Rotor assembly and servo motor

Abstract

The present disclosure relates to a rotor assembly (1) comprising a plurality of first magnets (2) for generating a magnetic field of the rotor assembly (1), a rotor carrier (3) on which the plurality of first magnets (2) is arranged, the rotor carrier (3) being integrally formed and having a cylindrical section (31) and a cover portion (32) at least partially closing the cylindrical section (31) at one end, a positioning frame (4) arranged to abut against the cover portion (32) along an inner surface of the cylindrical section (31) and to positionally hold the plurality of first magnets (2) relative to each other and relative to the rotor carrier (3). Further, a servo motor is related.

Description

Technical Field

[0001] This disclosure relates to a rotor assembly and a servo motor. Background Technology

[0002] Split rotor assemblies are a widely used structural form, especially in robot servo motors. However, in practice, this structure also faces a series of technical challenges.

[0003] First, the air gap between the stator and rotor of a robot servo motor is typically within an extremely small range of 0.5 to 2 mm, requiring very high assembly precision. However, in current assembly processes, magnets are bonded to the rotor housing via a magnetic yoke. Dimensional and positional deviations in these components lead to radial runout errors in the rotor assembly. These errors accumulate due to variations in the assembly sequence, ultimately affecting the required air gap between the stator and rotor.

[0004] Furthermore, robot servo motors, in particular, face frequent forward and reverse rotation and short-term start-stop operations. This makes the rotor base and yoke, which rely on interference fits and adhesive bonding for positioning, prone to relative displacement. Over long-term operation, this positioning or fixing method may gradually fail, leading to a decrease in the coaxiality accuracy of the rotor assembly. This not only affects motor performance but also causes problems such as increased vibration and noise. Summary of the Invention

[0005] This disclosure aims to provide a rotor assembly and a servo motor that at least partially solve the aforementioned problems.

[0006] The rotor assembly and servo motor proposed in this disclosure overcome the aforementioned disadvantages and bring other technical benefits by adopting the following technical features.

[0007] According to a first aspect of this disclosure, a rotor assembly is proposed, the rotor assembly comprising:

[0008] A plurality of first magnets are used to generate a magnetic field for the rotor assembly;

[0009] A rotor bracket, on which the plurality of first magnets are arranged, the rotor bracket being integrally formed and having a cylindrical section and a cover that at least partially closes one end of the cylindrical section;

[0010] A positioning frame is arranged to abut against the cover along the inner surface of the cylindrical section and to position and hold the plurality of first magnets relative to each other and relative to the rotor bracket.

[0011] In some embodiments, the positioning frame has an annular base and protrusions that protrude axially from the base and are evenly distributed circumferentially, with each of the plurality of first magnets held between two protrusions.

[0012] In some embodiments, the distance between adjacent protrusions is equal to the width of the first magnet, and the radial thickness of the protrusion is greater than or equal to the radial thickness of the first magnet.

[0013] In some embodiments, the positioning frame is made of plastic.

[0014] In some embodiments, the rotor bracket is made of low-carbon steel.

[0015] In some embodiments, the rotor assembly further includes a rotor shaft that passes through and is secured in a shaft hole constructed on the cover.

[0016] In some embodiments, a plurality of through holes are provided on the cover portion.

[0017] In some embodiments, the plurality of through holes are evenly distributed around the shaft hole.

[0018] In some embodiments, a groove is provided on one end of the rotor shaft, and a second magnet is fixed in the groove. The second magnet is used to determine the rotation angle and position of the rotor assembly.

[0019] In some embodiments, the groove and the shaft hole are spaced apart from each other.

[0020] In some embodiments, the rotor shaft is manufactured using a powder metallurgy process.

[0021] In some embodiments, the rotor shaft is provided with a bearing mounting surface, a spline, and / or a transmission part.

[0022] In some embodiments, a positioning identification structure is formed on the cover portion.

[0023] In some embodiments, the positioning identification structure is a positioning hole.

[0024] In some embodiments, the positioning frame is bonded to the inner surface of the cylindrical section of the rotor bracket.

[0025] According to a second aspect of this disclosure, a servo motor is proposed, the servo motor including a stator assembly and a rotor assembly as described in this disclosure, the stator assembly being disposed within the rotor assembly.

