Joint motor unit integrated with liquid cooling heat dissipation structure, joint module and robot thereof

Abstract

The application relates to a joint motor unit integrated with a liquid cooling heat dissipation structure, a joint module and a robot, the internal passage of a hollow pipe body coil is directly communicated with a liquid cooling chamber integrated in a shell wall, and an integrated closed cooling circuit is constructed. The application realizes 'in-situ cooling' of the coil winding, shortens the heat transfer path to the physical limit, reduces the thermal resistance to the minimum, thereby allowing the motor to continuously operate under extremely high current density, and the upper limit of the power density is greatly improved; moreover, a complex fluid distribution and confluence network is 'internalized' in the shell and the winding structure, all external pipelines are abandoned, the maximum sharing of the motor electromagnetic space and the cooling function space is realized, and a structural foundation is laid for the extreme miniaturization and light weight of the robot joint.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and more specifically, to a joint motor unit with an integrated liquid cooling structure. The invention also relates to a joint module including the joint motor unit, and a robot including the joint module. Background Technology

[0002] With the rapid development of robotics technology, especially humanoid robot technology, the performance requirements for its joint drive units have reached unprecedented levels. Humanoid robot joints, such as elbows, knees, and hips, need to achieve high torque, high speed, and high dynamic response within extremely limited space and weight envelope to perform complex movements such as walking, running, jumping, and carrying. This means that the joint motors must possess extremely high power density (power output per unit volume or unit mass).

[0003] However, high power density inevitably comes with high loss density, the most significant of which is Joule heat (commonly known as "copper loss") generated by energizing the winding coils. When the current is increased to enhance torque within a confined space, the heat generation increases exponentially. Simultaneously, hysteresis and eddy current losses (commonly known as "iron losses") caused by the alternating magnetic field in the stator core also constitute a significant heat source. If this heat cannot be dissipated from the motor in a timely and efficient manner, the internal temperature will rise sharply, leading to a series of serious consequences: irreversible demagnetization of the permanent magnets at high temperatures, resulting in a permanent decrease in the motor's torque constant; accelerated aging, embrittlement, and even breakdown of the winding insulation layer, causing short-circuit faults; and increased winding resistance with rising temperature, further increasing copper losses, creating a vicious cycle and reducing motor efficiency. These problems severely restrict the performance of the joint motor, and can even lead to motor burnout, directly affecting the robot's task execution capabilities and lifespan.

[0004] To address the issue of motor heat dissipation, the industry has developed various technical solutions, but when applied to the specific scenario of humanoid robot joints, they all reveal obvious limitations.

[0005] The first existing solution is air cooling, including natural air cooling and forced air cooling. Natural air cooling relies on natural convection and radiation heat exchange between the motor casing and the surrounding air. Due to the extremely low thermal conductivity of air and its small convective heat transfer coefficient, its heat dissipation capacity is extremely limited, making it only suitable for micro-motors with very low power consumption. Forced air cooling, by adding a fan to enhance airflow, can improve the convective heat transfer coefficient, but it is still far below the level of liquid cooling. More importantly, humanoid robot joints typically require high levels of protection to prevent water and dust damage. Introducing a fan would compromise the motor's seal, and the fan itself, as a moving part, would generate noise and vibration, and there are issues with its lifespan and reliability. Therefore, air cooling solutions are no longer adequate for the increasingly high power density of humanoid robot joints.

[0006] The second existing solution is indirect liquid cooling, which is currently the mainstream heat dissipation method for medium- and high-power-density motors. Its typical structure involves machining water channels (often called "water jackets") inside the motor housing wall, or winding independent cooling pipes between the stator core and the housing. An external pump station drives the circulation of coolant (such as water, water-glycol solution, or cooling oil) to carry away heat. Compared to air cooling, this solution significantly improves heat dissipation capacity. However, its fundamental technical drawback lies in the fact that there is a long, multi-interface, and high-thermal-resistance conduction chain between the heat-generating core (winding coil) and the cooling medium. Specifically, the heat generated by the winding must pass through the following pathways in sequence: the internal heat conduction path of the coil (from the center of the copper wire to the surface), the insulating varnish layer of the enameled wire, the air gap or potting compound layer between the winding and the stator core slots (air has extremely low thermal conductivity and is the main thermal resistance), the silicon steel sheet stacks of the stator core (poor thermal conductivity in the lamination direction), the assembly gap or contact surface between the core and the housing or cooling pipe, and the wall thickness of the housing or cooling pipe itself, before finally being transferred to the cooling medium within the flow channel via convection. Each link in this path represents a series thermal resistance, resulting in a significant temperature difference between the winding core temperature and the coolant temperature. Even if the coolant temperature is low, the winding temperature may still far exceed the limits allowed by its insulation class. This "thermal bottleneck" effect prevents the heat dissipation potential of indirect liquid cooling solutions from being fully utilized, especially in humanoid robot joint motors with extremely high heat flux densities.

[0007] The third type of solution is phase change cooling. One method utilizes the latent heat of phase change material (PCM) to absorb heat during its solid-liquid phase change. This method is effective in dealing with short-term, transient power surges (such as a robot's instantaneous acceleration or jump), but its biggest limitation is heat capacity saturation. The total heat absorption of PCM is limited by its mass and latent heat of phase change. Within the space-constrained joint module, the amount of PCM filling is very limited. Once it completely melts, its heat absorption capacity drops sharply, and the motor temperature will rapidly spiral out of control. Therefore, the PCM solution cannot meet the heat dissipation requirements of continuous robot walking and long-term high-load operation.

