screw for parking braking are provided separately. This results in a problem: the number of components is increased, the layout becomes more complex, and therefore manufacturing costs are increased.

[0006] Therefore, there is a need to solve this problem.

[0007] From DE 602 22 989 T2, an electromechanical multi-disc brake actuator for a transport device is known. The actuator comprises a first reversible unit, which includes a central screw, a first electric motor which is intended to rotate the central screw, a first nut which can be axially displaced on the central screw when the latter is set in rotation, and devices which are inserted between the central screw and the first nut to enable a reversible displacement of at least one of these two devices; and a second irreversible unit comprising an annular screw rigidly connected externally to the first nut, a second electric motor designed to rotate the annular screw and the first nut, a second nut that is locked in rotation relative to the frame but can be axially displaced on the annular screw when the latter is set in rotation, the annular screw and the second nut being engaged by means of their threads which make their displacement irreversible, and a piston provided at one end of the second nut to press the discs against each other to ensure service braking of the transport device when the first motor is actuated and parking braking when the second motor is actuated.

[0008] A parking brake device is known from DE 20 2020 105 157 U1. The device comprises a bolt that is rotated by a drive force transmitted by an actuator, one or more pistons arranged on one or both sides of the bolt, one or more nuts that are received in the piston, screwed to one end of the bolt and moved together with the rotation of the bolt, one or more elastic elements arranged around the nut in the piston that are elastically deformed in response to a displacement of the nut while the nut is moved by a defined distance to push the piston towards a brake shoe, and a load transmission unit arranged in the piston and designed to transmit a displacement of the nut to the piston.if the nut moves more than the specified distance, thereby pushing the piston towards the brake shoe.

[0009] From US patent 2001 / 0037919A1, a brake device actuator and a brake device with such an actuator are known.

[0010] The background of the present disclosure is disclosed in Korean patent KR 10 2 288 508 B1 (registered on August 4, 2021 and entitled “Electronic Parking Brake”). SUMMARY

[0011] One objective of the present disclosure is to provide a drum brake and an electronic parking brake that are capable of using a simple structure in which a service brake and a parking brake share a screw.

[0012] According to one aspect of the present disclosure, a drum brake is provided comprising: a bolt screw which is rotated in conjunction with a drive of a first motor; a nut piston which is connected to a circumference of the bolt screw by a bolt-nut fastening and which, in conjunction with the rotation of the bolt screw, is moved in a direction in which the nut piston presses against a shoe; and a pressure nut which, in conjunction with the bolt-nut fastening, is connected to a circumference of the nut piston and is moved in an axial direction in conjunction with a drive of a second motor, is brought into contact with the bolt screw and thus prevents the nut piston from being pressed due to a reaction force of the shoe.

[0013] In a drum brake, the first motor, bolt, and nut piston can be components of a service brake for reducing a vehicle's speed or for bringing the vehicle to a sudden stop; the second motor and pressure nut can be components of a parking brake for parking the vehicle or for holding the vehicle at a standstill; and the pressure nut and bolt bolt can be axially spaced apart in a state where the nut piston is driven by the first motor against the brake shoe, and the pressure nut can be moved by the drive of the second motor towards the bolt bolt and thus be brought into contact with the bolt bolt.

[0014] In the drum brake, an inner circumferential section of the nut piston and an outer circumferential section of the bolt screw can have a screw structure in which, in a state where the nut piston presses against the shoe when the first motor stops being driven, the nut piston is not self-locking in response to the reaction force of the shoe, and an inner circumferential section of the pressure nut and an outer circumferential section of the nut piston can have a screw structure in which, in a state where the pressure nut is brought into contact with the bolt screw in the axial direction when the second motor stops being driven, the nut piston is self-locking in response to the reaction force of the shoe.

[0015] In the drum brake, the first motor, the bolt, and the nut piston can be components of a service brake for reducing the speed of a vehicle or for bringing the vehicle to a sudden stop, wherein the service brake can further comprise a first drive force transmission device that transmits a rotational force from the first motor to the bolt, wherein the first drive force transmission device can comprise: a drive gear which is supplied with drive force from the first motor and is thereby rotated; and a driven gear which is in mesh with the drive gear, is thereby rotated at a reduced speed, and is combined coaxially with the bolt.

[0016] In the drum brake, the bolt may comprise: a gear assembly section with a polygonal cross-section, installed in such a way that it passes through a bolt combination hole in the driven gear and is moved sliding along the bolt combination hole in the axial direction; and a bolt extension section formed in such a way that it is coaxially continuous with the gear assembly section and is combined with the nut piston by the bolt-nut fastening.

[0017] In the drum brake, the screw extension section may have a smaller diameter than the gear assembly section, and the pressure nut may be arranged in such a way that it faces a first-sided side surface section in the axial direction of the gear assembly section.

[0018] In the drum brake, the bolt screw can have: a gear assembly section to which a rotational force is supplied by the first motor; a screw extension section formed in such a way that it continues coaxially and continuously with the gear assembly section and is connected to the nut piston by the bolt-nut fastening; and a pressure contact section arranged on the gear assembly section or the screw extension section in such a way that it faces the pressure nut in the axial direction and is brought into contact with the pressure nut.

[0019] In the drum brake, the bolt may comprise: a gear assembly section supplied with a rotational force from the first motor; a bolt extension section combined with the nut piston by the bolt-nut fastening; a fastening section formed between the gear assembly section and the bolt extension section, and formed in a manner that is coaxially continuous with the gear assembly section and the bolt extension section; a pressure plate attached to the fastening section and arranged in a manner that projects further in a radial direction than the bolt extension section; and a pressure contact section arranged on the pressure plate in a manner that is opposite the pressure nut in the axial direction and is brought into contact with the pressure nut.

[0020] In the drum brake, the gear assembly section can have a smaller diameter than the screw extension section, and the pressure nut can be arranged in such a way that it is opposite a first-side side surface section in the axial direction of the pressure plate.

[0021] In the case of the drum brake, the mounting section can be provided with an external thread, and the pressure plate can be fastened by combining an internally pinned ring element with the mounting section via the bolt-nut fastening.

[0022] In the case of the drum brake, the second motor and the pressure nut can be components of a parking brake for parking a vehicle or for holding the vehicle when stopped, wherein the parking brake can further comprise a second drive force transmission device which transmits a rotational force from the second motor to the pressure nut, and wherein the second drive force transmission device can comprise: a first gear connected to the second motor; and a second gear, of which a first-sided section engages with the first gear, thereby rotating it at a reduced speed, and of which a second-sided section engages with the pressure nut.

[0023] In the case of the drum brake, the pressure nut, which has a larger diameter than the second gear, can be brought into engagement with the second gear and have such a length in the axial direction that the pressure unit is movable in such a way that it is brought into contact with or spaced apart from the bolt screw while remaining engaged with the second gear.

[0024] The drum brake can further comprise a housing with a connecting space in which the bolt, the nut piston and the pressure nut are housed, wherein the housing can comprise: a first housing unit in which a section of a service brake is housed; a second housing unit in which a section of a parking brake is housed; and a combination cylinder unit, which is designed in the form of a hollow cylinder in a section in which the first housing unit and the second housing unit are combined, and which accommodates the bolt, the nut piston and the pressure nut.