[0026] A method for assembling a rotor assembly as described in this disclosure, the method comprising the following steps:

[0027] Prepare rotor bracket;

[0028] Prepare the positioning frame;

[0029] Position the rotor bracket in the corresponding holding device;

[0030] An adhesive is applied along the inner surface of the cylindrical section of the rotor bracket in the region adjacent to the cover.

[0031] Place the positioning frame into the cylindrical section until it abuts against the cover;

[0032] The plurality of first magnets are bonded to the inner surface of the cylindrical section and held in place relative to each other and relative to the rotor bracket by the positioning frame.

[0033] High assembly efficiency and low error accumulation are achieved by following the method disclosed herein.

[0034] In some embodiments, the method includes the following steps:

[0035] The positioning frame has an annular base and protrusions that extend axially from the base and are evenly distributed circumferentially. The plurality of first magnets are respectively bonded to the inner surface of the cylindrical section between the protrusions.

[0036] In some embodiments, the method includes the following steps:

[0037] A positioning hole is provided on the cover of the rotor bracket. The rotor bracket is rotated to a certain angle according to the positioning hole, and then the plurality of first magnets are respectively bonded to the inner surface of the cylindrical section between the protrusions.

[0038] In some embodiments, the method includes the following steps:

[0039] A rotor shaft is prepared and installed in a shaft hole constructed on the cover, wherein a groove is provided at one end of the rotor shaft;

[0040] The second magnet is installed in the groove of the rotor shaft and bonded to the rotor shaft.

[0041] The embodiments of this disclosure will be described in more detail below with reference to the accompanying drawings, so that the features and advantages of this disclosure can be readily understood. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments of this disclosure will be briefly described below. The drawings are merely illustrative of some embodiments of this disclosure and are not intended to limit all embodiments of this disclosure to them.

[0043] Figure 1 An exploded perspective view of the rotor assembly according to this disclosure is shown;

[0044] Figure 2 A perspective view of the rotor bracket according to this disclosure is shown;

[0045] Figure 3 A perspective view of the positioning frame according to this disclosure is shown;

[0046] Figure 4 A perspective view of the rotor shaft according to this disclosure is shown;

[0047] Figure 5 A perspective view showing the installation status of the first magnet, the positioning frame, and the rotor bracket;

[0048] Figure 6 A cross-sectional view of the rotor assembly in its assembled state is shown.

[0049] List of reference numerals

[0050] 1 Rotor assembly

[0051] 2 First Magnet

[0052] 3 rotor brackets

[0053] 31 cylindrical sections

[0054] 32 cover

[0055] 321 shaft hole

[0056] 322 through hole

[0057] 323 positioning hole

[0058] 4 positioning frames

[0059] 41 matrix

[0060] 42 protrusions

[0061] 5 rotor shafts

[0062] 51 grooves

[0063] 52 First bearing assembly surface

[0064] 53 Second bearing assembly surface

[0065] 54 splines

[0066] 55 Transmission Unit

[0067] 6. Second Magnet

[0068] 7 First Bearing

[0069] 8 Second bearing Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0071] Compared to the embodiments shown in the accompanying drawings, feasible embodiments within the scope of this disclosure may have fewer components, other components not shown in the drawings, different components, components arranged differently, or components with different connections, etc. Furthermore, two or more components in the drawings may be implemented in a single component, or a single component shown in the drawings may be implemented as multiple separate components.

[0072] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this patent application specification do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not necessarily indicate a quantity limitation. The terms “comprising” or “including” and similar terms mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, which may change accordingly when the absolute position of the described object changes.

[0073] Figure 1 An exploded perspective view of a rotor assembly according to this disclosure is shown. The rotor assembly 1 shown includes a plurality of first magnets 2, such as magnets, which generate a magnetic field of the rotor assembly 1 to interact with the electromagnetic field of the stator assembly to produce electromagnetic torque, thereby driving the motor to rotate. A rotor bracket 3 is also visible in the figure, on which the plurality of first magnets 2 are arranged in the assembled state of the rotor assembly. The rotor bracket 3 is a one-piece component. Figure 2 The rotor bracket 3 is visible in the image and has a cylindrical section 31 and a cover 32 that at least partially closes one end of the cylindrical section 31. Figure 1The positioning frame 4 of the rotor assembly 1 is also visible. The positioning frame 4 is arranged to abut against the cover 32 along the inner surface of the cylindrical section 31 when the rotor assembly is assembled, and to position and hold the plurality of first magnets 2 relative to each other and relative to the rotor bracket 3. The positioning frame 4 can be glued to the inner surface of the rotor bracket 3, or more specifically, the inner surface of the cylindrical section 31 of the rotor bracket 3. The first magnets 2 can also be glued to the rotor bracket. This achieves a secure connection between the components. Figure 5 The installation status of the first magnet 2, the positioning frame, and the rotor bracket is shown.

