Actuating mechanism for drum brake in electronic braking system

Abstract

The utility model discloses an actuating mechanism for a drum brake in an electronic braking system, which belongs to the field of electronic braking systems and comprises a motor, a speed reducing mechanism, a lead screw nut mechanism and a push rod. The speed reducing mechanism comprises a driving gear and a driven gear which are in transmission connection, the tooth number of the driven gear is larger than that of the driving gear, the lead screw nut mechanism comprises a lead screw and a nut arranged on the periphery of the lead screw in a sleeving mode, and the push rod is connected with the nut. The motor is fixedly connected with the driving gear and located on the lower side of the driving gear, the lead screw is fixedly connected with the driven gear and located on the lower side of the driven gear, the motor drives the driving gear to rotate, the driving gear drives the lead screw to rotate through the driven gear when rotating, and the lead screw drives the push rod to move in the axial direction of the lead screw through the nut when rotating. Therefore, the application range of the actuating mechanism can be widened.

Description

Technical Field

[0001] The utility model belongs to the technical field of electronic brake systems, and in particular relates to an actuator for a drum brake in an electronic brake system. Background Art

[0002] With the continuous development of the automotive industry, the market demand for electrification, networking, intelligence, and sharing is driving the evolution of automobiles from purely mechanical structures to a multidisciplinary and multi-industry complex integrating mechanics, electrical engineering, big data, artificial intelligence, and other elements. Simultaneously, this is placing increasingly higher demands on the performance of braking systems. As a new braking technology, the electromechanical brake (EMB) system, with its advantages of fast response, high braking precision, and the ability to control by wire, has become a hot topic in current automotive braking system research. Drum brakes utilize a brake transmission mechanism to force the brake shoe to press the brake pad against the inside of the brake drum, generating braking force to decelerate the wheels or stop the vehicle in the shortest possible distance.

[0003] Typically, an electromechanical braking system consists of a brake and an actuator, which drives the brake to achieve braking. A common actuator for drum brakes includes a motor, a planetary gear reduction mechanism, and a screw-nut mechanism, which are arranged in sequence. The planetary gear reduction mechanism includes a sun gear and planetary gears, with the motor connected to the sun gear, and the planetary gears connected to the screw-nut mechanism. With this structure, the motor drives the sun gear, which in turn drives the planetary gears, which in turn drive the screw-nut mechanism in a linear motion to drive the drum brake to achieve braking. However, because the motor, planetary gear reduction mechanism, and screw-nut mechanism are arranged sequentially in a single direction, the actuator's overall height is relatively high, making it difficult to use in vehicles with limited underbody mounting space, such as commercial vehicles. This, in turn, limits the actuator's applicability. Utility Model Content

[0004] In order to solve the above problems existing in the prior art, the present invention provides an actuator for a drum brake in an electronic brake system. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] In the first aspect, the utility model provides an actuator for a drum brake in an electronic braking system, comprising a motor, a reduction mechanism, a screw-nut mechanism and a push rod; the reduction mechanism comprises a driving gear and a driven gear in a transmission connection, the number of teeth of the driven gear is greater than the number of teeth of the driving gear, the screw-nut mechanism comprises a screw and a nut sleeved on the outer circumference of the screw, and the push rod and the nut are connected; the motor and the driving gear are fixedly connected and located on the lower side of the driving gear, the screw and the driven gear are fixedly connected and located on the lower side of the driven gear, the motor drives the driving gear to rotate, and when the driving gear rotates, the screw is driven to rotate through the driven gear, and when the screw rotates, the push rod is driven to move along the axial direction of the screw through the nut.

[0006] In one embodiment of the present invention, it also includes a lower shell, an upper cover, a first bearing and a second bearing. The driving gear is installed on the lower shell through the first bearing, and the screw rod is installed on the lower shell through the second bearing. The upper cover and the lower shell are detachably connected.

[0007] In one embodiment of the present invention, the speed reduction mechanism further includes a transition gear, which is disposed between the driving gear and the driven gear, with one side of the transition gear meshing with the driving gear and the other side meshing with the driven gear.

