Integrated electronic mechanical braking device

Abstract

The invention relates to an integrated electronic mechanical braking device, and belongs to the technical field of braking equipment. The brake caliper assembly comprises a mounting frame, a brake caliper body assembly and an MGU assembly. The MGU assembly comprises an electronic control unit, a speed reducing and distance increasing unit and a parking unit. The brake caliper body assembly is provided with a brake caliper body, and the brake caliper body is installed on the installation frame in a sliding mode. The speed reducing and distance increasing unit comprises a power shaft and a speed reducing gear set; the electronic control unit comprises a control assembly, a brake motor and a parking power part. The parking unit comprises a ratchet wheel and a pawl; one end of the power shaft is connected with the brake motor through the reduction gear set, and the other end of the power shaft serves as a power output end and is connected with the brake caliper body. The ratchet wheel is connected with the power shaft, the pawl is installed on the installation frame, and one end of the pawl is connected with the parking power piece. The braking motor and the parking power piece are electrically connected with the control assembly. The control assembly is integrated, an additional ECU does not need to be connected, the space utilization rate of the chassis is effectively increased, and the parking braking function is achieved while the service braking requirement is met.

Description

Technical Field

[0001] The present application relates to an integrated electronic mechanical braking device, belonging to the technical field of braking equipment. Background Art

[0002] With the development of automobile electronics and intelligence, as well as the rise of electric vehicles and autonomous driving technology, higher requirements have been placed on the braking system. EMB technology has emerged and has developed rapidly in recent years. At present, many domestic and foreign OEMs and brake manufacturers have completed the trial production and road testing of EMB products; compared with the traditional hydraulic braking system, the wire-controlled electronic mechanical brake (EMB) system has improved energy efficiency, high braking accuracy, fast response time, and shorter braking distance. It is more suitable for the technical development needs of new energy vehicles that are fully electronic and intelligent, and can be more closely integrated with other vehicle systems to achieve a higher level of vehicle dynamic control and autonomous driving.

[0003] In the prior art, due to the limited space between the steering wheel hub and the drive shaft of the vehicle chassis, the overall volume of the EMB, especially the axial dimension, must be compact while ensuring the braking performance. In the existing publicly released EMB structure, the driving part is large in size and does not integrate the parking brake function. The parking mechanism in some patents is relatively complex. In addition, the existing electromechanical brake needs to be connected to an additional external ECU electronic control unit, which has a low space utilization rate. Therefore, an electromechanical brake device is needed to solve the problem in the prior art that the existing electromechanical brake device has a large overall volume, no parking brake function, and requires an external ECU, resulting in low space utilization rate due to the limited chassis installation space. Summary of the invention

[0004] In view of the problems and shortcomings in the prior art, the present application provides an integrated electromechanical braking device to solve the above-mentioned technical problems.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions: a mounting frame, a brake caliper assembly and an MGU assembly, the MGU assembly including an electronic control unit, a deceleration and distance increasing unit and a parking unit; the brake caliper assembly is provided with a brake caliper body, and the brake caliper body is slidably mounted on the mounting frame; the deceleration and distance increasing unit includes a power shaft and a reduction gear set; the electronic control unit includes a control assembly, a brake motor and a parking power component; one end of the power shaft is connected to the brake motor through the reduction gear set, and the other end is connected to the brake caliper body as a power output end; one end of the parking unit is connected to the parking power component, and the other end is connected to the power shaft to limit the rotational movement of the power shaft; the brake motor and the parking power component are electrically connected to the control assembly respectively.

[0006] Specifically, the mounting frame is provided with a mounting shell, two mounting cavities are provided inside the mounting shell, and a partition is provided between the two mounting cavities; the control component is installed in one of the mounting cavities to form a first mounting cavity, and the deceleration and distance increasing unit and the parking unit are installed in the other mounting cavity to form a second mounting cavity; an axial hole is provided on the mounting shell on one side of the second mounting cavity for the power shaft to extend, and the brake caliper body assembly is installed on the axial hole side of the second mounting cavity.

