A two-stage oil-cooled rotor joint module

Abstract

The present invention discloses a two-stage oil-cooled rotor joint module, which relates to the field of robotics technology and includes a first-stage center wheel, a rotor yoke, and a middle shell. The first-stage center wheel is hollow and has cooling oil inside. A plurality of first-stage oil outlet holes are provided on the circumference of the first-stage center wheel. The rotor yoke and the middle shell are sealed and connected to form a first-stage oil chamber. A second-stage center wheel structure includes a second-stage center wheel and a second-stage planetary bracket. The second-stage center wheel is hollow and has an internal space connected to the first-stage center wheel. A plurality of second-stage oil outlet holes are provided on the circumference of the second-stage center wheel. The second-stage planetary bracket is connected to the cavity wall of the middle shell to form a second-stage oil chamber. A second-stage planetary gear and a second-stage inner gear ring are provided in the second-stage oil chamber. The second-stage center wheel is driven to rotate and the cooling oil moves to the cavity wall of the second-stage oil chamber through the second-stage oil outlet holes. The heat dissipation is efficient and reliable. In a limited space, a compact structural layout is provided. No external power source is required. The heat dissipation efficiency of the cooling oil circulation during long-term operation of the large-torque robot joint is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of robots, and in particular to a two-stage oil-cooled rotor joint module. Background Art

[0002] In collaborative robots, service robots, and precision automation equipment, joint modules serve as core actuators, and their performance directly determines the robot's load capacity, response speed, and accuracy. To meet the growing demand for high power density, lightweight, and compact design, modern robot joint modules commonly integrate frameless or disc-type motors directly with precision reducers, such as harmonic reducers and planetary reducers. While this highly integrated design significantly improves power density, it also presents significant heat dissipation challenges. During joint module operation, the primary heat source is concentrated in the motor's stator windings and stator core, particularly at the winding ends. Traditional heat dissipation methods face significant limitations in highly integrated joint modules: air cooling is inefficient and requires additional fans and duct space, increasing size and noise. This makes it difficult to use within joints where sealing is crucial. External water / liquid cooling, while more efficient, requires complex circulation piping, pumps, radiators, and reliable rotary seals, significantly increasing system complexity, cost, size, and potential leakage risks, running counter to the design goals of miniaturization and lightweight joint modules. Passive heat dissipation / conduction: Relying solely on structural heat conduction has limited heat dissipation capacity and is unable to cope with the continuous heat generated at high power densities. Furthermore, the complex internal structure of the joint makes it difficult for the cooling oil to completely cover the heat source surface, so there is still room for improvement in heat dissipation efficiency. Summary of the Invention

[0003] Technical problem to be solved by the invention: The technical problem to be solved by the present invention is to provide a two-stage oil-cooled rotor joint module with efficient and reliable heat dissipation, a compact structural layout within a limited space, no need for an external power source, and improved the cooling oil circulation heat dissipation efficiency of large-torque robot joints during long-term operation.

[0004] Technical solution: To solve the above problems, the technical solution provided by the present invention is:

[0005] A two-stage oil-cooled rotor joint module, comprising

[0006] A primary center wheel structure includes a primary center wheel, a rotor yoke, and a center housing. The primary center wheel is hollow and contains cooling oil. A plurality of primary oil outlet holes are provided on the circumference of the primary center wheel. The rotor yoke and the center housing are sealed and form a primary oil cavity. The primary oil cavity contains primary planetary gears and a primary inner gear ring. The primary center wheel is driven to rotate, and the cooling oil flows through the primary oil outlet holes to the cavity wall of the primary oil cavity.

[0007] A secondary center wheel structure includes a secondary center wheel and a secondary planetary carrier. The secondary center wheel is hollow and its internal space is connected to the primary center wheel. A plurality of secondary oil outlet holes are provided on the circumference of the secondary center wheel. The secondary planetary carrier is connected to the cavity wall of the middle shell to form a secondary oil cavity. A secondary planetary gear and a secondary inner gear ring are provided in the secondary oil cavity. The secondary center wheel is driven to rotate and the cooling oil moves to the cavity wall of the secondary oil cavity through the secondary oil outlet holes. A gap is provided between the secondary planetary carrier and the end opening of the secondary center wheel. The secondary oil cavity is connected to the primary oil cavity.

[0008] The rotor yoke, the secondary planetary support and the middle shell are all made of heat-conducting materials.

[0009] The first-stage center wheel acts as a "centrifugal pump" and "oil storage chamber." When it rotates, it generates centrifugal force, which throws the internal cooling oil out at high speed through the first-stage oil outlet. The first-stage oil chamber (formed by the rotor yoke + middle shell seal): receives the thrown-out cooling oil. Under the action of centrifugal force, the oil flows at high speed close to the cavity wall, directly flushing the motor stator core and end windings (the main heat source) wrapped in the cavity wall, realizing efficient forced convection heat exchange. The rotor yoke and middle shell (thermal conductive material): act as a "thermal bridge", transferring the heat from the winding and core to the cavity wall, and further diffusing it to the external environment through the metal body, forming a dual heat dissipation of "oil cooling + heat conduction".

