A compact robot joint

Abstract

The application relates to the technical field of robots, and particularly discloses a compact robot joint arranged between an upper arm and a forearm, which comprises a central shaft, a motor assembly and a gear set; the central shaft penetrates through the motor assembly, and stators and rotors in the motor assembly are alternately arranged in the axial direction of the central shaft in three layers; the stators or the rotors at the two ends of the motor assembly in the axial direction can independently rotate; the gear set comprises two gear rings and bevel gears which are simultaneously engaged with the two gear rings; the two gear rings are respectively connected with the stators or the rotors at the two ends of the motor assembly in the axial direction; after energization excitation, the motor assembly drives the stators or the rotors at the two ends to rotate, drives the two gear rings to rotate, and drives the bevel gears to realize revolution and / or rotation through meshing transmission. Two degrees of freedom are realized by driving the gear set to move through the motor assembly, and the compact robot joint has the technical effects of simple structure, small required installation space and low cost.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more specifically to a compact robot joint. Background Technology

[0002] In existing robot joint designs, freedom of movement is typically achieved using components such as motors and bearings. Each degree of freedom usually corresponds to an independent drive unit, meaning one motor controls a single movement of one joint. When multiple degrees of freedom need to be achieved, an equal number of motors must be used, such as the multi-axis linkage required for industrial robotic arms or humanoid robots. This directly leads to increased overall weight, larger space requirements, and higher manufacturing costs. If a single motor drives two or more degrees of freedom simultaneously, complex transmission mechanisms are needed to change the direction of torque transmission, such as differentials or reversing gear sets. However, this design not only makes the structure exceptionally complex but also further encroaches on limited space due to the addition of extra transmission components. It may even introduce transmission backlash and energy loss, ultimately affecting the joint's accuracy and response speed.

[0003] Patent CN121515150B discloses a joint module that uses an axial flux motor integrated along the same rotation axis. This configuration can only achieve one degree of freedom of motion in a direction at an angle to the axis. Patent CN118478382A discloses an axial flux motor joint module and a robot with this module, which also only achieves a single degree of freedom. Patent CN121777195A discloses a configuration of an axial flux joint module, which is based on an axial flux motor and is still limited to a single degree of freedom output. Patent CN121863757A discloses an axial flux electric joint module system for modular robots, whose technical focus is on achieving high torque output, but the number of degrees of freedom is still only one. In summary, existing axial flux motor joint modules have failed to overcome the single degree of freedom limitation.

[0004] To achieve two or more degrees of freedom using a single motor, a more complex mechanical configuration is required. For example, the differential rotational power device disclosed in patents CN117249218A and CN220748966U can realize rotation or compound motion in two mutually perpendicular planes. Its core components include a harmonic geared motor, a key cross ring, and a harmonic reduction unit. However, such solutions are complex in structure and expensive, making it difficult to meet the practical need for a simpler structure and lower cost. Therefore, how to achieve two degrees of freedom using a single motor while maintaining structural simplicity and cost control has become an urgent technical problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention discloses a compact robot joint. This joint achieves two degrees of freedom of motion by driving a gear set through a motor assembly. This overcomes the shortcomings of existing technologies, which have complex structures and require one motor to achieve one degree of freedom of motion. It has the advantages of simple structure, small installation space, and low cost.

[0006] The technical solution disclosed in this invention is as follows: A compact robot joint, located between the upper arm and the forearm, includes a central shaft, a motor assembly, and a gear set. The upper arm is fixedly connected to the central shaft. The central shaft passes through the motor assembly, and the stator and rotor inside the motor assembly are stacked alternately along the central shaft axis, with a total of three stacked layers. The stator or rotor at both ends of the motor assembly axis can rotate independently. The gear set includes two gear rings and bevel gears that mesh with the two gear rings simultaneously. The two gear rings are respectively connected to the stator or rotor at both ends of the motor assembly axis. After being energized, the motor assembly drives the stator or rotor at both ends to rotate, thereby driving the two gear rings to rotate. Through meshing transmission, the bevel gears are driven to achieve revolution and / or rotation.

[0007] Preferably, the stator and rotor inside the motor assembly are arranged in three alternating layers, with a single rotor in the middle, stators arranged on both sides of the rotor, and two gear rings connected to each stator on both sides.