[0074] By adopting the design of this disclosure, the traditional separate rotor base and magnetic ring are integrated into a single component, namely the rotor bracket. The rotor bracket can be manufactured, for example, using a stamping process. The rotor bracket 3 can be made of low-carbon steel, such as 10# or 20# steel, which has good magnetic permeability. Compared to the traditional separate structure, which consists of a die-cast aluminum support and a machined magnetic yoke, this integrated rotor bracket according to this disclosure has significant advantages: higher strength, better dimensional stability (smaller deformation), better resistance to dynamic impacts, and significantly reduced manufacturing costs, making it particularly suitable for automated mass production.

[0075] like Figure 3 As shown in the perspective view, the positioning frame 4 has an annular base 41 and protrusions 42 that protrude axially from the base 41 and are evenly distributed circumferentially. These protrusions 42 form grooves with each other, and each of the plurality of first magnets 2 can be mounted, for example, glued into these grooves and thus held between two protrusions 42. The distance between adjacent protrusions 42 is equal to the width of the first magnet 2, and the radial thickness of the protrusion 42 is greater than or equal to the radial thickness of the first magnet 2. The protrusions 42 of the positioning frame can precisely guide the installation position of the first magnets 2 during installation and ensure that the first magnets 2 are evenly distributed angularly in the circumferential direction, thereby generating a uniform permanent magnet induced magnetic field. The distance between adjacent protrusions 42 is the width of the first magnet 2. The radial thickness of the protrusion 42 is greater than or equal to the thickness of the first magnet 2 to ensure sufficient contact surface for close contact and firm support of the end faces of the first magnets 2. The positioning frame 4 can be made of a suitable material, such as plastic.

[0076] The rotor assembly 1 also includes a rotor shaft 5, such as Figure 4 As shown. In the installed state, the rotor shaft 5 passes through and is fixed in the shaft hole 321 constructed on the cover 32 of the rotor bracket 3. The shaft hole 321 can be designed as follows: Figure 2The inner flange hole is shown in the figure. The rotor shaft 5, as a key component for power transmission and support, can be assembled with the shaft hole 321 of the rotor bracket in a suitable manner, such as an interference fit. To significantly improve the connection reliability of the components under dynamic impact and high-temperature conditions, a spline 54 or a rib is specially designed on the mating surface of the rotor shaft 5 and the shaft hole 321, and additional reinforcement and fixation can be achieved with adhesive. The rotor shaft adopts a double-bearing support structure. The first bearing 7, along the axial direction of the rotor shaft, is mounted on the first bearing mounting surface 52 inside the motor housing, while the second bearing 8 is mounted on the second bearing mounting surface 53 inside the gearbox, as shown in the figure. Figure 6 As shown, a transmission section 55, such as a toothed section, is machined at the end of the rotor shaft facing the gearbox. This toothed section can be equivalent to the sun gear in a planetary gear transmission system and is used to directly drive the gearbox.

[0077] A groove 51 is provided on one end of the rotor shaft 5, and in the installed state of the rotor assembly, the groove 51 is spaced apart from the shaft hole 5. A second magnet 6 (see...) is fixed in the groove 51. Figure 1 The second magnet 6 can be used to determine the rotation angle and position of the rotor assembly 1. The shape of the second magnet 6 is adapted to the groove 51. It uses a linear Hall-sensing end face magnetic field to determine the rotation angle and position of the rotor assembly, and therefore can be called a signal magnet. The relative position of its magnetic field direction with that of the first magnet 2 has an important influence on high-precision motion control.

[0078] The rotor shaft 5 can be manufactured using powder metallurgy. The bearing assembly surface needs to be machined in the subsequent process to ensure the dimensional and relative positional tolerances of the two bearing assembly surfaces. The spline 54, transmission part 55 and groove 51 are powder metallurgy machined surfaces and do not require special machining treatment.

