Parallel high-efficiency composite flexible-cylinder harmonic reducer with built-in outer rotor motor

Abstract

The present invention discloses a parallel type high-efficiency composite flexible cylinder type harmonic reducer with a built-in external rotor motor. The flexible cylinder with integrated flexible bearing outer ring raceways on the inner surfaces at both ends, gears on the outer surface and equal diameter in the middle, and wave generators with the same structural size and perpendicular long axes and flexible bearing inner ring raceways on the outer surface integrated at both ends of the motor outer rotor are assembled into the moving part of the above reducer through two identical ball or spherical roller retainer assemblies; the motor inner stator with cover-shaped rigid wheels at both ends is fixed to form the static part of the reducer; by using the orthogonal anti-symmetric deformation of the flexible cylinder, half of the motor input torque is amplified by two harmonic transmission assemblies with the same modulus and the same difference in the number of teeth, and is output by the variable stiffness connection part on the outer circle after the middle section of the constant circle flexible cylinder is superimposed, and the two harmonic transmission assemblies are actually parallel and proportional reduction. Because the middle section of the flexible cylinder has no circularity constraint, and the outer ring of the composite flexible bearing of the flexible cylinder reduces the wall thickness of the elastic part, the transmission efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the field of mechanical transmission technology, and particularly relates to a parallel-type high-efficiency composite flexible-cylinder harmonic reducer with a built-in outer rotor motor. The invention proposes the idea of ​​two harmonic transmission components working in parallel, and makes the active harmonic reducer compact in structure, small in size and high in transmission efficiency by integrating some static and dynamic components, reducing non-working materials of flexible components to reduce their deformation energy consumption, and building and integrating the driving source - the outer rotor motor - into the reducer. Background Art

[0002] Harmonic reducers, characterized by their compact size, high transmission ratio, light weight, and high transmission accuracy, are core transmission components for automated control devices such as robots, mechanical equipment, and medical equipment. As more and more equipment moves toward automation and intelligence, the performance requirements for harmonic reducers are increasing. Unlike conventional transmissions, the core principle of a harmonic reducer is to utilize the elastic deformation of a flexible component during operation to generate harmonic motion to transmit motion and power. It primarily consists of a wave generator, a flexible bearing, a flexspline with teeth on the end, and a rigid wheel with internal teeth of the same module. The wave generator is a non-circular cam. The flexible bearing is mounted on the wave generator and embedded in the inner bore of the flexspline. When the wave generator is in operation, it causes the flexspline to undergo controlled elastic deformation, causing the teeth on both ends of the deformed long shaft of the flexspline to mesh simultaneously with the inner teeth of the rigid wheel. Due to the small tooth difference between the rigid and flexsplines, the teeth on the deformed short shaft of the flexspline completely disengage from the inner teeth of the rigid wheel, forcing the flexspline to generate harmonic deformation motion to transmit motion and torque, achieving a high reduction ratio.

[0003] The flexible bearing outer ring and the flexspline are the two core elastic components of the harmonic reducer, but they are manufactured as separate parts. Both retain elastic wall thickness material required for the independent part processing but not required for operation. However, this elastic wall thickness also produces elastic deformation during reducer operation, consuming energy. The flexible bearing inner ring is manufactured as a circular shape before the wave generator is installed. However, after installation, the inner ring becomes non-circular, matching the wave generator and is subject to assembly bending stress. The non-circular wave generator also changes the curvature of the outer raceway grooves in each radial section, affecting the high-speed operation and force of the bearing rolling elements. The assembly of discrete parts inevitably increases the number of interfaces in the force or torque transmission path, complicating the constraints between the components and reducing the structural strength of each component.

[0004] Existing flexible-wheel harmonic reducers have only a single harmonic transmission component, that is, one end of the flexible wheel generates harmonic deceleration motion and amplifies torque, while the torque output at the other end of the flexible wheel must rely on its diaphragm structure such as the cup bottom or hollow flange, or the circular constraint of the meshing rigid wheel with the same number of teeth. These constraint structures consume elastic deformation energy to generate or limit the deformation of the flexible wheel during operation. This is one of the main reasons for the low transmission efficiency of existing flexible-wheel harmonic reducers. In essence, it sacrifices transmission efficiency to achieve a large reduction ratio with a small reducer.