[0008] Preferably, the stator and rotor inside the motor assembly are arranged in three alternating layers, with a single stator in the middle and rotors arranged on both sides of the stator, and two gear rings connected to each rotor on both sides respectively.

[0009] Preferably, the stator or rotor at both ends of the motor assembly is rotatably mounted on the central shaft via bearings, and the stator or rotor in the middle of the motor assembly is fixedly connected to the central shaft.

[0010] Preferably, when the stator or rotor at both ends of the motor assembly rotates in the same direction and at the same speed, the bevel gear only revolves around the central axis; when the stator or rotor at both ends of the motor assembly rotates in opposite directions at the same speed, the bevel gear only rotates around its own axis; when the stator or rotor at both ends of the motor assembly rotates in the same direction but at different speeds, or in opposite directions at different speeds, the bevel gear simultaneously revolves and rotates, and the rotation directions of the combined motion are different under the two working conditions.

[0011] Preferably, the gear set is further provided with a bevel gear carrier, which is rotatably assembled with the bevel gear and the central shaft respectively.

[0012] Preferably, one end of the bevel gear carrier is rotatably connected to the bevel gear via a bearing, and the other end is mounted on the central shaft via a bearing.

[0013] Preferably, the stator and rotor within the motor assembly are plate-shaped or block-shaped.

[0014] Preferably, the bevel gear is fixedly connected to the forearm.

[0015] Compared with the prior art, the compact robot joint of the present invention achieves two degrees of freedom of motion by driving the movement of the gear set through the motor assembly. Moreover, the structure of the motor assembly and gear set is simple, requires little installation space, has many application scenarios, and is low in cost. Attached Figure Description

[0016] Figure 1 Schematic diagram of the structure of this invention; Figure 2 A cross-sectional view of the single rotor and dual stator configuration in the motor assembly of the present invention; Figure 3 This diagram shows the positional relationship between a motor assembly consisting of a single rotor and two stators and its two gear rings. Figure 4 A cross-sectional view of the single stator and dual rotor configuration in the motor assembly of the present invention; Figure 5 This is a diagram showing the positional relationship between a motor assembly consisting of a single stator and two rotors and the two gear rings. Figure 6 A schematic diagram of the connection structure between the bevel gear and the bevel gear carrier of the present invention.

[0017] Among them, the upper arm 1, the forearm 2, the central shaft 3, the stator 4, the rotor 5, the gear ring 6, the bevel gear 7, and the bevel gear carrier 8. Specific Implementation The principles of this disclosure will now be described with reference to several exemplary embodiments illustrated in the accompanying drawings. Although exemplary embodiments of this disclosure are illustrated in the drawings, it should be understood that these embodiments are described only to enable those skilled in the art to better understand and implement this disclosure, and not to limit the scope of this disclosure in any way.

[0019] The purpose of this invention is to provide a compact robot joint that can achieve two degrees of freedom. This joint is driven by only a single axial flux motor, and has a simple overall structure and compact axial spatial arrangement.

[0020] The compact robot joint disclosed in this invention achieves two degrees of freedom that mimic the human elbow joint, which are two mutually perpendicular degrees of freedom. This elbow joint, however, drives the rotation of the forearm.

[0021] Degrees of freedom refer to the number of independent directions of motion.

[0022] In this invention, the upper arm refers to a human-like upper arm. However, if the joint of this invention is used in other devices or other parts of a robot, such as the shoulder joint, hip joint, or knee joint, any part that has the same function as the upper arm in this application can be called the upper arm.

[0023] In this invention, the forearm refers to a human-like forearm. However, if the joints of this invention are used in other devices or other parts of robots, such as the shoulder joint, hip joint, or knee joint, any part that functions the same as the upper arm in this application can be called the forearm.

[0024] In this application, the rotor includes an iron core, permanent magnets, etc., and the stator is composed of a stator iron core (silicon steel sheets stacked), stator windings (such as three-phase windings) and a frame (cast iron or cast steel).