[0007] Specifically, the reduction gear set is a planetary reduction gear set with a reduction ratio range of 10-80, which includes a sun gear, an inner ring gear and a planetary gear set; the sun gear, the inner ring gear and the planetary gear set are made of powder metallurgy material or powder metallurgy material and plastic material; the planetary gear set includes a planet carrier and a plurality of planetary gears; a plurality of planetary gear mounting cavities are evenly distributed along the circumference of the planetary carrier, and planetary pins are provided in the planetary gear mounting cavities, on which planetary pins are rotatably mounted through bearings; the inner ring gear is fixedly mounted on the mounting frame, and the planetary carrier is meshed with the inner ring gear of the inner ring gear through a plurality of planetary gears, and is rotatably mounted on the inner ring gear; the sun gear is rotatably mounted on the planet carrier by meshing with a plurality of planetary gears; the power shaft is mounted on the frame of the planetary carrier away from the planetary gears; one end of the sun gear is connected to the brake motor.

[0008] Specifically, the sun gear is a double gear structure, including an integrally formed first gear and a second gear, and the first gear is made of plastic material, and the second gear is made of metal material; a driving gear is fixedly installed on the power end of the brake motor, and the brake motor is meshed with the first gear through an idler gear arranged between the driving gear and the first gear; the second gear is meshed with a plurality of planetary gears.

[0009] Specifically, the parking unit includes a ratchet and a pawl; the pawl is mounted on a mounting frame, and one end of the pawl is connected to the power end of the parking power member; the ratchet is fixedly mounted on the planetary carrier through a wheel body and connected to the power shaft.

[0010] Specifically, the control component is provided with an ECU circuit board, and the ECU circuit board is installed in the first installation cavity; the second installation cavity has installation holes on both sides of the axial hole, which are used to install the brake motor and the parking power component respectively.

[0011] Specifically, the parking power component is a parking electromagnet, which includes an electromagnetic coil, a push rod motor, a push rod and an electromagnet; the electromagnetic coil and the push rod motor are integrated into one, the push rod is connected to the power end of the push rod motor, and the electromagnet is installed at the end of the push rod; the pawl is rotatably installed on the mounting frame, and one end of it faces the electromagnet, forming a magnetic attraction end, and the other end is provided with a pawl structure, forming a locking end.

[0012] Specifically, the pawl includes a first pawl body, a second pawl body, a rotating shaft and a torsion spring; the rotating shaft is fixedly installed on the mounting frame, the torsion spring is sleeved on the rotating shaft, one end of the first pawl body and the second pawl body are respectively hinged to the rotating shaft, and a torsion spring is arranged between the first pawl body and the second pawl body, the second pawl body is stopped at the mounting frame by a limit pin, forming a fixed end, a pawl structure is provided at the end of the first pawl body, forming a locking end, and the fixed end is located within the movement trajectory of the push rod.

[0013] Specifically, the brake caliper body assembly includes a caliper body bracket, a slide rail, a ball screw pair, a piston and a brake lining; the slide rail is fixedly installed on the caliper body bracket, the brake caliper body is slidably installed on the slide rail, and one end of the caliper body is fixedly connected to the nut end of the ball screw pair through the piston, the screw of the ball screw pair is rotatably installed on the mounting frame, and one end of the caliper body is connected to the power shaft; the brake lining is fixedly installed on the brake caliper body.

[0014] Specifically, the first gear, the second gear and the power shaft of the sun gear are coaxially arranged; the driving gear and the power end of the brake motor are coaxially arranged; the axes of the brake motor, the idler gear and the sun gear are arranged parallel to each other; the idler gear and the inner gear ring are made of plastic material.

[0015] Compared with the prior art, the beneficial effects of this application are: 1. The present application integrates a brake caliper assembly and an MGU assembly on a mounting frame, wherein the MGU assembly includes an electronic control unit, a deceleration and distance increasing unit and a parking unit, and the parking unit includes a ratchet and a pawl, and the deceleration and distance increasing unit includes a power shaft and a reduction gear set, and is connected to the deceleration and distance increasing unit through the brake motor of the electronic control unit, and is used to decelerate and increase the braking force of the brake motor, thereby driving the brake caliper of the brake caliper assembly to slide along the mounting frame to perform service braking. At the same time, by installing the ratchet of the parking unit on the power shaft, the ratchet is driven by the parking unit of the electronic control unit to lock the ratchet, thereby achieving the effect of parking braking. The electronic mechanical brake device of the present application is integrated with an ECU control component, and does not need to be connected to an additional ECU, which effectively improves the space utilization rate of the entire vehicle chassis, and has the function of parking braking while meeting the service braking requirements.