[0008] In one embodiment of the present invention, two sets of guide assemblies are further included, and the guide assemblies include a guide rod and a connecting frame. The guide rod is fixedly connected to the lower shell, and the length direction of the guide rod is parallel to the axial direction of the screw rod. The connecting frame and the nut are detachably connected, and an ear hole is provided on the connecting frame, and the guide rod is inserted into the ear hole. The two sets of guide assemblies are symmetrically arranged on both sides of the nut.

[0009] In one embodiment of the present invention, the guide assembly further includes a ball guide sleeve, the ball guide sleeve is nested in the ear hole, and the guide rod is sleeved in the ball guide sleeve.

[0010] In one embodiment of the present invention, an electromagnetic clutch is further included. The electromagnetic clutch is disposed in the motor and is used to lock the motor shaft of the motor to prevent the motor from reversing.

[0011] In one embodiment of the present invention, it also includes a fixing sleeve and a connecting fork. A through hole is provided on the lower shell body. The first end of the fixing sleeve is sleeved on the outer periphery of the nut, and the second end extends into the through hole along the circumference of the screw rod. The second end of the fixing sleeve is provided with a groove. One end of the push rod is fixed in the groove, and the other end extends through the through hole and is connected to the connecting fork. A fastening sleeve is provided between the groove and the push rod.

[0012] In one embodiment of the present invention, one end of the push rod is a spherical structure, the groove is a spherical groove matching the spherical structure, and the spherical structure is arranged in the spherical groove.

[0013] In one embodiment of the present invention, a boss is provided on the outer periphery of the nut, and a guide seat is provided between the fixing sleeve and the boss. The guide seat is provided on the outer surface of the nut, and the guide seat abuts against the boss and the fixing sleeve on both sides of the nut's axis.

[0014] In one embodiment of the present invention, an annular positioning block is provided on the outer periphery of the screw rod, and a receiving cavity for accommodating the screw rod and nut mechanism is provided in the lower housing. A through hole is provided on the upper surface of the receiving cavity, and one end of the screw rod extends through the through hole and is fixedly connected to the driven gear via a flat key.

[0015] A pressure sensor is provided between the annular positioning block and the upper surface of the accommodating cavity, and a thrust needle roller bearing is provided between the pressure sensor and the annular positioning block.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] In the above-mentioned solution of the present application, the actuator includes a motor, a reduction mechanism, a screw-nut mechanism, and a push rod. The reduction mechanism includes a driving gear and a driven gear in a transmission connection, the driven gear having a larger number of teeth than the driving gear. The screw-nut mechanism includes a screw and a nut sleeved around the screw, and the push rod and the nut are connected. The motor is fixedly connected to the driving gear and located below the driving gear, while the screw is fixedly connected to the driven gear and located below the driven gear. With this structure, the motor can drive the driving gear to rotate. When the driving gear rotates, the screw can be driven by the driven gear to rotate. When the screw rotates, the nut drives the push rod to move axially along the screw. When the push rod moves, it can apply force to the drum brake, enabling the drum brake to brake. Furthermore, the motor and screw-nut mechanism can be located on the same side of the reduction mechanism, thereby reducing the overall height of the actuator. This makes the actuator suitable for vehicles with limited underbody mounting space, such as commercial vehicles, and expands the scope of application of the actuator.

[0018] In addition, the present invention uses a motor, a driving gear, and a driven gear to drive the screw-nut mechanism, resulting in a faster actuator drive speed and improved braking response speed of the drum brake. Simultaneously, the high-precision screw-nut mechanism drives the push rod, improving the braking accuracy of the drum brake. Furthermore, compared to traditional hydraulic brake systems, the mechanical structure consisting of the gear reduction mechanism and the screw-nut mechanism reduces the use of hydraulic components, reduces the risk of leakage, and improves system reliability. Furthermore, the electromechanical brake system can be controlled by electronic signals, making it easier to integrate with other electronic systems to achieve brake-by-wire control and enhance the vehicle's intelligence.

[0019] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the actuator provided by the embodiment of the present utility model;

[0021] Figure 2 yes Figure 1 Cross-sectional view along line CC.

