Skewed-pole frameless motor based on screw key connection and design method

Abstract

The invention discloses a helical key connection-based skewed-pole frameless motor and a design method, the helical key connection-based skewed-pole frameless motor comprises a stator assembly and a rotor assembly, the stator assembly comprises a stator iron core and an armature winding, the rotor assembly comprises a magnetic ring, and at least one magnetic ring helical key groove is processed in the inner hole wall of the magnetic ring; rotating shaft spiral key grooves matched with the magnetic ring spiral key grooves in number and shape are formed in the outer surface of a shaft section, matched with the magnetic ring, of the magnetic conductive rotating shaft; the number and the shape of the spiral keys are matched with those of the magnetic ring spiral key groove and the rotating shaft leakage selection key groove, and the spiral keys are embedded between the magnetic ring spiral key groove and the rotating shaft spiral key groove and used for transmitting torque between the rotating shaft and the magnetic ring; the spiral lead angle of the spiral key is set to achieve self-locking.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of frameless motor, and particularly relates to a skew pole frameless motor based on screw key connection and a design method. BACKGROUND

[0002] With the continuous development of industrial automation, robots, aerospace and high-end servo systems, the performance requirements of driving motors are increasingly improved. Frameless motors are widely used due to their compact structure, easy integration into loads, significant reduction in system volume and weight, and other advantages. However, frameless motors also face some unique challenges during operation, especially in terms of suppressing torque ripple, which is crucial for reducing speed unevenness, vibration and noise, and ensuring the positioning accuracy and smoothness of high-precision servo systems. As one of the most widely used and effective technical means for suppressing cogging torque and torque ripple, reducing vibration and noise of frameless motors, the rotor skew pole technology has attracted widespread attention.

[0003] The mainstream methods for realizing rotor skew poles at present mainly include magnetic steel segmented misalignment method and integral magnetic ring inclined magnetization method. The magnetic steel segmented misalignment method divides the rotor core or permanent magnet into several segments along the axial direction, each segment is misaligned by a small electrical angle in the circumferential direction, and then is sequentially pressed into the shaft. The integral magnetic ring inclined magnetization method is to manufacture an integral permanent magnet ring through bonding or sintering process, and to use special magnetizing equipment to make the magnetization direction continuously change along the axial direction, forming an integral skew pole magnetic ring, which helps to maintain the continuity of the magnetic circuit.

[0004] However, the above two technical solutions still have certain deficiencies. The magnetic steel segmented misalignment method has a high degree of process complexity, requires processing multiple segmented cores or magnetic steels and ensuring the shape and position tolerances of each segment, and needs special tooling fixtures to control the misalignment angle during assembly, resulting in slow production rhythm and high cost; at the same time, the non-magnetic gap between the segments will cause the magnetic field to be discontinuous, causing the magnetic resistance on the main magnetic field path to change abruptly, not only affecting the efficiency, but also possibly causing axial magnetic pull, damaging the bearing life; in addition, the segmented structure also weakens the overall stiffness of the rotor, which may induce vibration problems at high speed.

[0005] The integral magnetic ring inclined magnetization method faces challenges in structural connection. The traditional flat key connection has limited contact area when transmitting torque, and the contact stress is large, while the permanent magnet material is usually brittle, and stress concentration is easy to form at the right angle of the key groove, increasing the risk of magnetic ring cracking; the flat key connection also has an unavoidable lateral gap, which may cause rotor dynamic eccentricity, and further cause electromagnetic imbalance and vibration problems; if only interference fit is used, a very high pressing force is required, and the magnetic ring is also easy to be damaged during assembly.

[0006] In summary, the existing rotor skew pole technology still has deficiencies in process complexity, cost control, connection reliability and structural strength, and it is difficult to fully meet the comprehensive needs of frameless motors in high-precision application scenarios. Therefore, it is of great technical significance and market value to research frameless motors with excellent electromagnetic performance, high structural reliability, simple process and lower cost. SUMMARY

[0007] The embodiment of the present application provides a skew pole frameless motor based on screw key connection and a design method thereof, and solves the technical problems of large torque fluctuation, high harmonic content of back electromotive force, stress concentration and easy damage of the fixed magnetic ring and torque transmission structure, and complex assembly process and high cost of the traditional segmented skew pole structure, realizes the assembly efficiency of the frameless motor and the connection reliability of the frameless motor, and reduces the assembly and manufacturing cost and the process complexity.