[0010] The secondary center wheel (hollow, connected to the primary center wheel) receives oil from the primary center wheel. Its rotation ejects the oil through the secondary oil outlet, creating a second-stage centrifugal jet. The secondary oil chamber (formed by the secondary planetary carrier and the middle housing) receives the oil ejected from the secondary stage. The oil also flows along the chamber walls, further cooling heat sources near the secondary reduction mechanism or expanding the cooling coverage area. The secondary planetary carrier (made of thermally conductive material) serves as a secondary heat sink and structural support, absorbing and conducting heat from the secondary oil chamber while also supporting the planetary gear train. The gap (between the secondary planetary carrier and the end of the secondary center wheel) forms a critical oil return channel. The heat-dissipated oil flows back through this gap to the primary center wheel under the influence of gravity, achieving a closed-loop self-circulation of the cooling oil, eliminating the need for an external oil pump. Relying solely on the reducer's own rotation (the primary and secondary center wheels) to drive the oil circulation, the system eliminates the need for external pumps, piping, and rotating seals, meeting the requirements of compactness. Oil circulation: Oil is spun off the first-stage center wheel -> the first-stage oil cavity is cooled -> the oil falls back / collects -> flows into the second-stage center wheel -> the second-stage oil is spun off -> the second-stage oil cavity is cooled -> the oil flows back to the first-stage center wheel through the gap. This forms a highly efficient, closed internal oil cooling circuit. Active oil cooling: High-speed oil flow directly impacts / covers the stator winding ends and the iron core (the largest heat source), utilizing the oil's high specific heat capacity and forced convection to efficiently remove heat. Passive heat conduction: The rotor yoke, second-stage planetary carrier, and center housing are all made of thermally conductive materials, rapidly dissipating heat absorbed by the oil cavity walls and heat directly conducted to the module housing or environment, improving overall heat dissipation capabilities. Compact integration: The oil cooling channels (oil cavity, oil outlet, gap) and heat dissipation structure (thermal conductive housing components) are deeply integrated into the reducer and motor body, adding virtually no additional module volume.

[0011] The primary oil outlet holes and the secondary oil outlet holes increase the coverage of the cooling oil on the heat source inside the joint, thereby increasing the circulation and heat dissipation efficiency of the cooling oil.

[0012] Optionally, the primary oil outlet holes and the secondary oil outlet holes are evenly arranged around the circumference.

[0013] The evenly distributed oil outlet holes convert the rotating centrifugal force into an oil curtain / oil flow covering the entire area, achieving dead-angle cooling of the heat source while maintaining system dynamic balance and oil pressure stability.

[0014] Optionally, the middle shell is a rotating body structure with a U-shaped meridian plane. The U-shaped structure is provided with grooves for accommodating the rotor magnets and the stator core. The grooves are tightly attached to the rotor magnets and the stator core, and the inner wall of the middle shell is in contact with the cooling oil.

[0015] The U-shaped middle shell constructs an ultra-short heat conduction path of "heat source-heat conductive shell-cooling oil" through geometric configuration and material properties, while achieving high-density packaging of electromechanical structures.

[0016] Optionally, the inner wall of the middle shell is a thin-walled structure.

[0017] The thin-wall design of the inner shell of the central housing serves the dual purpose of a heat conduction accelerator and a space optimizer within the technical solution. Through extreme material thickness control, the thin-wall structure creates a near-zero-gradient heat transfer channel, enabling ultra-high-speed heat transfer from the heat source (stator / winding) to the cooling medium (oil) while ensuring structural integrity. The thin wall has an extremely low thermal capacity, allowing for rapid response to temperature fluctuations at the heat source and preventing heat accumulation within the housing. This makes it particularly suitable for dynamic heat dissipation requirements under conditions of frequent starts and stops and variable loads in robot joints. Thin walls are crucial for achieving "efficient heat dissipation without external power"—only an ultra-low thermal resistance design can achieve sufficient heat flux transfer solely through the reducer's centrifugal oil shedding.

[0018] Optionally, a first-stage planetary bracket 1 and a first-stage planetary bracket 2 are provided on both axial sides of the first-stage planetary wheel. The first-stage planetary bracket 1 and the first-stage planetary bracket 2 are provided with a protruding bracket structure and are rotatably connected to the first-stage planetary wheel. The cooling oil is attached to the bracket structure.

[0019] The axially extended bracket significantly increases the metal surface area, fully soaking it with splashing / flowing cooling oil, creating a multi-stage "heat sink fin" effect. Compared to traditional integral planetary carriers, this increases the heat dissipation contact area by 50%-100%. Direct heat transfer from the heat source to the cooling medium: The bracket is directly connected to the first-stage planetary gear (meshing heat source), allowing heat to be transferred to the surface oil film with zero loss through the highly thermally conductive bracket body, avoiding the heat losses associated with traditional solutions that require multi-stage transmission.

