Hollow joint planetary gear motor

Abstract

The invention discloses a hollow joint planetary gear motor, which realizes internal wiring by designing an integrated hollow channel penetrating through a motor rotor shaft and a final output planet carrier; meanwhile, the double magnetic encoder assemblies directly installed on the rotor shaft and the output shaft respectively are adopted, and high-precision position and speed detection without an intermediate transmission link is achieved; and in combination with an optimized two-stage planetary speed reduction structure and a special bearing support and torque transmission design, compact joint driving with high torque density and high control precision is realized on the premise of ensuring the strength and rigidity of the hollow structure. Back clearance errors, elastic deformation and abrasion caused by movement transmission through intermediate links such as a gear in the prior art are fundamentally eradicated, the control problems that precision is low and high-precision absolute position and multi-turn counting cannot be considered at the same time due to single or indirect encoder feedback are solved, high-torque-density transmission is ensured, and meanwhile the control precision is improved. And neat integrated wiring and ultrahigh-precision motion control capability are realized.

Description

Technical Field

[0001] This invention relates to the field of geared motor technology, and in particular to a hollow joint planetary geared motor. Background Technology

[0002] In the field of robot joint drive technology, planetary geared motors are widely used due to their advantages such as compact structure, large transmission ratio, and strong load-bearing capacity. Traditional planetary geared motors mostly adopt a solid shaft structure, with a solid output shaft design, which makes it impossible to run cables internally. The cables for the robot's motors, sensors, power supplies, etc., can only be routed externally or via external cable chains. This wiring method not only occupies external space of the robot and affects the overall structural compactness, but also easily leads to cable wear, tangling, or even breakage when the joint rotates frequently, reducing system reliability and service life. In addition, existing joint motors usually only use a single encoder for position feedback, making it difficult to simultaneously achieve high-precision position detection and multi-turn counting, which limits the robot's performance in high-dynamic, high-precision application scenarios.

[0003] However, while some existing technologies have attempted to integrate wiring channels within joints, their structures are often complex, costly to manufacture, and struggle to guarantee transmission accuracy and structural rigidity. Furthermore, encoders are typically mounted indirectly via gear pairs or couplings, leading to issues such as accumulated transmission errors and response delays, which affect control accuracy and fail to meet the comprehensive requirements of modern robots for compactness, reliability, and control precision. Summary of the Invention

[0004] Therefore, it is necessary to provide a hollow joint planetary geared motor to address the technical challenge of achieving both hollow wiring and saving wiring space, while also integrating high-precision dual encoders and improving motion control accuracy.

[0005] A hollow joint planetary geared motor, the hollow joint planetary geared motor comprising:

[0006] Motor assembly, including a hollow rotor shaft;

[0007] The planetary reduction gear assembly is connected to the rotor shaft, and its final output end is a secondary planetary carrier, which has an axially through hollow output hole.

[0008] The hollow channel of the rotor shaft is coaxially connected with the hollow output hole of the secondary planetary carrier to form a hollow wiring channel that runs through the motor and the reducer.

[0009] It also includes a first encoder component and a second encoder component;

[0010] The first encoder assembly includes a first magnetic ring disposed at the output end of the secondary planetary carrier and a corresponding first read head for directly detecting the angular position of the secondary planetary carrier;

[0011] The second encoder assembly includes a second magnetic ring disposed on the rotor shaft and a corresponding second reading head for directly detecting the rotation information of the rotor shaft.

[0012] In one embodiment, the planetary reduction assembly is a two-stage planetary reduction mechanism, including a first-stage reduction section and a second-stage reduction section;

[0013] The first-stage reduction section includes a first-stage sun gear connected to the rotor shaft, at least one first-stage planet gear meshing with the first-stage sun gear, and a first-stage internal gear ring meshing with the first-stage planet gear.

[0014] The secondary reduction section includes a secondary sun gear, at least one secondary planet gear meshing with the secondary sun gear, and a secondary internal gear ring meshing with the secondary planet gear;

[0015] The first-stage planetary gear is supported by the first-stage planetary carrier, and the second-stage planetary gear is supported by the second-stage planetary carrier.

[0016] In one embodiment, the primary planetary carrier and the secondary sun gear are integrally formed components.

[0017] In one embodiment, the secondary planetary carrier is supported on the housing of the geared motor by a thin-walled crossed roller bearing.

[0018] In one embodiment, the secondary internal gear ring is connected to the housing of the geared motor via at least one pin to transmit torque and prevent relative rotation.

[0019] In one embodiment, the rotor shaft is supported by a pair of deep groove ball bearings located at the near-motor end and the far-motor end of the rotor shaft, respectively.