[0008] The embodiment of the present application provides a skew pole frameless motor based on screw key connection, comprising a stator assembly and a rotor assembly, wherein the stator assembly comprises a stator core and an armature winding, and the rotor assembly comprises: a magnetic ring, at least one magnetic ring screw key groove is processed on the inner hole wall of the magnetic ring; a magnetically conductive rotating shaft, a rotating shaft screw key groove matched with the number and shape of the magnetic ring screw key groove is processed on the outer surface of the shaft segment matched with the magnetic ring; a screw key, the number and shape of the screw key are matched with the magnetic ring screw key groove and the rotating shaft screw key groove, and the screw key is embedded between the magnetic ring screw key groove and the rotating shaft screw key groove, and is used for transmitting torque between the rotating shaft and the magnetic ring; The helix angle of the screw key is achieved self-locking by setting.

[0009] Preferably, the magnetic ring adopts skew pole.

[0010] Preferably, the magnetization direction of the magnetic ring is continuously twisted by 7.5 degrees of electrical angle in the axial direction.

[0011] Preferably, the magnetic ring is 12-pole, Preferably, the magnetic ring screw key groove has two.

[0012] Preferably, the magnetic ring is provided with a compression end ring at both ends, and the compression end ring is fixedly connected with the threaded hole of the end part of the rotating shaft through a screw.

[0013] The embodiment of the present application also provides a design method of a skew pole frameless motor based on screw key connection, which is used for designing the skew pole frameless motor based on screw key connection as described in the above claims, and the design method of the helix angle comprises: Step S1, a mechanical model of the screw key connection is established, the interaction between the screw key and the key groove is equivalent to a slope friction model; Step S2: according to the friction coefficient of the screw key and the key groove material pair, the equivalent friction angle is calculated, and the theoretical upper limit of the helix angle is determined according to the self-locking condition; Step S3: introduce the safety factor, modify the helix angle, to deal with the friction coefficient fluctuation, dynamic load and machining error.

[0014] Preferably, the self-locking condition in step S2 is: β ≤ ρ Wherein, β is the helix angle, ρ is the equivalent friction angle; ρ = arctan(μ), μ is the friction coefficient of the screw pair material.

[0015] Preferably, the safety factor in step S3 is: Wherein, S d is the dynamic load coefficient, S w is the friction coefficient; S m is the machining accuracy.

[0016] Preferably, the helix angle is 3° to 8°.

[0017] One or more technical solutions provided in the embodiments of the application have at least the following technical effects or advantages: 1. The application solves the technical problems of discontinuous magnetic circuit, large torque fluctuation and high harmonic loss of the skew rotor by adopting the integrated skew pole magnetic ring which is integrally formed by a special mold and continuously twisted in the axial direction along the magnetization direction. The seamless continuous transition of the magnetic circuit is realized, the suppression effect of the cogging torque and the ripple torque reaches the theoretical optimum, the simulation results show that the torque fluctuation can be reduced by 30%-50%, a better torque source is provided for high-precision servo control. The sinusoidal nature of the back EMF waveform is greatly improved, the total harmonic distortion (THD) is significantly reduced, the controller calculation burden and iron loss are reduced, and the motor efficiency and stability are improved 2. The application solves the key technical problem that the coupling components in the rotor are prone to looseness or even disengagement when the frameless motor is frequently started and stopped, reversed and subjected to impact load by the standardization design scheme of the helix angle of the screw key. The self-locking effect of the screw key can be generated when the screw key is subjected to a reverse torque or an impact, the automatic disengagement of the coupling is prevented, the running reliability of the motor in harsh working conditions is greatly improved, and the absolute reliable self-locking of the magnetic ring and the shaft is realized by a standardized design scheme: 3、The application fixes the magnetic ring by the mode of "helical key connection torque transmission + end ring axial compression", the helical key provides several times effective contact area of the flat key. The unique helical structure makes the force decomposed into circumferential and radial components when transmitting torque, the radial component makes the magnetic ring and the rotating shaft combine more tightly like "pre-tightening force", the torque transmission capacity can reach more than 2-3 times of the same size flat key. The smooth transition of the helical key groove completely eliminates the stress concentration phenomenon at the right angle corner of the flat key groove, which helps to reduce the risk of permanent magnet cracking. The helical key connection as a whole has strong structure and can well absorb and disperse impact energy, and its fatigue life is higher than that of the segmented structure and flat key connection.

