A hybrid stepping motor with permanent magnet insert in stator

Abstract

The application relates to the technical field of stepping motors, in particular to a stator-inlaid permanent magnet hybrid stepping motor which comprises a stator assembly, a rotor assembly and a stator winding. The stator assembly comprises a stator core which is uniformly provided with a plurality of large poles in the circumferences, each large pole is uniformly provided with small teeth near the rotor side, tooth slots are formed between the adjacent small teeth, permanent magnet magnetic strips are embedded in the tooth slots, and the magnetic field polarity of the magnetic strips facing the rotor side is the same as that of the corresponding end of the rotor. The rotor assembly comprises a rotating shaft and an axially magnetized permanent magnet magnetic strip, the two sides of the permanent magnet magnetic strip are attached to magnetic conductors, a rotor core is arranged outside the magnetic conductors, the two form an overlapping area in the axial projection direction, a local magnetic barrier is formed in the tooth slot through the same polarity repulsion principle of the magnetic strips on the stator side, the magnetic flux overflowing from the rotor side is forced to be gathered to the coupling area of the tooth top air gap of the stator and rotor, meanwhile, the overlapping area on the rotor side gathers the axial magnetic flux, and the leakage magnetic flux is suppressed in a bidirectional and cooperative manner; on the premise of not improving the excitation current, the output torque of the motor is improved, and the iron loss and temperature rise are reduced.

Description

Technical Field

[0001] This invention relates to the field of motor technology, specifically to a hybrid stepper motor with a stator inlaid with permanent magnets. Background Technology

[0002] Hybrid stepper motors combine the high torque density of permanent magnet stepper motors with the small step pitch and high precision of reactive stepper motors, and are widely used in CNC machine tools, automation equipment, precision transmission devices and other fields.

[0003] In existing conventional hybrid stepper motors, the magnetic flux generated by the rotor's main permanent magnet is prone to leakage from the axial end of the rotor core. The magnetic resistance of the path from the permanent magnet to the rotor teeth is too high, and the magnetic flux in the rotor tooth coupling area overflows laterally between the teeth, forming lateral leakage flux. Both parts of leakage flux together cause the effective magnetic flux utilization rate of the motor to be low, and the output torque is limited. If the winding current is simply increased to improve the torque, it will lead to problems such as increased winding heating, increased energy consumption, and worsened temperature rise.

[0004] Existing patent document CN202311057435.5 discloses a rotor flux guiding structure, which can only solve the problem of magnetic leakage at the axial end of the rotor and cannot suppress the lateral magnetic leakage generated between the stator teeth and rotor teeth. Furthermore, the improved scheme of a single stator inlaid magnetic strip can only optimize the lateral magnetic leakage, and the problem of rotor axial flux loss still exists. Therefore, there is an urgent need for a new type of stepper motor that can simultaneously suppress axial and radial bidirectional magnetic leakage and achieve synergistic efficiency enhancement of the stator-rotor magnetic circuit. Summary of the Invention

[0005] The purpose of this invention is to provide a stator-embedded permanent magnet hybrid stepper motor to solve the problems of dual losses in the prior art, namely rotor axial leakage flux and stator-rotor inter-tooth lateral leakage flux, low magnetic flux utilization and insufficient output torque.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A stator-embedded permanent magnet hybrid stepper motor includes a stator assembly, a rotor assembly, and stator windings. The stator assembly includes a stator core with several large poles evenly arranged circumferentially. Each large pole has several small teeth evenly distributed on the side near the rotor assembly, forming a tooth groove between adjacent small teeth. A permanent magnet strip is embedded in each tooth groove, and the magnetic field polarity of the side of the permanent magnet strip facing the rotor assembly is the same as the magnetic field polarity of the rotor assembly at the corresponding position. The rotor assembly includes a coaxially assembled shaft and a permanent magnet strip. The permanent magnet strip is axially magnetized and fixed in the middle of the shaft. Magnetic conductors are attached to the axial end faces on both sides of the permanent magnet strip, and the rotor core is disposed on the axial outer side of the magnetic conductors. The magnetic conductors and the rotor core on the same side are independent separate components, and they form an overlapping area with overlapping axial projections in the radial direction, constituting a soft magnetic low-resistance bypass for axial magnetic flux flowing from the permanent magnet strip through the magnetic conductors to the teeth of the rotor core.

[0007] Preferably, the permanent magnet strips of the toothed groove are arranged with the same polarity throughout the entire area, and the permanent magnet strips of the same large pole and adjacent large poles have the same polarity, forming a continuous magnetic barrier of the same polarity inside the stator core.

[0008] Preferably, the tooth groove opening is formed with an inwardly recessed magnetic shielding step, which is formed by protruding inward from the top of the groove walls on both sides of the tooth groove. The plane of the magnetic shielding step is parallel to the radial direction of the stator core and satisfies that the groove opening width is less than the internal width of the tooth groove, forming a continuous ferromagnetic shielding wall between the tooth groove and the air gap of the rotor core.