[0020] Optionally, the first-stage planetary bracket 1 and the second-stage planetary bracket are fixedly connected by a first-stage pin, and the second-stage planetary bracket is fixedly connected by a second-stage pin, and the first-stage pin and the second-stage pin are cylindrical structures.

[0021] The primary pin (connecting the dual planetary carriers) and the secondary pin (connecting the primary and secondary planetary carriers) form a through-type cylindrical shear key, efficiently transferring planetary gear meshing torque from the primary carrier to the secondary carrier to the output port, avoiding the bending stress concentration associated with traditional bolted connections. Shear-resistant topology: The cylindrical surface evenly bears shear forces, reducing the stress concentration factor by over 50% compared to special-shaped pins, ensuring fatigue life under high cyclic loads (especially suitable for the frequent start-stop conditions of collaborative robots). The cylindrical structure facilitates the concentration and return of cooling oil to the primary center wheel, improving heat dissipation and return flow efficiency.

[0022] Optionally, the first-level oil outlet hole is located between the first-level planetary bracket 1 and the second-level planetary bracket, and part of the cooling oil flows back to the first-level oil outlet hole.

[0023] The double-bracket positioning and partial oil return design of the first-level oil outlet hole construct a dual mechanism of heat source targeted cooling and fluid dynamic circulation self-enhancement in the technical solution. The double-bracket sandwich layout of the oil outlet hole embeds the cooling oil injection point into the core heat source area of ​​the planetary gear system, while partial oil return forms a local microcirculation, realizing an adaptive closed loop of "high-temperature hotspot → efficient cooling → fluid supply" with zero additional energy consumption.

[0024] Optionally, the secondary center wheel is rotatably connected to the secondary planetary support via a bearing, and a space where the bearing is located is connected to the secondary oil chamber and an end opening of the secondary center wheel.

[0025] The bearing-connected design of the secondary center wheel-planetary bracket constructs a triple functional hub for active bearing cooling, dynamic oil circuit balance, and axial force management in the technical solution. The through-connected design of the bearing cavity and the oil cavity transforms the rotating support interface into an oil-cooling heat exchanger. At the same time, the communicating vessel principle is used to reconstruct the oil circuit pressure difference system, realizing the coordinated control of "zero bearing overheating - oil flow self-balancing - axial force decoupling".

[0026] Optionally, a retaining ring is engaged at the end of the secondary center wheel, and a through hole is provided on the retaining ring.

[0027] The through hole of the retaining ring reconstructs the dynamic balance of the oil circuit with geometric constraints, and at the same time realizes zero-compromise locking of axial displacement through the locking mechanism, achieving coordinated control of "oil quantity self-adjustment-bearing hard protection-failure melting" within the millimeter-level space.

[0028] Optionally, end covers are provided on both sides of the middle shell, and heat sinks are provided on the circumferences of the middle shell and the end covers.

[0029] The circumferential heat sink group transforms the static shell into an active rotating radiator through three-dimensional surface area proliferation and aerodynamic reconstruction, achieving the ultimate synergy of three-dimensional heat transfer of "conduction-convection-radiation" with zero additional energy consumption.

[0030] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0031] The technical solution proposed in this invention utilizes the centrifugal force of the reducer's two-stage center wheel as an internal power source, driving the circulation of cooling oil within a sealed internal oil chamber. This achieves direct and efficient oil cooling of the motor winding ends and core (core heat source). Simultaneously, a supplementary heat conduction path is established through structural components (rotor yoke, planetary carrier, and center housing) constructed of highly thermally conductive materials. This combined heat dissipation mechanism of "self-driven two-stage oil cooling + integrated heat conduction" effectively overcomes the critical heat dissipation bottleneck of high-power density joint modules, significantly improving their continuous operation and reliability, without requiring external cooling devices or significantly increasing their size, weight, or complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is an overall cross-sectional view of a two-stage oil-cooled rotor joint module proposed in Example 1 of the present invention;

[0033] Figure 2 A partial cross-sectional view of a first-stage oil chamber of a two-stage oil-cooled rotor joint module according to embodiment 1 of the present invention;

[0034] Figure 3 This is a schematic diagram of the internal structure of a two-stage oil-cooled rotor joint module proposed in Example 1 of the present invention;

[0035] Figure 4 A partial cross-sectional view of the end portion of a secondary center wheel of a two-stage oil-cooled rotor joint module according to embodiment 1 of the present invention;

[0036] Figure 5 This is a schematic structural diagram of a two-stage oil-cooled rotor joint module proposed in Example 2 of the present invention;

[0037] Figure 6 This is a schematic structural diagram of a first-stage center wheel of a two-stage oil-cooled rotor joint module proposed in Example 1 of the present invention;

[0038] Figure 7 This is a schematic structural diagram of a secondary center wheel of a two-stage oil-cooled rotor joint module proposed in Example 2 of the present invention;

[0039] 1. First-stage center wheel; 101. First-stage oil outlet hole; 2. Second-stage center wheel; 201. Second-stage oil outlet hole; 3. First-stage planetary gear; 4. First-stage inner ring gear; 5. Rotor magnet; 6. Stator core; 7. Middle housing; 8. Skeleton seal ring; 9. Rotor yoke; 10. Second-stage planetary carrier; 11. Second-stage inner ring gear; 12. First-stage oil chamber; 13. Second-stage oil chamber; 14. End return gap; 15. Retaining ring; 16. Second-stage planetary gear; 17. First-stage planetary carrier one; 18. First-stage planetary carrier two; 19. End cover. DETAILED DESCRIPTION

[0040] In order to further understand the content of the present invention, the present invention is described in detail with reference to the accompanying drawings and embodiments.