[0018] 4、The rotor assembly process of the application is only two main steps of "gluing - screwing in", without expensive segmented press-fitting equipment and complex angle positioning tooling, the assembly efficiency is high, the skill requirement for the operator is low. In batch production, the single piece cost is much lower than that of the segmented misalignment scheme, and has excellent cost scale effect. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the overall structure schematic diagram of the frameless motor in the embodiment of the application; Figure 2 is the overall structure schematic diagram of the frameless motor in the embodiment of the application; Figure 3 is the axial cross-section structure schematic diagram of the frameless motor in the embodiment of the application; Figure 4 is the rotor assembly schematic diagram in the embodiment of the application; Figure 5 is the rotor shaft and helical key installation schematic diagram in the embodiment of the application; Figure 6 is the magnetic ring cross-section magnetic induction intensity in the embodiment of the application; Figure 7 is the magnetic circuit display implementation diagram of the cross-section of the frameless motor in the embodiment of the application.

[0020] In the figure: 1, stator core; 2, armature winding; 3, magnetic ring; 4, elastic heat-conducting gasket; 5, rotating shaft; 6, compression end ring; 7, screw; 8, helical key; 31, magnetic ring helical key groove; 51, rotating shaft helical key groove. DETAILED DESCRIPTION

[0021] In order to better understand the above technical solutions, the above technical solutions will be described in detail in combination with the drawings of the specification and specific embodiments.

[0022] Embodiment one The application provides a skew-pole frameless motor based on helical key coupling, which mainly comprises a stator assembly and a rotor assembly. The stator assembly is of a conventional frameless structure, comprising a stator core made of silicon steel sheets and an armature winding embedded in the slot thereof.

[0023] The rotor assembly comprises a magnetic ring, a magnetic conductive rotating shaft and a helical key.

[0024] The magnetic ring is an integrated magnetic ring, which is of a whole circular structure made of high-performance permanent magnetic material, and at least one magnetic ring helical key groove is processed on the inner hole wall of the magnetic ring; The rotating shaft is made of a magnetic conductive material, and the outer surface of the shaft section matched with the integrated magnetic ring is processed with a rotating shaft helical key groove which is completely matched with the number and parameters of the magnetic ring helical key groove; The helical key is at least two in number, and the shape thereof is adapted to the helical cavity formed by the magnetic ring and the rotating shaft helical key groove; The integrated magnetic ring is sleeved on the corresponding shaft section of the rotating shaft through the inner hole thereof, and the helical key grooves of the two are aligned with each other to form a continuous helical cavity; the helical key is embedded in the helical cavity to build a torque transmission path between the rotating shaft and the integrated magnetic ring; the helical pitch β of the helical key is set to have a self-locking characteristic to ensure the reliability of the coupling under the conditions of variable load and impact; The integrated magnetic ring is preferably made of sintered neodymium iron boron or bonded neodymium iron boron material. According to the designed number of magnetic pole pairs and skew angle, a special mold is manufactured, which contains a core column for forming the magnetic ring inner hole helical key groove. After filling the permanent magnetic powder into the mold, the compression molding is carried out under the conditions of strong magnetic field orientation and high pressure, and then the sintering process (for sintered neodymium iron boron) or solidification process (for bonded neodymium iron boron) is carried out, so as to finally obtain the integrated permanent magnetic ring with the helical key groove on the inner hole wall and the magnetization direction continuously twisted by a predetermined angle along the axial direction.

[0025] The integrated magnetic ring is radially magnetized, and the magnetic pole axis is not parallel to the motor axis, but is continuously twisted in a helical shape along the axial direction, and the twist angle is defined as the skew angle, which can be controlled within the range of 5° to 30° electrical angle according to the design requirement. The continuously changing magnetization direction effectively averages the air gap magnetic field harmonics in the axial direction, thereby significantly suppressing the torque ripple.

[0026] The outer surface of the shaft section matched with the integrated magnetic ring of the rotating shaft is processed with a helical key groove which is completely matched with the magnetic ring inner hole helical key groove through precise grinding or numerical control cyclone milling process. When the magnetic ring is sleeved on the rotating shaft, the helical key grooves of the two form a continuous helical cavity.

[0027] The screw key adopts a metal rod with a rectangular or circular cross section, which is pre-bent into a spiral shape consistent with the spiral cavity. The material should have high strength and hardness, and high-strength alloy steel or stainless steel is adopted. During installation, the screw key is pressed or hammered into the spiral cavity to achieve torque transmission between the shaft and the magnetic ring.