[0020] In one embodiment, the integrated component is supported within the housing of the geared motor by a pair of bearings.

[0021] In one embodiment, the first magnetic ring is fixedly disposed on an output end cover, and the output end cover is fixedly connected to the output end of the secondary planetary carrier.

[0022] In one embodiment, a bearing end cap is also included, which is connected to the housing by screws and axially presses and fixes the secondary internal gear ring and the outer ring of the thin-walled crossed roller bearing.

[0023] In one embodiment, the first-stage planetary gear is mounted on a first-stage pin via a needle roller bearing, and the first-stage pin is fixed to the first-stage planetary carrier; the second-stage planetary gear is mounted on a second-stage pin via a needle roller bearing, and the second-stage pin is fixed to the second-stage planetary carrier.

[0024] The aforementioned hollow-joint planetary geared motor effectively solves the technical problems of space occupation, motion interference, and cable wear caused by external wiring in robot joints by constructing an integrated through-path wiring channel of "hollow channel in rotor shaft - hollow hole in planetary carrier". This achieves internal cable protection and significantly improves the robot's structural compactness and motion reliability. Simultaneously, the solution employs dual encoder components directly connected to the rotor shaft and output shaft respectively, fundamentally eliminating backlash errors, elastic deformation, and wear caused by traditional motion transmission through intermediate links such as gears. This solves the control problems of low accuracy and inability to simultaneously achieve high-precision absolute position and multi-turn counting inherent in single or indirect encoder feedback. The combination of these two core features enables the joint motor to ensure high torque density transmission while possessing neat integrated wiring and ultra-high precision motion control capabilities, providing a crucial drive solution for high-performance robots. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the hollow joint planetary geared motor in one embodiment;

[0026] Figure 2 for Figure 1 A schematic diagram of the disassembly structure of the hollow joint planetary gear motor in the embodiment shown;

[0027] Figure 3 for Figure 1 A structural schematic diagram of the hollow joint planetary geared motor in the embodiment shown from another perspective;

[0028] Figure 4 for Figure 3 A schematic cross-sectional view of AA in the illustrated embodiment;

[0029] Figure 5 for Figure 3 A schematic cross-sectional view of CC in the illustrated embodiment;

[0030] Figure 6 for Figure 3 A schematic cross-sectional view of the DD in the illustrated embodiment;

[0031] Figure 7 This is a partial structural schematic diagram of a hollow joint planetary geared motor in one embodiment;

[0032] Figure 8 This is a partial structural schematic diagram of a hollow joint planetary geared motor in one embodiment;

[0033] Figure 9 for Figure 8 A structural schematic diagram of a local structure from another perspective in the illustrated embodiment;

[0034] Figure 10 for Figure 9 A cross-sectional view of the EE in the illustrated embodiment;

[0035] Figure 11 This is a partial structural schematic diagram of a hollow joint planetary geared motor in one embodiment;

[0036] Figure 12 for Figure 11 A structural schematic diagram of a local structure from another perspective in the illustrated embodiment;

[0037] Figure 13 for Figure 12 A cross-sectional view of the FF in the illustrated embodiment;

[0038] Figure 14 This is a partial structural schematic diagram of a hollow joint planetary geared motor in one embodiment;

[0039] Figure 15 for Figure 11 A structural schematic diagram of a local structure from another perspective in the illustrated embodiment;

[0040] Figure 16 for Figure 2 An enlarged structural schematic diagram of part P in the illustrated embodiment;

[0041] Figure 17 for Figure 2 A magnified schematic diagram of the Q part in the embodiment shown;

[0042] Figure 18 for Figure 4 An enlarged structural diagram of part R in the illustrated embodiment. Detailed Implementation

[0043] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. In the description of the present invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and 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 orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0047] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0048] To address the aforementioned technical problems, this invention provides a hollow joint planetary geared motor. Its core inventive concept lies in: designing an integrated hollow channel that runs through the motor rotor shaft and the final output planetary carrier to achieve internal wiring; simultaneously, employing dual magnetic encoder assemblies directly mounted on the rotor shaft and output shaft respectively to achieve high-precision position and speed detection without intermediate transmission links; and combining an optimized two-stage planetary gear structure, special bearing support, and torque transmission design to achieve a compact joint drive with high torque density and high control precision while ensuring the strength and rigidity of the hollow structure.

[0049] According to one aspect of the present invention, a hollow joint planetary geared motor is provided, comprising a motor assembly, a planetary gear reducer assembly, and a dual encoder feedback system. The motor assembly includes a hollow rotor shaft. The planetary gear reducer assembly is driveably connected to the rotor shaft, and its final output end is a secondary planetary carrier, which has an axially penetrating hollow output hole. The hollow channel of the rotor shaft and the hollow output hole of the secondary planetary carrier are coaxially connected, forming a continuous hollow wiring channel running through the entire motor and reducer, for robot cables such as power cables, signal cables, encoder cables, and air hoses to pass through.