[0008] The fourth approach is direct winding cooling, which is theoretically the most advanced solution, minimizing the heat dissipation path. Chinese patent CN2023200758502 discloses a brushless motor stator that proposes setting the winding coil as a hollow tubular structure (such as a copper tube) with an internal cavity, containing a cooling medium. This approach achieves direct contact between the cooling medium and the heat-generating conductor (coil), significantly reducing thermal resistance and embodying the concept of "in-situ cooling."

[0009] However, before this existing technical solution can be truly put into practical use, especially when applied to humanoid robot joints with extremely high integration and performance requirements, the following three key technical problems remain unresolved:

[0010] 1) Insufficient integration and additional space occupation: This solution only focuses on the winding itself as a flow channel, but the introduction and extraction of coolant still rely on leading out the copper pipe end and connecting it to an external fluid circulation device and pipeline. In the confined joint space of a humanoid robot, these additional connectors, hoses, distributors, etc., not only occupy valuable volume and increase system complexity, but also introduce more potential leakage points and assembly processes, making it impossible to achieve the ultimate integration of the motor and cooling system.

[0011] 2) The problem of electrical performance loss has not been recognized or resolved: This solution completely fails to mention the negative impact on the motor's electrical performance after replacing traditional solid enameled copper wire with hollow copper tubing. Due to the reduction in the effective cross-sectional area of ​​the conductor, the DC resistance of hollow copper tubing will inevitably increase compared to solid copper wire of the same outer diameter. Increased resistance leads to: i) a further increase in copper losses (heat generation) at the same current, partially offsetting the benefits of improved heat dissipation; ii) a decrease in motor efficiency; and iii) the need to reduce the current to maintain the same temperature rise, resulting in a decrease in torque output capability. How to compensate for or even optimize the motor's electromagnetic performance while introducing an "internal winding cooling" structure is a technical hurdle that this solution must overcome to move from concept to high-performance application.

[0012] 3) Insufficient consideration of systemic thermal management: This scheme focuses entirely on winding cooling, but fails to propose targeted and efficient heat dissipation measures for another major heat source inside the motor—the iron losses in the stator core. In actual high-power-density motors, iron losses are equally significant. If the core does not dissipate heat effectively, localized hot spots will form, and heat will be conducted back to the windings, weakening the effect of the main cooling system, leading to uneven temperature fields inside the motor, generating thermal stress, and affecting lifespan and reliability.

[0013] In summary, existing heat dissipation technologies for humanoid robot joint motors are either inefficient due to their heat dissipation mechanisms (air cooling), have limited potential due to thermal resistance bottlenecks (indirect liquid cooling), have limited application scenarios (phase change), or have significant shortcomings in terms of integration, electromagnetic performance assurance, and system-level thermal management (existing winding internal cooling solutions).

[0014] Therefore, there is an urgent need for a new solution that can fundamentally break through the heat transfer bottleneck, achieve ultra-low thermal resistance "in-situ cooling", and at the same time be extremely integrated with the motor structure without sacrificing or even optimizing electrical performance, and achieve comprehensive system-level thermal management, so as to promote the development of humanoid robot joint motors towards higher power density and higher reliability. Summary of the Invention

[0015] The present invention aims to solve at least one technical problem existing in the prior art, and provides a joint motor unit with an integrated liquid cooling structure that has significant advantages in terms of heat dissipation efficiency, structural integration, electromagnetic performance and system reliability, as well as a joint module and robot including the unit.

[0016] To achieve the above objectives, the present invention provides the following technical solutions. The composition, technical principles, and beneficial effects of each technical solution will be described below in conjunction with the claims of the present invention.

[0017] This invention discloses a joint motor unit with an integrated liquid cooling structure, comprising a housing, a stator core, coil windings, a rotor, and an output shaft. The housing has a liquid cooling chamber within its wall. The stator core is fixed inside the housing. The coil windings consist of hollow tubular coils wound around the stator core, with the hollow internal channels of the tubular coils forming liquid cooling channels. The rotor is coaxially aligned with the stator core and can rotate relative to it. The output shaft is fixedly connected to the rotor to output torque. The coil windings form a shunt at their axial ends, and the tubular coils are directly connected to the liquid cooling chamber through the shunt, thus forming a closed cooling circuit for the circulation of the cooling medium between the liquid cooling chamber and the liquid cooling channels.

[0018] The outer shell not only serves as the supporting frame and protective housing for the entire motor unit, but also contains a liquid-cooled chamber within its wall. This liquid-cooled chamber is a cavity structure formed within the outer shell wall thickness to accommodate and guide the flow of the cooling medium. It can be manufactured using mature processes such as precision casting (e.g., 3D printed sand casting), machining followed by welding, or friction stir welding. In this invention, the cooling medium circulates within a cooling circuit formed by the liquid-cooled chamber and the coil cooling channel. That is, the cooling medium is enclosed and stored within this cooling circuit and can circulate within both the liquid-cooled chamber and the coil cooling channel. Furthermore, direct connection between the coil's busbar and the liquid-cooled chamber can be achieved through welding, and short circuits can be prevented by applying an insulating coating (e.g., epoxy insulating varnish).