[0025] like Figure 1 As shown, the compact robot joint of the present invention is located between the upper arm 1 and the forearm 2, and includes a central shaft 3, a motor assembly, and a gear set. The upper arm 1 is fixedly connected to the central shaft 3. The central shaft 3 passes through the motor assembly. The stator 4 and rotor 5 inside the motor assembly are stacked alternately along the central shaft 3, with a total of three stacked layers. The stator 4 or rotor 5 at both ends of the motor assembly can rotate independently. The gear set includes two gear rings 6 and a bevel gear 7. The two gear rings 6 are respectively connected to the stator 4 or rotor 5 at both ends of the motor assembly, and the bevel gear 7 meshes with the two gear rings 6 at the same time. After being energized, the motor assembly drives the stator 4 or rotor 5 at both ends to rotate, which drives the two gear rings 6 to rotate relative to each other. Through meshing transmission, the bevel gear 7 is driven to revolve and / or rotate.

[0026] This invention enables compact robot joints to achieve dual-degree-of-freedom motion using only a single motor assembly and a simple gear set. The motor assembly employs a three-layer axially alternating stator 4 and rotor 5 structure, resulting in a compact, lightweight design that occupies little installation space. Different speed differences are output through the stator 4 or rotor 5 at both ends of the motor assembly, which can rotate independently. The forearm 2 can achieve individual revolution, individual rotation, or a combination of revolution and rotation simply by relying on the meshing transmission of bevel gears 7. This eliminates the need for multiple additional drive motors and complex reduction and reversing mechanisms, effectively reducing the overall weight and manufacturing cost of the joint. At the same time, it reduces transmission backlash and energy loss caused by multi-stage transmission, thereby improving the joint's motion accuracy and response speed.

[0027] Furthermore, when the stator 4 or rotor 5 at both ends of the motor assembly rotate in the same direction and at the same speed, the bevel gear 7 only revolves around the central axis 3; when the stator 4 or rotor 5 at both ends of the motor assembly rotate in opposite directions at the same speed, the bevel gear 7 only rotates around its own axis; when the stator 4 or rotor 5 at both ends of the motor assembly rotate in the same direction but at different speeds, or in opposite directions at different speeds, the bevel gear 7 simultaneously revolves and rotates, and the rotation direction of the compound motion is different under the two working conditions. By controlling the rotation direction and speed difference of the stator 4 or rotor 5 at both ends of the motor assembly, the three output states of the bevel gear 7—revolving only, rotating only, and synchronous compound motion of revolving and rotating—can be flexibly switched. Moreover, the direction of the compound motion is distinguished under different speed change working conditions. The forearm 2 can be adjusted to any posture without interruption using only a single motor assembly, and the motion mode switching is flexible, adapting to the needs of multi-posture operation.

[0028] Example 1 like Figure 2 and Figure 3 As shown, the stator 4 and rotor 5 inside the motor assembly are arranged in three alternating layers, with a single rotor 5 in the middle, stators 4 arranged on both sides of the rotor 5, and two gear rings 6 connected to each side of the stator 4.

[0029] The above scheme adopts a three-layer arrangement structure with a central single rotor 5 and two stators 4 on both sides. The two stators 4 can independently output torque and drive the corresponding gear rings 6 to rotate. The stators 4 directly serve as the power output end without additional transmission adapters. The structure is simple to assemble and can stably generate speed differences to drive the bevel gears 7 to complete multi-mode compound motion. The stators 4 are located on the outside of the motor assembly. The two stators 4 on both sides are fixedly connected to the two gear rings 6 respectively. The bevel gears 7 mesh with the two gear rings 6. After being energized, when the two stators 4 rotate in the same direction and at the same speed, the two gear rings 6 drive the bevel gears 7 to rotate around the central axis 3, making revolution; when the two stators 4 rotate in opposite directions and at the same speed, the bevel gears 7 rotate around their own axis; when the two stators 4 rotate in the same direction but at different speeds or in opposite directions but at different speeds, the bevel gears 7 both revolve and rotate.

[0030] In practical implementation, independent conductive slip ring assemblies can be added to the back of the two rotatable stators 4. The stationary slip ring is fixed to the central shaft, and the rotating slip ring rotates synchronously with the stator 4. The three-phase excitation wires pass through the internal channel of the central shaft and are connected to the stationary slip ring, while the rotating slip ring leads are directly connected to the stator windings. At the same time, axial magnetic attraction force offset disc spring washers are added between the stator 4 and the central rotor 5. These washers, together with the end face thrust bearings, share the axial magnetic pull force, which solves the problem of continuous power supply to the rotating stator windings and eliminates the end face friction caused by the axial magnetic attraction force between the stator and rotor, thus fully completing the electromagnetic and mechanical realization conditions of the rotatable stator.