[0041] Example 1

[0042] Combined with attachment Figure 1-3A two-stage oil-cooled rotor joint module comprises a primary center gear structure and a secondary center gear structure. The primary center gear structure comprises a primary center gear 1, a rotor yoke 9, and a middle housing. The secondary center gear structure comprises a secondary center gear 2 and a secondary planetary carrier 10. The primary center gear 1 meshes with a plurality of primary planetary gears 3. The primary planetary gears 3 orbit the primary center gear 1 and are rotatably disposed between a first planetary carrier 17 and a second planetary carrier 18. The outer periphery of the primary planetary gears 3 meshes with a primary inner ring gear 4, which is embedded in an annular step on the inner edge of the middle housing. The meshing of the teeth generates heat due to friction and contact, also serving as a heat source.

[0043] like Figure 1 As shown, the left side of the middle shell and the rotor yoke 9 is the reducer assembly, which is connected to the motor part on the right side through the rotor yoke 9, wherein the stator core 6 with winding is assembled outside the middle shell, which is conducive to heat conduction when the module is running. An oil hole is opened at the end of the secondary center wheel 2 of the reducer, and an oil return groove is designed at the end cover 19. The liquid lubricating oil of the reducer part is thrown out when the reducer center wheel rotates to cool the winding position at the end of the motor position. After the grease returns, it falls back to the inside of the center wheel along the oil groove of the planetary frame. An oil hole is opened at the end of the primary center wheel 1 of the reducer. When the motor rotor drives the primary center wheel 1 to rotate at high speed, the internal liquid oil is thrown to the inside of the winding to dissipate heat from the winding. This reciprocating motion dissipates heat from the stator core 6 with winding, which is the largest heat source, so that the joint module achieves better heat dissipation effect. It solves the problem that the heat of the motor body of the current joint module solution is buried inside, causing the module to break down due to overheating after the robot runs for more than ten minutes.

[0044] like Figure 2 、 6As shown in Figure 7, the first-stage center wheel 1 is hollow and has cooling oil inside. A number of first-stage oil outlet holes 101 are provided on the circumference of the first-stage center wheel 1. The first-stage oil outlet holes 101 and the second-stage oil outlet holes 201 are evenly arranged around the circumference. The ends of the motor stator windings are distributed circumferentially and are the main heat-generating areas. The evenly arranged oil outlet holes allow the cooling oil to be radially and evenly thrown out by centrifugal force, forming a continuous, gap-free annular oil film or oil mist flow on the oil cavity wall, ensuring that the winding ends and the core surface in the entire circumferential direction are directly flushed by the oil, eliminating local overheating dead corners. Secondary extended cooling balance: The second-stage oil outlet holes 201 similarly ensure the uniform dissipation of heat around the second-stage planetary gear 16 system, avoiding excessive local temperature rise in the reducer. The even opening of the holes prevents the rotating parts (center wheel, planetary carrier) from being subjected to periodic impact forces due to asymmetric oil injection, significantly reducing vibration and noise, and improving the motion accuracy and life of the joint module. Uniform circumferential oil distribution ensures radial symmetry in the oil pressure applied to the oil chamber walls, preventing deformation of structural components due to unilateral pressure, ensuring gear meshing accuracy and sealing reliability, and optimizing fluid dynamic stability. Continuous oil film enhances heat transfer: Uniform oil flow forms a thin film that completely covers the chamber walls, increasing the oil-metal contact area and improving heat transfer efficiency (compared to discrete oil droplet impact). This improves heat capacity utilization, avoids excessive oil concentration or loss in localized areas, ensures that every unit of cooling oil contributes to effective heat transfer, and reduces the overall oil temperature rise. This improves posture insensitivity, allowing for the robot's joints to operate at varying angles. The uniform oil spray design ensures cooling effectiveness is unaffected by gravity, ensuring complete coverage of the heat source in any posture. Improved oil circuit anti-interference capability: Uniform flow reduces turbulence in the oil circuit, ensuring stable oil collection in return channels (such as the gap between the secondary planetary carriers), maintaining self-circulation reliability.

[0045] The rotor yoke 9 and the middle shell are sealed and connected to form a first-level oil chamber 12. The first-level planetary gear 3 and the first-level inner ring gear 4 are arranged in the first-level oil chamber 12. The first-level center gear 1 is driven to rotate and the cooling oil moves to the cavity wall of the first-level oil chamber 12 through the first-level oil outlet hole 101.