[0016] 2. On the basis of the foregoing, the mounting bracket of the electronic mechanical braking device of the present application is provided with a mounting shell, and two mounting cavities are provided inside the mounting shell. The control component is installed in one of the mounting cavities to form a first mounting cavity, and the deceleration and distance increasing unit and the parking unit are installed in the other mounting cavity to form a second mounting cavity. A partition is provided between the two mounting cavities to achieve the effect of isolating the grease of the mechanical parts of the deceleration and distance increasing unit and the parking unit from contacting the ECU circuit board through the partition, so as to protect the control component.

[0017] 3. On the basis of the above, the reduction gear set of the electronic mechanical brake device of the present application is a planetary reduction gear set, which includes a sun gear, an inner gear ring and a planetary gear set including a plurality of planetary gears, wherein the sun gear is a double gear structure, which includes a first gear and a second gear, and a driving gear is fixedly installed on the power end of the brake motor, and the brake motor meshes with the first gear by setting an idler gear between the driving gear and the first gear, and the second gear acts as a sun gear and meshes with the planetary gear set to drive the planetary carrier of the planetary gear set to rotate, so as to drive the power shaft to output power. At the same time, the driving gear and the power end of the brake motor are set as one body, and the sun gear adopts a double gear structure to reduce the possible slippage or movement problems when the driving gear and the power end of the brake motor and the first gear and the second gear are matched. The present application arranges the ratchet in the middle of the double gear, and forms the meshing space of the planetary gear through a fixed connection with the inner gear ring and the planetary carrier, so there is no need to reserve an additional axial arrangement space for the parking ratchet, thereby greatly reducing the axial size of the MGU assembly.

[0018] 4. On the basis of the foregoing, the first gear, the second gear and the power shaft of the sun wheel of the present application are coaxially arranged; the driving gear and the power end of the brake motor are coaxially arranged; the axes of the brake motor, the idler gear and the sun wheel are arranged parallel to each other, so as to save axial space while making the overall structure of the electronic mechanical brake device compact and occupying little space.

[0019] 5. On the basis of the above, the parking unit of the electronic mechanical brake device of the present application adopts a parking electromagnet, and the pawl includes a first pawl body, a second pawl body, a rotating shaft and a torsion spring. One end of the first pawl body and the second pawl body are respectively hinged to the rotating shaft, and a torsion spring is arranged between the first pawl body and the second pawl body. The second pawl body is stopped on the mounting frame by a limit pin to form a fixed end. The end of the first pawl body is provided with a pawl structure to form a locking end, and the fixed end is located within the movement trajectory of the push rod, so that when the parking electromagnet contacts the second pawl body, the first pawl body is magnetically attracted by the electromagnet and moves in a direction away from the ratchet wheel to release the parking brake. On the contrary, the first pawl body drives the pawl structure to lock on the ratchet wheel under the elastic force of the torsion spring to realize the function of the parking brake. The parking unit of the present application has a fast response, adopts magnetic attraction to drive the pawl movement, has small component wear and a long service life. The parking mechanism can achieve a dual holding force design when driving and parking. It uses its own mechanical structure to achieve long-term retention of force both when parking and driving. The electromagnet does not require continuous power supply and can be highly efficient and energy-saving.

[0020] 6. On the basis of the foregoing, the deceleration and distance increasing unit of the MGU assembly of the present application has a large adjustable range of reduction ratio, which can meet the braking force adjustment requirements of vehicles of different tonnages. The designed reduction gear set adopts powder metallurgy or a combination of powder metallurgy and plastic gears to meet the low-noise design requirements of automobiles, especially new energy vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of the integrated electromechanical brake device of this embodiment; Figure 2 is a structural exploded diagram of the integrated electromechanical brake device of this embodiment; Figure 3 is a schematic structural diagram of the MGU component of the integrated electronic mechanical brake device of this embodiment; Figure 4 An exploded view of the structure of the MGU assembly of the integrated electronic mechanical brake device of this embodiment; Figure 5 Schematic diagram of the structure of the brake caliper assembly of the integrated electromechanical brake device of this embodiment. DETAILED DESCRIPTION