[0005] In the existing flexible-wheel harmonic reducer, each point on the circumference of the open end of the flexible wheel swings outward and inward with the cup bottom cross-section point on the respective flexible wheel generatrix as the center of the circle during rotation, and the swing value is the largest. That is, the swing value of each point on the axial direction of the end spur gear is not equal, but the teeth on the rigid and flexible wheels are all processed as spur gears parallel to the axis, resulting in additional elastic constraints when the rigid and flexible wheels mesh at the long shaft end, and increasing the sliding friction and wear of the meshing tooth surfaces. Summary of the Invention

[0006] To address the aforementioned shortcomings of the prior art, the present invention provides a parallel, high-efficiency, composite flexible-cylinder harmonic reducer with an internal external rotor motor. Its core principle is to utilize the orthogonal, antisymmetric deformation of a thin-walled flexible cylinder with a constant diameter in the middle due to coaxially mounted wave generators of the same structural dimensions and perpendicular long axes at both ends (the core principle of invention patent application publication number CN 117330313 A). Two harmonic drive assemblies at either end of the flexible cylinder, each with the same module and tooth number difference, amplify half of the torque from the same input source in equal proportion. The amplified, identically oriented torques at both ends are superimposed on the central cross-section of the constant-circle flexible cylinder and output by a variable-stiffness coupling on its outer circumference. The two harmonic drive assemblies effectively perform the same reduction in speed in parallel.

[0007] The reducer is compactly assembled, diametrically and axially, with an integrated moving component, an integrated stationary component, and an elastic coupling output element with low axial stiffness and high circumferential stiffness. The integrated moving component comprises a flexible cylinder with flexible bearing outer ring raceways integrated on both ends, a gear on the outer surface, and a uniformly thin-walled central structure. Two wave generators of the same structural dimensions, with perpendicular long axes and flexible bearing inner ring raceways integrated on the outer surfaces, are integrated at both ends of the motor's outer rotor. These wave generators are assembled via two identical ball or spherical roller cage assemblies. In the unassembled, free state, the central cross-section of the flexible cylinder, along its axis, is a uniformly circular ring.

[0008] The integrated stationary component consists of the motor's internal stator and two end cap-shaped rigid wheels fixedly connected to the ends of the stator shaft. The two sets of rigid wheel internal gears have the same module and tooth count difference as the flexible cylinder external gear. They can mesh harmonically with the flexible cylinder's maximum expansion angle parallel to the cylinder's, or with internal bevel gears, with the inclined end faces. Because each point on the flexible cylinder's end circumference oscillates with the maximum oscillation value around the midsection of the flexible cylinder's generatrix, the axial oscillation values ​​of each point on the end gear teeth parallel to the axis vary. Therefore, the long generatrix of the rigid wheel teeth in parallel-axis harmonic meshing should be parallel to the maximum expansion angle of the flexible cylinder. By chamfering the tooth ends, the disengagement clearance is set to 2 / 5 or less of the difference between the long and short axis lengths of the wave generator, and the gear meshing height is set to 3 / 5 or more of this half-length difference. Similarly, in order to make full use of the composite elastic material and the external angle of the flexible cylinder end, the oblique end faces are harmonically meshed, and the rigid wheel uses an internal bevel gear to mesh with the flexible cylinder conical gear.

[0009] Taking advantage of the characteristic that the flexible cylinder's mid-section remains circular during operation, with only slightly varying deflections, torque is output on the outer side of the flexible cylinder wall at this section using a bridge-shaped ridge connection or toothed meshing pair with low axial stiffness near the wall and high circumferential stiffness at the far wall. This reduces the constraints imposed by the output coupling on the slightly varying deflections at various points around the circumference of the flexible cylinder's mid-section. A pair of angular contact ball bearings on the rotating housing of the variable-stiffness coupling withstand the radial and axial forces external to the torque output end.