[0031] Example 2 like Figure 4 and Figure 5 As shown, the stator 4 and rotor 5 inside the motor assembly are arranged in three alternating layers, with a single stator 4 in the middle and rotors 5 arranged on both sides of the stator 4. The two rotors 5 on both sides are respectively connected to two gear rings 6.

[0032] The above scheme adopts a three-layer arrangement structure with a single stator 4 in the middle and two rotors 5 on both sides. The rotors 5 on both sides rotate independently and drive two gear rings 6 respectively. The stator 4 is fixed to the central shaft 3 as the main body of magnetic field generation. The permanent magnet rotors 5 are arranged in a lightweight manner, which can output greater torque. The rotors 5 are located on the outside of the motor assembly. The two gear rings 6 are fixedly connected to the two rotors 5 respectively. The bevel gears 7 mesh with the two gear rings 6. After being energized, when the two rotors 5 rotate in the same direction and at the same speed, the two gear rings 6 drive the bevel gears 7 to rotate around the central shaft 3, making revolution; when the two rotors 5 rotate in opposite directions and at the same speed, the bevel gears 7 rotate around their own axis; when the two rotors 5 rotate in the same direction but at different speeds or in opposite directions but at different speeds, the bevel gears 7 both revolve and rotate.

[0033] In practice, axial limiting retaining rings and bidirectional thrust bearings can be set on the outer sides of the rotors 5 on both sides to counteract the axial permanent magnet attraction between the stator and rotor. The back of the rotor 5 integrates an annular permanent magnet, which does not require rotor power supply. It drives the rotor 5 to rotate by generating an alternating magnetic field through the central fixed stator winding. The rotor adopts a stepped inner ring with a clearance fit with the central shaft bearing. A flexible anti-disengagement snap ring is added in the circumferential direction to achieve radial limiting. When running at high speed, the triple constraint of bearing, retaining ring and snap ring counteracts the magnetic bias attraction, thus improving the mechanical limiting and magnetic attraction balance structure of the rotor 5 at high speed.

[0034] Furthermore, the stator 4 or rotor 5 at both ends of the motor assembly are rotatably mounted on the central shaft 3 via bearings, while the stator 4 or rotor 5 in the middle of the motor assembly is fixedly connected to the central shaft 3. This method of rotatably mounting the stator 4 or rotor 5 at both ends to the central shaft 3 via bearings, and fixing the middle rotor 5 or stator 4 to the central shaft 3, ensures that the outer two layers of components can rotate independently and output power without obstruction, while relying on the middle component to achieve overall positioning and support of the motor, thereby improving the operational stability of the motor assembly and reducing rotational friction loss.

[0035] Furthermore, such as Figure 6 The gear set also includes a bevel gear carrier 8, which is rotatably assembled with the bevel gear 7 and the central shaft 3. Specifically, one end of the bevel gear carrier 8 is rotatably connected to the bevel gear 7 via a bearing, and the other end is mounted on the central shaft 3 via a bearing. The addition of the bevel gear carrier 8, which is rotatably assembled with the bevel gear 7 and the central shaft 3, provides stable and limiting support for the bevel gear 7, constrains its movement trajectory, and ensures that the bevel gear 7 can revolve around the central shaft 3 and rotate on its own axis. This prevents misalignment and jamming during meshing, improving the meshing accuracy and operational smoothness of the gear transmission. The bearing connection enables low-friction rotational engagement at both locations, significantly reducing the rotational resistance during the bevel gear 7's revolution and rotation, minimizing transmission wear and energy loss, while also improving the smoothness of the bevel gear 7's movement and extending the long-term service life of the joints.

[0036] Furthermore, the stator 4 and rotor 5 within the motor assembly are plate-shaped or block-shaped, effectively reducing the axial space occupied by the joints. In some embodiments of the present invention, there is one stator 4 and two rotors 5, or two stators 4 and one rotor 5.