[0028] The helix angle β of the screw key is a key design parameter. To ensure the self-locking of the connection and prevent loosening under variable load or impact conditions, the helix angle β should be designed to be smaller than the equivalent friction angle of the screw pair, and the preferred value range is 3° to 8°.

[0029] To further improve the connection reliability and anti-loosening performance, high-strength anaerobic glue or epoxy structural glue can be applied in the screw key slot before installation. This measure not only fills the fitting gap, but also provides additional cementing strength and damping effect.

[0030] A small interference fit is adopted between the shaft and the inner hole of the magnetic ring, which together with the screw key forms a multiple safeguard mechanism. In addition, pressure plates can be added at both ends of the magnetic ring, which are fixedly connected with the shaft end through screws, so as to apply axial compression force to the magnetic ring to resist the huge centrifugal force generated during high-speed operation.

[0031] Example two As shown in Figure 1 , Figure 2 , Figure 3 The present application provides a skew pole frameless motor based on screw key connection, which comprises a stator assembly and a rotor assembly. The stator assembly comprises a frameless stator core 1 and an armature winding 2 embedded in the slot. The rotor assembly comprises a shaft 5 and an integrated magnetic ring 3.

[0032] As shown in Figure 4 , Figure 5 The surface of the shaft 5 is processed by numerical control whirlwind milling to form two symmetrical screw key grooves 51 with rectangular cross section and helix angle β = 5.5°. The integrated magnetic ring 3 is made of sintered neodymium iron boron N52SH material, which is integrally pressed and sintered by a mold. Two magnetic ring screw key grooves 31 are provided on the inner hole wall of the integrated magnetic ring 3, which are completely matched with the shaft screw key grooves 51. The magnetic ring 3 is a 12-pole structure, and the magnetization direction is continuously twisted by 7.5° electric angle along the axial direction, so as to realize the integrated skew pole structure.

[0033] The screw key 8 is made of GCr15 bearing steel and cold-bent into a rectangular cross section long strip, and is subjected to quenching and tempering treatment, so that its hardness is higher than that of the key groove of the shaft 5 and the magnetic ring 3, and the number is two.

[0034] In the assembly process, first clean all parts, make sure the magnetic ring screw key groove 31 and the shaft screw key groove 51 are free of impurities. Apply high-strength anaerobic glue evenly in the screw key groove of the shaft 5 and the integrated magnetic ring 3. Put the integrated magnetic ring 3 on the shaft 5, align the screw key groove starting end of the two. Use a special tool to align the starting end of the first screw key 8 with the key groove starting position, while rotating the magnetic ring 3 at a constant speed, smoothly push the screw key 8 into the screw cavity. Repeat the process to install the second screw key 8. Clean up the excess glue, and let the assembled rotor assembly stand for 24 hours to allow the adhesive to fully cure. Finally, perform dynamic balance correction by removing material from the balance holes at both ends of the shaft 5 to control the unbalance to within G2.5 level.

[0035] When the motor is running, the armature winding 2 passes three-phase current to generate a rotating magnetic field, driving the integrated magnetic ring 3 and the shaft 5 to rotate. The torque is transmitted between the shaft 5 and the magnetic ring 3 through the screw key 8. Because the magnetic ring 3 adopts an integrated skew pole design, the air gap magnetic field harmonics generated by it are averaged in the axial direction, thus outputting smooth torque. The large contact area and self-locking characteristics of the screw key 8 ensure that the coupling is absolutely reliable even under frequent forward and reverse rotation and impact loads.

[0036] To cope with high-speed application scenarios, a compression end ring 6 is added at both ends of the integrated magnetic ring 3. The compression end ring 6 is fixedly connected with the threaded hole at the end of the shaft 5 through the screw 7, thereby applying axial compression force to the integrated magnetic ring 3 to resist the huge centrifugal force and prevent the magnetic ring from separating radially from the shaft. In addition, interference fit can be used between the screw key 8 and the screw key groove, and liquid nitrogen cooling of the screw key 8 or heating of the shaft 5 and the magnetic ring 3 hot fitting process is required during installation, further saving the adhesive and improving the coupling strength.