[0010] The outer rotor of the motor built into the flexible cylinder is supported by the meshing of the gear teeth at both ends of the long axis of the flexible cylinder or suspended in the teeth of two rigid wheels with the help of two ball or spherical roller cage assemblies with the same deformation, and is coaxial with the two rigid wheels due to the two wave generators with the same structural dimensions and perpendicular long axes in the integrated moving parts. The axial displacement of the ball or spherical roller cage assembly is constrained by the mutually perpendicular outward and inward deformation of the flexible cylinder ports, as well as the non-parallel axis meshing constraint between the axisymmetric rigid wheels and flexible cylinder teeth. In addition, the rigid rotating shell supported by the angular contact ball bearing can assist in constraining the radial and axial displacement of the outer rotor through the flexible cylinder through the variable stiffness connection outside the cross section of the flexible cylinder. Therefore, there is no need for bearing support between the stator and rotor of the built-in outer rotor motor, and the entire reducer is like a low-speed, high-torque motor with rotating shell.

[0011] Since the cross-section of the flexible cylinder always remains naturally circular during the working process, and the variable stiffness connection output member has little restraining effect on the different micro-deflection deformations at various circumferential points of the cross-section, the energy consumption of the reducer output end during operation is extremely small; also, because the three flexible parts, the flexible cylinder and the outer rings of the two flexible bearings, are combined into one, the wall thickness of the elastic parts required by the processing technology of the original two separate parts but not required during operation is greatly reduced, so the deformation energy loss of the most core elastic parts in the harmonic reducer during operation can also be greatly reduced; the two harmonic drive components working in parallel are reduced by half because the load is reduced by half. Under the conditions of the same flexible component bending stiffness and wall thickness, the wall thickness of the elastic parts of the parallel high-efficiency composite flexible cylinder harmonic reducer can be less than half of that of the single harmonic drive component, so the transmission efficiency of the reducer is high and the failure rate of the flexible parts is low.

[0012] Even if the dynamic and static parts of the reducer are assembled with separate parts without corresponding integration, the word "composite" can be removed from the name, but the functions and advantages of the flexible cylinder harmonic reducer are still there, except that the radial size is slightly larger, the transmission efficiency is lower, the number of interfaces in the force or torque transmission path is more, and its manufacturing process is relatively more mature and simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the elastic deformation of the flexible-wheel harmonic reducer structure and the flexible bearing outer ring during operation;

[0014] Figure 2 This is a schematic structural diagram of a preferred embodiment of the present invention - a parallel high-efficiency composite flexible-cylinder harmonic reducer with a built-in outer rotor motor;

[0015] Figure 3 This is a schematic diagram of a motor outer rotor of the present invention, in which two wave generators of the same structural size and perpendicular long axes are integrated at both ends, and the outer surface has a flexible bearing inner ring raceway;

[0016] Figure 4 2. It is a schematic diagram comparing the structures of the present invention in which the moving parts and the static parts are integrated or not;

[0017] Figure 5 It is a structural schematic diagram of a parallel type high-efficiency composite flexible cylinder harmonic reducer of the present invention using a spherical roller cage assembly and a tapered roller bearing support and an oblique end face harmonic meshing and a variable stiffness tooth meshing pair connection member. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] In the following description, specific details, such as certain internal procedures and techniques, are provided for purposes of illustration and not limitation to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0020] like Figure 1 As shown in a, the flexible wheel type harmonic reducer consists of a wave generator 102, a flexible bearing 103, a flexible wheel 101 and a rigid wheel 104, that is, it contains only one set of harmonic transmission components, wherein the flexible bearing 103 is installed on the wave generator 102, becomes a non-circular shape, and then is embedded in the flexible wheel 101, forcing the flexible wheel 101 to deform. When the wave generator 102 is running, the flexible wheel 101 can produce controllable elastic deformation, and the gear teeth on the outer circle at both ends of the long axis of the flexible wheel 101 are meshed with the inner circle gear teeth of the rigid wheel 104 at the same time. Moreover, since there is a tooth difference of several teeth between the gears on the rigid wheel 104 and the flexible wheel 101, the gear teeth at the short axis of the deformed flexible wheel 101 are completely disengaged from the inner gear teeth of the rigid wheel 104, forcing the flexible wheel 101 to produce harmonic deformation motion to transmit motion and torque, thereby achieving the purpose of a large reduction ratio. The deformation diagram of the flexible bearing outer ring 103A is shown in FIG. Figure 1 As shown in b, the long axis end is expanded outward and the short axis end is contracted inward, so this type of harmonic reducer has the three disadvantages described in the background art.