[0022] Figure markings: 1-motor, 2-mounting plate, 3-driving gear, 4-first bearing, 5-transition gear, 6-upper cover, 7-driven gear, 8-gear box, 9-second bearing, 10-pressure sensor, 11-thrust needle roller bearing, 12-nut, 13-guide seat, 14-screw, 15-fixing sleeve, 16-screw housing, 17-fastening sleeve, 18-push rod, 19-connecting fork, 20-connecting frame, 21-ball guide sleeve, 22-guide rod. DETAILED DESCRIPTION

[0023] The present invention will be described in further detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0024] See Figure 1 and Figure 2 The embodiment of the utility model provides an actuator for a drum brake in an electronic braking system, including a motor 1, a reduction mechanism, a screw-nut mechanism and a push rod 18; the reduction mechanism includes a driving gear 3 and a driven gear 7 that are transmission-connected, the number of teeth of the driven gear 7 is greater than the number of teeth of the driving gear 3, the screw-nut mechanism includes a screw 14 and a nut 12 sleeved on the outer circumference of the screw 14, and the push rod 18 is connected to the nut 12; the motor 1 is fixedly connected to the driving gear 3 and is located on the lower side of the driving gear 3, the screw 14 is fixedly connected to the driven gear 7 and is located on the lower side of the driven gear 7, the motor 1 drives the driving gear 3 to rotate, and when the driving gear 3 rotates, the screw 14 is driven to rotate through the driven gear 7, and when the screw 14 rotates, the push rod 18 is driven to move along the axial direction of the screw 14 through the nut 12.

[0025] In some embodiments of the present application, the motor 1 may be a torque brushless motor.

[0026] In some embodiments of the present application, the screw-nut mechanism may be a ball screw-nut mechanism or a slider screw-nut mechanism.

[0027] In some embodiments of the present application, the axis of the driving gear 3 is parallel to the axis of the driven gear 7 , and the axis of the motor shaft in the motor 1 is parallel to the axis of the screw rod 14 .

[0028] In some embodiments of the present application, a drum brake includes an adjustment arm, a cam, a brake shoe, and a brake drum, and a push rod 18 is connected to the adjustment arm. When the motor 1 drives the push rod 18 to move through the reduction mechanism and the screw-nut mechanism, the push rod 18 pushes the adjustment arm to rotate. When the adjustment arm rotates, the cam rotates. When the cam rotates, the brake shoe is spread open, so that the brake shoe abuts against the brake drum, and braking is achieved by the friction between the brake shoe and the brake drum. Specifically, during service braking, the motor 1 starts and outputs torque. After the reduction mechanism reduces the torque and increases the torque, it drives the screw 14 to rotate. When the screw 14 rotates, it drives the nut 12 to move linearly along the axis of the screw 14, thereby driving the push rod 18 out. After the push rod 18 is pushed out, it applies a force to the adjustment arm, causing the adjustment arm to rotate. When the adjustment arm rotates, it drives the cam to rotate. When the cam rotates, it spreads the brake shoe to achieve braking. When the brake is released, the motor 1 is controlled to reverse and return to the initial position. When the parking brake is applied, the motor 1 can be controlled to cut off the power, and the electromagnetic clutch can be used to lock the motor shaft to prevent the motor 1 from reversing, thereby preventing the screw nut mechanism from retreating, so that the brake shoe and brake drum of the drum brake can remain locked. When the brake is released, the electromagnetic clutch can be controlled to release the motor shaft.