[0037] Furthermore, the upper arm 1 is fixedly connected to the central shaft 3, and the bevel gear 7 is fixedly connected to the forearm 2, so that the upper arm 1, the central shaft 3, the bevel gear 7, and the forearm 2 form a stable transmission link, which allows the motor output torque to be transmitted to the forearm 2, thereby improving the reliability of joint movement.

[0038] The gear meshing area can be filled with grease or have lubricating oil channels installed. The lubricant reduces the coefficient of friction between the bevel gear and the gear ring, suppressing wear and heat generation during transmission, reducing transmission noise, and preventing corrosion of the gear meshing surfaces, ensuring long-term stable operation of the gear set. The motor assembly can adopt an axial flux disc type motor structure. Permanent magnets and excitation coils can be arranged on the stator and rotor. The permanent magnets can be bonded and fixed to the rotor or stator disc surface. A uniform air gap is reserved between the stator and rotor, which can be filled with an insulating and heat-conducting medium to improve heat dissipation during motor operation and enhance the motor's ability to continuously output torque.

[0039] Finally, it should be noted that in the description of this invention, the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compact robot joint, disposed between the upper arm (1) and the forearm (2), characterized in that, Includes a central shaft (3), a motor assembly and a gear set, with the upper arm (1) fixedly connected to the central shaft (3); The central shaft (3) runs through the motor assembly. The stator (4) and rotor (5) inside the motor assembly are stacked and alternately arranged along the central shaft (3). The total number of stacked layers is three. The stator (4) or rotor (5) at both ends of the motor assembly can rotate independently. The gear set includes two gear rings (6) and a bevel gear (7) that meshes with the two gear rings (6) at the same time. The two gear rings (6) are respectively connected to the stator (4) or rotor (5) at both ends of the motor assembly. After being energized, the motor assembly drives the stator (4) or rotor (5) at both ends to rotate, which in turn drives the two gear rings (6) to rotate. Through meshing transmission, the bevel gear (7) is driven to revolve and / or rotate.

2. The compact robot joint according to claim 1, characterized in that, The motor assembly has a three-layer alternating arrangement of stator (4) and rotor (5), with a single rotor (5) in the middle and stators (4) arranged on both sides of the rotor (5), and two gear rings (6) connected to the stators (4) on both sides respectively.

3. The compact robot joint according to claim 1, characterized in that, The motor assembly has a three-layer alternating arrangement of stator (4) and rotor (5) with a single stator (4) in the middle and rotors (5) arranged on both sides of the stator (4). The rotors (5) on both sides are respectively connected to two gear rings (6).

4. The compact robot joint according to claim 1, 2 or 3, characterized in that, The stator (4) or rotor (5) at both ends of the motor assembly are rotatably mounted on the central shaft (3) via bearings, and the stator (4) or rotor (5) in the middle of the motor assembly is fixedly connected to the central shaft (3).

5. The compact robot joint according to claim 1, 2 or 3, characterized in that, When the stator (4) or rotor (5) at both ends of the motor assembly rotate in the same direction and at the same speed, the bevel gear (7) revolves only around the central axis (3); When the stator (4) or rotor (5) at both ends of the motor assembly rotate in opposite directions at the same speed, the bevel gear (7) rotates only around its own axis. When the stator (4) or rotor (5) at both ends of the motor assembly rotate in the same direction but at different speeds or in opposite directions at different speeds, the bevel gear (7) simultaneously generates revolution and rotation. The rotation direction of the compound motion under the two working conditions is different.

6. The compact robot joint according to claim 1, 2 or 3, characterized in that, The gear set is also provided with a bevel gear carrier (8), which is rotatably assembled with the bevel gear (7) and the central shaft (3).

7. The compact robot joint according to claim 6, characterized in that, One end of the bevel gear holder (8) is rotatably connected to the bevel gear (7) via a bearing, and the other end is mounted on the central shaft (3) via a bearing.

8. The compact robot joint according to claim 1, 2, 3 or 7, characterized in that, The stator (4) and rotor (5) in the motor assembly are in the form of plates or blocks.

9. The compact robot joint according to claim 1, 2, 3 or 7, characterized in that, The bevel gear (7) is fixedly connected to the forearm (2).

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