[0022] The present application will be further described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0023] See also Figure 1-Figure 5 The present embodiment discloses an integrated electronic mechanical braking device, comprising a mounting frame, a brake caliper assembly 2 and an MGU assembly 1, wherein the MGU assembly 1 comprises an electronic control unit, a deceleration and distance increasing unit and a parking unit; the brake caliper assembly 2 is provided with a brake caliper body 2-0, and the brake caliper body 2-0 is slidably mounted on the mounting frame; the deceleration and distance increasing unit comprises a power shaft 1-19 and a reduction gear set; the electronic control unit comprises a control assembly, a brake motor 1-4 and a parking power member; the parking unit comprises a ratchet 1-9 and a pawl; one end of the power shaft is connected to the brake motor through the reduction gear set, and the other end is connected to the brake caliper body as a power output end; the ratchet 1-9 is connected to the power shaft 1-19, the pawl is mounted on the mounting frame, and one end thereof is connected to the power end of the parking power member; the brake motor and the parking power member are electrically connected to the control assembly respectively.

[0024] Furthermore, the mounting frame is provided with a mounting shell, and two mounting cavities are provided inside the mounting shell, and a partition is provided between the two mounting cavities; the control component is installed in one of the mounting cavities to form a first mounting cavity, and the control component of this embodiment is provided with an ECU circuit board 1-3, and the ECU circuit board 1-3 is installed in the first mounting cavity, and a mounting shell cover 1-1 is provided on the outside of the first mounting cavity to form a closed mounting cavity. The deceleration and distance increasing unit and the parking unit are installed in another mounting cavity to form a second mounting cavity; an axial hole is provided on the mounting shell on one side of the second mounting cavity for the power shaft to extend, and the brake caliper body assembly is installed on the axial hole side of the second mounting cavity, and mounting holes are provided on both sides of the axial hole of the second mounting cavity of this embodiment, respectively, for installing the brake motor 1-4 and the parking power part.

[0025] The reduction gear set of this embodiment is a planetary reduction gear set, and the reduction ratio range is 10-80, which includes a sun gear 1-7, an inner ring gear 1-17 and a planetary gear set; the sun gear, the inner ring gear and the planetary gear set are made of powder metallurgy material or powder metallurgy material and plastic material; the planetary gear set includes a planet carrier 1-18 and a plurality of planetary gears 1-15; the interior of the planet carrier 1-18 is provided with a plurality of planetary gear mounting cavities evenly distributed along the circumference, and a planetary pin 1-16 is provided in the planetary gear mounting cavity, and the planetary pin 1-15 is rotatably mounted on the planetary pin through a bearing; the inner ring gear 1-17 is fixedly mounted on the mounting frame, and the planetary carrier is meshed with the inner ring gear of the inner ring gear through a plurality of planetary gears, and is rotatably mounted on the inner ring gear; the sun gear 1-7 is rotatably mounted on the planet carrier by meshing with a plurality of planetary gears; the power shaft 1-19 is mounted on the frame of the planet carrier away from the planetary gear side; one end of the sun gear is connected to the power end of the brake motor.

[0026] In addition, the sun gear 1-7 of this embodiment is a double gear structure, including an integrally formed first gear and a second gear; the first gear is made of plastic material, and the second gear is made of metal material; a driving gear 1-20 is fixedly installed on the power end of the brake motor, and the brake motor is meshed with the first gear by setting an idler gear 1-6 between the driving gear and the first gear; the second gear is meshed with a number of planetary gears. The ratchet 1-9 is fixedly installed on the planetary carrier 1-18 through the wheel body using a connecting bolt 1-8, and is connected to the power shaft. In addition, the first gear, the second gear and the power shaft of the sun gear of this embodiment are coaxially arranged; the driving gear and the power end of the brake motor are coaxially arranged; the axes of the brake motor, the idler gear and the sun gear are arranged parallel to each other.