[0025] In the drum brake, the second housing unit can comprise: a motor mounting unit that accommodates the second motor; a gear mounting unit that accommodates a second drive force transmission device that transmits a rotational force from the second motor to the pressure nut; and a piston mounting unit, one end section of which, facing the first housing unit, is combined with the first housing unit, thereby forming the combination cylinder unit, and the other section of which, facing the shoe, has the mother piston installed by passing through it, the piston mounting unit being designed in a manner that communicates with the gear mounting unit, and the second motor being arranged in front of a backplate in a manner that is parallel to the mother piston and the pressure nut.

[0026] According to a further aspect of the present disclosure, an electronic parking brake is provided comprising: a second motor; a pressure nut connected by a bolt-nut fastening to a circumference of a nut piston of a service brake, which presses against a shoe, in connection with the drive of the second motor, which is moved in an axial direction and is brought into contact with a bolt screw connected by the bolt-nut fastening to the nut piston, thereby preventing the nut piston from being pushed due to a reaction force of the shoe; and a second drive force transmission device which transmits a rotational force of the second motor to the pressure nut.

[0027] In the electronic parking brake, the pressure nut can have: a nut main body arranged on a circumference of the nut piston; a screw combination section formed on an inner circumferential section of the nut main body and combined with the nut piston by the bolt-nut fastening; a toothed section formed on an outer circumferential section of the nut main body and supplied with the rotational force from the second motor; and a screw fastening release section formed on an end section of the nut main body and brought into contact with the bolt screw in the axial direction when the nut main body is moved.

[0028] In the electronic parking brake, the screw fastening release section may comprise: a limiting clamping jaw formed on an end section in the axial direction of the nut main body in such a way that it projects inwards towards the axial center and is arranged in such a way that it faces the nut piston positioned inside the nut main body in the axial direction; and a screw contact section formed on the limiting clamping jaw in such a way that it projects in the axial direction and faces the bolt screw in the axial direction and is then brought into contact with it.

[0029] In the electronic parking brake, the inner circumferential sections of the limiting clamping jaw and the screw contact section can each have a larger diameter than the bolt and be spaced apart from a circumference of the bolt, and the driving force transmitted from the second motor to the main nut body can serve as a load exerted on the bolt in the axial direction via the screw contact section.

[0030] In the electronic parking brake, when the second motor is driven in a forward direction, the pressure nut can be moved to one side in the axial direction until the screw contact section is pressed against the bolt screw in the axial direction and brought into contact with it, and when the second motor is driven in a reverse direction, the pressure nut can be moved to the other side in the axial direction until the limiting clamping jaw is brought into contact with the nut piston in the axial direction.

[0031] In the electronic parking brake, at least one section of the second motor can be housed together in a housing containing the bolt, the nut piston and the pressure nut, and can be arranged on one side of a plate surface of a back plate in a manner parallel to the bolt, the nut piston and the pressure nut.

[0032] The drum brake according to the present disclosure has a structure in which the service brake and the parking brake are coaxially combined. In particular, according to the present disclosure, the drum brake has a structure in which the bolt and the nut piston of the service brake and the pressure nut of the parking brake are coaxially combined by the bolt-nut connection. In other words, the parking brake according to the present disclosure has a simple structure in which the pressure nut is additionally connected to the circumference of the nut piston provided in the service brake by the bolt-nut connection. That is to say, the drum brake according to the present disclosure has a simple structure in which the service brake and the parking brake share a screw corresponding to the bolt.

[0033] Accordingly, the structures described above, as disclosed herein, offer the following advantages when compared to the case where the service brake and the parking brake are arranged independently in the related prior art; in other words, when compared to the case where the service brake and the parking brake are spaced apart and thus separated from each other. The number of components and the volumetric weight of the service brake and the parking brake can be significantly reduced, and space utilization and layout design freedom can be further improved. Furthermore, manufacturing costs and productivity can be enhanced.

[0034] Furthermore, the parking brake is applied by pressing against the bolt using the pressure nut, thus preventing the piston from rotating. Consequently, compared to the prior art parking brake where the shoe is directly pressed, the parking brake can be applied stably with a significantly lower load. This allows for a smaller motor, drive power transmission device, and housing, resulting in a reduction in weight. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view schematically showing a drum brake according to a first embodiment of the present disclosure. Fig. Figure 2 is a perspective view showing essential components of the drum brake in Fig. 1 shows. Fig. Figure 3 is a cross-sectional view showing the essential components of the drum brake in Fig. 1 shows. Fig. Figure 4 is a perspective view showing other essential components of the drum brake in Fig. 1 shows. Fig. Figure 5 is a perspective exploded view showing the other essential components of the drum brake in Fig. 1 shows. Fig. Figure 6 is an operating view showing a state in which a service brake according to the first embodiment of the present disclosure is performing a braking action. Fig. Figure 7 is an operating view showing a state in which braking is performed by a parking brake according to the first embodiment of the present disclosure. Fig. Figure 8 is a cross-sectional view schematically showing essential components of a drum brake according to a second embodiment of the present disclosure. Fig. Figure 9 is a perspective view that schematically shows the essential components of the drum brake according to the second embodiment of the present disclosure. Fig. Figure 10 is a perspective exploded view schematically showing the essential components of the drum brake according to the second embodiment of the present disclosure. Fig. Figure 11 is an operating view showing a state in which braking is performed by a service brake according to the second embodiment of the present disclosure. Fig. Figure 12 is an operating view showing a state in which braking is performed by a parking brake according to the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE ILLUSTRATED EXECUTION FORMS

[0035] A drum brake and an electronic parking brake according to embodiments of the present disclosure are described below with reference to the accompanying drawings. For the sake of clarity and simplicity of description, the line thicknesses, component sizes, and the like may be shown in the drawings in an approximate proportion. Furthermore, a term to be assigned to a component according to the present disclosure is defined taking into account a function of the component and may vary depending on the intention of a user or manager, or based on established engineering practices. Therefore, the term should be defined in the context of this specification.

[0036] Fig. Figure 1 is a perspective view schematically showing a drum brake 1 according to a first embodiment of the present disclosure. Fig. Figure 2 is a perspective view showing essential components of the drum brake in Fig. 1 shows. Fig. Figure 3 is a cross-sectional view showing the essential components of the drum brake in Fig. 1 shows.

[0037] With reference to the Fig. 1, Fig. 2 to Fig. 3 The drum brake 1 according to the first embodiment of the present disclosure has a configuration in which a service brake 2 for reducing the speed of a vehicle or for suddenly stopping the vehicle and a parking brake 3 for parking the vehicle or for holding the vehicle at a standstill share a screw element corresponding to a bolt 23 and are arranged in a common connection space.

[0038] The service brake 2 according to the first embodiment of the present disclosure performs a pushing and sliding operation against a shoe 5 by rotating the bolt screw 23 in conjunction with a drive of a first motor 21 and moving a nut piston 24, which is connected to a circumference of the bolt screw 23 by a bolt-nut fastening, in an axial direction (see Fig. 6).

[0039] The parking brake 3 according to the first embodiment of the present disclosure is combined by the bolt-nut fastening with a circumference of the nut piston 24 in a manner that overlaps a pressure nut 33, and performs an operation which prevents the nut piston 24 from being pushed in the opposite direction due to a reaction force of the jaw 5 by moving the pressure nut 33 in the axial direction in conjunction with a drive of a second motor 31 and thus pressing against the pressure nut 33 in the axial direction and thus bringing the pressure nut 33 into contact with the bolt screw 23 (see Fig. 7).

