Multi-assembly halbach ring of inner rotor of robot joint motor

Abstract

The utility model relates to motor rotor technical field especially discloses a kind of robot joint motor inner rotor multi-combination Halbach magnet ring, including rotor core and coaxially arranged on the magnet ring assembly outside rotor core;The magnet ring assembly is composed of multiple permanent magnet modules arranged along the circumferential direction of rotor core Multiple permanent magnet modules head-to-tail arrangement form magnet ring assembly (2), permanent magnet module is composed of multiple permanent magnet block arrangement combination, the same permanent magnet module in adjacent permanent magnet block is set with angle between magnetization direction, to make the air gap side magnetic field of magnet ring assembly enhancement, rotor core side magnetic field weakening.The utility model constructs a multi-order, modular Halbach array, using the vector superposition of different direction magnetic moment, make magnetic field intensity realize same direction superposition and enhance in air gap side, realize reverse cancellation and weaken in rotor core side, significantly improve air gap magnetic density, to output higher torque under same volume and magnet consumption.

Description

Technical Field

[0001] This utility model relates to the field of motor rotor technology, and in particular discloses a multi-combination Heilbeck magnet ring for the inner rotor of a robot joint motor. Background Technology

[0002] Robot joints, especially those of high-precision industrial robots and collaborative robots, require drive motors with high torque density, low torque ripple, high response speed, and compact structure. Permanent magnet synchronous motors are widely used due to their superior performance.

[0003] Traditional permanent magnet motor rotors typically use surface-mounted magnets, arranged uniformly with alternating N and S poles. This method produces an air gap magnetic field waveform with poor sinusoidal characteristics and high harmonic content, resulting in significant torque ripple in the motor. This affects the robot's stability and positioning accuracy at low speeds. Furthermore, the traditional magnet arrangement does not optimize magnet utilization, limiting further improvements in motor torque density.

[0004] Therefore, there is an urgent need for a new rotor magnet structure that is deeply optimized for the characteristics of robot joint motors and can simultaneously achieve ultra-high torque density, extremely low torque ripple, and high mechanical reliability. Utility Model Content

[0005] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this utility model is to provide a novel rotor magnet structure that simultaneously achieves ultra-high torque density, extremely low torque ripple and high mechanical reliability.

[0006] To achieve the above objectives, this invention provides a multi-combination Hellbeck magnet ring for the inner rotor of a robot joint motor, comprising a rotor core and a magnet ring assembly coaxially disposed on the outer side of the rotor core. The magnet ring assembly consists of multiple permanent magnet modules arranged along the circumference of the rotor core, with these modules arranged end-to-end to form the magnet ring assembly. Each permanent magnet module is composed of multiple sets of permanent magnet blocks arranged in combination. The magnetization directions of adjacent permanent magnet blocks within the same module are set at an angle to enhance the magnetic field on the air gap side and weaken the magnetic field on the rotor core side. This invention constructs a multi-order, modular Hellbeck array, utilizing the vector superposition of magnetic moments in different directions to achieve unidirectional superposition and enhancement of the magnetic field strength on the air gap side, while achieving opposite cancellation and weakening on the rotor core side. This significantly improves the air gap magnetic flux density, thereby outputting higher torque and increasing torque density with the same volume and number of magnets.

[0007] Furthermore, the permanent magnet blocks are arranged in four groups, with the magnetization directions of the four groups of permanent magnet blocks at 0°, 45°, 90°, and 135° relative to the radial direction, respectively. This structure represents an excellent balance between performance and cost. It can generate an air gap magnetic field with excellent waveform, the technology is mature, the effect is significant, and it is easy to engineer and mass-produce.

[0008] Furthermore, the permanent magnet blocks are provided in five groups, with the magnetization directions of the five groups of permanent magnet blocks being 0°, 36°, 72°, 108°, and 144° relative to the radial direction, respectively. Due to the smoother change in magnetization direction (36° interval), an air gap magnetic field with lower harmonic content and closer to an ideal sine wave can be generated, thereby further reducing the torque pulsation and operating noise of the motor.

[0009] Furthermore, in the permanent magnet module, the diameter of the cross-section of each permanent magnet block gradually increases from the inner side near the rotor core to the outer side away from the rotor core. The outer side is wider, resulting in a larger contact area with the air gap, which is more conducive to the output of magnetic flux. This is a topology optimization that adapts to the magnetic field distribution, while also improving the overall integrity and mechanical stability of the module and its resistance to centrifugal force.