[0037] As shown in Figure 6 The magnetic ring cross-section magnetic induction intensity in the embodiment of the application is shown in Figure 7 The magnetic circuit display implementation diagram of the frameless motor cross-section in the embodiment of the application is shown in

[0038] Example Three This embodiment proposes a design method for a skew pole frameless motor based on screw key coupling, the helical pitch angle β of the screw key is a key design parameter, and the following is a design method for the helical pitch angle of the skew pole frameless motor based on screw key coupling: To ensure the coupling under the absolute reliable change in direction load and impact, automatic release does not occur, beta must be less than the equivalent friction angle of the screw pair (i.e. < p, wherein p = arctan (mu), mu is the friction coefficient of the screw key and the keyway material pair). After in-depth analysis and optimization, the preferred value range of beta is 3 to 8 degrees. Within this range, the coupling can meet the strict self-locking condition, provide excellent impact and vibration resistance, and also consider the assembly process, avoid the problem of excessive assembly torque caused by small angle of rise.

[0039] Step S1, a mechanical model of the screw key coupling is established, and the stress state of the screw key coupling can be simplified as a classical inclined plane friction model. The screw line is developed along the pitch diameter, and the interaction of the screw key and the keyway is equivalent to the movement of a slider on an inclined plane.

[0040] Step S2, the friction coefficient is determined according to the screw key material, the equivalent friction angle is calculated, and the screw rise angle is determined according to the self-locking condition.

[0041] According to the mechanical principle, the self-locking condition of the screw pair is determined by the formula beta <= p; the equivalent friction angle p = arctan (mu) is calculated, wherein mu is the friction coefficient of the screw pair material; The screw key pair of the application is a material pair of "high-strength alloy steel-sintered neodymium iron boron". According to the consultation of mechanical design manual and tribology data, the friction coefficient mu of the material pair under dry or trace lubrication condition is in the range of 0.10 ~ 0.15.

[0042] Accordingly, the calculated equivalent friction angle is: P_min = arctan (0.10) = 5.7° P_max = arctan (0.15) = 8.5° Therefore, to ensure the absolute reliable self-locking, the theoretical upper limit of the screw rise angle beta must be less than p_min, that is, beta < 5.7°.

[0043] Step S3, the screw rise angle obtained in step S2 is corrected based on the safety factor.

[0044] Simple beta < 5.7° is not the optimal design. In engineering practice, the following factors must be considered, and sufficient safety margin must be introduced: Friction coefficient fluctuation: wear and lubrication condition change after long-term operation may cause mu to decrease.

[0045] The influence of dynamic load: impact and vibration caused by motor start-stop, commutation and overload.

[0046] Processing error: roughness of keyway surface, shape tolerance.

[0047] Therefore, the present application does not simply set β below the theoretical value, but further introduces a safety factor S, and modifies the design target to β ≤ ρ_min / S. According to the mechanical reliability design criterion, S is usually taken as 1.2 ~ 1.5 for such a key coupling.

[0048] The corrected design upper limit is calculated as: β ≤ 5.7° / 1.2 ≈ 4.75°. This explains why limiting the range to 8° is a safe, theoretically corrected value, and 7°-8° close to the theoretical critical value needs to be used with caution.

[0049] According to Newton's second law, the additional load borne by the helical key under dynamic working conditions is: where m is the equivalent mass of the magnetic ring assembly; a max is the maximum impact acceleration. The static load of the helical key is: where g p is the equivalent acceleration corresponding to the pre-tightening force. The total axial force considering the dynamic load is: Therefore, the dynamic load coefficient is: .

[0050] By introducing a dimensionless empirical coefficient k to correct the dynamic response characteristics of the system, the final dynamic load coefficient is obtained: .

[0051] Archard's wear theory in tribology shows that wear will cause material loss, thereby changing the geometry and friction characteristics of the contact surface. Generally, the friction coefficient will change after wear: where is the friction coefficient at the initial assembly of the helical pair; is the expected stable lower limit friction coefficient after the full life cycle wear.

[0052] Based on tolerance analysis, the influence of machining precision is quantified, where, is the manufacturing error of the helix angle; is the design value of the helix angle.

[0053] Therefore, the comprehensive safety Considering that each factor does not always occur at the worst case simultaneously, according to the load combination principle in reliability engineering, the above product result can be appropriately reduced.

[0054] The helix angle β of the helical key is a key design parameter. To ensure absolute reliability under variable load and impact without automatic loosening, β must be less than the equivalent friction angle ρ of the helical pair (i.e. β < ρ, where ρ = arctan(μ), μ is the friction coefficient of the helical key and the keyway material pair).