[0021] In view of the above problems, the present invention will describe a parallel high-efficiency composite flexible-cylinder harmonic reducer with a built-in outer rotor motor in combination with embodiments.

[0022] Example 1

[0023] like Figure 2 As shown, this embodiment provides a parallel, high-efficiency, composite flexible-cylinder harmonic reducer for a built-in outer rotor motor. In this embodiment, the reducer is compactly assembled in the radial and axial directions by an integrated moving component, an integrated static component, and an elastic coupling output member with low axial stiffness and high circumferential stiffness. The integrated moving component comprises a flexible cylinder 11 with integrated flexible bearing outer ring raceways on both ends of the inner surface, a gear on the outer surface, and a uniform diameter in the middle. It is assembled with two wave generators 8 of the same structural dimensions, with mutually perpendicular long axes, and flexible bearing inner ring raceways on the outer surface, integrated at both ends of the motor's outer rotor. These wave generators are assembled via two identical ball retainer assemblies 10.

[0024] like Figure 2As shown, the integrated stationary component consists of the motor's internal stator 6 and two end cap-shaped rigid wheels 1 fixedly connected to the ends of the stator shaft 2. The internal gears of the two sets of rigid wheels 1 and the external gears of the flexible cylinder 11 have the same module and tooth number difference. The rigid wheel teeth mesh harmonically with the flexible cylinder teeth, parallel to the maximum external angle of the flexible cylinder 11. As shown in the functional block diagram, these two harmonic drive components are effectively connected in parallel, performing the same proportional reduction. The motor's internal stator 6 and the two rigid wheels 1 are axially fixed to the stator shaft 2 by a retaining ring 5 and a spring collar 4. The power cord 3 passes through the inner hole of the stator shaft 2 to electrically connect to the internal stator 6.

[0025] like Figure 2 As shown, a bridge-hole ridge connector 11A, with low axial stiffness near the wall and high circumferential stiffness at the far wall, is fastened to the rotating housing 12 via screws on the outer circumference of the flexible cylinder's midsection. This variable-stiffness connection reduces the constraint imposed by the output coupling on the varying micro-deflections and deformations at various points along the circumference of the flexible cylinder's midsection, effectively reducing energy consumption at this location. The rotating housing 12 is supported by a pair of angular contact ball bearings 9, which are pre-tightened on the rigid wheel 1 by screws on the end cap 7. The rotating housing 12 outputs amplified torque at a low rotational speed while also withstanding external radial and axial forces.

[0026] Figure 3 A schematic volume view of a motor outer rotor is given, in which two wave generators 8 with the same structural dimensions and perpendicular long axes are integrated at both ends and the outer surfaces are provided with flexible bearing inner ring raceways.

[0027] like Figure 2 As shown, the characteristic that each point on the circumference of the flexible cylinder 11 end is to swing outward and inward with the mid-section point on the respective cylinder generatrix as the center during rotation and the swing value is the largest, that is, the swing value of each point on the axial direction of the end spur gear teeth parallel to the axis is not the same, so the length generatrix of the rigid wheel 1 tooth in parallel axis harmonic meshing should be as follows Figure 4 As shown in the partial enlarged figure in the middle, it is parallel to the maximum external angle of the flexible cylinder 11. In this case, by means of tooth end chamfering, 2 / 5 or less of half the difference between the long and short axis lengths of the wave generator 8 is used as the disengagement clearance, and 3 / 5 or more of half the length difference is used as the gear meshing height to increase the meshing area. In addition, the meshing between the gear teeth at both ends of the long axis of the flexible cylinder 11 and the gear teeth of the rigid wheel 1 is a straight tooth meshing, which optimizes the force. Similarly, in order to fully utilize the composite elastic material of the flexible cylinder end and the external angle, the oblique end face harmonic meshing can be used. Figure 5 As shown, the inner bevel gear of the rigid wheel 1 is meshed, and the gear of the flexible cylinder 11 is conical. By using part of the rib material of the outer raceway of the flexible bearing, the end material of the flexible cylinder 11 is reduced to maximize the meshing area and reduce the deformation energy consumption of the flexible cylinder 11 at this location.