[0079] To effectively reduce the moment of inertia while ensuring the structural strength and deformation control of the support, multiple through holes 322 are provided on the cover 32. Figure 2 Six are shown, but other numbers are also conceivable. This not only reduces weight but also improves the dynamic response sensitivity of the rotor assembly. To ensure the stability of the rotor assembly during rotation, the plurality of through holes 322 are evenly distributed around the shaft hole 321.

[0080] To meet the requirement of precisely positioning the circumferential position of the gaps between the protrusions of the positioning frame in automated production assembly, a positioning identification structure is constructed on the cover 32. This structure ensures that the first magnet 2 is accurately installed between the protrusions in the circumferential direction. The figure shows that the positioning identification structure is a positioning hole. Of course, other structures that can achieve positioning identification are also conceivable, such as protrusions.

[0081] In the integrated rotor bracket according to this disclosure, while achieving functional integration, the performance is effectively improved and the requirements of automated production are met through the optimization of the through hole 322 and the positioning recognition structure, and it comprehensively surpasses the traditional split structure in terms of strength, stability, impact resistance and cost-effectiveness.

[0082] The rotor assembly 1 according to this disclosure can be used in electric motors, particularly servo motors (not shown). The servo motor also includes a stator assembly disposed inside the rotor assembly 1.

[0083] The following describes a method for assembling rotor assembly 1, the method comprising the following steps:

[0084] Prepare the rotor bracket 3. Prepare the positioning frame 4. For example, using an automated assembly system, the rotor bracket 3 is positioned in the corresponding holding device by a robotic arm. This holding device may, for example, have a corresponding circumferential surface so as to mate with, for example, the outer circumferential surface of the cylindrical section of the rotor bracket 3 to ensure the positioning of the central axis of the rotor bracket 3.

[0085] For example, adhesive is applied along the inner surface of the cylindrical section 31 of the rotor bracket 3 in the area adjacent to the cover 32 using an adhesive application device.

[0086] Then, for example, the positioning frame 4 is placed into, for example, the cylindrical section 31 by a robotic arm until it abuts against the cover 32.

[0087] The plurality of first magnets 2 are bonded to the inner surface of the cylindrical section 31 and held in place relative to each other and relative to the rotor bracket 3 by the positioning frame 4.

[0088] The positioning frame 4 has an annular base 41 and protrusions 42 that protrude axially from the base 41 and are evenly distributed in the circumferential direction. The plurality of first magnets 2 are respectively bonded to the inner surface of the cylindrical section 31 between the protrusions 42.

[0089] A positioning and identification structure is provided on the cover 32 of the rotor bracket 3. This structure can be designed for positioning and identification, such as protrusions. In this example, it is designed as a positioning hole. The positioning hole 323 of the rotor bracket can be determined by a scanning device. Then, the rotor bracket 3 is rotated to a predetermined angle according to the positioning hole 323. The plurality of first magnets 2 are then bonded to the inner surface of the cylindrical section 31 between the protrusions 42 in an alternating N / S pole configuration. This precise positioning installation method avoids interference between the first magnets and the protrusions of the positioning frame. Specifically, in the installation step of the positioning frame 4, after the scanning device reads the angle of the positioning hole 323 of the rotor bracket 3 through an automated image recognition program, it installs the positioning frame 4 into the rotor bracket 3 with a fixed angle relationship between one of the gaps between the protrusions and the positioning hole 323, based on the relative angle relationship between the first magnet 2 and the positioning hole 323 set by the system. Then, when installing the first magnet 2, this angle relationship can be continued, thereby allowing all the first magnets 2 to be smoothly and without jamming into the positioning frame.

[0090] The method may further include preparing a rotor shaft 5 and pressing the rotor shaft vertically into a shaft hole provided on the cover of the rotor bracket using a press, thereby forming a rigid connection through the spline of the rotor shaft and the inner hole surface of the shaft hole of the rotor bracket.

[0091] The method may further include providing a groove 51 on one end of the rotor shaft 5, and then installing the second magnet 6 in the groove 51 of the rotor shaft 5 and bonding it to the rotor shaft 5, using the outer cylindrical surface of the rotor shaft end as a reference. In the installation step of the second magnet 6, since the position reference of the rotor bracket 3 remains unchanged, the second magnet 6 can also be installed into the groove 51 of the rotor shaft according to the relative angle relationship between the second magnet 6 and the positioning hole 323 set by the system, thereby ensuring the relative angle relationship between the second magnet 6 and the first magnet 2.