[0019] The stator core is fixed inside the outer casing. It is made of stacked silicon steel sheets with high magnetic permeability, and has multiple slots formed on its inner or outer circumference to accommodate and position the coil windings. The stator core is a major component of the motor's magnetic circuit and also the source of heat generated by iron losses.

[0020] The coil winding is the core component of this invention, integrating electromagnetic and thermal functions. It consists of a hollow tubular coil wound around the slots of the stator core. The tubular coil is preferably made of copper tubing with high electrical and thermal conductivity, and its internal hollow channel constitutes the coil's liquid cooling channel. The outer surface of the tubular coil is covered with an insulating layer with high insulation strength and high thermal conductivity. This structure enables the coil winding to simultaneously possess three major functions: 1) acting as a current carrier to generate a driving magnetic field (electromagnetic function); 2) acting as the main heat generator (Joule heat source); and 3) acting as a conduit for the flow of cooling medium (thermal management function).

[0021] The rotor and stator core are coaxially arranged and can rotate relative to each other. In a specific embodiment, the rotor is provided with a permanent magnet to establish an excitation magnetic field in the air gap, which interacts with the armature magnetic field generated by the stator coil to generate electromagnetic torque.

[0022] The output shaft is fixedly connected to the rotor, and outputs the torque generated by the rotor to an external load, such as a speed reducer.

[0023] The most innovative structural feature of this technical solution lies in the integration of the fluid circuit. A manifold is formed at the axial end of the coil winding. This manifold is a physical structure for collecting multiple tube coil ports; it can be a separate manifold plate or an interface area integrally formed with the outer shell. The tube coil is directly connected to the liquid-cooled chamber of the shell through this manifold.

[0024] Here, "direct connection" means that there are no intermediate transition pipes, hoses, or joints between the ends (inlet and outlet) of the tube coil and the liquid-cooled chamber of the shell. Instead, they are directly connected in space through a reliable sealing connection method (such as expansion joint, welding, interference fit with sealing ring, etc.), making the inner hole of the tube coil and the chamber inside the shell wall a continuous whole in terms of hydrodynamics. Thus, the liquid-cooled chamber of the shell and all the parallel coil liquid-cooling channels together form a closed cooling loop for the circulation of the cooling medium.

[0025] The cooling circulation path of the motor unit in this application is as follows: A low-temperature cooling medium is pre-sealed within the hollow channels of the housing liquid-cooled chamber and the coil tubes. Based on the connection between the housing liquid-cooled chamber and the coil cooling channels, it is evenly distributed to each branch coil tube, i.e., directly entering the inlet (i.e., the liquid-cooled channel of each individual coil) of each parallel coil tube. During its flow within the coil tube, the cooling medium absorbs Joule heat generated by the tube wall (i.e., the heating conductor itself) with extremely high efficiency. The cooled medium, having absorbed heat and increased in temperature, flows out from the outlet of the coil tube and directly merges into the housing liquid-cooled chamber within the outer shell wall from another area, completing a full cooling cycle.

[0026] In this application, the coil winding serves as both the heating element and the cooling pipe; the outer casing functions as both a structural component and a fluid manifold. This fusion produces the following significant beneficial effects:

[0027] First, it achieved "in-situ cooling," reducing thermal resistance to the theoretical limit.

[0028] The biggest bottleneck of traditional motor cooling solutions (whether air-cooled or indirect liquid-cooled) lies in the excessively long heat conduction path and high thermal resistance between the heat-generating conductor (copper wire) and the cooling medium. In this solution, the cooling medium flows directly inside the heated copper tube. After heat is generated inside the copper tube, it only needs to travel half the thickness of the copper tube wall (usually only a fraction of a millimeter) to reach the cooling medium interface by conduction, and is then absorbed and carried away by the flowing cooling medium through forced convection. According to Fourier's law of thermal conductivity, because the heat conduction distance approaches a minimum, even if the thermal conductivity of the material remains unchanged, the thermal resistance decreases by orders of magnitude. At the same time, the forced convection heat transfer coefficient inside the tube is much higher than the equivalent heat transfer coefficient of natural convection or indirect contact. This ultra-low thermal resistance compresses the temperature difference between the winding core and the coolant to a minimum. This means that even under extremely high current density and heating power, the motor winding temperature can be effectively controlled within a safe range, allowing the motor to continuously output higher torque and power, significantly increasing the upper limit of power density. This is a fundamental overhaul of traditional heat dissipation architecture.

[0029] Second, it achieves ultimate structural integration, significantly saving joint space.

[0030] This solution internalizes the entire traditional liquid cooling system within the motor housing and coil interior. The housing's liquid cooling chamber acts as a built-in "fluid manifold," while the coil's confluence section forms a "port array" directly connected to this manifold. The entire cooling circuit has no additional pipes or connectors inside the motor. This is revolutionary for humanoid robot joints where internal space is extremely limited. It allows the motor's outer diameter and axial length to be fully utilized for electromagnetic design (such as increasing the core length or diameter to enhance torque) without requiring any additional space for heat dissipation structures, thus removing the biggest spatial obstacle to achieving flatter, lighter, and higher torque density joint modules.

[0031] Third, it eliminates the risk of internal leakage and improves system reliability.