[0050] The dual encoder feedback system includes a first encoder assembly and a second encoder assembly. The first encoder assembly includes a first magnetic ring (or first encoder magnet) fixedly mounted on the output end of the secondary planetary carrier, and a first read head fixedly mounted on the housing or end cover, opposite to the first magnetic ring, for directly and without backlash detecting the absolute angular position of the secondary planetary carrier (i.e., the final output end). The second encoder assembly includes a second magnetic ring (or second encoder magnet) fixedly mounted on the rotor shaft, and a second read head fixedly mounted on the housing or mounting plate, opposite to the second magnetic ring, for directly detecting the rotational speed and multi-turn count of the rotor shaft. The signals from both encoders are provided to the controller to achieve full-range, high-precision closed-loop control of the joint position.

[0051] In a preferred embodiment, the planetary reduction assembly is a two-stage planetary reduction mechanism, comprising a primary reduction section and a secondary reduction section. The primary reduction section includes a primary sun gear connected to the rotor shaft, at least one primary planet gear meshing with it, and a primary internal gear ring meshing with the primary planet gear. The secondary reduction section includes a secondary sun gear, at least one secondary planet gear meshing with it, and a secondary internal gear ring meshing with the secondary planet gear. The primary planet gears are supported by a primary planet carrier, and the secondary planet gears are supported by the secondary planet carrier. To further simplify the structure and improve rigidity, the primary planet carrier and the secondary sun gear are preferably designed as an integrally formed component.

[0052] To ensure the stability and high precision of the hollow output end under complex loads (radial force, axial force, overturning moment), the secondary planetary carrier is supported on the housing of the geared motor by a thin-walled crossed roller bearing. This bearing is particularly suitable for the high rigidity and high precision support requirements of hollow structures.

[0053] To prevent the secondary internal gear ring from sliding relative to the housing when transmitting large torques, the secondary internal gear ring is circumferentially positioned and torque transmitted to the housing of the geared motor via at least one pin. This is a reliable connection method suitable for thin-walled housing structures.

[0054] The rotor shaft is supported at both ends by a pair of deep groove ball bearings, ensuring the smoothness and coaxiality of the rotor rotation. The integrated component (first-stage planetary carrier / second-stage sun gear) is also supported within the housing by a pair of bearings, forming a stable intermediate transmission support.

[0055] The beneficial effects of this invention are as follows:

[0056] First, it achieves efficient internal wiring: the through-hole channel allows all cables to pass through the inside of the joint, which greatly saves the robot's external space, makes the structure more compact, avoids the tangling and wear problems caused by external wiring, and improves the system's reliability and lifespan.

[0057] Secondly, it improves control accuracy: The direct-drive dual-encoder design completely eliminates backlash, elastic deformation, and wear errors caused by intermediate transmission links such as gears and synchronous belts, ensuring high-precision position feedback from the signal source. The dual encoders work together to simultaneously meet the requirements of high-precision absolute position detection and multi-turn counting, significantly improving the robot's motion control accuracy and repeatability.

[0058] Third, the structure is compact and the rigidity is high: the integrated design of the first-stage planetary carrier and the second-stage sun gear eliminates intermediate connecting parts, shortens the transmission chain, and reduces the assembly interface, which not only makes the structure more compact and the axial dimension smaller, but also greatly improves the overall rigidity of the transmission system.

[0059] Fourth, high load-bearing capacity and reliable operation: The output end is supported by thin-walled crossed roller bearings, which can simultaneously withstand multi-dimensional loads, ensuring stable output of the hollow joint under high loads. The pin-shaft connection to the internal gear ring provides reliable torque transmission. The optimized bearing layout ensures smooth operation of all rotating parts.

[0060] Fifth, superior overall performance: This invention organically integrates features such as hollow wiring, high-precision feedback, high torque density deceleration, and high rigidity support, providing a highly integrated and high-performance drive solution suitable for high-performance robot joints.

[0061] To further illustrate the hollow joint planetary geared motor of the present invention, please refer to the following: Figures 1 to 7 This embodiment provides a hollow joint planetary geared motor, which has an overall cylindrical structure and an axially penetrating hollow channel, making it particularly suitable for robot joint modules.

[0062] To further illustrate the overall structure and hollow wiring channel of this invention, such as Figures 1 to 17 As shown, the geared motor mainly includes, from right to left (taking the direction shown in the figure as an example): output end assembly, second-stage planetary reduction section, first-stage planetary reduction section, motor assembly, and rear end cover assembly. All components are assembled in the housing 6 along the same central axis.