[0092] The installation method disclosed herein facilitates tooling design and automated process implementation. Furthermore, all subsequent components are installed using a firmly positioned rotor bracket as a reference, effectively avoiding reference conversion errors. This minimizes error accumulation, ensures high dimensional accuracy of the assembled rotor assembly, and results in excellent initial dynamic balance. Engineering practice shows that when the stamped rotor bracket meets the key accuracy requirements—namely, the concentricity between the inner wall surface and the inner hole surface is no greater than 0.03 mm and the roundness of the inner hole is no greater than 0.05 mm—the assembled rotor assembly exhibits extremely low vibration and noise, high initial dynamic balance accuracy, and essentially eliminates the need for additional dynamic balancing correction processes. These two key dimensional tolerances are entirely and reliably guaranteed by current stamping processes.

[0093] The exemplary implementation of the solution proposed in this disclosure has been described in detail above with reference to the embodiments. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the spirit of this disclosure, and various combinations can be made to the various technical features and structures proposed in this disclosure without exceeding the protection scope of this disclosure.

Claims

1. A rotor assembly (1), characterized in that, The rotor assembly (1) includes: A plurality of first magnets (2) are used to generate a magnetic field for the rotor assembly (1); The rotor bracket (3) is provided with the plurality of first magnets (2) arranged on the rotor bracket (3), the rotor bracket (3) being integrally formed and having a cylindrical section (31) and a cover (32) that at least partially closes the cylindrical section (31) at one end. Positioning frame (4) is arranged to abut against the cover (32) along the inner surface of the cylindrical section (31) and to position and hold the plurality of first magnets (2) relative to each other and relative to the rotor bracket (3).

2. The rotor assembly (1) as claimed in claim 1, characterized in that, The positioning frame (4) has an annular base (41) and protrusions (42) that protrude axially from the base (41) and are evenly distributed in the circumferential direction, each of the plurality of first magnets (2) being held between two protrusions (42).

3. The rotor assembly (1) as claimed in claim 2, characterized in that, The distance between adjacent protrusions (42) is equal to the width of the first magnet, and the radial thickness of the protrusion (42) is greater than or equal to the radial thickness of the first magnet.

4. The rotor assembly (1) as claimed in claim 1, characterized in that, The positioning frame (4) is made of plastic.

5. The rotor assembly (1) as claimed in claim 1, characterized in that, The rotor bracket (3) is made of low carbon steel.

6. The rotor assembly (1) as claimed in claim 1, characterized in that, The rotor assembly (1) also includes a rotor shaft (5) which passes through and is fixed in a shaft hole (321) constructed on the cover (32).

7. The rotor assembly (1) as claimed in claim 6, characterized in that, A plurality of through holes (322) are provided on the cover (32).

8. The rotor assembly (1) as claimed in claim 7, characterized in that, The plurality of through holes (322) are evenly distributed around the shaft hole (321).

9. The rotor assembly (1) as claimed in claim 6, characterized in that, A groove (51) is provided on one end of the rotor shaft (5), and a second magnet (6) is fixed in the groove. The second magnet (6) is used to determine the rotation angle and position of the rotor assembly (1).

10. The rotor assembly (1) as claimed in claim 9, characterized in that, The groove (51) and the shaft hole (321) are spaced apart from each other.

11. The rotor assembly (1) as claimed in claim 6, characterized in that, The rotor shaft (5) is manufactured by powder metallurgy.

12. The rotor assembly (1) as claimed in claim 6, characterized in that, The rotor shaft (5) is provided with a bearing mounting surface, a spline (54) and / or a transmission part (55).

13. The rotor assembly (1) as claimed in claim 1, characterized in that, A positioning identification structure is constructed on the cover (32).

14. The rotor assembly (1) as claimed in claim 13, characterized in that, The positioning and identification structure is a positioning hole.

15. The rotor assembly (1) as claimed in claim 1, characterized in that, The positioning frame (4) is bonded to the inner surface of the cylindrical section (31) of the rotor bracket (3).

16. A servo motor, characterized in that, The servo motor includes a stator assembly and a rotor assembly (1) as described in any of the preceding claims, the stator assembly being disposed inside the rotor assembly (1).

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