[0010] Furthermore, in the permanent magnet module, the radial width of each permanent magnet block decreases sequentially from the inner side closest to the rotor core to the outer side furthest from the rotor core. This defines a sequential decrease in the radial height of each magnet block from the inside to the outside of the permanent magnet module. This is a lightweight and harmonic suppression design with "unequal heights," reducing the mass of the outermost part of the rotor and lowering the centrifugal stress during high-speed rotation. By adjusting the volume (magnetomotive force source) of the magnet blocks at different positions, specific orders of magnetic field harmonics can be specifically weakened, further optimizing the waveform.

[0011] Furthermore, the rotor core has a cylindrical structure, and its outer circumferential surface serves as a mounting surface for the magnets of the magnet ring assembly. The rotor core has an outwardly protruding edging at its edge, which serves to stop and limit the movement of the magnet ring assembly. This edging provides axial mechanical stopping and limiting for the core magnet ring assembly, providing a precise reference for rotor assembly, ensuring the accuracy of the magnetic pole position, and preventing axial movement of the magnet ring.

[0012] Furthermore, the height of the edging is less than or equal to half the height of the magnetic ring assembly. This height design ensures that the edging effectively limits the movement without excessively obstructing the end of the magnetic ring, thus guaranteeing sufficient structural strength while minimizing its impact on the magnetic circuit and heat dissipation.

[0013] Furthermore, a groove is provided between the mounting surface of the magnet and the edge banding. This groove is used to fill the groove with adhesive to bond the rotor core and the magnet ring assembly. This increases the bonding area and the thickness of the adhesive layer, creating a "glue nail" effect, which greatly enhances the bonding strength and reliability.

[0014] Furthermore, the inner circumferential surface of the shaft hole of the rotor core is provided with annular reinforcing ribs arranged circumferentially. The annular reinforcing ribs are circular ring structures that protrude from the inner circumferential surface towards the axis. The annular reinforcing ribs act like built-in "hoops," significantly resisting radial expansion at high speeds and compensating for the weakening of the core caused by structures such as cooling channels. At the same time, they form multi-line contact with the shaft, improving the connection stiffness and thermal conductivity of the interference fit.

[0015] Furthermore, all permanent magnet blocks of the same permanent magnet module are arranged in a Heilbeck array along the arrangement direction.

[0016] The beneficial effects of this invention are as follows: By employing four or five permanent magnet blocks with continuously varying magnetization directions within each magnetic pole, a high-order Heilbeck array is constructed, achieving the classic lateral magnetic field concentration effect. Simultaneously, a shield made of magnetically conductive material further short-circuits the leaking magnetic field and guides it to the air gap, working together to concentrate the magnetic flux to the maximum extent within the working air gap. This allows the motor to output greater torque with the same volume and number of magnets, resulting in a revolutionary improvement in torque density, perfectly meeting the core requirements of robot joints for miniaturization and high torque.

[0017] High-order Hellbeck arrays (such as 0° / 45° / 90° / 135° or 0° / 36° / 72° / 108° / 144°) can generate air-gap magnetic fields with extremely low harmonic content and highly sinusoidal waveforms. Furthermore, the trapezoidal cross-section and unequal height design of the permanent magnet blocks specifically suppress magnetic field harmonics of certain orders. These measures purify the magnetic field at its source, thereby significantly reducing motor torque ripple and operating noise, ensuring smooth robot movement and precise positioning at low speeds. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the Heilbeck-type magnet ring of this utility model;

[0019] Figure 2 This is a schematic diagram of the permanent magnet module according to the first embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the permanent magnet module of the second embodiment of the present invention;

[0021] Figure 4 This is a cross-sectional schematic diagram of the Heilbeck-type magnet ring of this utility model;

[0022] Figure 5 for Figure 4 A partial schematic diagram of A in the middle;

[0023] Figure 6 This is a cross-sectional schematic diagram of the Heilbeck-type magnet ring according to the third embodiment of this utility model;

[0024] Figure 7 for Figure 6 A partial schematic diagram of B in the diagram.

[0025] The reference numerals in the figures include:

[0026] 1. Rotor core; 2. Magnet ring assembly; 3. Permanent magnet module; 4. Permanent magnet block; 5. Magnet mounting surface; 6. Edge banding; 7. Glue groove; 8. Annular reinforcing rib; 9. Shielding cover. Detailed Implementation

[0027] To further illustrate the technical means and effects adopted by this utility model in order to achieve the intended utility model purpose, the following detailed description of the specific implementation methods, structure, features and effects of this utility model is provided in conjunction with the accompanying drawings and preferred embodiments.