[0040] In Fig. 3 The bolt 23 is arranged in a manner extending in a transverse direction. For simplicity, the transverse direction is defined below as the axial direction or as the left-right direction. A positional relationship and a combinational relationship between the components are described below according to this definition. A section of the bolt 23 that is brought into contact with the pressure nut 33 in the axial direction is referred to in this description as a pressure contact section 235.

[0041] The pressure nut 33 is located between the pressure contact section 235 on the left side of Fig. 3 and the mother piston 24 on its right side. A section of the left side of the pressure nut 33 is detachably attached to the pressure contact section 235 according to its position in the axial direction of the pressure nut 33. Although the position in the axial direction of the pressure nut 33 varies, a section of the right side of the pressure nut 33 is always held in conjunction with the circumference of the mother piston 24 by the bolt-nut attachment.

[0042] When the pressure nut 33 is brought into contact with the pressure contact section 235 of the bolt 23 while being moved axially in a state where it is connected to the nut piston 24, the pressure nut 33 additionally pushes against the nut piston 24 to the left and the bolt 23 to the right. Accordingly, the nut piston 24 can be prevented from being pushed towards the pressure contact section 235 due to the reaction force of the jaw 5.

[0043] According to the first embodiment of the present disclosure, as described above, braking to parking can be carried out by moving the pressure nut 33 with the drive of the second motor 31 into a state in which the nut piston 24 with the drive of the first motor 21 presses against the jaw 5. At this point, at least under a load high enough to limit rotation of the nut piston 24 (return to a stationary position), Fig. 3 (waiting position shown), the pressure nut 33 must be brought into contact with the pressure contact section 235.

[0044] The parking brake 3 in the related prior art is provided and configured separately from the service brake 2 to press directly against the shoe 5. Accordingly, the related art requires a second motor 31, a second drive force transmission device 32, and the like to ultimately apply a load of 1200 to 1400 kg. However, according to the present disclosure, braking for parking can be carried out stably by applying a remarkably low load of 10 to 20 kg.

[0045] Fig. Figure 4 is a perspective view showing other essential components of the brake drum. Fig. 1 shows. Fig. Figure 5 is a perspective exploded view showing the other essential components of the brake drum in Fig. 1 shows.

[0046] Referring to Fig. 3, Fig. 4 to Fig. 5 comprises the service brake 2 according to the first embodiment of the present disclosure comprising the first motor 21, a first drive force transmission device 22, the bolt screw 23 and the nut piston 24.

[0047] In relation to Fig. In the first embodiment, the bolt 23 and the nut piston 24 are arranged in front of a backplate 6 (on one side of a plate surface therein), and the first motor 21 is arranged behind the backplate 6 (on the other side of the plate surface therein). The first drive force transmission device 22 is arranged on the backplate 6 in such a way that it penetrates it and transmits a rotational force from the first motor, which is arranged behind the backplate 6, to the bolt 23 located in front of the backplate 6. The first drive force transmission device 22 according to the first embodiment of the present disclosure comprises a drive gear 221 and a driven gear 222.

[0048] The drive gear 221 is a gear element connected to an output shaft of the first motor 21. The drive gear 221 has a worm gear structure and is driven by the first motor 21, causing it to rotate in a regular position. The driven gear 222 is a gear element that transmits a rotational force from the drive gear 221 to the bolt 23. The driven gear 222 has a gear-to-gear structure, is installed in such a way that it engages with the drive gear 210, and is rotated by it in a regular position at a reduced speed.

[0049] The driven gear 222 has a screw combination hole 223. The bolt 23 is combined with the screw combination hole 223 by passing through it. The bolt 23 is installed in the screw combination hole 223 by passing through it axially. When the first motor 21 is driven, the bolt 23 rotates with the same rotational movement as the driven gear 222. The bolt 23 according to the first embodiment of the present disclosure comprises a gear assembly section 231, a bolt extension section 232, and the pressure contact section 235.

[0050] The gear assembly section 231 is a section of the bolt 23, which is supplied with a rotational force by the first motor 21 via the first drive force transmission device 22. The gear assembly section 231 is installed such that it extends axially through the bolt combination hole 223 in the driven gear 222 and has a cross-section with a fixed shape with respect to the axial direction. Accordingly, the bolt 23 is slidably movable in the axial direction when guided by an edge section of the bolt combination hole 223.

[0051] Furthermore, the gear assembly section 231 and the screw combination hole 223 each have a non-circular cross-section, for example, a polygonal cross-section. Accordingly, when the driven gear 222 is rotated, the screw 23 can be rotated stably with the same rotational movement as the driven gear 222.

[0052] The screw extension section 232 is a section of the bolt 23 that is connected to the nut piston 24 by the bolt-nut connection. The screw extension section 232 is formed such that it is coaxially connected to the gear assembly section 231. A circumference of the screw extension section 232 is externally threaded such that the nut piston 24 can be connected to the screw extension section 232 by the bolt-nut connection. The externally threaded screw extension section 232 according to the first embodiment of the present disclosure has a tap-and-screw structure.

[0053] The screw extension section 232 has a smaller diameter than the gear assembly section 231. The screw extension section 232 has a circular cross-section, while the gear assembly section 231 as a whole has a cross-section that is not circular. Accordingly, a right-hand side surface section of the gear assembly section 231, located at a boundary between the gear assembly 231 and the screw extension section 232, has the shape of a hook-shaped clamping jaw.

[0054] The gear assembly section 231 is arranged such that its right-hand side surface section faces a left-hand side surface section of the pressure nut 33, which is connected to the circumference of the nut piston 24 by the bolt-nut fastening, in the axial direction. When the pressure nut 33 is moved to the left, the surface section of its right side is pressed against the pressure nut 33 and brought into contact with it. That is, the right-hand side surface section of the gear assembly section 231, which is designed to project further in a radial direction than the screw extension section 232, is the pressure contact section 235 to which the pressure nut 33 is detachably attached.

[0055] The mother piston 24 is connected to the circumference of the bolt 23 by the bolt-nut fastening and is moved axially (to the right) in conjunction with a rotation of the bolt 23, thereby pressing against and pushing the jaw 5. The mother piston 24 has a helical structure in which, in response to the reaction force of the jaw 5, the mother piston 24 is not self-locking when the first motor 21 is no longer driven in a state where the mother piston 24 presses against the shoe 5. An end section of the mother piston 24, which is brought into contact with the jaw 5, has a pincer-like shape such that this end section faces the front and rear surface sections of the jaw 5 and is then brought into contact with them. Accordingly, the mother piston 24 can only be moved axially, without being rotated.

[0056] When the master piston 24 is described as non-self-locking in this description, this means the following: In a state where the bolt 23 is rotated in a forward direction in connection with the drive of the first motor 21, and where the master piston 24 is moved to the right, thereby pressing against and pushing the jaw 5, the master piston 24 will be pushed to the left by itself due to the reaction force of the jaw 5 exerted on the master piston 24 when the first motor 21 ceases to be driven, i.e., when the braking action for the service brake of the vehicle is no longer performed. At this point, the master piston 24 only has a linear motion in the axial direction, so that the bolt 23 is rotated in the opposite direction.