[0032] By integrating all fluid connection points within a sealed housing and employing highly reliable permanent connection processes such as expansion and welding, the risks of aging, loosening, vibration, and wear leakage inherent in traditional solutions due to the extensive use of external hoses and quick-connect fittings are completely eliminated. The cooling medium is strictly confined within a robust circuit comprised of a metal housing and metal tubing, resulting in a significant improvement in the overall reliability of the system.

[0033] Fourth, it achieves electrical isolation between the windings and the coolant.

[0034] Although the cooling medium flows inside the copper tube, the copper tube itself is a continuous metallic conductor, and its outer surface is covered with a high-performance insulating layer. Therefore, the cooling medium is completely isolated from the live parts of the motor (the copper tube wall through which the current flows). The cooling medium only flows in the "non-electrical" space inside the copper tube, without contacting any area outside the insulating layer, thus fundamentally ensuring electrical safety.

[0035] Furthermore, the coil winding is configured to include at least two sets of winding branches connected in parallel in the circuit to compensate for the increased equivalent resistance of the winding due to the use of an inner hollow tube coil. This design enables the present invention to solve the problem of electrical performance loss caused by the "internal cooling of the winding" scheme. Specifically, after replacing solid wires with hollow tubes, the DC resistance of a single tube coil will be greater than that of a solid wire of the same outer diameter due to the reduction in the effective cross-sectional area of ​​the conductor. If not compensated, this will lead to increased copper losses and decreased efficiency in the motor. This application compensates for this physical loss by introducing circuit topology optimization, based on the principle of parallel resistance: the coils that may originally be connected in series are divided into at least two (e.g., two, three or more) parallel branches, each branch still consisting of coils with the required number of turns connected in series.

[0036] This design has brought about many significant benefits:

[0037] 1) Effective compensation for copper losses, ensuring and improving motor efficiency: Due to the reduction in equivalent resistance, the total copper losses of the motor decrease when the same phase current is applied. This directly offsets the negative impact of increased single-tube resistance caused by the use of hollow tubes, allowing the motor to achieve maximum heat dissipation while maintaining its efficiency (especially in terms of copper losses) at a high level, or even exceeding it. This breaks the traditional perception that "performance must be sacrificed to improve heat dissipation," and achieves synergistic optimization of the two core functions of thermal management and electromagnetic drive.

[0038] 2) Increase the motor's torque / current constant: Lower winding resistance means that a larger current can be driven at the same terminal voltage, thus generating greater electromagnetic torque. In other words, a smaller voltage drop across the resistor results in higher motor efficiency while producing the same torque.

[0039] 3) Provides electrical redundancy and enhances system robustness: The parallel branch structure provides inherent electrical redundancy. In extreme cases, if one parallel branch disconnects for any reason, the other branches can still carry some current, allowing the motor to continue operating in derating mode and avoiding catastrophic immediate shutdown. This is of great value for robot applications with extremely high safety requirements (such as humanoid robots that may fall and be damaged if they suddenly stop during dynamic walking).

[0040] 4) Improve back EMF waveform and reduce torque pulsation: The design of parallel branches can be coordinated with the distribution of stator slots. By reasonably arranging the positions of different branch coils in space, it can weaken harmonics and improve the sinusoidal nature of the back EMF waveform, thereby reducing the torque pulsation of the motor, making the operation smoother and the control accuracy higher.

[0041] In summary, the technical feature of setting the coil winding to include at least two sets of winding branches connected in parallel in the circuit is not a simple change in the circuit connection method, but a solution with a clear causal relationship and technical contribution proposed for a specific technical problem (increased resistance of hollow conductor). It is interdependent and synergistic with the "winding internal cooling" structure of claim 1, and together they constitute a whole with breakthrough performance in both thermal and electrical aspects.

[0042] Furthermore, the coil is a copper tube coil, with an insulating layer covering its outer surface. Copper has extremely low resistivity, which minimizes resistive losses during power transmission. Simultaneously, copper has extremely high thermal conductivity, ensuring rapid heat conduction within the tube wall and reducing thermal resistance from the inner to the outer surface (if necessary) or within the tube wall. In addition, copper has good plasticity and ductility, facilitating the shaping into the desired coil form through cold or hot working processes such as bending and expanding.

[0043] In addition, the insulation layer covering the copper tube must meet a series of requirements: 1) High dielectric strength, capable of withstanding voltage stress between turns and between phases to prevent breakdown and short circuit; 2) High thermal conductivity, although the main heat dissipation path is to dissipate heat to the coolant in the inner hole, some heat may still need to be conducted to the iron core or the surrounding environment through the insulation layer, so the thermal resistance of the insulation layer should be as low as possible; the present invention preferably uses insulation materials with better thermal conductivity, such as polyimide (PI) coating or polyether ether ketone (PEEK) coating; 3) Good adhesion and flexibility: during the bending process of winding the coil, the insulation layer must be able to deform with the copper tube without cracking or peeling; 4) Resistance to coolant corrosion: even if the coolant does not directly contact the outer surface, the insulation layer should have chemical stability in potential leakage or humid environments.

[0044] By adopting a structure in which copper tubes are covered with a high-performance insulation layer, all the physical functions required for "in-situ liquid cooling" are achieved in the simplest structural form while ensuring electrical safety and high-efficiency conductivity.