[0028] Please see Figures 1 to 7 As shown, this invention discloses a multi-combination Hellbeck magnet ring for the inner rotor of a robot joint motor, comprising a rotor core 1 and a magnet ring assembly 2 coaxially disposed on the outer side of the rotor core 1. The magnet ring assembly 2 is composed of multiple permanent magnet modules 3 arranged along the circumference of the rotor core 1. The multiple permanent magnet modules 3 are arranged end-to-end to form the magnet ring assembly 2. The permanent magnet modules 3 are composed of multiple sets of permanent magnet blocks 4 arranged and combined. The magnetization directions of adjacent permanent magnet blocks 4 within the same permanent magnet module 3 are set at an angle to enhance the magnetic field on the air gap side of the magnet ring assembly 2 and weaken the magnetic field on the rotor core 1 side. This invention constructs a multi-order, modular Hellbeck array, utilizing the vector superposition of magnetic moments in different directions to achieve unidirectional superposition and enhancement of magnetic field strength on the air gap side, and unidirectional cancellation and weakening on the rotor core 1 side, significantly improving the air gap magnetic flux density. Thus, with the same volume and number of magnets, higher torque is output, and torque density is improved.

[0029] A high-order Heilbeck array is constructed by combining multiple (four or five) permanent magnet blocks 4 with continuously varying magnetization directions within each magnetic pole. This array can maximize the "push" and concentration of magnetic flux in the air gap, while simultaneously weakening the magnetic flux passing through the rotor core 1 by "cancelling" each other. This effect (i.e., lateral concentration of the magnetic field) significantly increases the air gap magnetic flux density with the same amount of magnets, thereby significantly improving the torque density of the motor. At the same time, the optimized magnetic field waveform has extremely low harmonic content, ensuring smooth motor operation and small torque fluctuations. Combined with the highly reliable rotor core 1 structure and shielding cover 9, an internal rotor system particularly suitable for high-performance robot joint motors is finally formed.

[0030] Unlike the traditional simple alternating N and S poles, and also unlike the radial Helbeck array (previously described in the prior art) which mainly solves the problem of magnetic pole consistency using three magnets, the core of this invention lies in pursuing and achieving a higher-order magnetic field optimization through the overarching concept of "multiple combinations." The goal is directly aimed at maximizing torque density and stability, which is a fundamental difference in technical concept.

[0031] Preferably, in the first embodiment, the permanent magnet block 4 is provided in four groups, and the magnetization directions of the four groups of permanent magnet blocks 4 are respectively 0°, 45°, 90°, and 135° relative to the radial direction. This structure represents an excellent balance between performance and cost. It can generate an air gap magnetic field with excellent waveform, the technology is mature, the effect is significant, and it is easy to engineer and mass-produce.

[0032] Traditional three-pole radial Helbeck designs aim to strengthen and regulate the radial magnetic field at the center of a single pole using symmetrically tilted magnets. This primarily optimizes the magnetic field distribution within the pole, improving consistency and can be seen as an optimization of traditional radial magnetic circuits, improving the square wave peak of a single pole, but the harmonic content remains high. Four magnets arranged in a magnetization direction sequence of 0°, 45°, 90°, and 135° aim to "pump" the magnetic field from one side to the other through continuous rotation of the magnetization direction. This results in synergistic magnetic field enhancement on the air gap side and counteracting magnetic field weakening on the core side, creating a novel, highly asymmetrical magnetic circuit. The 0° and 45° magnets jointly "push" the magnetic flux outwards, while the 90° and 135° magnets "cut off" the inward magnetic path, forming a standard Halbach effect. The increase in air gap magnetic flux density far exceeds that of traditional three-pole radial Helbeck designs. This produces an air gap magnetic field closer to an ideal sine wave, significantly reducing torque ripple and noise. For robot joints, this means smoother low-speed operation and higher positioning accuracy, representing a qualitative leap in performance.

[0033] Preferably, in the second embodiment, the permanent magnet block 4 is provided in five groups, and the magnetization directions of the five groups of permanent magnet blocks 4 are respectively 0°, 36°, 72°, 108° and 144° relative to the radial direction. Because the magnetization direction changes more smoothly (36° interval), an air gap magnetic field with lower harmonic content and closer to an ideal sine wave can be generated, thereby further reducing the torque pulsation and operating noise of the motor.