[0057] Various factors, such as the helix angle of a threaded surface, the pitch, the number of threads, the type of screw, the material, and the surface roughness, can be comprehensively considered when designing a screw assembly in which the nut piston 24 is not self-locking. For example, the larger the helix angle of the threaded surface, the lower the force that can be exerted to rotate it under an axial load. In other words, the larger the helix angle, the more easily the nut piston 24 can be displaced by the reaction force of the jaw 5. In this way, a design in which the nut piston 24 is not self-locking can be easily implemented.

[0058] The service brake 2 according to the first embodiment of the present disclosure is described above to disclose the service brake 2 according to a preferred embodiment of the present disclosure and is not intended to specifically limit a 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, including those in the related prior art, as long as it has a configuration in which, in conjunction with the drive of the first motor 21, the screw 23 is rotated and the nut piston 24 is moved in the axial direction.

[0059] As in the Fig. 3, Fig. 4 to Fig. As shown in Figure 5, the parking brake 3 according to the first embodiment of the present disclosure comprises the second motor 31, the second drive force transmission device 32 and the pressure nut 33.

[0060] The second motor 31 can be provided separately from the first motor 21 and arranged in front of the backplate 6 (on one side of the plate surface) in a manner parallel to the bolt 23 and the nut piston 24. The second motor 31 can also be arranged together with the first motor 21 behind the backplate 6. However, the smaller the second motor 31, the easier it is to arrange the second motor 31 together with the second drive force transmission device 32 in front of the backplate 6.

[0061] The second motor 31, if intended to be positioned in front of the backplate 6, is arranged in a state in which one or all sections thereof are housed in a casing 40 which has a connecting space in which the bolt 23, the piston 24 and the pressure nut 33 are housed. The second motor 31 can be arranged in a second casing unit 42 (described below) of the casing 40 and can thus be arranged parallel to the backplate 6 together with the bolt 23, the piston 24 and the pressure nut 33.

[0062] In a case where the second motor 31 is arranged in front of the backplate 6, there is no need to create a through-hole in the backplate 6 to transmit the output of the second motor 31 to the pressure nut 33. Therefore, the overall structural rigidity of a device including the backplate 6 can be more reliably ensured. Furthermore, since the second motor 31 is positioned closer to the pressure nut 33, the drive force can be transmitted more efficiently, and the second drive force transmission device 32 can also be miniaturized.

[0063] The second drive force transmission device 32 transmits a rotational force from the second motor 31 to the pressure nut 33. The second drive force transmission device 32 according to the first embodiment of the present disclosure comprises a first gearbox 321 and a second gearbox 322.

[0064] The first gear 321 is a transmission element connected to an output shaft of the second motor 31. The second gear 322 is a speed-reducing gear element that transmits a rotational force from the first gear 321 to the pressure nut 33. The second gear 322 has a larger diameter than the first gear 321 and meshes with the first gear 321. A first-sided section of a circumference of the second gear 322, which has teeth, meshes with the first gear 321, and a second-sided section of this meshes with an outer circumferential section of the pressure nut 33, more precisely with a toothed section 333 (described below) of the pressure nut 33.

[0065] The pressure nut 33 has a larger diameter than the second gear 322. The pressure nut 33 is connected to the circumference of the nut piston 24 by the bolt-nut fastening and engages with the second gear 322. The screw extension section 232 of the bolt 23 has a smaller diameter than the gear assembly section 231. The pressure nut 33 is moved axially in conjunction with the drive of the second motor 31 and is thereby brought into contact with or spaced apart from the bolt 23 in the axial direction.

[0066] More precisely, the pressure nut 33 is arranged on the same axis as the screw extension section 232, but in such a way that it faces a first-sided side surface section in the axial direction of the gear assembly section 231. In a state where it is brought into contact with the bolt 23 in the axial direction, the pressure nut 33 prevents the nut piston 24 from being depressed due to the reaction force of the jaw 5. The pressure nut 33 according to the first embodiment of the present disclosure comprises a nut main body 331, a screw connection section 332, the toothed section 333, and a screw fastening / unfastening section 334.

[0067] The main body of the nut 331 is a section of the pressure nut 33 that forms a main body of the pressure nut 33. The main body of the nut 331 has the shape of a tube, a pipe, or a ring with inner and outer circumferential sections and is arranged on the circumference of the nut piston 24. The main body of the nut 331 maintains a state in which the screw connection section 332 is connected to the nut piston 24 by the bolt-nut fastening and in which the toothed section 333 is engaged with the second gear 322, and has such a length in the axial direction that the screw fastening-release section 334 is movable in such a way that it is brought into contact with or spaced apart from the bolt 23.

[0068] The screw connection section 332 is a section of the pressure nut 33 that is connected to the circumference of the nut piston 24 by the bolt-nut fastening. The screw connection section 332 is formed as an internal threaded section on the inner circumferential section of the nut main body 331. In this configuration, the screw connection section 332 has the screw structure in which the nut piston 24 is self-locking in response to the reaction force of the jaw 5.

[0069] In a state where the vehicle's speed is reduced or where pressure is applied against the shoe 5 to bring the vehicle to a sudden stop, i.e., in a service braking state, the piston 24 has a structure in which it is not self-locking in response to the reaction force of the shoe 5 when the first motor 21 ceases to be driven, e.g., due to a helix angle so large that the piston 24 is not self-locking. In this structure, the piston 24 is connected to the bolt 23 by means of a bolt-nut fastening.

[0070] In contrast, when the pressure nut 33 is pressed axially against and in contact with the bolt 23 to park or hold the vehicle stationary (i.e., in a parking brake state), it has a structure in which the nut piston 24 is self-locking in response to the reaction force of the shoe 5 when the second motor 31 is no longer driven. With this structure, the pressure nut 33 is connected to the nut piston 24 by the bolt-nut connection.

[0071] That is, the screw connection section 332 of the pressure nut 33 is connected to the nut piston 24 by the bolt-nut fastening, with the screw structure in which, when it is turned, the pressure nut 33 is moved along the nut piston 24 in the axial direction, but when the nut piston 24 is pushed in the axial direction, the pressure nut 33 can be held stationary without being turned, for example with such a small helix angle that the nut piston 24 can be self-locking.

[0072] The gear section 333 is a section of the pressure nut 33 that is supplied with a rotational force by the second motor 31. The gear section 333 is formed on the outer circumferential section of the main nut body 331. If the first gear 321 and the second gear 322 have a spur gear structure, the gear section 333 can also have a corresponding spur gear structure. This gear is not specifically limited in its structure and type. In addition to the spur gear structure, any structure capable of transmitting the rotational force can be used.

[0073] The screw fastening release section 334 is located at an end section in the axial direction (an end section on the left side of Fig. 3) of the main nut body 331. When the main nut body 331 is moved to the left, the screw fastening and release section 334 is brought into contact with the bolt 23 in the axial direction. The screw fastening and release section 334 according to the first embodiment of the present disclosure comprises a limiting clamping jaw 335 and a screw contact section 336.