[0046] like Figure 1 As shown, the secondary center wheel 2 is hollow and its internal space is connected to the primary center wheel 1. A number of secondary oil outlet holes 201 are provided on the circumferential side of the secondary center wheel 2. The primary planetary bracket 2 18 is provided with a coaxial edging on the periphery of the secondary oil outlet hole 201. The edging is also provided with a through hole radially penetrating the secondary oil outlet hole 201 for passing cooling oil.

[0047] The secondary planetary carrier 10 is connected to the cavity wall of the middle shell to form a secondary oil cavity 13. The secondary oil cavity 13 is provided with a secondary planetary gear 16 and a secondary inner ring gear 11. The secondary center gear 2 is driven to rotate and the cooling oil moves to the cavity wall of the secondary oil cavity 13 through the secondary oil outlet hole 201.

[0048] like Figure 4As shown, a gap is provided between the secondary planetary carrier 10 and the end opening of the secondary center wheel 2 , and the secondary oil chamber 13 is communicated with the primary oil chamber 12 .

[0049] The rotor yoke 9, secondary planetary carrier 10, and center housing are all made of thermally conductive materials. They are constructed from aluminum alloy (λ ≥ 180 W / m·K) or copper alloy (λ ≥ 350 W / m·K), replacing traditional structural steel (λ ≈ 40 W / m·K). This reduces the thermal resistance from the stator winding ends (heat source) to the oil-cooling interface (heat dissipation) by 70%-85%.

[0050] The middle housing is a U-shaped rotor structure with a meridian plane. The U-shaped structure features grooves for accommodating the rotor magnets 5 and stator core 6. The grooves are in close contact with the rotor magnets 5 and stator core 6, and the inner wall of the middle housing is in contact with the cooling oil. The grooves are in close contact with the magnets and stator core 6: the geometry of the U-shaped grooves precisely matches the outer diameter of the rotor magnets 5 and the inner diameter of the stator core 6, forming a large area of ​​direct metal-to-metal contact (typically filled with a highly thermally conductive insulating material). This eliminates the air gap thermal resistance found in traditional assemblies and efficiently directs heat generated by the motor's primary heat sources (core losses and winding copper losses, which are conducted to the core through slot insulation) into the middle housing. Near-end cooling of the winding ends is achieved: the bottom of the U-shaped structure is located near the motor winding ends (the primary overheating area), allowing heat to be conducted to the inner wall of the housing via a very short path, which is in contact with the cooling oil. This significantly reduces the thermal resistance from the heat source to the heat sink.

[0051] Generation of efficient heat exchange interface for cooling oil

[0052] Fully oil-free inner wall: The U-shaped inner surface serves directly as the cooling wall for the primary oil chamber 12, completely covered and flushed by the centrifugally ejected cooling oil. Highly thermally conductive materials (such as aluminum alloy and copper alloy) combined with a thin-wall design ensure rapid heat transfer from the housing to the oil.

[0053] Turbulence enhancement design: The curved surface of the rotating body guides the oil flow to form turbulence, destroys the boundary layer, and significantly improves the convective heat transfer coefficient (30%-50% higher than flat wall).

[0054] Compact mechatronic integration

[0055] Triple function integration: A single U-shaped structure simultaneously realizes: electromagnetic component carrier (fixing stator core 6 / rotor magnet 5 through grooves); reducer sealing cavity (forming a closed oil chamber with rotor yoke 9 / planetary bracket); heat dissipation structure body (heat conduction + oil cooling interface).

[0056] Maximize space utilization: The U-shaped cross-section converts the axial overlap area between the motor and reducer into effective heat dissipation space, avoiding the redundant axial length caused by the motor-reducer flange connection in traditional solutions.

[0057] Structural stiffness and thermal deformation control

[0058] Closed-type anti-torsion design: The U-shaped continuous rotating body provides ultra-high torsional rigidity, resisting gear meshing shock and ensuring transmission accuracy. Thermal expansion compatibility: Symmetrical geometry and uniform heat dissipation ensure axisymmetric distribution of thermal deformation, avoiding seal failure or gear misalignment caused by unbalanced loads.

[0059] The inner wall of the midshell is thin-walled. According to Fourier's law (Q = -kA·(dT / dx)), thermal resistance is positively correlated with material thickness. Thin walls minimize the heat transfer path, significantly reducing the heat transfer resistance from the heat source (stator core 6 / winding) to the metal shell and then to the cooling oil. This improves thermal efficiency several times over thick-walled structures.

[0060] Transient response optimization: The thin-wall structure has extremely low thermal capacity and can quickly respond to temperature fluctuations of the heat source to avoid heat accumulation inside the shell. It is especially suitable for dynamic heat dissipation requirements under frequent start-stop and variable load conditions of robot joints.

[0061] Bidirectional heat penetration enhancement:

[0062] Inner wall → oil: Thin walls bring the shell temperature closer to the oil temperature, significantly increasing the convective heat transfer temperature difference (ΔT) and driving heat into the oil flow efficiently.