[0009] Preferably, the permanent magnet strip has an axially segmented structure with unequal thickness, wherein the thickness of the middle section along the axial direction is greater than the thickness of the two ends, and a non-magnetic insulating gap is reserved between the permanent magnet strip and the bottom of the groove.

[0010] Preferably, it further includes a non-magnetic pad that is slidably installed in the tooth groove. The non-magnetic pad is a long strip-shaped thin plate arranged along the axial direction of the stator core. The side of the non-magnetic pad near the tooth groove opening is integrally formed with a snap-fit ​​groove, and the permanent magnet strip is correspondingly provided with a snap-fit ​​end. The non-magnetic pad is provided with a plurality of strip-shaped through holes extending along the axial direction of the stator core. Each strip-shaped through hole is evenly distributed along the width direction of the non-magnetic pad, and the hole wall of the strip-shaped through hole is provided with a heat-conducting layer.

[0011] Preferably, a non-magnetic shielding sleeve is provided between the inner wall of the motor housing and the outer circumference of the stator core. The non-magnetic shielding sleeve has guide holes at the positions of the outlets at both ends of the strip-shaped through hole along the axial direction. The guide holes are connected to the external cooling flow path.

[0012] Preferably, the non-magnetic pad has a hollow structure inside, with an elastic cantilever clamp rotatably mounted inside. The non-magnetic pad has an opening that communicates with the interior, and a locking block is slidably mounted inside the opening. A push rod is fixedly mounted on the locking block, and the elastic cantilever clamp is hinged to the end of the push rod. A spherical air cushion is fixedly mounted between the locking block and the side wall of the opening of the non-magnetic pad.

[0013] Preferably, a boss is provided on the inner sidewall of the tooth groove, a groove is provided on the non-magnetic pad, and the elastic cantilever card passes through the groove and is embedded in the corresponding insertion hole on the boss.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. By embedding permanent magnet strips in the stator-side slots, the magnetic field polarity of the side of the strip facing the rotor is the same as that of the corresponding position on the rotor. Utilizing the principle of like poles repulsion, a local magnetic barrier is formed in each slot, forcibly converging the lateral magnetic flux overflowing from the rotor to the air gap coupling area at the stator and rotor tooth tips. Simultaneously, the rotor uses a magnetic conductor and rotor core as independent separate components, forming an overlapping area with overlapping axial projections in the radial direction. This constitutes a soft magnetic low-resistance bypass for axial magnetic flux flowing from the permanent magnet through the magnetic conductor to the rotor core teeth, converging the axial leakage magnetic flux to the rotor teeth. The lateral leakage magnetic constraint on the stator side and the low-resistance axial magnetic flux guidance on the rotor side work together to significantly increase the effective coupling magnetic flux between the stator and rotor teeth without increasing the excitation current, thereby greatly improving the motor output torque while reducing iron loss and temperature rise.

[0015] 2. By adding a non-magnetic pad inside the tooth groove, the thickness of the pad is the unique and definite value of the magnetic gap between the magnetic strip and the bottom of the groove, thus improving the consistency of the magnetic gap accuracy. The pad has an integrally formed snap-fit ​​groove on the radial inner side, which cooperates with the snap-fit ​​end of the magnetic strip to form a modular unit that can be installed and removed as a whole. When replacing, there is no need to operate the magnetic strip separately, simplifying the maintenance process. The pad has an axially extending strip-shaped through hole with a heat-conducting layer on the hole wall, forming multiple parallel axial heat dissipation channels inside the tooth groove. The heat of the magnetic strip is conducted to the hole wall and then carried away by the cooling airflow flowing through the through hole, effectively eliminating local hot spots and improving the demagnetization margin of the magnetic strip.

[0016] 3. A non-magnetic shielding sleeve is installed between the inner wall of the motor housing and the outer circumference of the iron core. The shielding sleeve has guide holes at both ends of the axial outlet corresponding to the strip-shaped through hole, which are connected to the external cooling flow path. This directly connects the heat dissipation channel inside the tooth groove with the external cooling system of the housing, forming a heat dissipation closed loop from the inside of the stator tooth groove to the external cooling flow path, which greatly shortens the heat dissipation path. At the same time, the shielding sleeve is made of non-magnetic material, which isolates the eddy current loss of the housing and avoids the generation of additional eddy current loss in the housing. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the overall structure of the present invention; Figure 2 This is an exploded view of the structure of the present invention; Figure 3 This is a schematic diagram of the internal structure of the stator assembly of the present invention; Figure 4 This is a schematic diagram of the exploded structure of the rotor assembly of the present invention; Figure 5 This is a schematic diagram of the overall structure of the rotor assembly of the present invention; Figure 6 for Figure 3 Enlarged view of the A-structure; Figure 7 This is a schematic diagram of the non-magnetic pad structure of the present invention; Figure 8 This is a schematic diagram of the internal structure of the non-magnetic pad of the present invention.