[0074] The limiting clamping jaw 335 is located at one end section in the axial direction (one end section on the left side in Fig. 3) of the main body of the nut 331 is designed such that it projects inwards towards the axial center. The limiting clamping jaw 335 is arranged such that it projects in the axial direction (in the left-right direction) towards an end section of the left side of the nut piston 24, which is located inside the main body of the nut 331. Fig. 3) is opposite and defines a limit to which the pressure nut 33 is moved to the right in relation to the mother piston 24.

[0075] The limit clamping jaw 335 is shaped such that it projects inwards in the direction of the axial center, but extends to a position spaced apart from the bolt 23 without coming into contact with it. In other words, if the limit clamping jaw 335 has the shape of a circle as a whole, the limit clamping jaw 335 has an inner circumferential section that has a larger diameter (width) than the screw extension section 232 of the bolt 23. That is, the limit clamping jaw 335 is spaced apart from the circumference of the bolt 23.

[0076] The screw contact section 336 is formed on the limiting clamping jaw 335 in such a way that it projects from it in the axial direction, in particular in the direction of the gear assembly section 231 and the pressure contact section 235 (to the left in Fig. 3) The screw contact section 336 is formed at a position on the limiting clamping jaw 335 facing the pressure contact section 235, in such a way that it projects away from it. An inner circumferential section of the screw contact section 336 is spaced apart from the circumference of the bolt 23.

[0077] More precisely, the pressure contact section 235 is shaped like a ring such that its radial width corresponds to the difference in diameter between the gear assembly section 231 and the screw extension section 232, and the screw contact section 336 has an annular cross-section such that it is aligned with the pressure contact section 235. Accordingly, when the pressure nut 33 is moved to the left, the screw contact section 336 can be pressed precisely against the pressure contact section 235 and brought into contact with it. The driving force transmitted from the second motor 31 to the pressure nut 33 ultimately acts as a load that is exerted axially through the screw contact section 336 onto the pressure contact section 235 of the bolt 23.

[0078] When the second motor 31 is driven in the forward direction, the pressure nut 33 can be moved to a maximum position to the left, until the screw contact section 336 is pressed against the bolt 23 and makes axial contact with it. When the second motor 31 is driven in the reverse direction, the pressure nut 33 can be moved to a maximum position to the right, until the limit clamping jaw 335 makes axial contact with the nut piston 24.

[0079] The drum brake 1 according to the first embodiment of the present disclosure has a configuration in which the service brake 2 and the parking brake 3 share a screw element corresponding to the bolt 23 and are arranged in a communication space. With reference to the Fig. 1, Fig. 2 to Fig. 3. According to the first embodiment of the present disclosure, the drum brake 1 can comprise the housing 40 as a constitutive element that forms a connecting space for it.

[0080] The housing 40 has a structure in which the bolt 23, the piston nut 24, and the pressure nut 33 may be housed in a connection space. The housing 40 according to the first embodiment of the present disclosure comprises a first housing unit 41, a second housing unit 42, and a combination cylinder unit 43.

[0081] The first housing unit 41 has a structure in which the service brake 2 may be housed. The second housing unit 42 has a structure in which the parking brake 3 may be housed. The combination cylinder unit 43 is a section of the housing 40 in which the bolt 23, the nut piston 24, and the pressure nut 33 are housed. The combination cylinder unit 43 is formed in the form of a hollow cylinder in a section in which the first housing unit 41 and the second housing unit 42 are combined.

[0082] A section other than a section of the service brake 2, which is housed in the combination cylinder unit 43, may be housed in the first housing unit 41. A section other than a section of the parking brake 3, which is housed in the combination cylinder unit 43, may be housed in the second housing unit 42. The second housing unit 42 according to the first embodiment of the present disclosure comprises a motor mounting unit 421, a transmission mounting unit 422, and a piston mounting unit 423.

[0083] The engine mounting unit 421 is designed to accommodate possibly one or all sections of the second engine 31. The transmission mounting unit 422 is designed to accommodate possibly the second drive power transmission device 32. The piston mounting unit 423 is designed to be combined with the first housing unit 41 and to possibly form the combination cylinder unit 43.

[0084] A terminal section (a terminal section on the left side of Fig. 3) The piston receiving unit 423, which faces the first housing unit 41, is connected to the first housing unit 41, and the piston receiving unit 423 forms the combination cylinder unit 43. The mother piston 24 is attached to the other end section (an end section on the right side of Fig. 3) the piston receiving unit 423, which faces the jaw 5, is arranged in a manner that passes through the combination cylinder unit 43 from the inside to the outside.

[0085] Fig. Figure 6 is an operating view showing a state in which braking is carried out by the service brake 2 according to the first embodiment of the present disclosure. Fig. Figure 7 is an operating view showing a state in which braking is carried out by the parking brake 3 according to the first embodiment of the present disclosure.

[0086] In relation to Fig. 6. According to the first embodiment of the present disclosure, the service brake 2 performs the operation of pressing and pushing the shoe 5 by rotating the bolt screw 23 in conjunction with the drive of the first motor 21 and moving the nut piston 24, which is connected to the circumference of the bolt screw 23 by the bolt-nut fastening, in the axial direction.

[0087] With reference to Fig. 7 The parking brake 3 according to the first embodiment of the present disclosure is connected to the circumference of the nut piston 24 by the bolt-nut fastening in a manner that overlaps the pressure nut 33, and carries out the process of preventing the nut piston 24 from being pushed in the opposite direction due to the reaction force of the jaw 5 by moving the pressure nut 33 in the axial direction in conjunction with the drive of the second motor 31 and pressing against the pressure nut 33 in the axial direction and thus bringing the pressure nut 33 into contact with the gear assembly section 231 of the bolt screw 23.

[0088] In an initial state, as in Fig. Figure 3 shows that the first motor 21 is driven in the forward direction, and the mother piston 24 is, as in Fig. Figure 6 shows the jaw being moved to the right, pushing a right-hand jaw 5 of a pair of jaws 5 to the right and pressing against the jaw 5 on the right side. This action performs the service braking. At this point, the pressure nut 33 and the gear assembly section 231 of the bolt 23 are spaced apart axially.

[0089] Then, when the second motor 31 is driven in the forward direction, the pressure nut 33 is, as in Fig. As shown in Figure 7, the pressure nut 33 moves towards the gear assembly section 231 and the pressure contact section 235 of the bolt 23 and comes into contact with it. At this point, in a state where a first-sided side section of the pressure nut 33 is engaged with the nut piston 24, a second-sided side section of it is brought into contact with the bolt 23 in the axial direction, thus braking to park. Subsequently, although the second motor 31 ceases to be driven, this parking brake state is maintained due to the self-locking structure.

[0090] As in Fig. As shown in Figure 6, in a state where the pressure nut 33 is not in contact with the bolt 23, when the first motor 21 stops being driven (i.e., when only service braking is performed instead of braking to park), the nut piston 24 is pressed by itself due to the reaction force of the shoe 5, and the bolt 23 is turned in the opposite direction and reverses, as shown in Figure 6. Fig. 3 shown, back to their initial state.

[0091] In a case where the brake is released for parking, the following process can be carried out continuously. The first motor 21 is driven in the forward direction. This pushes the nut piston 24 further towards the shoe 5, and the pressure nut 33 is removed from the pressure contact section 235 of the bolt 23. Then the second motor 31 is driven in the opposite direction. By carrying out this process of releasing the brake for parking, the bolt 23, the nut piston 24, and the pressure nut 33 can be returned to their respective initial states, as shown in Fig. 3 shown.