[0045] Furthermore, a heat dissipation plate is installed between the back yoke of the stator core and the inner wall of the outer casing. The heat dissipation plate has an evaporation side and a condensation side. The evaporation side is in close contact with the back yoke of the stator core, and the condensation side is in close contact with the inner wall of the outer casing. By introducing the heat dissipation plate, the problem of efficient heat dissipation of another important heat source inside the motor—the stator core—is solved, thus constructing a system-level, flawless thermal management system.

[0046] The "internal cooling" circuit described above can efficiently handle the largest proportion of heat generated by winding copper losses. However, the heat generated by hysteresis losses and eddy current losses (iron losses) in the stator core due to alternating magnetic fields is still significant, especially under high-frequency and high-magnetic-density operating conditions. If this heat cannot be dissipated in time, it will cause the core temperature to rise, forming localized hot spots. This heat will be conducted to the windings through the teeth, increasing the burden on the winding cooling system; on the other hand, it will cause changes in the core material properties and thermal stress deformation with the outer shell.

[0047] A vapor chamber is a passive element that utilizes the gas-liquid phase change of a working fluid for efficient heat transfer. It contains a small amount of low-boiling-point working fluid (such as deionized water) encapsulated under vacuum and features capillary structures (such as a sintered copper powder layer and microgrooves). Its working principle is as follows: when heat is transferred from the heat source (stator core) to the evaporation side of the vapor chamber, the liquid working fluid in that area absorbs heat and vaporizes. Driven by a small pressure difference, the vapor flows to the cooler condensation side (near the outer shell), where it releases latent heat and condenses into liquid. The condensate then flows back to the evaporation side via capillary forces from the capillary structure, completing a highly efficient two-phase heat transfer cycle.

[0048] Placing a vapor chamber between the core back yoke and the inner wall of the outer shell has several beneficial effects: it establishes a "thermal superconducting" pathway from the core to the shell, specifically significantly reducing the thermal resistance between them. Compared to direct contact between the core and shell (which involves microscopic air gaps and high contact thermal resistance) or filling with ordinary thermally conductive adhesive (which has limited thermal conductivity), the vapor chamber provides an order-of-magnitude reduction in thermal resistance, allowing heat from the core to be conducted away rapidly and efficiently. Furthermore, it makes the outer shell a highly efficient auxiliary radiator: heat transferred to the inner wall of the shell can continue to dissipate along two paths: first, directly to the cooling medium flowing in the liquid-cooled chamber of the shell (since the liquid-cooled chamber is located within the outer shell wall); second, through convection and radiation to the surrounding environment via the outer surface of the shell. The first path, in particular, works synergistically with the main cooling circuit, allowing for more efficient utilization of the entire cooling system's heat capacity.

[0049] Moreover, by arranging heat spreaders, local hot spots can be eliminated and thermal uniformity can be improved: the heat spreader's temperature uniformity effect can smooth out any uneven temperature distribution that may exist on the iron core back yoke, avoid thermal stress concentration and material performance degradation caused by local high temperature, and improve the motor's operational reliability and lifespan.

[0050] Based on the design of the heat sink, this application constructs a parallel and efficient auxiliary heat dissipation path, ensuring that both the windings and the core can receive efficient cooling that matches their heat generation, thus achieving "full coverage" and "no shortcomings" in the internal thermal management of the motor.

[0051] Furthermore, the heat spreader is an arc-shaped heat spreader or an annular heat spreader, the curvature of which matches the back yoke surface of the stator core and the inner wall surface of the outer shell. Preferably, the heat spreader is manufactured or formed into an arc-shaped (if multiple pieces are spliced ​​to cover the entire circumference) or annular (if integrally formed) structure that matches the contact surface. The radius of curvature of its inner arc surface is consistent with the outer circle radius of the stator core after grinding, and the radius of curvature of its outer arc surface is consistent with the inner hole radius of the outer shell after finishing.

[0052] By precisely shaping the heat spreader into an arc that matches the mating surfaces and applying appropriate pre-tightening force (such as through a heat jacket), the tiny protrusions at the interface can be forced to undergo elastoplastic deformation, squeezing out air and significantly increasing the actual contact area. This ensures that both sides of the heat spreader (evaporation side and condensation side) can form a tight, large-area surface contact with the stator core and the outer casing, respectively, thus truly maximizing the heat spreader's ultra-low thermal resistance advantage.

[0053] Furthermore, the outer casing is assembled to the outside of the stator core and the heat spreader by applying a radial preload to the heat spreader. The process can be described as follows: utilizing the physical property of thermal expansion and contraction of materials, the outer casing is first uniformly heated to a certain temperature, causing its inner diameter to increase due to thermal expansion. Then, at room temperature, the stator core assembly with the heat spreader attached is smoothly placed into the heated and expanded outer casing. When the outer casing cools to room temperature, it contracts, and its inner diameter attempts to return to its original size. However, because the stator core and heat spreader are already installed inside, the contraction is hindered, thus generating a continuous and uniform radial compressive stress among the stator core, heat spreader, and outer casing.

[0054] This radial preload is key to achieving low contact thermal resistance. The greater the applied radial preload (within the material's elastic limit), the flatter the microscopic protrusions at the interface are, resulting in a larger actual contact area and lower contact thermal resistance.