[0028] Example 2

[0029] Another type of parallel high-efficiency flexible-cylinder harmonic reducer with built-in external rotor motor is Figure 4 As shown in the figure, it provides a schematic diagram of the structure comparison of whether the dynamic and static parts of the reducer are integrated. Figure 4 As shown on the right, when the dynamic and static components are assembled from separate parts, two wave generators 16 of identical dimensions and perpendicular long axes are tightly fitted at each end of the motor's outer rotor 14. Flexible bearings 15 are mounted on these wave generators, forming a non-circular shape. These bearings are then embedded within the ends of the flexible cylinder 13, which has gears at both ends. Variable-stiffness connectors 13A, located on the outer diameter of the cylinder's midsection, are screwed to the rotating housing 12. The word "composite" is removed from the name, but the functions and advantages of this flexible-cylinder harmonic reducer remain. The designation is slightly larger, resulting in lower transmission efficiency and a greater number of interfaces in the force or torque transmission path. However, the manufacturing process is relatively more mature and simpler. In this case, the rotating housing 12 is supported by a pair of angular contact ball bearings 17. The end caps 7 use screws to position and pre-tighten the angular contact ball bearings 17 against the rigid wheel 1. The rotating housing 12 outputs amplified torque at a low speed while withstanding external radial and axial forces.

[0030] Example 3

[0031] like Figure 5 As shown, the third parallel type high-efficiency composite flexible cylinder harmonic reducer of the built-in outer rotor motor provided in this embodiment is still composed of an integrated moving part, an integrated static part and an elastic connection output member with low axial stiffness and high circumferential stiffness in a compact manner in the radial and axial directions. The integrated moving part is composed of a flexible cylinder 11 with integrated flexible bearing outer ring raceways on both ends of the inner surface, gears on the outer surface and the same diameter in the middle, and two wave generators 8 with the same structural dimensions and perpendicular long axes and flexible bearing inner ring raceways on the outer surface integrated at both ends of the motor outer rotor, which are assembled through two identical spherical roller retainer assemblies 18. The integrated static part is composed of exactly the same Figure 2 However, the internal bevel gear of the rigid wheel 1 meshes harmonically with the bevel end faces. To fully utilize the composite elastic material and the external angle of the flexible cylinder end, the internal bevel gear of the rigid wheel 1 meshes with the conical external bevel gears at both ends of the flexible cylinder 11. By utilizing some of the rib material of the flexible bearing's outer raceway, the material required at the ends of the flexible cylinder 11 is reduced, maximizing the meshing area and minimizing deformation energy loss at this location. A toothed connector 11B with low axial stiffness near the wall and high circumferential stiffness meshes with the internal gear of the rotating housing 12 on the outer circumference of the flexible cylinder's mid-section. The rotating housing 12 is supported by a pair of tapered roller bearings 19. The end cap 7 uses screws to position and pre-tighten the tapered roller bearings 19 onto the rigid wheel 1. The rotating housing 12 outputs amplified torque at a low speed and withstands external radial and axial forces.

[0032] The above describes in detail three preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solution that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A parallel high-efficiency composite flexible-cylinder harmonic reducer with a built-in outer rotor motor, characterized in that: With the help of the orthogonal antisymmetric deformation of the thin-walled composite flexible cylinder with equal diameter in the middle due to the wave generators with long axes coaxially installed at both ends and perpendicular to each other, two harmonic drive components with the same modulus and tooth number difference at both ends of the composite flexible cylinder are used to respectively amplify half of the torque of the same input source in parallel with the same proportion; after the amplified same steering torque at both ends is superimposed on the middle section of the composite flexible cylinder of constant circle, the variable stiffness connecting piece on the outer circle of the section is output through its rotating shell; the variable stiffness connecting piece is a bridge hole type ridge plate connector or a tooth type connector with low axial stiffness at the near wall end and high circumferential stiffness at the far wall end, which is arranged on the middle section of the composite flexible cylinder, so as to reduce the constraint of the output connecting piece on the different micro-deflection deformation at each point of the circumference of the middle section of the flexible cylinder, and effectively reduce the constraint energy consumption here; The radial and axial external forces on the outside of the rotating torque output end are borne by a pair of angular contact ball bearings through the rotating shell of the variable stiffness connection.