[0092] Fig. Figure 8 is a cross-sectional view schematically showing essential components of a drum brake 1 according to a second embodiment of the present disclosure. Fig. Figure 9 is a perspective view that schematically shows the essential components of the drum brake 1 according to the second embodiment of the present disclosure. Fig. Figure 10 is a perspective exploded view in which the essential components of the drum brake 1 according to the second embodiment of the present disclosure are shown schematically.

[0093] With reference to the Fig. 8, Fig. 9 to Fig. 10. The drum brake 1 according to the second embodiment of the present disclosure differs from the drum brake 1 according to the first embodiment of the present disclosure, which is described in Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 is shown in that, in the drum brake 1 according to the second embodiment, the gear assembly section 231 of the bolt screw 23 has a smaller diameter than the screw extension section 232 and that the bolt screw 23 further comprises a fastening section 233 and a pressure plate 234.

[0094] Components of the drum brake 1 according to the second embodiment of the present disclosure, which are compared with those of the drum brake 1 according to the first embodiment of the present disclosure, which are described in the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. Items shown in section 7, which are identical, similar, or correspond to them, will not be described again below.

[0095] As in the Fig. 8, Fig. 9 to Fig. As shown in Figure 10, the bolt screw 23 according to the second embodiment of the present disclosure comprises the gear assembly section 231, the screw extension section 232, the fastening section 233, the pressure plate 234 and the pressure contact section 235.

[0096] The gear assembly section 231 is a section of the bolt 23, which is supplied with a rotational force by the first motor 21 via the first drive force transmission device 22. The gear assembly section 231 is installed such that it extends axially through the bolt connection hole 223 in the driven gear 222 and has a cross-section with a fixed shape with respect to the axial direction. Accordingly, the bolt 23, when guided through the edge section of the bolt connection hole 223, is slidably movable in the axial direction.

[0097] Furthermore, the gear assembly section 231 and the bolt connection hole 223 each have a non-circular cross-section, e.g., a polygonal cross-section. Accordingly, when the driven gear 222 is driven, the bolt 23 can be rotated stably with the same rotational movement as the driven gear 222.

[0098] The screw extension section 232 is a section of the bolt 23 that is connected to the nut piston 24 by the bolt-nut connection. The screw extension section 232 is formed on the same axis as the gear assembly section 231. The circumference of the screw extension section 232 is provided with an external thread so that the nut piston 24 can be connected to the screw extension section 232 by the bolt-nut connection. The screw extension section 232 according to the second embodiment of the present disclosure is provided with an external thread in such a way that it has a ball screw structure.

[0099] Normally, in a case where, as in the first embodiment of the present disclosure, the circumference of an end section of a rod-shaped element is internally threaded, depending on the ease with which the rod-shaped element is machined, a central section is pre-machined in the longitudinal direction of the rod-shaped element and then a rear end section thereof is machined. Accordingly, the end section that is internally threaded has a relatively smaller diameter than the central section. This can be applied to the bolt 23 according to the first embodiment of the present disclosure.

[0100] Unlike the case where the circumference of the end section of the rod-shaped element is internally threaded, in a case where, as in the second embodiment of the present disclosure, a ball screw is formed on the circumference of the end section of the rod-shaped element, the end section is pre-machined in the longitudinal direction of the rod-shaped element, and then the central section thereof is machined. Accordingly, the end section on which the ball screw is formed has a relatively larger diameter than the central section. This can be applied to the bolt 23 according to the second embodiment of the present disclosure.

[0101] The externally threaded screw extension section 232 of the bolt 23 according to the first embodiment of the present disclosure has a tap-and-screw structure. In contrast, the screw extension section 232 of the bolt 23 according to the second embodiment of the present disclosure has a ball-and-screw structure. In this way, the bolt 23 according to the present disclosure can have a diameter and a cross-section that each vary with position in a longitudinal direction, taking into account various conditions such as machining conditions, component specifications, and a layout relationship between the bolt 23 and each of the adjacent other components.

[0102] The fastening section 233 is a section of the bolt 23 to which the pressure plate 234 is attached. The fastening section 233 is formed between the gear assembly section 231 and the bolt extension section 232 and is designed such that it is coaxial with the gear assembly section 231 and the bolt extension section 232. According to the second embodiment of this disclosure, the fastening section 233 has a smaller diameter than the bolt extension section 232 and a larger diameter than the gear assembly section 231.

[0103] Accordingly, the pressure plate 234, which has the shape of a ring, can be guided through a circumference of the gear assembly section 231 and moved smoothly to the mounting section 233. When the pressure plate 234 reaches the mounting section 233, it is clamped at a boundary between the mounting section 233 and the screw extension section 232, which forms a stepped clamping jaw. This reliably prevents the pressure plate 234 from moving towards the screw extension section 232. The pressure plate 234 can thus be held firmly in a setting position where it is in contact with the screw extension section 232.

[0104] The pressure plate 234 is attached to the mounting section 233 and is arranged to project further in the radial direction than the screw extension section 232. Accordingly, a right-side side surface section of the pressure plate 234, which is brought into contact with or opposite the screw extension section 232, has the form of a hook clamping jaw.

[0105] The pressure plate 234 is arranged such that its right-hand side surface section faces the side surface section of the left side of the pressure nut 33, which is connected to the circumference of the nut piston 24 by the bolt-nut fastening, in the axial direction. When the pressure nut 33 is moved to the left, its right-hand side surface section is pressed against the pressure nut 33 and brought into contact with it. That is, the right-hand side surface section of the pressure plate 234, which is designed to project further in the radial direction than the screw extension section 232, is the pressure contact section 235 to which the pressure nut 33 is detachably attached.

[0106] The pressure plate 234 according to the second embodiment of the present disclosure has the shape of a ring. A section of the right side of the pressure plate 234, which faces the screw extension section 232, may have a larger diameter than a section of the left side thereof. An end section of the left side may have a polygonal cross-section, considering that the end section of the left side is intended to engage with a tool. This shape is disclosed as a desired example of the pressure plate 234 according to the present disclosure and is not intended to represent a limitation of the pressure plate 234.

[0107] Each pressure plate 234, which can form the hook clamping jaw in this way, can have various shapes, including the shape of a ring, and can be arranged on the mounting section 233. The pressure plate 234 can be fastened to the mounting section 233 by various methods, such as screw and nut fastening, pressure fixing (plastic deformation), and wrench insertion.

[0108] With regard to the structure, according to the second embodiment of the present disclosure, an inner circumferential section of the pressure plate 234 is provided with an internal thread and is fastened to the externally threaded mounting section 233 by means of a bolt-nut fastening. In a state in which the pressure plate 234 is fastened to the mounting section 233 in this manner by means of the bolt-nut fastening, the pressure plate 234 is pressed against the mounting section 233 and plastically deformed. For example, an internally threaded section of the pressure plate 234 can be pressed so strongly against an externally threaded section of the mounting section 233 that they can be crushed and permanently prevented from being separated from each other.