[0063] One of the core features of this invention is the formation of a continuous hollow wiring channel. For details, please refer to [the relevant documentation / reference]. Figures 1 to 6 , Figures 11 to 15 The rotor shaft 11 of the motor assembly is a hollow shaft with a precision-machined through hole inside, forming the first section of the hollow channel. The right end (motor end) of the rotor shaft 11 is open, and the left end (reduction end) is connected to the first-stage sun gear 14. The center of the first-stage sun gear 14 also has a through hole, aligned with the through hole of the rotor shaft 11. The integrated component 25 of the first-stage planetary carrier (which is also the second-stage sun gear) has a larger through hole in its center. The center of the second-stage planetary carrier 33 (i.e., the output flange) has an axially penetrating hollow output hole. The through holes of the rotor shaft 11, the first-stage sun gear 14, the integrated component 25, and the hollow output hole of the second-stage planetary carrier 33 are strictly coaxial after assembly, forming a smooth and continuous hollow wiring channel L that runs from the rear end of the motor to the front end of the joint. The diameter of this channel L can be designed according to wiring requirements, typically from 6mm to 20mm, and can accommodate the robot's motor power lines, encoder feedback lines, brake lines, sensor lines, and even air and liquid pipes. The cable is introduced through the central hole of the rear cover 18, passes through the inside of the rotor shaft 11, and then passes through the central holes of the integrated component 25 and the secondary planetary carrier 33 in sequence, finally exiting from the central hole of the output end cover 1 to connect to the next joint or end effector. This internal wiring method completely eliminates the need for external cable chains or flexible cable bundles, resulting in a clean appearance of the robot arm, interference-free movement, and well-protected cables.

[0064] To further illustrate the dual encoder feedback system of the present invention, such as Figure 2 , Figure 4 , Figure 16 and Figure 17 As shown, this invention employs a unique dual-encoder direct feedback system to achieve high-precision control.

[0065] The first encoder assembly (also called the output absolute position encoder): This assembly is used to accurately measure the angular position of the final output end (secondary planetary carrier 33). The first encoder magnet 15 is fixed to an output end cover 1. In this embodiment, specifically: the output end cover 1 extends integrally with a hollow cylinder with openings on both sides through a hollow wiring channel L, and the first encoder magnet 15 is fixed to this cylinder. The output end cover 1 is tightly fixed to the output end face of the secondary planetary carrier 33 by multiple screws and rotates synchronously with the secondary planetary carrier 33. The first encoder magnet 15 is typically a ring-shaped multipole magnet with its N / S poles arranged alternately along the circumference. Opposite to the first encoder magnet 15, the stationary first encoder read head (integrated on the control board 17, or separately installed in the corresponding position of the housing 6) faces the magnet 15 with a small gap. When the secondary planetary carrier 33 rotates, the magnet 15 rotates accordingly, and its magnetic field change is sensed by the first read head and converted into a high-resolution digital signal, thereby obtaining the absolute angular position of the output shaft in real time and accurately. Since the magnet 15 is directly fixed on the output end cover 1, without any gears, couplings or other transmission links in between, the measurement error caused by transmission backlash, elastic deformation and wear is completely avoided. The measurement accuracy depends only on the resolution of the encoder itself and the concentricity of the installation.

[0066] The second encoder assembly (also known as a motor rotor speed / multi-turn encoder): This assembly is used to measure the rotational speed and number of revolutions of the motor rotor. The second encoder magnet 16 is directly fixed to the rotor shaft 11 (e.g., by interference fit or bonding to a shoulder of the rotor shaft 11). The second encoder read head (also integrated into the control board 17 or mounted on a mounting plate) is fixed and opposite to the second encoder magnet 16. The second encoder magnet 16 rotates at high speed with the rotor shaft 11, and its magnetic field changes are detected by the second read head, outputting a pulse signal proportional to the rotor speed or a direct digital position signal. By counting and processing this signal, the controller can accurately determine the motor rotor speed, rotation direction, and cumulative angle over multiple revolutions.

[0067] It should be noted that the collaborative working principle of the control system of this invention is as follows: the control board 17 receives motion commands (such as target position and speed) from the host computer. Simultaneously, it acquires the absolute position signal from the output terminal of the first encoder and the rotor speed / multi-turn signal from the second encoder. Through built-in control algorithms (such as position loop, speed loop, and current loop), the controller can calculate the precise motor drive current to drive the motor stator 8. Specifically, because the first encoder provides the direct absolute position of the output terminal, the system can achieve high-precision positioning. The multi-turn rotor information provided by the second encoder, combined with the high-precision single-turn information from the first encoder, allows the system to accurately determine the absolute position of the output terminal within the entire stroke range even after a power outage and restart, eliminating the need for a zero-return operation and achieving true full closed-loop absolute position control. This dual direct-drive encoder configuration is the key to achieving ultra-high control precision in this invention.