[0055] The beneficial effects achieved by this design are multifaceted, specifically: 1) Ensuring long-term stable low thermal resistance: Unlike bonding solely with thermally conductive adhesive, the pre-tightening force generated by the heat jacket is a mechanical pre-stress that does not rely on any aging or deteriorating filler materials. It can maintain a tight contact at the interface stably for a long time, thereby ensuring the long-term reliability and consistency of heat dissipation performance; 2) Achieving fastener-free fixing: With sufficient interference, the friction generated by the heat jacket process is sufficient to firmly fix the stator core, preventing it from circumferentially rotating under torque or axially moving under vibration. This eliminates the need for traditional fasteners such as keys, pins, or screws, simplifying the structure and saving space and weight; 3) Providing uniform clamping force: The force generated by the shrinkage of the outer shell is evenly distributed along the entire circumference, avoiding the uneven pressure and local deformation problems that may be caused by using local screws for tightening. This is especially beneficial for precision components such as heat spreaders with internal vacuum cavities.

[0056] Furthermore, it also includes a temperature sensor, a pump body, and a controller. The temperature sensor is used to detect the temperature of the coil windings and / or the stator core. The controller is signal-connected to the temperature sensor to adjust the flow of the cooling medium in the cooling circuit based on the detected temperature signal. This adds an intelligent temperature control subsystem to the joint motor unit of the present invention, upgrading it from passive heat dissipation to active, closed-loop thermal management. The temperature sensor (such as a thermistor, thermocouple, or platinum resistance thermometer) is embedded at key temperature measurement points, such as embedded in the end of the coil windings or in slots, or attached to the back yoke of the stator core. It senses the temperature of these core heat-generating components in real time and converts the temperature signal into an electrical signal. The pump body is the power source of the cooling circulation system, used to drive the cooling medium to circulate in the closed cooling circuit. The pump body can be a micro-pump, small in size, capable of being installed at the connection between the coil cooling channel of the tube coil and the liquid cooling chamber of the housing. The controller (which can be the main controller of the motor or an independent sub-controller) receives the signal from the temperature sensor and compares it with a preset temperature threshold or control algorithm (such as PID control). Based on the comparison results, the controller outputs a control signal to adjust the pump speed or the opening of the flow control valve, thereby regulating the flow rate of the cooling medium flowing through the cooling circuit.

[0057] Furthermore, the cooling medium is a water-ethylene glycol mixture or an insulating fluorinated liquid.

[0058] The second aspect of this application also discloses a joint module, which includes a joint motor unit as disclosed above, and a reducer that is drively connected to the output shaft of the joint motor unit.

[0059] A third aspect of this application also discloses a robot comprising multiple joints, at least one joint including a robot joint module disclosed in the second aspect of this application.

[0060] Beneficial Effects: In the joint motor unit with the integrated liquid-cooled heat dissipation structure of this invention, an integrated closed cooling circuit is constructed by creatively connecting the internal channel of the hollow tube coil directly to the liquid-cooled chamber integrated within the outer shell. This structural design brings three revolutionary beneficial effects:

[0061] First, a revolution in thermal management performance: "In-situ cooling" of the main heat source—the windings—is achieved, shortening the heat transfer path to the physical limit and minimizing thermal resistance, thereby allowing the motor to operate continuously at extremely high current densities, resulting in a leapfrog improvement in the upper limit of power density.

[0062] Second, the revolution in spatial integration: the complex fluid distribution and confluence network is "internalized" into the shell and winding structure, eliminating all external pipelines and maximizing the sharing of the motor electromagnetic space and cooling functional space, laying the structural foundation for the extreme miniaturization and lightweighting of robot joints.

[0063] Third, innovation in electromagnetic performance assurance: By combining with the parallel winding topology, the loss of electrical performance caused by structural changes is cleverly compensated, and the heat dissipation capacity and electromagnetic performance are synergistically optimized, rather than sacrificing one for the other.

[0064] The joint motor unit, joint module, and robot of the integrated liquid cooling heat dissipation structure of the present invention are disclosed in detail below with reference to the embodiments shown in the accompanying drawings and the reference numerals. Attached Figure Description

[0065] Figure 1 This is a partial structural diagram of the articulated motor unit in this application.

[0066] Figure 2 This is a schematic diagram of the closed cooling circuit formed by the coil winding and the outer casing in this application.

[0067] Figure 3 This is an axial schematic diagram showing the coil winding and the outer casing in a connected state in this application.

[0068] Figure 4 This is a schematic diagram of the parallel connection of coil windings in this application.

[0069] Figure Labels

[0070] 1. Outer casing; 2. Stator core; 3. Coil winding; 4. Rotor; 5. Output shaft; 6. Heat dissipation plate; 7a of the first winding and 7b of the second winding. Detailed Implementation

[0071] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0072] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0073] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0074] Example 1

[0075] This embodiment provides a joint motor unit with an integrated liquid cooling structure, which is particularly suitable for joint parts of humanoid robots with stringent requirements for size and power density.

[0076] Figure 1 This is a partial structural diagram of the articulated motor unit in this application. Figure 2 This is a schematic diagram of the closed cooling circuit formed by the coil winding and the outer casing in this application. Figure 3 This is an axial schematic diagram showing the coil winding and the outer casing in a connected state in this application. Figure 4 This is a schematic diagram of the parallel connection of coil windings in this application.