[0109] The pressure contact section 235 is formed on an end section of the right side of the pressure plate 234, which faces the pressure nut 33 in the axial direction. When the pressure nut 33 is moved in the axial direction, the pressure contact section 235 is brought into contact with or separated from an end section of the left side of the pressure nut 33. More precisely, the pressure contact section 235 can be shaped in the form of a ring such that its width in the radial direction corresponds to the difference in diameter between the pressure plate 234 and the screw extension section 232.

[0110] The screw contact section 336 has an annular cross-section oriented towards the pressure contact section 235. Accordingly, when the pressure nut 33 is moved to the left, the screw contact section 336 presses the pressure nut 33 precisely against the pressure contact section 235 and brings it into contact. The driving force transmitted from the second motor 31 to the pressure nut 33 ultimately acts as a load that is exerted in the axial direction via the screw contact section 336 onto the pressure contact section 235 of the bolt 23.

[0111] Fig. Figure 11 is an operating view showing a state in which braking is performed by the service brake 2 according to the second embodiment of the present disclosure. Fig. Figure 12 is an operating view showing a state in which braking is performed by the parking brake 3 according to the second embodiment of the present disclosure.

[0112] Referring to Fig. 11, according to the second embodiment of the present disclosure, the service brake 2 performs the operation of pushing and sliding the shoe 5 by rotating the bolt screw 23 in conjunction with the drive of the first motor 21 and moving the nut piston 24, which is connected to the circumference of the bolt screw 23 by the bolt-nut fastening, in the axial direction.

[0113] With reference to Fig. 12 The parking brake 3 according to the first embodiment of the present disclosure is connected to the circumference of the nut piston 24 by the bolt-nut fastening in a manner that overlaps the pressure nut 33, and performs the operation of preventing the nut piston 24 from being pushed in the opposite direction due to the reaction force of the jaw 5 by moving the pressure nut 33 in the axial direction in conjunction with the drive of the second motor 31 and pressing against the pressure nut 33 in the axial direction and thus bringing the pressure nut 33 into contact with the pressure plate 234 of the bolt screw 23.

[0114] In the initial state, as in Fig. Figure 8 shows that when the first motor 21 is driven in the forward direction, the mother piston 24 is, as in Fig. As shown in Figure 11, the jaw 5 moves to the right, pushing the right-hand jaw 5 of the pair of jaws 5 to the right and pressing against the jaw 5 on the right side. This action performs the service braking. At this point, the pressure nut 33 and the pressure plate 234 of the bolt 23 are spaced apart axially.

[0115] Subsequently, when the second motor 31 is driven in the forward direction, the pressure nut 33 is, as in Fig. As shown in Figure 12, the pressure nut 33 moves towards the pressure plate 234 and the pressure contact section 235 of the bolt 23 and comes into contact with it. At this point, in the state where a first-sided section of the pressure nut 33 is engaged with the nut piston 24, a second-sided section of it comes into contact with the bolt 23 in the axial direction, thus braking to park. Subsequently, although the second motor 31 ceases to be driven, this parking brake state is maintained due to the self-locking structure.

[0116] As in Fig. As shown in Figure 11, in the state where the pressure nut 33 is not in contact with the bolt 23 when the first motor 21 stops being driven, i.e., when only the service brake is applied instead of the parking brake, the nut piston 24 is pushed by itself due to the reaction force of the jaw 5, and the bolt 23 is turned in the opposite direction and reverses, as shown in Figure 11. Fig. 8 shown, back to their initial state.

[0117] When the parking brake is released, the following process can be carried out continuously. The first motor 21 is driven in the forward direction. This pushes the nut piston 24 further towards the shoe 5, and the pressure nut 33 is moved away from the pressure contact section 235 of the bolt 23. Then the second motor 31 is driven in the opposite direction. By carrying out this process to release the brake for parking, the bolt 23, the nut piston 24, and the pressure nut 33 can each be returned to their initial positions, as shown in Fig. 8 shown.

[0118] The drum brake 1 according to the present disclosure has a structure in which the service brake 2 and the parking brake 3 are coaxially combined. More precisely, according to the present disclosure, the drum brake 1 has a structure in which the bolt 23 and the piston nut 24 of the service brake 2 and the pressure nut 33 of the parking brake 3 are coaxially combined by the bolt-nut connection. In other words, the parking brake 3 according to the present disclosure has a simple structure in which the pressure nut 33 is additionally connected to the circumference of the piston nut 24 provided in the service brake 2 by the bolt-nut connection. That is to say, according to the present disclosure, the drum brake 1 has a simple structure in which the service brake 2 and the parking brake 3 share a bolt corresponding to the bolt 23.

[0119] Accordingly, the structures mentioned above, as disclosed herein, offer the following advantages when compared to the case in which the service brake 2 and the parking brake 3 are arranged independently of one another in the related prior art; in other words, when compared to the case in which the service brake 2 and the parking brake 3 are arranged in such a way that they are spaced apart and thus separated from one another. The number of components and the volumetric weights of the service brake 2 and the parking brake 3 can be significantly reduced, and space utilization and layout design freedom can be further improved. In addition, manufacturing costs and productivity can be improved.

[0120] Furthermore, according to the present disclosure, if the pressure nut 33 is brought into contact with the pressure contact section 235 only by applying a load high enough to limit the rotation of the nut piston 24, the braking to park can be performed. Accordingly, braking to park can be performed stably, compared to the prior art parking brake 3, where the shoe 5 is directly pressed, by applying a remarkably small load. Therefore, the second motor 31, a motor corresponding to the second drive force transmission device 32, and a drive force transmission device, as well as a housing that accommodates them, can be reduced in size and weight.

[0121] The embodiments of the present disclosure are largely described above. It would be understandable to a person with ordinary knowledge of the field to which the present disclosure relates that the present disclosure may be practiced in modified form within its scope, which does not deviate from the nature and essence of the present disclosure. Therefore, the disclosed embodiments should be considered from an explanatory, rather than a limiting, point of view. The scope of the present disclosure is defined in the claims, not in the description, and all equivalent differences should be interpreted as falling within the scope of the present disclosure.