[0068] It is worth mentioning that the cooperative working principle of the above control system can be further explained through the following dual encoder signal processing and control path:

[0069] 1. Command input:

[0070] Host computer / main controller: issues high-level motion commands to the robot.

[0071] Command content: Target position (θ), target velocity (ω).

[0072] 2. Feedback signal acquisition (core of the invention):

[0073] First encoder assembly (output absolute position encoder):

[0074] Sensing element: The first magnetic ring (15) rotates with the second-stage planetary carrier (33, i.e. the output end).

[0075] Signal: Outputs a high-precision absolute angular position signal θ_out for the output shaft.

[0076] Second encoder assembly (rotor speed / multi-turn encoder):

[0077] Sensing element: The second magnetic ring (16) rotates with the rotor shaft (11).

[0078] Signals: Output rotor shaft angular velocity signal ω_rotor and multi-turn count signal N_rotor.

[0079] 3. Control Panel 17—Signal Processing and Decision-Making Center:

[0080] Data fusion and location calculation module:

[0081] Input: Receive θ_out, ω_rotor, N_rotor.

[0082] Function: Combining the two-stage reduction ratio i, the global high-precision absolute position θ_global and global speed ω_global of the motor rotor side are calculated.

[0083] Output: θ_global, ω_global.

[0084] Control algorithm module (three-loop controller):

[0085] Position loop (P): Compares the target position θ* with the feedback θ_global to generate the target velocity command ω_cmd.

[0086] Speed ​​Loop (PI): Compares ω_cmd with the feedback ω_global to generate the target current (torque) command Iq_cmd.

[0087] Current loop (PI): Compares Iq_cmd with the actual current feedback Iq_fb from the motor driver to generate the final control voltage signal Uq.

[0088] 4. Driving and Execution:

[0089] Motor drivers (such as three-phase inverters):

[0090] Input: Receive control voltage signal Uq.

[0091] Function: Performs space vector modulation (SVPWM) to convert control signals into three-phase alternating current.

[0092] Output: Drive current is sent to the motor stator (8).

[0093] Motor assembly execution: The stator (8) generates a rotating magnetic field, which drives the permanent magnet rotor (9,10,11) to rotate, outputting torque and speed.

[0094] 5. Mechanical transmission and closed-loop formation:

[0095] The rotor torque is reduced and increased in two stages through the planetary reduction assembly (14,22,7,25,29,5), which ultimately drives the second-stage planetary carrier (33, output end) to rotate.

[0096] The rotation at the output end is detected by the first encoder, and the rotation of the rotor shaft is detected by the second encoder. The signals are fed back to the control board, thus forming a complete closed-loop control.

[0097] For a further detailed explanation of the output terminal and the secondary reduction section of this invention, please refer to [link / reference]. Figures 4 to 10 The output end is the part that is directly connected to the external load and bears the main load.

[0098] The secondary planetary carrier 33, serving as the final torque output component, is typically made of high-strength alloy steel (such as 42CrMo) and undergoes quenching and tempering. Its main body is a flange structure, with the aforementioned hollow output hole at the center. On one side of the carrier (facing the motor interior), multiple (usually 3-4) planetary gear mounting arms or bosses are evenly distributed circumferentially. Each boss has precision-machined pin holes for mounting the secondary planetary gear pins 31. On the other side of the carrier (output side), screw holes and locating stops are machined for mounting the output end cover 1. The outer cylindrical surface of the secondary planetary carrier 33 is interference-fitted with the inner ring of the thin-walled crossed roller bearing 2.

[0099] The thin-walled crossed roller bearing 2 is a key component supporting the output end. Its outer ring is mounted in a precision-machined bearing housing at the front end of the housing 6, while its inner ring mates with the secondary planetary carrier 33. The rollers of the thin-walled crossed roller bearing are arranged in a crossed pattern (typically at 90 degrees). This structure allows it to simultaneously withstand radial loads, axial loads, and overturning moments, while exhibiting extremely high rigidity and rotational accuracy. Compared to using a pair of angular contact ball bearings, a single thin-walled crossed roller bearing saves axial space, is more suitable for hollow structures, and provides better overall support performance. The bearing clearance or preload can be adjusted via a subsequent end cap.