[0077] This application provides a joint motor unit with an integrated liquid cooling structure, which includes a housing 1, a stator core 2, a coil winding 3, a rotor 4, and an output shaft 5. The housing 1 has a housing liquid cooling chamber inside its housing wall. The stator core 2 is fixed inside the housing 1. The coil winding 3 is formed by winding a hollow tube coil on the stator core 2, and the hollow channel inside the tube coil forms a coil liquid cooling channel. The rotor 4 is coaxially arranged with the stator core 2 and can rotate relative to it. The output shaft 5 is fixedly connected to the rotor 4 to output torque. The coil winding 3 forms a busbar at its axial end, and the tube coil is directly connected to the housing liquid cooling chamber through the busbar, so that the housing liquid cooling chamber and the coil liquid cooling channel together form a closed cooling circuit for circulating cooling medium.

[0078] That is, the joint motor unit includes a rotor 4 and a stator sleeved outside the rotor 4, and a coil winding 3 wound on the stator. The coil winding 3 is characterized in that the coil body is a hollow tube coil. The joint motor unit also includes an outer shell 1 located on the outside. The shell wall of the outer shell 1 is provided with a shell liquid cooling chamber. The coil winding 3 as a whole is directly connected to the shell liquid cooling chamber by means of its own tube coil and forms a circulating cooling circuit.

[0079] In this embodiment, the outer casing 1 is the base of the motor unit. Figure 1As shown, an annular liquid-cooled chamber is cast inside the shell wall of the outer casing 1. Multiple inwardly protruding teeth are evenly distributed on the inner circumference of the stator core 2, forming a groove between adjacent teeth, and the coil is wound in the groove. The stator core 2 is fixed inside the outer casing 1 by a heat-shrinking process.

[0080] In a preferred embodiment of the present invention, the cooling medium circulates in a cooling circuit formed by the housing liquid cooling chamber and the coil cooling channel. That is, the cooling medium is stored in a closed loop in the cooling circuit formed by the housing liquid cooling chamber and the coil cooling channel, and can circulate in the housing liquid cooling chamber and the coil cooling channel.

[0081] In other embodiments, the outer casing 1 is machined with a main liquid inlet and a main liquid outlet. Both the main liquid inlet and the main liquid outlet are standard G1 / 8 threaded holes for connecting to an external liquid cooling circulation system, so that the cooling circuit of the present invention can be connected to the external liquid cooling circulation system.

[0082] In one specific embodiment, the tube coil is a copper tube coil with an insulating layer covering its outer surface. The coil winding 3 is configured to include at least two sets of winding branches connected in parallel in the circuit to compensate for the increased winding equivalent resistance due to the use of an internally hollow tube coil.

[0083] The coil winding 3 is formed by winding a hollow tubular coil onto the slots of the stator core 2. The tubular coil is made of high-purity oxygen-free copper tubing. Before winding, the copper tubing undergoes electrostatic spraying and high-temperature sintering processes to form a polyimide (PI) insulating layer approximately 0.1 mm thick on its outer surface. The hollow internal channel of this copper tubing constitutes the coil's liquid cooling channel. To address the increased resistance caused by the copper tubing's effective cross-sectional area being smaller than that of a solid wire of the same outer diameter, the coil winding 33 in this embodiment is designed as a two-way parallel structure in the circuit. Figure 4 As shown in the electrical schematic, each phase winding consists of two parallel winding branches—the first winding branch 7a and the second winding branch 7b. Each branch is composed of several coils connected in series. Through this parallel topology, the equivalent resistance of each phase is reduced to half that of a single branch, effectively compensating for resistance losses.

[0084] In one specific embodiment, a heat spreader 6 is disposed between the back yoke of the stator core 2 and the inner wall of the outer casing 1. The heat spreader 6 has an evaporation side and a condensation side. The evaporation side is in close contact with the back yoke of the stator core 2, and the condensation side is in close contact with the inner wall of the outer casing 1. The heat spreader 6 is an arc-shaped heat spreader 6 or an annular heat spreader 6, and its curvature matches the back yoke surface of the stator core 2 and the inner wall surface of the outer casing 1. The outer casing 1 is assembled to the outside of the stator core 2 and the heat spreader 6 by applying a radial preload to the heat spreader 6.

[0085] Four arc-shaped heat spreaders 6 are installed between the back yoke (outer circular surface) of the stator core 2 and the inner wall of the outer casing 1. The heat spreaders 6 are made of copper and encapsulate deionized water as the working fluid. The inner arc surface (evaporation side) is tightly attached to the ground outer circular surface of the stator core 2 with thermally conductive silicone grease; the outer arc surface (condensation side) is in close contact with the inner wall of the outer casing 1 during assembly through a heat-shrinking process and is subjected to a continuous radial preload. After the outer casing 1 is heated, it is fitted into the stator core 2 with the heat spreaders 6, and after cooling and shrinkage, the fixing is completed.

[0086] In this application, the rotor 4 is made of magnetically conductive material and is coaxially disposed inside the stator core 2. High-performance neodymium iron boron permanent magnets are attached to the outer circumference of the rotor 4. The center of the rotor 4 is fixedly connected to the output shaft 5 by a flat key and set screws. The output shaft 5 is supported on the front and rear end covers of the housing 1 by a pair of bearings.