Claims

[1] Drum brake (1) comprising: a bolt screw (23) which is turned in conjunction with a drive of a first motor (21); a mother piston (24) which is connected to a circumference of the bolt screw (23) by a bolt-nut fastening and is moved in a direction in conjunction with the rotation of the bolt screw (23) in which the mother piston (24) presses against a jaw (5); and a pressure nut (33), which is connected to a circumference of the nut piston (24) by the bolt-nut fastening, is moved in an axial direction in conjunction with a drive of a second motor, is brought into contact with the bolt screw (23) and thus prevents the nut piston (24) from being pressed due to a reaction force of the jaw (5), wherein the first motor, the bolt (23) and the piston nut are components of a service brake (2) for reducing the speed of a vehicle or for bringing the vehicle to a sudden stop, the service brake (2) further comprises: a first drive force transmission device (22) which transmits a rotational force of the first motor (21) to the bolt screw (23), wherein the first drive force transmission device (22) comprises: a drive gear which is supplied with driving force by the first motor (21) and is thereby rotated; and a driven gear which engages with the drive gear, is thereby rotated at a reduced speed and is combined coaxially with the bolt (23), wherein the bolt (23) has: a gear assembly section with a polygonal cross-section, installed in such a way that it passes through a screw connection hole in the driven gear and is moved axially along the screw connection hole; and a screw extension section shaped in such a way that it is coaxially continuous with the gear assembly section and is connected to the nut piston (24) by the screw and nut fastening. [2] Drum brake (1) according to claim 1, wherein the first motor, the bolt (23) and the piston nut are components of a service brake (2) for reducing the speed of a vehicle or for bringing the vehicle to a sudden stop, wherein the second motor and the pressure nut (33) are components of a parking brake for stopping the vehicle or for holding the vehicle in a standstill, wherein the pressure nut (33) and the bolt screw (23) are spaced apart axially in a state in which the nut piston (24) presses against the jaw (5) by the drive of the first motor (21) and the pressure nut (33) is moved towards the bolt screw (23) by the drive of the second motor and is thus brought into contact with the bolt screw (23), wherein an inner circumferential section of the mother piston (24) and an outer circumferential section of the bolt screw (23) have a screw structure in which, in a state where the mother piston (24) presses against the jaw (5) when the first motor ceases to be driven, the mother piston (24) is not self-locking in response to the reaction force of the jaw (5), and wherein an inner circumferential section of the pressure nut (33) and an outer circumferential section of the nut piston (24) have a screw structure in which, in a state in which the pressure nut (33) is brought into contact with the bolt screw (23) in the axial direction when the second motor ceases to be driven, the nut piston (24) is self-locking in response to the reaction force of the jaw (5). [3] Drum brake (1) according to one of claims 1 to 2, wherein the bolt screw (23) comprises: a gear assembly section that is supplied with a rotational force by the first motor (21); a screw extension section formed in such a way that it is coaxially continuous with the gear assembly section and is connected to the nut piston (24) by the bolt-nut fastening; and a pressure contact section which is arranged on the gear assembly section or the screw extension section in such a way that it faces the pressure nut (33) in the axial direction and which is brought into contact with the pressure nut (33). [4] Drum brake (1) according to claim 3, wherein the screw extension section has a smaller diameter than the gear assembly section, and wherein the pressure nut (33) is arranged in such a way that it faces a first-sided side surface section in the axial direction of the gear assembly section. [5] Drum brake (1) according to one of claims 1 to 4, wherein the bolt screw (23) comprises: a gear assembly section which is supplied with a rotational force by the first motor (21); a screw extension section which is connected to the nut piston (24) by the bolt-nut fastening; a fastening section formed between the gear assembly section and the screw extension section and formed in such a way that it is coaxially continuous with the gear assembly section and the screw extension section; a pressure plate that is attached to the fastening section and is arranged in such a way that it projects further in a radial direction than the screw extension section; and a pressure contact section which is arranged on the pressure plate in such a way that it faces the pressure nut (33) in the axial direction and is brought into contact with the pressure nut (33). [6] Drum brake (1) according to claim 5, wherein the gear assembly section has a smaller diameter than the screw extension section, and wherein the pressure nut (33) is arranged in such a way that it faces a first-sided side surface section in the axial direction of the pressure plate. [7] Drum brake (1) according to claim 5 or 6, wherein the fastening section is provided with an external thread, and wherein the pressure plate is fastened to the fastening section by means of a bolt-nut fastening by combining a ring element with an internal thread. [8] Drum brake (1) according to any one of claims 1 to 7, wherein the second motor and the pressure nut (33) are components of a parking brake for parking a vehicle or for holding the vehicle at a standstill, wherein the parking brake further comprises: a second drive force transmission device (22) which transmits a rotational force of the second motor to the pressure nut (33), and wherein the second drive force transmission device (22) comprises: a first gear connected to the second motor; and a second gear, of which a first-sided section engages with the first gear, thereby causing it to rotate at a reduced speed, and of which a second-sided section engages with the pressure nut (33), wherein the pressure nut (33), which has a larger diameter than the second gear, engages with the second gear and has such a length in the axial direction that the pressure nut (33) is movable in such a way as to be brought into contact with or spaced apart from the bolt (23) while being held in engagement with the second gear. [9] Drum brake (1) according to any one of claims 1 to 8, further comprising: a housing with a connecting space in which the bolt screw (23), the nut piston (24) and the pressure nut (33) are housed, the case features: a first housing unit in which a section of a service brake (2) is housed; a second housing unit containing a section of a parking brake; and a combination cylinder unit formed in the form of a hollow cylinder in a section in which the first housing unit and the second housing unit are combined and accommodate the bolt screw (23), the nut piston (24) and the pressure nut (33), wherein the second housing unit comprises: a motor mounting unit that accommodates the second motor; a gear mounting unit in which a second drive force transmission device (22) is housed, which transmits a rotational force of the second motor to the pressure nut (33); and a piston receiving unit, one end section of which, facing the first housing unit, is combined with the first housing unit, thereby forming the combination cylinder unit, and the mother piston (24) is installed on the other section of which, facing the jaw (5), by passing through it, the piston receiving unit being formed in a manner that is connected with the gear receiving unit. [10] Having an electronic parking brake: a second engine; a pressure nut (33) which is connected by a bolt-nut connection to a circumference of a nut piston (24) of a service brake (2) which presses against a shoe (5), is moved in an axial direction in conjunction with a drive of the second motor and is brought into contact with a bolt screw (23) which is connected to the nut piston (24) by the bolt-nut connection, thereby preventing the nut piston (24) from being pushed due to a reaction force of the shoe (5); and a second drive force transmission device (32) which transmits a rotational force of the second motor to the pressure nut (33), wherein the pressure nut (33) comprises: a main mother body arranged on a circumference of the mother piston (24); a screw combination section formed on an inner circumferential section of the nut main body and connected to the nut piston (24) by the bolt-nut fastening; a toothed section formed on an outer circumferential section of the main body of the mother and to which the rotational force is supplied by the second motor; and a screw fastening release section formed at an end section of the nut main body and brought into contact with the bolt (23) in the axial direction when the nut main body is moved, wherein the screw fastening release section has: a limiting clamping jaw formed at an end section in the axial direction of the main nut body in such a way that it projects inwards in a direction of the axial center, and which is arranged in such a way that it is opposite the nut piston (24) positioned inside the main nut body in the axial direction; and a screw contact section formed on the limiting clamping jaw in a manner projecting in the axial direction, and which faces the bolt (23) in the axial direction and is then brought into contact with it, wherein inner circumferential sections of the limiting clamping jaw and the screw contact section each have a larger diameter than the bolt (23) and are spaced apart from a circumference of the bolt (23), and wherein the driving force (22) transmitted from the second motor to the main body of the mother serves as a load which is exerted on the bolt screw in the axial direction via the screw contact section. [11] Electronic parking brake according to claim 10, wherein, when the second motor is driven in a forward direction, the pressure nut (33) is movable to one side in the axial direction to a position in which the screw contact section is pressed against the bolt screw in the axial direction and brought into contact with it, and wherein, when the second motor is driven in a reverse direction, the pressure nut (33) is movable to the other side in the axial direction to a position in which the limiting clamping jaw is brought into contact with the nut piston (24) in the axial direction. [12] Electronic parking brake according to one of claims 10 to 11, wherein at least one section of the second motor is housed together in a housing in which the bolt, the nut piston (24) and the pressure nut (33) are housed, and is arranged on one side of a plate surface of a back plate in a manner that is parallel to the bolt, the nut piston (24) and the pressure nut (33).

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