[0100] The bearing end cover 3 is secured to the front face of the housing 6 by multiple hexagon socket head cap screws 32. The screw shank of the screw 32 may be a reamed bolt, which engages with the reamed holes on the housing 6 and the end cover 3 to withstand some shear force and ensure the rigidity and reliability of the connection. The inner end face of the bearing end cover 3 directly presses against the outer ring end face of the thin-walled crossed roller bearing 2, axially fixing it within the housing 6. Simultaneously, a sealing ring (not shown in the figure) is provided between the inner hole of the end cover 3 and the output journal of the secondary planetary carrier 33 to prevent dust and liquid intrusion.

[0101] The secondary internal gear ring 5 is connected to the pin shaft and is press-fitted into the inner hole in the middle of the housing 6. To prevent circumferential slippage between the internal gear ring 5 and the housing 6 under high torque, the pin shaft 4 is used for torque transmission and positioning. Figure 5 As shown, several (e.g., 3-6) corresponding radial holes are machined circumferentially on the mating end faces of the housing 6 and the internal gear ring 5. By pressing the pin 4 (usually a cylindrical pin or a tapered pin) into these aligned holes, the internal gear ring 5 and the housing 6 can be rigidly connected together circumferentially. This connection method is more reliable than simply relying on an interference fit, and is especially suitable for thin-walled structures that need to transmit large torques.

[0102] Each second-stage planetary gear 29 is supported on a second-stage planetary gear pin 31 by a needle roller bearing 30. One end of the pin 31 is pressed into a pin hole in the second-stage planetary carrier 33, and the other end may be secured by a snap ring or pressure plate. The needle roller bearing 30 has a small radial cross-section, allowing the planetary gears to have a large journal size within a limited space, thereby improving load-bearing capacity. The second-stage planetary gear 29 simultaneously meshes with the external teeth of the integrated component 25 (as the second-stage sun gear) and the internal teeth of the second-stage internal gear ring 5, completing the second-stage reduction.

[0103] To further illustrate the first-stage deceleration unit and key integrated components of the present invention, please refer to [link / reference needed]. Figures 4 to 15 The power needs to go through two stages of reduction to be transmitted from the motor to the output.

[0104] Integrated component 25 (first-stage planetary carrier / second-stage sun gear): This is another core innovative component of the invention. This part is forged and precision-machined from a single piece of alloy steel, integrating the functions of the first-stage planetary carrier and the second-stage sun gear, which are separate in traditional designs, into one unit. Figure 4 , Figure 8 and Figure 10 As can be seen, its structure can be divided into two parts: the right part (near the motor side) is a flange or bracket structure with holes evenly distributed around its circumference for mounting the first-stage planetary gear pins 24; this part acts as the first-stage planetary carrier. The left part (near the output side) is a shaft section with an external gear; this part acts as the second-stage sun gear. The center of the integrated component 25 is a large through hole, which connects to the hollow wiring channel L. This integrated design brings multiple benefits: (a) it completely eliminates the connecting shafts, keys, couplings, and other parts between the two-stage reduction gears, reducing the number of parts and potential failure points; (b) it eliminates the fit error and connection stiffness loss caused by the connection interface, significantly improving the torsional and bending stiffness of the transmission chain; and (c) it shortens the axial dimension, making the joint structure more compact.

[0105] The assembly 25 is supported within the housing 6 by a pair of angular contact ball bearings 21 and 27. The outer rings of bearings 21 and 27 are pressed into bearing seats at both ends of the housing 6, and the inner rings are press-fitted onto the journals at both ends of the assembly 25. This pair of bearings provides precise radial and axial positioning for the assembly 25, ensuring the alignment of its axis of rotation with the main axis.

[0106] The first-stage planetary gear 22 is mounted on the first-stage planetary gear pin 24 via a needle roller bearing 23. The pin 24 is pressed into the pin hole of the integrated component 25 (which serves as the first-stage planetary carrier part). The first-stage planetary gear 22 simultaneously meshes with the external teeth of the first-stage sun gear 14 and the internal teeth of the first-stage internal gear ring 7, completing the first-stage reduction.

[0107] It should be noted that the installation of the primary internal gear ring 7 and the motor stator 8 is as follows: the primary internal gear ring 7 is press-fitted into the housing 6. The outer circle of the iron core of the motor stator 8 and the inner hole at the left end of the primary internal gear ring 7 are interference-fitted and may be positioned by the end face. The coil leads of the motor stator 8 are led out from its rear and connected to the control board 17. This design of pressing the stator 8 into the internal gear ring 7 not only fixes the stator but also assists in the axial positioning of the primary internal gear ring 7.

[0108] For a more detailed explanation of the motor assembly structure of the present invention, please refer to [link / reference]. Figure 4 , Figure 14 as well as Figure 15 The motor assembly is responsible for converting electrical energy into mechanical energy, and is the source of power.