[0087] In one embodiment, the system further includes a temperature sensor, a pump body, and a controller. The temperature sensor detects the temperature of the coil winding 3 and / or the stator core 2. The controller is signal-connected to the temperature sensor to adjust the flow of the cooling medium in the cooling circuit based on the detected temperature signal. Specifically, temperature sensors (such as PT100 platinum resistance temperature sensors) are embedded in the slots of the stator core 2 and at the ends of the coil winding 3. The signal lines of the temperature sensors are led to an external controller (not shown). The controller adjusts the pump speed according to a preset temperature-flow curve or a PID algorithm, thereby controlling the flow rate or velocity of the cooling medium.

[0088] Furthermore, the cooling medium is a water-ethylene glycol mixture or an insulating fluorinated liquid.

[0089] When the joint motor unit in the above embodiment is working, the controller drives the current to flow into the two parallel coil windings 3, generating a rotating magnetic field that drives the rotor 4 and output shaft 5 to rotate and output torque. Simultaneously, the cooling medium pre-sealed in the liquid-cooled chamber of the housing circulates between the liquid-cooled chamber and the coil cooling channel of the tube coil under the action of the pump. After directly absorbing the Joule heat generated by the copper tube, its temperature rises, and it then flows back into the liquid-cooled chamber of the housing, completing the circulation. The iron loss heat of the stator core 2 is efficiently transferred to the outer shell 1 through the heat spreader 6. Part of it is absorbed by the coolant in the liquid-cooled chamber of the housing, and part is dissipated through the outer surface of the outer shell 1. Throughout the process, the temperature sensor monitors the temperature in real time, and the controller dynamically adjusts the coolant flow rate to ensure that the motor operates efficiently at a safe temperature.

[0090] Example 2

[0091] This embodiment provides a robot joint module. It includes a joint motor unit with an integrated liquid-cooled heat dissipation structure as described in Embodiment 1, and a reducer. In this embodiment, the reducer is a harmonic reducer, with its wave generator fixedly connected to the output shaft 5 of the joint motor unit, its rigid wheel connected to the output flange (not shown), and the flexible wheel serving as the reduction output end. The high-speed, low-torque power provided by the joint motor unit is reduced and amplified by the harmonic reducer to output the low-speed, high-torque required by the robot joint. Due to the excellent heat dissipation capacity and compact size of the joint motor unit, the entire joint module can continuously output high power within a very small spatial envelope, and the temperature rise is controllable.

[0092] Example 3

[0093] This embodiment provides a humanoid robot. Several key moving joints of this humanoid robot, such as the hip, knee, and elbow joints, all utilize the robot joint modules described in Embodiment 2. Because these joint modules integrate the high-efficiency liquid-cooled joint motor unit of this invention, the humanoid robot can maintain stable and strong power output at its joints even when performing prolonged, high-intensity dynamic tasks such as running, jumping, and carrying, without experiencing performance degradation or triggering protective shutdown due to overheating. This significantly improves the actual task execution capability and environmental adaptability of the humanoid robot 400.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A joint motor unit with an integrated liquid-cooled heat dissipation structure, characterized in that, include: The outer shell (1) has a liquid cooling chamber (11) inside its shell wall. The stator core (2) is fixed inside the outer casing (1); The coil winding (3) is formed by a hollow tube coil (31) wound on the stator core (2), and the hollow channel inside the tube coil (31) forms a coil liquid cooling channel. The rotor (4) is coaxially arranged with the stator core (2) and can rotate relative to it; The output shaft (5) is fixedly connected to the rotor (4) to output torque; The coil winding (3) forms a busbar at its axial end, and the tube coil (31) is directly connected to the liquid cooling chamber (11) of the shell through the busbar, so that the liquid cooling chamber (11) of the shell and the liquid cooling channel of the coil together form a closed cooling circuit for circulating cooling medium.

2. The joint motor unit according to claim 1, characterized in that, The coil winding (3) includes at least two sets of winding branches (32, 33) that are connected in parallel in the circuit.

3. The joint motor unit according to claim 2, characterized in that, The tube coil (31) is a copper tube coil with an insulating layer covering its outer surface.

4. The joint motor unit according to claim 1, characterized in that, A heat spreader (7) is provided between the back yoke of the stator core (2) and the inner wall of the outer shell (1). The heat spreader (7) has an evaporation side and a condensation side. The evaporation side is in close contact with the back yoke of the stator core (2), and the condensation side is in close contact with the inner wall of the outer shell (1).

5. The joint motor unit according to claim 4, characterized in that, The heat spreader (7) is an arc-shaped heat spreader or an annular heat spreader, and its curvature matches the back yoke surface of the stator core (2) and the inner wall surface of the outer shell (1).

6. The joint motor unit according to claim 5, characterized in that, The outer casing (1) is assembled to the outside of the stator core (2) and the heat spreader (7) in such a way that a radial preload is applied to the heat spreader (7).

7. The joint motor unit according to claim 1, characterized in that, It also includes a temperature sensor, a pump body, and a controller. The temperature sensor is used to detect the temperature of the coil winding and / or the stator core. The controller is signal-connected to the temperature sensor to adjust the flow of the cooling medium in the cooling circuit according to the detected temperature signal.

8. The joint motor unit according to claim 1, characterized in that, The cooling medium is a water-ethylene glycol mixture or an insulating fluorinated liquid.

9. A joint module, characterized in that, The joint module includes a joint motor unit according to any one of claims 1-8, and a reducer that is drively connected to the output shaft (5) of the joint motor unit.

10. A robot comprising multiple joints, characterized in that, At least one of the joints comprises the robot joint module according to claim 9.

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