2. The parallel high-efficiency composite flexible cylinder harmonic reducer with built-in outer rotor motor as claimed in claim 1, characterized in that: The reducer is composed of integrated moving parts, integrated static parts and variable stiffness connecting parts in a compact radial and axial manner; the integrated moving parts are composed of a thin-walled composite flexible cylinder with flexible bearing outer ring raceways integrated on the inner surfaces of both ends, gears on the outer surface and equal diameter in the middle, and two wave generators with the same structural dimensions and long axes perpendicular to each other and flexible bearing inner ring raceways on the outer surface are integrated on both ends of the outer rotor of the built-in motor, and are assembled through two identical ball or spherical roller cage assemblies.

3. The parallel high-efficiency composite flexible cylinder harmonic reducer of the built-in outer rotor motor according to claim 2, characterized in that: The integrated static component is composed of a stator inside a built-in motor and two end cover-shaped rigid wheels fixedly connected to the two ends of the stator shaft; the internal gears on the two rigid wheels have the same module and tooth number difference as the external gear of the composite flexible cylinder, and the rigid wheel teeth are harmonically meshed with the composite flexible cylinder gear in a manner parallel to the maximum external angle of the composite flexible cylinder, or can be harmonically meshed on the oblique end face of the maximum external angle of the composite flexible cylinder in an internal bevel gear meshing manner.

4. The parallel high-efficiency composite flexible cylinder harmonic reducer of the built-in outer rotor motor according to claim 1 or 3, characterized in that: The characteristic that each point on the circumference of the composite flexible cylinder port swings outward and inward with the mid-section point on the generatrix where each point is located as the center of the circle and the swing value is the largest when rotating, that is, the swing values ​​of each point on the axial direction of the end spur gear teeth parallel to the axis are not equal, so the long generatrix of the rigid wheel teeth in parallel axis harmonic meshing should be parallel to the maximum external angle of the composite flexible cylinder. In this case, with the help of tooth end chamfering, 2 / 5 or less of half of the difference between the long and short axes of the wave generator is used as the disengagement clearance, and 3 / 5 or more of half of the length difference is used as the gear meshing height to increase the meshing area; similarly, in order to make full use of the elastic material and external angle of the composite part at the end of the flexible cylinder, for the harmonic meshing of the oblique end face, the meshing of the inner bevel gear of the rigid wheel and the conical gear of the composite flexible cylinder can be used to borrow part of the rib material of the outer raceway of the flexible bearing to reduce the material at the end of the composite flexible cylinder, so as to maximize the meshing area and reduce the deformation energy consumption of the composite flexible cylinder here.

5. The parallel high-efficiency composite flexible cylinder harmonic reducer of the built-in outer rotor motor according to claim 4, characterized in that: The outer rotor of the built-in motor is supported by the meshing of the gear teeth at both ends of the long axis of the composite flexible cylinder or suspended in the gear teeth of the two rigid wheels by means of two ball or spherical roller cage assemblies with the same deformation, and is coaxial with the two rigid wheels because of the two wave generators with the same structural size and long axes perpendicular to each other in the integrated moving parts. The axial displacement of the ball or spherical roller cage assembly is constrained by the mutually perpendicular anti-symmetric deformation of the outward expansion and inward contraction of the two ends of the composite flexible cylinder, and by the non-parallel axis meshing constraint between the axisymmetric rigid wheels and composite flexible cylinder teeth. In addition, the rigid rotating shell supported by the angular contact ball bearing can assist in constraining the radial and axial displacements of the outer rotor through the cross section of the composite flexible cylinder through the variable stiffness connecting piece. Therefore, the stator and rotor of the built-in outer rotor motor do not need to be supported by bearings, thereby simplifying the reducer structure and reducing the friction and wear power consumption of the moving parts.

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