[0109] The rotor shaft 11, as part of the motor rotor and the power output shaft, is made of high-strength steel. Its right end (motor end) is supported by a deep groove ball bearing 12. The outer ring of the bearing 12 is pressed into an intermediate fixing plate (or directly pressed into the corresponding structure of the housing 6). The left end (reduction end) of the rotor shaft 11 is connected to the first-stage sun gear 14 via an interference fit, and may be further keyed to improve torque transmission capability. The center hole of the first-stage sun gear 14 is aligned with the hollow channel of the rotor shaft 11. The left end of the first-stage sun gear 14 is supported by a deep groove ball bearing 26, the outer ring of which is mounted and limited on the inner wall of the integrated component 25 of the first-stage planetary carrier (which is also the second-stage sun gear). The inner rings of the two bearings are respectively press-fitted onto the journals of the rotor shaft 11 and the first-stage sun gear 14, forming stable end supports to ensure the concentricity and smoothness of the rotation of the rotor shaft 11 and the first-stage sun gear 14.

[0110] Multiple magnets 9 are distributed and installed on the outside of the rotor support 10. The rotor support 10 is usually made of aluminum alloy or silicon steel sheets, and is fixedly connected to the central flange of the rotor shaft 11 by multiple screws 13 to form a whole. Multiple permanent magnets (magnets 9) are attached to the outer circumference of the rotor support 10 with alternating N and N poles by high-strength adhesive to form the permanent magnet rotor of the motor.

[0111] To further illustrate the assembly relationship and working principle of the present invention, the assembly sequence is briefly described as follows: First, press the secondary internal gear ring 5 into the housing 6 and drive in the pin 4. Press the outer ring of the thin-walled crossed roller bearing 2 into the front end of the housing 6. Pre-assemble the integrated component 25 along with the bearings 21 and 27 on it and the primary planetary gear assembly (22, 23, 24), and then install it from the rear end of the housing 6, positioning the outer rings of bearings 21 and 27. Press the primary internal gear ring 7 and the motor stator 8 assembly into the housing 6. Install the rotor assembly (11, 10, 9, 14, 12, 26, etc., pre-assembled) from the rear end of the housing 6, meshing the primary sun gear 14 with the primary planetary gear 22, while simultaneously positioning the bearings 12 and 26 of the rotor shaft 11. Install the rear cover 18 and secure it with screws 19, locking the bearing 26 with a snap ring 20. Install the secondary planetary carrier 33 (with planetary gears 29, 30, and 31 already installed) from the front end of the housing 6, so that it meshes with the integrated component 25 (secondary sun gear section) and the secondary internal gear ring 5, while its outer circle mates with the inner ring of the thin-walled crossed roller bearing 2. Install the bearing end cover 3 and tighten it with screws 32 to press the outer ring of the bearing 2 and the secondary internal gear ring 5. Finally, install the output end cover 1, encoder magnets 15 and 16, and control board 17.

[0112] To further illustrate the power transmission path of the present invention, in one embodiment, after energization, the motor stator 8 generates a rotating magnetic field, driving the permanent magnet rotor (9, 10, 11) to rotate. Torque is transmitted from the rotor shaft 11 to the first-stage sun gear 14. The first-stage sun gear 14 drives the first-stage planetary gears 22 rotating around it. The first-stage planetary gears 22 mesh with the fixed first-stage internal gear ring 7, thereby forcing the first-stage planetary gears 22 to revolve around the sun gear 14 while rotating on their own axis, driving the first-stage planetary carrier (i.e., the left side of the integrated component 25) to rotate. This is the first stage of speed reduction, achieving the first reduction in speed and amplification of torque.

[0113] The rotation of the integrated component 25 drives the rotation of its right-side secondary sun gear. The secondary sun gear drives the secondary planetary gears 29. The secondary planetary gears 29 mesh with the fixed secondary internal gear ring 5, thus forcing the secondary planetary gears 29 to revolve around the secondary sun gear while rotating on their own axis, driving the secondary planetary carrier 33 to rotate. This is the second stage of reduction, achieving the final reduction in speed and amplification of torque. Finally, the high-torque, low-speed motion is output from the output flange of the secondary planetary carrier 33, driving the robot joints to rotate.

[0114] Throughout the process, the second encoder magnet 16 rotates synchronously with the rotor shaft 11, providing speed and revolution count feedback. The first encoder magnet 15 rotates synchronously with the secondary planetary carrier 33, providing absolute position feedback at the final output. The controller integrates both pieces of information to achieve precise closed-loop control. All cables pass neatly through the entire joint via the central hollow channel L.