[0029] In the above scheme of the present application, the actuator includes a motor 1, a reduction mechanism, a screw-nut mechanism and a push rod 18; the reduction mechanism includes a driving gear 3 and a driven gear 7 that are transmission-connected, the number of teeth of the driven gear 7 is greater than the number of teeth of the driving gear 3, the screw-nut mechanism includes a screw 14 and a nut 12 sleeved on the outer periphery of the screw 14, and the push rod 18 is connected to the nut 12; the motor 1 and the driving gear 3 are fixedly connected and located on the lower side of the driving gear 3, the screw 14 and the driven gear 7 are fixedly connected and located on the lower side of the driven gear 7. With this structure, the motor 1 can drive the driving gear 3 to rotate. When the driving gear 3 rotates, the screw 14 can be driven to rotate through the driven gear 7. When the screw 14 rotates, the push rod 18 can be driven along the axial direction of the screw 14 through the nut 12. When the push rod 18 moves, it can apply a force to the drum brake, so that the drum brake can achieve braking. Furthermore, the motor 1 and the screw-nut mechanism can be located on the same side of the reduction mechanism, thereby reducing the overall height of the actuator and making the actuator suitable for vehicles with limited bottom installation space, such as commercial vehicles, thereby increasing the scope of application of the actuator.

[0030] In addition, the present application drives the screw-nut mechanism through the motor 1, the driving gear 3, and the driven gear 7, resulting in a faster driving speed of the actuator, thereby improving the braking response speed of the drum brake. Simultaneously, the high-precision screw-nut mechanism drives the push rod 18, thereby improving the braking accuracy of the drum brake. Furthermore, compared to traditional hydraulic brake systems, the mechanical structure composed of the gear reduction mechanism and the screw-nut mechanism can reduce the use of hydraulic components, reduce the risk of leakage, and improve the reliability of the system. Furthermore, the electromechanical brake system can be controlled by electronic signals, making it easy to integrate with other electronic systems to achieve brake-by-wire control and improve the intelligence level of the vehicle.

[0031] In some embodiments of the present application, Figure 1 As shown, the actuator also includes a lower housing, an upper cover 6, a first bearing 4, and a second bearing 9. The driving gear 3 is mounted on the lower housing via the first bearing 4, and the screw rod 14 is mounted on the lower housing via the second bearing 9. The upper cover 6 and the lower housing are detachably connected. This structure improves the stability of the installation of the driving gear 3 and the screw rod 14, ensuring that the driving gear 3 and the screw rod 14 can rotate normally. The detachable connection between the upper cover 6 and the lower housing makes the disassembly and assembly of the actuator more convenient.

[0032] In some embodiments of the present application, the lower shell includes a gear box body 8 and a screw housing 16, the reduction assembly is installed in the gear box body 8, the screw nut mechanism is installed in the screw housing 16, the screw housing 16 and the gear box body 8 are detachably connected, and the motor 1 is installed on the gear box body 8 through the mounting plate 2.

[0033] In some embodiments of the present application, Figure 1 As shown, the reduction mechanism further includes a transition gear 5, which is disposed between the driving gear 3 and the driven gear 7, with one side of the transition gear 5 meshing with the driving gear 3 and the other side meshing with the driven gear 7. With this structure, the driving gear 3, the transition gear 5, and the driven gear 7 can form a multi-stage reduction mechanism. By adjusting the rotation speed of the screw rod 14 through the multi-stage reduction mechanism, the rotation speed of the screw rod 14 can be precisely controlled, thereby improving the braking response speed and braking accuracy of the drum brake.

[0034] In some embodiments of the present application, Figure 2As shown, the actuator also includes two sets of guide assemblies, which include a guide rod 22 and a connecting frame 20. The guide rod 22 is fixedly connected to the lower housing, and the length direction of the guide rod 22 is parallel to the axial direction of the screw rod 14. The connecting frame 20 and the nut 12 are detachably connected. The connecting frame 20 is provided with an ear hole, and the guide rod 22 is inserted into the ear hole. The two sets of guide assemblies are symmetrically arranged on both sides of the nut 12. With this structure, the guide assemblies can not only limit the rotation of the nut 12, ensuring that the nut 12 can move linearly under the rotation of the screw rod 14, but also improve the stability of the movement of the nut 12 and the push rod 18, thereby improving the overall stability of the actuator.

[0035] In some embodiments of the present application, the guide assembly further includes a ball guide sleeve 21, which is nested in the ear hole, and a guide rod 22 is sleeved in the ball guide sleeve 21. With this structure, the ball guide sleeve 21 is disposed between the guide rod 22 and the through hole, which can improve the stability of the movement of the guide rod 22, and thus improve the stability of the movement of the nut 12.