[0034] This structure is a higher-order Hellbeck array. It can be understood as a smoother, more continuous "rotation" of the magnetization direction within the magnetic pole range. The 0° and 36° magnets are primarily responsible for generating and guiding the magnetic flux toward the air gap side; the 72° magnet plays the main "pumping" role; while the 108° and 144° magnets work together to more efficiently "twist" the magnetic flux pointing toward rotor core 1, making it superimposed in the same direction as the magnetic flux on the air gap side, while almost completely canceling out the leakage flux on the core side. Due to the higher order and smoother change of the magnetization direction, the resulting air gap magnetic flux waveform has extremely low harmonic distortion. This directly results in: more extreme torque smoothness, with torque pulsation minimized to almost imperceptible levels, meeting the stringent requirements for motion smoothness in high-end collaborative robots and surgical robots; superior low-speed performance, with the motor achieving uniform torque output even at extremely low speeds, without crawling, and with higher positioning accuracy; and quieter operation, with further suppression of electromagnetic noise caused by magnetic field harmonics. Compared to a four-piece structure, a five-piece structure allows for more precise control of the magnetic field distribution inside and at the ends of the magnetic poles, resulting in weaker edge effects. This makes the magnetic field generated by each pole more spatially ideal and the transition between poles smoother.

[0035] In the permanent magnet module 3, the diameter of the cross-section of each permanent magnet block 4 gradually increases from the inner side near the rotor core 1 to the outer side away from the rotor core 1. The outer side is wider, resulting in a larger contact area with the air gap, which is more conducive to the output of magnetic flux. This is a topology optimization that adapts to the magnetic field distribution, while also improving the overall integrity and mechanical stability of the module and its resistance to centrifugal force.

[0036] Preferably, the permanent magnet block 4 is a neodymium iron boron permanent magnet.

[0037] In the permanent magnet module 3, the radial width of each permanent magnet block 4 decreases sequentially from the inner side closest to the rotor core 1 to the outer side furthest from the rotor core 1. This defines the radial height of each magnetic block in the permanent magnet module 3 as decreasing sequentially from the inside to the outside. This is a lightweight and harmonic suppression design with "unequal heights," reducing the mass of the outermost part of the rotor and lowering the centrifugal stress during high-speed rotation. By adjusting the volume (magnetomotive force source) of the magnetic blocks at different positions, specific orders of magnetic field harmonics can be specifically weakened, further optimizing the waveform.

[0038] The rotor core 1 has a cylindrical structure. The outer circumferential surface of the rotor core 1 is a magnet mounting surface 5 for mounting the magnet ring assembly 2. The rotor core 1 has an outwardly protruding edging 6, which is used to stop and limit the magnet ring assembly 2. The edging 6 provides axial mechanical stopping and limiting for the core magnet ring assembly 2, provides a precise reference for rotor assembly, ensures the accuracy of the magnetic pole position, and prevents the magnetic ring from moving axially.

[0039] The height of the edging 6 is less than or equal to half the height of the magnet ring assembly 2. This height design ensures that the edging 6 can effectively limit the movement without excessively obstructing the end of the magnet ring, thus guaranteeing sufficient structural strength while minimizing its impact on the magnetic circuit and heat dissipation.

[0040] A glue groove 7 is provided between the magnet mounting surface 5 and the edging 6. The glue groove 7 is used to fill the glue used to bond the rotor core 1 and the magnet ring assembly 2. This increases the bonding area and the glue layer thickness, forming a "glue nail" effect, which greatly enhances the bonding strength and reliability.

[0041] Preferably, the rotor core 1 is provided with at least three cooling channels that run through the axis, and the cooling channels are evenly distributed circumferentially with the rotor shaft as the center.

[0042] Preferably, multiple annular heat dissipation grooves are formed along the axial direction on the magnet mounting surface 5; the minimum wall thickness between the bottom of the annular heat dissipation groove and the cooling medium flow channel is 0.5 mm to 2 mm.

[0043] This structure combines internal forced cooling (cooling channels) with surface-enhanced heat dissipation (annular grooves), forming an active + passive collaborative cooling system for high-speed, high-power-density robot joint motors. The cooling channels can be directly circulated with coolant (such as oil) to remove heat from the rotor core 1 and the magnets transferred through conduction. The annular grooves significantly increase the heat transfer area between the rotor surface and the internal cooling channels. When the rotor rotates, the gas within the grooves forms turbulence, disrupting the static air layer adhering to the rotor surface and greatly enhancing surface convective heat transfer efficiency. The thin-walled design (0.5-2mm) ensures that heat can be rapidly conducted from the bottom of the annular grooves to the internal cooling channels, achieving an efficient thermal management path from the magnets to the coolant. This directly solves the core pain point of frequent start-stop and overload operation of robot joint motors—heat dissipation—and effectively prevents permanent magnets from demagnetizing due to high temperatures.

[0044] The rotor core 1 has an annular reinforcing rib 8 arranged circumferentially on the inner circumferential surface of the shaft hole. The annular reinforcing rib 8 is a circular ring structure that protrudes from the inner circumferential surface towards the axis. The annular reinforcing rib 8 acts like a built-in "hoop", which significantly resists radial expansion at high speeds and compensates for the weakening of the core caused by structures such as cooling channels. At the same time, it forms multi-line contact with the shaft, improving the connection rigidity and heat conduction effect of the interference fit.