[0115] Furthermore, such as Figure 18As shown, the wave spring washer 34 is installed between the output end cover 1 and the bearing 27. The wave spring washer 34 enables the second encoder magnet 16 to be axially positioned on the right side, which ensures the axial position of the second encoder magnet 16 and provides preload to the bearing, thereby improving its lifespan and reducing the dimensional tolerance requirements of the joint parts.

[0116] It should be noted that those skilled in the art will understand that various modifications can be made without departing from the core concept of this invention. For example:

[0117] The number of planetary gears can be selected as three, four, or more, depending on torque and size requirements.

[0118] The bearing type can be replaced with an equivalent one according to the specific load and precision requirements (e.g., replacing the thin-walled crossed roller bearing 2 with a pair of matched angular contact ball bearings, but sacrificing some compactness).

[0119] The encoder type is not limited to magnetic encoders; it can also be an optical encoder (sealing needs to be considered), but the core idea of ​​"direct mounting" remains unchanged.

[0120] The motor can be an internal rotor structure (as in this embodiment) or an external rotor structure. Through adaptive design, a hollow through shaft can also be achieved.

[0121] The reduction stages can be two, three, or more, but the design of the integrated components needs to be adjusted accordingly.

[0122] In summary, the hollow joint planetary geared motor provided by this invention, through its ingenious "hollow through shaft" and "dual direct-drive encoder" design, combined with a highly integrated transmission structure and optimized support scheme, successfully solves multiple technical challenges such as internal wiring of robot joints, high-precision control, and high-rigidity compact structure, and has extremely high practical value and promising industrial application prospects.

[0123] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A hollow-joint planetary reduction motor, characterized by, The motor assembly comprises a hollow rotor shaft. The planetary reduction assembly is drivingly connected to the rotor shaft, and has a final output end in the form of a two-stage planetary carrier, which is provided with an axially-through hollow output hole. The hollow channel of the rotor shaft is coaxially connected to the hollow output hole of the two-stage planetary carrier to form a hollow wiring channel extending through the motor and the reducer. The motor further comprises a first encoder assembly and a second encoder assembly. The first encoder assembly comprises a first magnetic ring arranged on the output end of the two-stage planetary carrier, and a corresponding first read head for directly detecting the angular position of the two-stage planetary carrier. The second encoder assembly comprises a second magnetic ring arranged on the rotor shaft, and a corresponding second read head for directly detecting the rotation information of the rotor shaft. The planetary reduction assembly is a two-stage planetary reduction mechanism comprising a first-stage reduction part and a second-stage reduction part.

2. The hollow joint planetary reduction motor of claim 1, wherein, The first-stage reduction part comprises a first-stage sun gear connected to the rotor shaft, at least one first-stage planetary gear meshing with the first-stage sun gear, and a first-stage inner ring gear meshing with the first-stage planetary gear. The second-stage reduction part comprises a second-stage sun gear, at least one second-stage planetary gear meshing with the second-stage sun gear, and a second-stage inner ring gear meshing with the second-stage planetary gear. The first-stage planetary gear is supported by a first-stage planetary carrier, and the second-stage planetary gear is supported by the second-stage planetary carrier. The first-stage planetary carrier and the second-stage sun gear are an integrated component.

3. The hollow joint planetary reduction motor of claim 2, wherein, The second-stage planetary carrier is supported on the housing of the reduction motor by a thin-wall cross roller bearing.

4. The hollow joint planetary reduction motor of claim 1, wherein, The second-stage inner ring gear is connected to the housing of the reduction motor by at least one pin shaft to transmit torque and prevent relative rotation.

5. The hollow joint planetary reduction motor of claim 2, wherein, The rotor shaft is supported by a pair of deep groove ball bearings, which are respectively located at the motor-close end and the motor-remote end of the rotor shaft.

6. The hollow joint planetary reduction motor of claim 1, wherein, The integrated component is supported in the housing of the reduction motor by a pair of bearings.

7. The hollow joint planetary reduction motor of claim 3, wherein, The first magnetic ring is fixedly arranged on an output end cover, which is fixedly connected to the output end of the two-stage planetary carrier.

8. The hollow joint planetary reduction motor of claim 1, wherein, A bearing end cover is connected to the housing by screws and axially presses and fixes the second-stage inner ring gear and the outer ring of the thin-wall cross roller bearing.

9. The hollow joint planetary reduction motor of claim 1, wherein, The first-stage planetary gear is installed on a first-stage pin shaft by a needle bearing, and the first-stage pin shaft is fixed to the first-stage planetary carrier.

10. The hollow joint planetary reduction motor of claim 2, wherein, The second-stage planetary gear is installed on a second-stage pin shaft by a needle bearing, and the second-stage pin shaft is fixed to the second-stage planetary carrier.

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