[0055] After in-depth analysis and optimization, the application preferably selects the value range of β as 3° to 8°. Within this range, the coupling can meet the strict self-locking condition, provide excellent impact and vibration resistance, and also take into account the assembly process, avoiding the problem of excessive assembly torque caused by too small angle.

[0056] The helical key pair adopts steel-steel and steel-permanent magnet cooperation. Under dry or lubricated conditions, the friction coefficient μ is usually between 0.1 and 0.15. To illustrate the effect of different design choices, the following table provides a theoretical analysis based on the friction coefficient μ = 0.12 (ρ = arctan(0.12) ≈ 7°): As can be seen from the above table, when β is less than 3°, assembly is extremely difficult; when β is greater than 8° and close to or exceeds the equivalent friction angle, the self-locking reliability of the coupling decreases sharply, and there is a risk of loosening. Therefore, the range of 3° to 8° selected by the application is the optimal interval for realizing a high-reliability, easy-to-assemble helical key coupling.

[0057] The embodiments of the specific embodiment are preferred embodiments of the application, and are not intended to limit the protection scope of the application, so that: any equivalent changes made in terms of structure, shape, principle, etc. according to the application shall be covered within the protection scope of the application. Although the preferred embodiments of the application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they understand the basic creative concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the application. Obviously, those skilled in the art can make various modifications and changes to the application without departing from the spirit and scope of the application. Thus, if these modifications and changes of the application fall within the scope of the claims of the application and their equivalent technologies, the application also intends to include these modifications and changes.

Claims

1. A frameless motor with slanted poles based on helical key connections, comprising a stator assembly and a rotor assembly, wherein the stator assembly includes a stator core and an armature winding, characterized in that, The rotor assembly includes: A magnetic ring, wherein at least one magnetic ring helical keyway is machined on the inner wall of the magnetic ring; A magnetically conductive shaft, wherein the outer surface of the shaft segment that mates with the magnetic ring is machined with a shaft helical keyway that matches the number and shape of the helical keyway of the magnetic ring; The spiral key, the number and shape of which match the spiral keyway of the magnetic ring and the spiral keyway of the rotating shaft, is embedded between the spiral keyway of the magnetic ring and the spiral keyway of the rotating shaft, and is used to transmit torque between the rotating shaft and the magnetic ring; The helix angle of the spiral key is set to achieve self-locking.

2. The frameless motor with slanted poles based on spiral key connection as described in claim 1, characterized in that, The magnetic ring uses skewed poles.

3. The frameless motor with slanted poles based on spiral key connection as described in claim 2, characterized in that, The magnetization direction of the magnetic ring is continuously twisted along the axial direction by 7.5° electrical angle.

4. The frameless motor with slanted poles based on spiral key connection as described in claim 3, characterized in that, The magnetic ring has 12 poles.

5. The frameless motor with slanted poles based on spiral key connection as described in claim 1, characterized in that, The magnetic ring has two spiral keyways.

6. The frameless motor with slanted poles based on spiral key connection as described in claim 1, characterized in that, The magnetic ring is provided with clamping end rings at both ends, and the clamping end rings are fixedly connected to the threaded holes at the ends of the rotating shaft by screws.

7. A design method for a frameless motor with slanted poles based on helical key connection, used to design a frameless motor with slanted poles based on helical key connection as described in any one of claims 1-6, characterized in that, The design method for the helix angle includes: Step S1: Establish a mechanical model of the spiral key connection, and equate the interaction between the spiral key and the keyway to an inclined plane friction model. Step S2: Calculate the equivalent friction angle based on the friction coefficient of the material pair between the helical key and the keyway, and determine the theoretical upper limit of the helix angle based on the self-locking condition; Step S3: Based on the dynamic load coefficient, friction coefficient, and machining accuracy, a safety factor is introduced to correct the helix angle.

8. A design method for a frameless slanted-pole motor based on a spiral key connection as described in claim 7, characterized in that, The self-locking condition in step S2 is: β ≤ ρ Where β is the helix angle and ρ is the equivalent friction angle; ρ = arctan(μ), μ is the friction coefficient of the helical pair material.

9. A design method for a frameless slanted-pole motor based on a spiral key connection as described in claim 7, characterized in that, The safety factor in step S3 is: Among them, S d S is the dynamic load factor. w S is the coefficient of friction; m For machining accuracy.

10. A design method for a frameless slanted-pole motor based on a spiral key connection as described in claim 7, characterized in that, The helix angle ranges from 3° to 8°.

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