[0036] In some embodiments of the present application, the actuator further includes an electromagnetic clutch, which is disposed in the motor 1 and is used to lock the motor shaft of the motor 1 to prevent the motor 1 from reversing. The electromagnetic clutch is an existing friction clutch that generates a clamping force by electromagnetic force. With this structure, the motor shaft of the motor 1 is locked by the electromagnetic clutch to prevent the motor 1 from reversing, which can avoid brake failure caused by the reversal of the motor 1 during drum brake braking, thereby improving the braking reliability of the drum brake. In addition, when the parking brake is applied, the motor 1 can be controlled to be powered off, and the motor shaft can be locked by the electromagnetic clutch to prevent the motor 1 from reversing, thereby preventing the screw nut mechanism from retreating, so that the brake shoe and brake drum of the drum brake can remain locked. When the brake is released, the electromagnetic clutch can be controlled to release the motor shaft.

[0037] In some embodiments of the present application, the actuator further includes a fixing sleeve 15 and a connecting fork 19. The lower housing is provided with a through-hole. The first end of the fixing sleeve 15 is sleeved around the outer circumference of the nut 12, and the second end extends into the through-hole along the circumference of the screw rod 14. The second end of the fixing sleeve 15 is provided with a groove. One end of a push rod 18 is fixed in the groove, and the other end extends through the through-hole and is connected to the connecting fork 19. A fastening sleeve 17 is provided between the groove and the push rod 18. With this structure, when the nut 12 moves axially along the screw rod 14, the fixing sleeve 15 can drive the push rod 18 to move axially along the screw rod 14, so that the push rod 18 can drive the adjustment arm to rotate. When the adjustment arm rotates, the cam rotates. When the cam rotates, the brake shoe is stretched, so that the brake shoe abuts against the brake drum, thereby utilizing the friction between the brake shoe and the brake drum to achieve braking.

[0038] In some embodiments of the present application, one end of the push rod 18 is a spherical structure, and the recess is a spherical groove that matches the spherical structure, and the spherical structure is disposed within the spherical groove. Because when the push rod 18 drives the adjustment arm to rotate, the adjustment arm drives the push rod 18 to swing to a certain extent, when adopting this structure, the push rod 18 can achieve a certain amount of swing during movement, thereby ensuring that the push rod 18 and the adjustment arm can move normally.

[0039] In some embodiments of the present application, a boss is provided on the outer periphery of the nut 12, and a guide seat 13 is provided between the fixing sleeve 15 and the boss. The guide seat 13 is sleeved on the outer surface of the nut 12, and the guide seat 13 abuts against the boss and the fixing sleeve 15 on both sides along the axial direction of the nut 12. With this structure, when the nut 12 moves, the fixing sleeve 15 can be driven to move by the boss and the guide seat 13, so that the fixing sleeve 15 can move along the axial direction of the screw rod 14 to drive the push rod 18 to move.

[0040] In some embodiments of the present application, an annular positioning block is provided on the outer periphery of the screw 14, and a housing for accommodating the screw-nut mechanism is provided within the lower housing. The upper surface of the housing is provided with a through-hole, through which one end of the screw 14 extends and is fixedly connected to the driven gear 7 via a flat key. A pressure sensor 10 is provided between the annular positioning block and the upper surface of the housing, and a thrust needle roller bearing 11 is provided between the pressure sensor 10 and the annular positioning block. With this structure, the pressure sensor 10 can detect the pressure applied by the screw-nut mechanism to the upper surface of the housing, and accurately control the current input to the motor 1 based on this pressure value, thereby precisely controlling the rotation angle and speed of the motor 1, thereby precisely controlling the movement distance of the push rod 18 and achieving precise braking. By providing the thrust needle roller bearing 11 between the pressure sensor 10 and the annular positioning block, the normal rotation of the screw 14 is ensured, preventing friction between the annular positioning block and the pressure sensor 10 from affecting the normal rotation of the screw 14 and the service life of the pressure sensor 10, while also improving the overall stability of the actuator.