[0063] Outer wall → stator: Thin walls reduce the longitudinal diffusion of heat to non-cooled areas, forcing the heat to be conducted radially to the oil contact surface.

[0064] The high curvature of the thin wall (due to its thinness and easy deformation) enhances the turbulence of the oil flow, destroys the thermal boundary layer, and improves the convective heat transfer coefficient.

[0065] Under the same outer dimensions, the thin-wall design expands the effective volume of the first-stage oil chamber 12, increases the oil storage capacity and heat buffering capability, and prolongs the continuous heat dissipation time.

[0066] A first-stage planetary carrier 17 and a second-stage planetary carrier 18 are located on either side of the first-stage planetary gear 3. These carriers feature extended support structures that are rotatably connected to the first-stage planetary gear 3. Cooling oil is applied to these support structures. The dual-sided planetary carriers, through their geometrically extended contact with the oil, transform the rotating components into active heat dissipation interfaces while also creating a highly rigid support system for the planetary gear train. The axially extended support structures significantly increase the metal surface area, allowing for full coverage and soaking by splashing / flowing cooling oil, creating a multi-stage "cooling fin" effect. Compared to traditional integral planetary carriers, this increases the heat dissipation contact area by 50%-100%. The rotating support structures continuously agitate the oil, disrupting local laminar flow in the oil chamber and improving heat exchange efficiency (similar to the principle of a blender). As the support structures rotate, oil adhering to their surfaces is radially ejected by centrifugal force, replenishing the oil flow at the edges of the first-stage oil chamber 12 and eliminating cooling dead zones. Oil droplets slide along the support surfaces to the chamber bottom, accelerating the return of oil to the center gear.

[0067] The first and second planetary carriers 17 and 18 are fixed together by a primary pin, while the second and second planetary carriers 18 and 10 are fixed together by a secondary pin. Both the primary and secondary pins are cylindrical in shape. This embodiment incorporates an adaptive thermal deformation compensation mechanism and an axial float tolerance. The cylindrical pins and pinholes utilize a micro-clearance fit (H7 / g6 grade) to accommodate differential axial thermal expansion (typically ΔL = 0.1-0.3mm) between the carriers due to temperature differences (e.g., the first carrier is closer to the motor heat source than the second carrier). This prevents thermal stress-induced structural deformation or bearing preload failure. A radial thermal alignment design utilizes the self-centering properties of the cylindrical geometry to ensure coaxiality (≤0.02mm) between the carriers after thermal deformation, protecting the planetary gear meshing accuracy.

[0068] The first-stage oil outlet 101 is located between the first-stage planetary carrier 17 and the second-stage planetary carrier 18, and some of the cooling oil flows back to this outlet. The meshing point of the first-stage planetary gear 3 (peak temperature ≥ 120°C) is located between the two planetary carriers. Positioning the oil outlet in this area allows the centrifugally ejected cooling oil to directly coat the gear meshing surfaces and bearings, instantly dissipating heat (shortening the oil spray path by over 60% compared to traditional housing-mounted oil spray). The high-speed oil flow impacts the gear pair, scattering into a micron-sized mist that penetrates the meshing tooth gap and the interior of the needle roller bearing, simultaneously optimizing lubrication and heat dissipation (reducing friction temperature by up to 30%). After completing the heat exchange, some of the cooling oil is attracted by the low-pressure eddy currents generated by the planetary carrier rotation and flows back through the carrier gap to the vicinity of the oil outlet. The return oil mixes with the fresh oil from the centrifugal spinner at the oil outlet, achieving: oil temperature buffering (return oil temperature rise ΔT≈15°C, reducing the impact temperature difference of the fresh oil); oil pressure stabilization (avoiding injection failure due to oil volume fluctuations); and oil vapor suppression (reducing oil cavitation in high-temperature areas). The multi-hole return flow creates a radial oil flow network, eliminating cooling differences between the planetary gears (inter-gear temperature difference ≤3°C). The curvature of the bracket surface guides the return oil film to adhere, reducing splash loss (increasing oil utilization by 25%). The kinetic energy of the return oil is converted into local turbulence in the oil cavity, enhancing the wall heat transfer coefficient.

[0069] The secondary center wheel 2 is rotatably connected to the secondary planetary carrier 10 via a bearing, and the space where the bearing is located is connected to the secondary oil chamber 13 and the end opening of the secondary center wheel 2.

[0070] Bearing microcirculation active cooling

[0071] Full oil immersion: The space where the bearing (typically an angular contact ball bearing) is located is connected to the secondary oil chamber 13. When rotating at high speed, a negative pressure siphon effect is formed, causing the cooling oil to continuously flow through the gap between the raceway and the cage ( Figure 1 ), taking away friction heat (heat density > 50W / cm²).

[0072] Thermal short-circuit blocking: Oil flow directly isolates heat conduction between the outer ring of the bearing (connected to the planetary carrier) and the inner ring (connected to the center gear), preventing heat from the motor side from being transferred to the precision bearing (temperature fluctuation of up to 40°C).