[0027] The parking power part of this embodiment is a parking electromagnet 1-13, including an electromagnetic coil, a push rod motor, a push rod and an electromagnet; the electromagnetic coil and the push rod motor are integrated into one, the push rod 1-21 is connected to the power end of the push rod motor, and the electromagnet is installed at the end of the push rod; the ratchet is rotatably installed on the mounting frame, and one end of it faces the electromagnet, forming a magnetic end, and the other end is provided with a ratchet structure, forming a locking end. The ratchet of this embodiment includes a first pawl body 1-11, a second pawl body 1-12, a rotating shaft 1-10 and a torsion spring 1-14; the rotating shaft is fixedly installed on the mounting frame, the torsion spring is sleeved on the rotating shaft, one end of the first pawl body and the second pawl body are respectively hinged to the rotating shaft, and a torsion spring is abutted between the first pawl body and the second pawl body, the second pawl body is abutted on the mounting frame through a limit pin, forming a fixed end, the end of the first pawl body is provided with a ratchet structure, forming a locking end, and the fixed end is located within the movement trajectory of the push rod.

[0028] In addition, the brake caliper body assembly 2 of the present embodiment includes a caliper body bracket 2-5, a slide rail, a ball screw pair, a piston 2-3 and a brake lining; the slide rail is fixedly installed on the caliper body bracket 2-5, the brake caliper body 2-4 is slidably installed on the slide rail, and one end of it is fixedly connected to the nut end 2-2 of the ball screw pair through the piston 2-3, the screw 2-1 of the ball screw pair is rotatably installed on the mounting frame, and one end of it is connected to the power shaft; the power shaft 1-19 of the present embodiment adopts an external spline structure, the screw pair adopts an internal spline structure, the power shaft and the screw are connected by splines, and the brake lining is fixedly installed on the brake caliper body 2-4.

[0029] Working principle: When the integrated electronic mechanical brake device provided in this embodiment is in use, during driving braking, the control component controls the brake motor to start. After the motor starts, the power end of the motor drives the idler wheel to rotate through the driving gear, and the idler wheel meshes and rotates with the first gear of the sun gear of the double gear, thereby driving the second gear to rotate. Since the second gear is respectively meshed with several planetary gears of the planetary gear set, the planetary gear is driven to rotate along the inner gear ring, thereby driving the planetary carrier to rotate, and finally driving the power shaft to output power, and realizing the deceleration and distance increase of the brake motor force. The power shaft rotates to drive the screw of the ball screw pair to rotate, thereby driving the nut end fixedly connected to the brake caliper body to slide along the screw, realizing that the brake caliper body slides along the slide rail toward the brake disc, and the brake is braked by the brake lining against the brake disc. When the parking brake is not needed, the control component controls the parking power part to start, and the push rod motor drives the push rod to extend toward the second claw body of the ratchet pawl and stop at the second claw body. Then the battery coil is started, and the electromagnet is magnetized to generate magnetic force to attract the first claw body toward the second claw body, so that the ratchet pawl releases the ratchet wheel. At this time, the planetary gear set can rotate normally. Conversely, when the parking brake is needed, the parking power part loses power, the push rod is extended back, the electromagnet loses magnetism, and the first claw body rotates toward the ratchet wheel under the elastic force of the torsion spring and stops at the ratchet wheel to achieve locking and complete the parking brake.

[0030] The implementation methods of the present application are described in detail above in conjunction with the embodiments, but the present application is not limited to the above-mentioned implementation methods. For ordinary technicians in this technical field, after knowing the contents recorded in the present application, they can make several equivalent changes and substitutions thereto without departing from the principles of the present application, and these equivalent changes and substitutions should also be regarded as belonging to the protection scope of the present application.

Claims

1. An integrated electromechanical brake device, comprising a mounting frame, a brake caliper assembly and an MGU assembly, characterized in that: The MGU assembly includes an electronic control unit, a deceleration and distance increasing unit and a parking unit; the brake caliper assembly is provided with a brake caliper body, and the brake caliper body is slidably mounted on a mounting frame; the deceleration and distance increasing unit includes a power shaft and a reduction gear set; the electronic control unit includes a control assembly, a brake motor and a parking power component; one end of the power shaft is connected to the brake motor through the reduction gear set, and the other end is connected to the brake caliper body as a power output end; one end of the parking unit is connected to the parking power component, and the other end is connected to the power shaft to limit the rotational movement of the power shaft; the brake motor and the parking power component are electrically connected to the control assembly respectively.

2. An integrated electromechanical brake device according to claim 1, characterized in that: The mounting frame is provided with a mounting shell, and two mounting cavities are provided inside the mounting shell, and a partition is provided between the two mounting cavities; the control component is installed in one of the mounting cavities to form a first mounting cavity, and the deceleration and distance increasing unit and the parking unit are installed in the other mounting cavity to form a second mounting cavity; an axial hole is provided on the mounting shell on one side of the second mounting cavity for the power shaft to extend, and the brake caliper body assembly is installed on the axial hole side of the second mounting cavity.