[0041] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0042] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0043] In this utility model, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, indirect connection through an intermediate medium, internal communication between two components, or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0044] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention cannot be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. An actuator for a drum brake in an electronic brake system, characterized in that: It includes a motor, a reduction mechanism, a screw-nut mechanism and a push rod; The reduction mechanism includes a driving gear and a driven gear in transmission connection, the number of teeth of the driven gear is greater than the number of teeth of the driving gear, the screw-nut mechanism includes a screw and a nut sleeved on the outer circumference of the screw, and the push rod is connected to the nut; The motor is fixedly connected to the driving gear and is located at the lower side of the driving gear. The screw rod is fixedly connected to the driven gear and is located at the lower side of the driven gear. The motor drives the driving gear to rotate. When the driving gear rotates, the screw rod is driven to rotate through the driven gear. When the screw rod rotates, the push rod is driven to move along the axial direction of the screw rod through the nut.

2. The actuator for a drum brake in an electronic brake system according to claim 1, characterized in that: It also includes a lower shell, an upper cover, a first bearing and a second bearing. The driving gear is mounted on the lower shell through the first bearing, and the screw rod is mounted on the lower shell through the second bearing. The upper cover and the lower shell are detachably connected.

3. The actuator for a drum brake in an electronic brake system according to claim 2, characterized in that: The speed reduction mechanism further includes a transition gear, which is arranged between the driving gear and the driven gear, and one side of the transition gear is meshed with the driving gear, and the other side of the transition gear is meshed with the driven gear.

4. The actuator for a drum brake in an electronic brake system according to claim 2, characterized in that: It also includes two groups of guide assemblies, which include a guide rod and a connecting frame. The guide rod is fixedly connected to the lower shell, and the length direction of the guide rod is parallel to the axial direction of the screw rod. The connecting frame and the nut are detachably connected, and the connecting frame is provided with an ear hole, and the guide rod is inserted into the ear hole. The two groups of guide assemblies are symmetrically arranged on both sides of the nut.

5. The actuator for a drum brake in an electronic brake system according to claim 4, characterized in that: The guide assembly further includes a ball guide sleeve, which is nested in the ear hole, and the guide rod is sleeved in the ball guide sleeve.

6. The actuator for a drum brake in an electronic brake system according to claim 2, characterized in that: It also includes an electromagnetic clutch, which is arranged in the motor and is used to lock the motor shaft of the motor to prevent the motor from reversing.

7. The actuator for a drum brake in an electronic brake system according to claim 2, characterized in that: It also includes a fixing sleeve and a connecting fork. The lower shell is provided with a through hole. The first end of the fixing sleeve is sleeved on the outer periphery of the nut, and the second end extends into the through hole along the circumference of the screw rod. The second end of the fixing sleeve is provided with a groove. One end of the push rod is fixed in the groove, and the other end extends through the through hole and is connected to the connecting fork. A fastening sleeve is provided between the groove and the push rod.

8. The actuator for a drum brake in an electronic brake system according to claim 7, characterized in that: One end of the push rod is a spherical structure, the groove is a spherical groove matching the spherical structure, and the spherical structure is arranged in the spherical groove.

9. The actuator for a drum brake in an electronic brake system according to claim 7, characterized in that: A boss is provided on the outer periphery of the nut, and a guide seat is provided between the fixing sleeve and the boss. The guide seat is provided on the outer surface of the nut, and the guide seat abuts against the boss and the fixing sleeve respectively on both sides of the nut axial direction.

10. The actuator for a drum brake in an electronic brake system according to claim 2, characterized in that: An annular positioning block is provided on the outer periphery of the screw rod, and an accommodating cavity for accommodating the screw rod and nut mechanism is provided in the lower housing. A through hole is provided on the upper surface of the accommodating cavity, and one end of the screw rod extends through the through hole and is fixedly connected to the driven gear via a flat key; A pressure sensor is provided between the annular positioning block and the upper surface of the accommodating cavity, and a thrust needle roller bearing is provided between the pressure sensor and the annular positioning block.

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