[0073] The connecting design forms a hydraulic communicating device between the bearing cavity and the secondary oil cavity 13, eliminating the pressure difference between the oil cavity and the bearing cavity caused by centrifugal force (the pressure difference in traditional design can reach 0.2MPa), and ensuring the stability of the oil outlet jet (flow rate fluctuation <5%).

[0074] No oil-gas cavitation in the bearing cavity

[0075] Optimized oil return path: Cooling oil flows into the opening at the end of the secondary center wheel 2 through the bearing gap. The centrifugal force of the center wheel's rotation accelerates oil return (70% more efficient than gravity return), preventing oil retention.

[0076] A retaining ring 15 with a through-hole engages the end of the secondary center gear 2. The interference fit (δ = 0.02-0.05mm) between the retaining ring 15 and the groove at the end of the center gear forms a mechanical stop, resisting the axial impact force (peak value ≥ 5kN) generated by the meshing of the secondary planetary gears 16 and preventing bearing preload failure. Retaining ring 15 is made of a high elastic modulus alloy (such as beryllium bronze), maintaining a stable locking force (fluctuation <10%) despite axial thermal expansion differences (ΔL ≤ 0.1mm).

[0077] When high-speed oil flows through the micropores, a Venturi effect occurs. Dissolved gases are released due to pressure drop, and bubbles are discharged through the guide grooves at the edge of the through-holes, ensuring the purity of the return oil (gas content <3%). During the moment of shutdown, negative pressure on the center wheel may draw excessive oil into the oil chamber. The damping effect of the through-holes limits reverse flow (Q reverse ≤ 0.3Q positive), preventing oil overflow in the bearing cavity.

[0078] End caps 19 are located on both sides of the middle shell, and heat sinks are installed around the sides of both the middle shell and the end caps 19. The heat sink base is integrally cast (or welded with high-thermal conductivity) with the middle shell / end caps 19, eliminating interfacial contact thermal resistance and allowing internal heat (residual heat from the oil cooling system + heat from metal conduction) to be transferred to the fin tips via the shortest path, reducing thermal resistance by 40%.

[0079] Axial gradient heat dissipation: The heat sink of the middle shell mainly covers the stator core 6 projection area (heat flux density>10 4 W / m²), the heat sink 19 on the end cover focuses on the heat conduction area of ​​the bearing (heat flux density ≈ 5×10³W / m²), forming axial heat load matching heat dissipation.

[0080] The planetary reducer's embedded inner rotor structure joint module has a stator that fits tightly against the front and rear housings, providing an optimal heat conduction path. The rotor yoke and the impeller structure at the tail of the rotor provide high-speed air cooling during motor operation, creating an optimal heat dissipation environment for the module's heat source.

[0081] Taking advantage of the rotation characteristics of the reducer part, an oil hole is opened at the end of the secondary center wheel 2 of the reducer, and an oil return groove is designed at the end cover 19 position. The liquid lubricating oil of the reducer part is thrown out when the reducer center wheel rotates to dissipate oil cooling heat at the end winding position of the motor position. After the grease returns, it falls back to the inside of the center wheel along the oil groove of the planetary frame. An oil hole is opened at the end of the primary center wheel 1 of the reducer. When the motor rotor drives the primary center wheel 1 to rotate at high speed, the internal liquid oil is thrown to the inside of the winding to dissipate heat to the winding. This reciprocating motion dissipates heat to the stator core 6 with the largest heat source.

[0082] Working principle of oil circuit:

[0083] Cooling oil is stored in the internal cavity of the first-stage center wheel 1. As it rotates at high speed, it is centrifugally ejected through the circumferentially evenly distributed first-stage oil outlet holes 101, forming a high-speed oil flow that flows closely against the walls of the first-stage oil chamber 12, directly flushing the motor stator core 6 and the winding ends (the core heat source). After absorbing heat, some of the oil falls back through the gaps in the planetary brackets, and some flows back to the first-stage oil outlet holes 101 for thermal buffering. The remaining oil flows into the second-stage center wheel 2 and is ejected a second time through the second-stage oil outlet holes 201 to cover the meshing surfaces and bearings of the second-stage planetary gears 16. Finally, the hot oil passes through the bearing cavity and enters the end of the second-stage center wheel 2. After throttling and regulating the flow rate through the through-holes in the retaining ring 15, it returns to the first-stage center wheel 1 to complete the cycle. This path does not require an external pump drive throughout, relying on two-stage centrifugal force to achieve dynamic oil balance, suppressing the winding temperature rise below 65°C in a compact space, achieving efficient thermal management of the high-power density joint module.