3. The integrated electromechanical brake device according to claim 1, characterized in that: The reduction gear set is a planetary reduction gear set with a reduction ratio range of 10-80, which includes a sun gear, an inner ring gear and a planetary gear set; the sun gear, inner ring gear and planetary gear set are made of powder metallurgy material or powder metallurgy material and plastic material; the planetary gear set includes a planet carrier and a plurality of planetary gears; the planet carrier is provided with a plurality of planetary gear mounting cavities evenly distributed along the circumference, and the planetary gear mounting cavities are provided with planetary pins, on which planetary pins are rotatably mounted through bearings; the inner ring gear is fixedly mounted on the mounting frame, and the planetary carrier is meshed with the inner ring gear of the inner ring gear through a plurality of planetary gears and is rotatably mounted on the inner ring gear; the sun gear is rotatably mounted on the planet carrier by meshing with a plurality of planetary gears; the power shaft is mounted on the frame of the planet carrier away from the planetary gear side; one end of the sun gear is connected to the brake motor.

4. The integrated electromechanical brake device according to claim 3, characterized in that: The sun gear is a double gear structure, including a first gear and a second gear that are integrally formed, and the first gear is made of plastic material, and the second gear is made of metal material; a driving gear is fixedly installed on the power end of the brake motor, and the brake motor is meshed with the first gear by arranging an idler gear between the driving gear and the first gear; the second gear is meshed with a plurality of planetary gears.

5. The integrated electromechanical brake device according to claim 3, characterized in that: The parking unit comprises a ratchet and a pawl; the pawl is mounted on a mounting frame, and one end of the pawl is connected to the power end of the parking power member; the ratchet is fixedly mounted on the planetary frame through a wheel body, and is connected to the power shaft.

6. The integrated electromechanical brake device according to claim 2, characterized in that: The control component is provided with an ECU circuit board, and the ECU circuit board is installed in the first installation cavity; the shaft hole of the second installation cavity is provided with installation holes on both sides, which are used to install the brake motor and the parking power component respectively.

7. The integrated electromechanical brake device according to claim 5, characterized in that: The parking power component is a parking electromagnet, which includes an electromagnetic coil, a push rod motor, a push rod and an electromagnet; the electromagnetic coil and the push rod motor are integrated into one, the push rod is connected to the power end of the push rod motor, and the electromagnet is installed on the end of the push rod; the pawl is rotatably installed on the mounting frame, and one end of it faces the electromagnet to form a magnetic attraction end, and the other end is provided with a pawl structure to form a locking end.

8. The integrated electromechanical brake device according to claim 7, characterized in that: The pawl includes a first pawl body, a second pawl body, a rotating shaft and a torsion spring; the rotating shaft is fixedly installed on the mounting frame, the torsion spring is sleeved on the rotating shaft, one end of the first pawl body and the second pawl body are respectively hinged to the rotating shaft, and a torsion spring is arranged between the first pawl body and the second pawl body, the second pawl body is stopped on the mounting frame by a limit pin, forming a fixed end, a pawl structure is provided on the end of the first pawl body, forming a locking end, and the fixed end is located within the movement trajectory of the push rod.

9. The integrated electromechanical brake device according to claim 1, characterized in that: The brake caliper body assembly includes a caliper body bracket, a slide rail, a ball screw pair, a piston and a brake lining; the slide rail is fixedly installed on the caliper body bracket, the brake caliper body is slidably installed on the slide rail, and one end of the caliper body is fixedly connected to the nut end of the ball screw pair through the piston, the screw of the ball screw pair is rotatably installed on the mounting frame, and one end of the caliper body is connected to the power shaft; the brake lining is fixedly installed on the brake caliper body.

10. The integrated electromechanical brake device according to claim 4, characterized in that: The first gear, the second gear and the power shaft of the sun gear are coaxially arranged; the driving gear and the power end of the brake motor are coaxially arranged; the axes of the brake motor, the idler gear and the sun gear are arranged parallel to each other; the idler gear and the inner gear ring are made of plastic material.

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