[0045] All permanent magnet blocks 4 of the same permanent magnet module 3 are arranged in a Heilbeck array along the arrangement direction.

[0046] Preferably, in the third embodiment, the magnet ring assembly 2 further includes a shield 9 covering the magnet ring assembly 2. The shield 9 is an integral structure and has an annular blind slot for accommodating the magnet ring assembly 2. The opening of the annular blind slot exposes the end face of the magnet ring assembly 2. For the magnetic flux that would normally leak inside the magnet ring assembly 2 (towards the rotor core 1), the shield 9 provides a shortcut with extremely low magnetic resistance, "capturing" these magnetic fluxes and forming a loop inside them. The magnet ring assembly 2, in conjunction with this, ultimately achieves the effect of a "single-sided magnetic field"—the magnetic field is almost completely "compressed" and concentrated on one side of the air gap, while there is almost no magnetic field on the other side.

[0047] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to a preferred embodiment, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present utility model. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A multi-combination Heilbeck type magnet ring for the inner rotor of a robot joint motor, comprising a rotor core (1) and a magnet ring assembly (2) coaxially disposed on the outer side of the rotor core (1); characterized in that: The magnet ring assembly (2) is composed of multiple permanent magnet modules (3) arranged along the circumference of the rotor core (1). The multiple permanent magnet modules (3) are arranged end to end to form the magnet ring assembly (2). The permanent magnet module (3) is composed of multiple sets of permanent magnet blocks (4) arranged and combined. The magnetization directions of adjacent permanent magnet blocks (4) in the same permanent magnet module (3) are set at an angle to enhance the magnetic field on the air gap side of the magnet ring assembly (2) and weaken the magnetic field on the rotor core (1) side.

2. The robot joint motor internal rotor multi-combination Heilbeck type magnet ring according to claim 1, characterized in that: The permanent magnet block (4) is provided in four groups, and the magnetization directions of the four groups of permanent magnet blocks (4) are 0°, 45°, 90° and 135° relative to the radial direction, respectively.

3. The robot joint motor internal rotor multi-combination Heilbeck type magnet ring according to claim 1, characterized in that: The permanent magnet block (4) is provided in five groups, and the magnetization directions of the five groups of permanent magnet blocks (4) are 0°, 36°, 72°, 108° and 144° relative to the radial direction, respectively.

4. The robot joint motor internal rotor multi-combination Heilbeck type magnet ring according to claim 1, characterized in that: In the permanent magnet module (3), from the inner side near the rotor core (1) to the outer side away from the rotor core (1), the diameter of the cross-section of each permanent magnet block (4) gradually increases.

5. The multi-combination Heilbeck magnet ring for the inner rotor of the robot joint motor according to claim 1, characterized in that: In the permanent magnet module (3), the radial width of each permanent magnet block (4) decreases sequentially from the inner side near the rotor core (1) to the outer side away from the rotor core (1).

6. The multi-combination Heilbeck type magnet ring for the inner rotor of the robot joint motor according to claim 1, characterized in that: The rotor core (1) has a cylindrical structure. The outer circumferential surface of the rotor core (1) is a magnet mounting surface (5) for mounting the magnet ring assembly (2). The rotor core (1) has an outwardly protruding edging (6) at its edge, which is used to stop and limit the magnet ring assembly (2).

7. The robot joint motor internal rotor multi-combination Heilbeck type magnet ring according to claim 6, characterized in that: The height of the edging (6) is less than or equal to half the height of the magnet ring assembly (2).

8. The multi-combination Heilbeck type magnet ring for the inner rotor of the robot joint motor according to claim 6, characterized in that: A glue groove (7) is provided between the magnet mounting surface (5) and the edging (6). The glue groove (7) is used to fill the glue used to bond the rotor core (1) and the magnet ring assembly (2).

9. The multi-combination Heilbeck type magnet ring for the inner rotor of the robot joint motor according to claim 6, characterized in that: The rotor core (1) has an annular reinforcing rib (8) arranged circumferentially on the inner circumferential surface of the shaft hole. The annular reinforcing rib (8) is a circular ring structure that protrudes from the inner circumferential surface towards the axis.

10. The multi-combination Heilbeck magnet ring for the inner rotor of the robot joint motor according to claim 1, characterized in that: All permanent magnet blocks (4) of the same permanent magnet module (3) are arranged in a Heilbeck array along the arrangement direction.

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