[0084] It not only solves the heat dissipation problem of the module under high torque, but also provides the best heat dissipation effect for the module, and solves the problem of excessive temperature rise of the high-torque robot joints during long-term operation;

[0085] By embedding the rotor yoke 9 in the planet, a compact structural layout is provided within the effective space, so that the module can achieve the best module performance effect with the minimum volume and weight;

[0086] In view of the rotation characteristics of the reducer part, an oil hole is opened at the output end of the reducer, and an oil return groove is designed at the end cover 19. The liquid lubricating oil of the reducer part is thrown out when the reducer center wheel rotates to dissipate the oil cooling heat at the end winding position of the motor position. After the grease returns, it falls back to the inner side of the center wheel along the oil groove of the planetary frame, and the reciprocating motion is repeated to dissipate the heat of the stator core 6 with the winding, which is the largest heat source.

[0087] An oil hole is opened at one end of the first-stage center wheel 1 of the reducer. When the motor rotor drives the first-stage center wheel 1 to rotate at high speed, the internal liquid oil is thrown to the inside of the winding to dissipate heat from the winding. This reciprocating motion dissipates heat from the stator core 6, which is the largest heat source.

[0088] Example 2

[0089] Combined with attachment Figure 5 Compared with the technical solution of Example 1, the two-stage oil-cooled rotor joint module of this embodiment can be improved as follows:

[0090] The inner and outer positions of the rotor magnet 5 and the stator core 6 are interchanged. In embodiment 1, it is an outer rotor structure, while in this embodiment, it is an inner rotor structure. The joint module of the two-stage oil cooling structure is applicable to both the outer rotor structure and the inner rotor structure.

[0091] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs a structure and embodiment similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. A two-stage oil-cooled rotor joint module, characterized in that: include A primary center wheel structure includes a primary center wheel, a rotor yoke, and a center housing. The primary center wheel is hollow and contains cooling oil. A plurality of primary oil outlet holes are provided on the circumference of the primary center wheel. The rotor yoke and the center housing are sealed and form a primary oil cavity. The primary oil cavity contains primary planetary gears and a primary inner gear ring. The primary center wheel is driven to rotate, and the cooling oil flows through the primary oil outlet holes to the cavity wall of the primary oil cavity. A secondary center wheel structure includes a secondary center wheel and a secondary planetary carrier. The secondary center wheel is hollow and its internal space is connected to the primary center wheel. A plurality of secondary oil outlet holes are provided on the circumference of the secondary center wheel. The secondary planetary carrier is connected to the cavity wall of the middle shell to form a secondary oil cavity. A secondary planetary gear and a secondary inner gear ring are provided in the secondary oil cavity. The secondary center wheel is driven to rotate and the cooling oil moves to the cavity wall of the secondary oil cavity through the secondary oil outlet holes. A gap is provided between the secondary planetary carrier and the end opening of the secondary center wheel. The secondary oil cavity is connected to the primary oil cavity. The rotor yoke, the secondary planetary support and the middle shell are all made of heat-conducting materials.

2. A two-stage oil-cooled rotor joint module according to claim 1, characterized in that: The primary oil outlet holes and the secondary oil outlet holes are evenly arranged around the circumference.

3. A two-stage oil-cooled rotor joint module according to claim 1, characterized in that: The middle shell is a rotating body structure with a U-shaped meridian plane. The U-shaped structure is provided with grooves for accommodating the rotor magnets and the stator core. The grooves are closely attached to the rotor magnets and the stator core. The inner wall of the middle shell is in contact with the cooling oil.

4. A two-stage oil-cooled rotor joint module according to claim 3, characterized in that: The inner wall of the middle shell is a thin-wall structure.

5. The two-stage oil-cooled rotor joint module according to claim 1, characterized in that: A first-stage planetary bracket 1 and a first-stage planetary bracket 2 are provided on both axial sides of the first-stage planetary gear. The first-stage planetary bracket 1 and the second-stage planetary bracket are provided with a protruding bracket structure and are rotatably connected to the first-stage planetary gear. The cooling oil is attached to the bracket structure.

6. A two-stage oil-cooled rotor joint module according to claim 5, characterized in that: The first-stage planetary bracket 1 and the second-stage planetary bracket are fixedly connected by a first-stage pin, and the second-stage planetary bracket is fixedly connected by a second-stage pin. The first-stage pin and the second-stage pin are cylindrical structures.

7. The two-stage oil-cooled rotor joint module according to claim 1, characterized in that: The first-level oil outlet hole is located between the first-level planetary bracket 1 and the second-level planetary bracket, and the cooling oil partially flows back to the first-level oil outlet hole.

8. The two-stage oil-cooled rotor joint module according to claim 1, characterized in that: The secondary center wheel is rotatably connected to the secondary planetary support via a bearing, and a space where the bearing is located is communicated with the secondary oil chamber and an end opening of the secondary center wheel.

9. The two-stage oil-cooled rotor joint module according to claim 8, characterized in that: A retaining ring is clamped at the end of the secondary center wheel, and a through hole is provided on the retaining ring.

10. A two-stage oil-cooled rotor joint module according to any one of claims 1 to 9, characterized in that: End covers are provided on both sides of the middle shell, and heat dissipation fins are provided on the circumferences of the middle shell and the end covers.

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