[0018] In the attached diagram, the components represented by each number are as follows: 10. Stator assembly; 11. Stator core; 12. Stator lamination; 13. Large pole; 131. Small tooth; 132. Tooth groove; 133. Magnetic isolation step; 134. Non-magnetic magnetic isolation gap; 135. Boss; 14. Permanent magnet strip; 141. Snap-fit ​​end; 15. Non-magnetic pad; 151. Snap-fit ​​groove; 152. Strip-shaped through hole; 153. Thermal conductive layer; 154. Flexible cantilever clip; 155. Opening; 156. Clip block; 157. Push rod; 158. Spherical air cushion; 159. Groove; 16. Non-magnetic shielding sleeve; 161. Guide hole; 20. Rotor assembly; 21. Shaft; 22. Permanent magnet strip; 23. Magnetic conductor; 24. Rotor core; 241. Rotor teeth; 30. Stator winding. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: As Figures 1-8 As shown, this embodiment provides a stator-embedded permanent magnet hybrid stepper motor, including a stator assembly 10, a rotor assembly 20, and a stator winding 30.

[0021] The stator assembly 10 includes a stator core 11, which is formed by stacking multiple stator laminations 12 along the axial direction to form an integral core structure. Several large poles 13 are evenly arranged in the circumferential direction of the stator core 11. In this embodiment, the number of large poles 13 is preferably eight, which are distributed at equal angles along the circumference. Each large pole 13 has several small teeth 131 evenly distributed on the side near the rotor assembly 20. Adjacent small teeth 131 form a tooth groove 132. The tooth shape of the small teeth 131 is trapezoidal with rounded corners at the tooth tips. Each tooth groove 132 is embedded with a permanent magnet strip 14. The permanent magnet strip 14 is magnetized in segments along the axial direction. In the axial direction, the magnetic field polarity of the side of each segment of permanent magnet strip 14 facing the rotor assembly 20 is the same as the magnetic field polarity of the rotor assembly 20 at the corresponding position in the axial direction. Moreover, the polarity of the permanent magnet strip 14 in the same axial segment in the stator circumferential direction and under the same large pole 13 is consistent, so that the stator side forms like repulsive magnetic barriers in the corresponding areas at both ends of the rotor axial direction.

[0022] The stator winding 30 is wound on the major poles 13, using the conventional two-phase or multi-phase hybrid stepper motor winding method. After being energized, it generates an excitation magnetic field, driving the rotor assembly 20 to rotate. The rotor assembly 20 includes a coaxially assembled shaft 21 and a permanent magnet strip 22. The shaft 21 is the output shaft of the motor. The permanent magnet strip 22 is an axially magnetized cylindrical shape and is fitted and fixed in the middle of the shaft 21. One end of the permanent magnet strip 22 is the N pole and the other end is the S pole. A magnetic conductor 23 is attached to both axial end faces of the permanent magnet strip 22. The magnetic conductor 23 is made of soft magnetic material (such as electrical pure iron or silicon steel). Its outer diameter is larger than the outer diameter of the permanent magnet strip 22, forming a radial extension. A rotor core 24 is provided on the outer side of the magnetic conductor 23. The inner end face of the rotor core 24 is attached to the outer end face of the magnetic conductor 23. Several rotor teeth 241 are distributed on the outer circumference of the rotor core 24. The rotor teeth 241 and the stator small teeth 131 are arranged radially opposite to each other to form an air gap.

[0023] It is worth noting that the magnetic conductor 23 and the rotor core 24 on the same side are independent separate parts. When they are assembled, they achieve axial contact by fitting their end faces together, and they form an overlapping area with overlapping axial projections in the radial direction. This overlapping area constitutes a soft magnetic low resistance bypass for the axial magnetic flux to flow from the permanent magnet strip 22 through the magnetic conductor 23 to the teeth of the rotor core 24. The stator winding 30 is the main excitation source, and the permanent magnet strip 14 is an auxiliary magnetic focusing element used to apply a static bias field to the tooth slot 132 region.

[0024] When the motor is running, the stator winding 30 is energized in a step sequence, generating a rotating excitation magnetic field in the stator core 11. In the rotor assembly 20, the permanent magnet bar 22 generates a permanent magnet flux in the axial direction. The flux of the permanent magnet bar 22 starts from the N end face and enters the magnetic conductor 23 on the same side. Since there is an overlap area where the magnetic conductor 23 and the rotor core 24 have a radial projection overlap, the flux diffuses radially outward in the magnetic conductor 23, flows directly into the teeth of the rotor core 24 through the overlap area, and then enters the stator small teeth 131 through the air gap from the rotor teeth 241. Finally, it closes and returns to the S end face of the permanent magnet bar 22 through the yoke of the stator core 11.

[0025] In this path, the overlapping area provides a low magnetic resistance bypass channel for the axial magnetic flux, which gathers and guides the leakage magnetic flux that might have leaked directly from the axial end face of the permanent magnet strip 22 to the axial end of the air gap to the rotor tooth 241, thereby increasing the magnetic flux density of the rotor tooth 241.

[0026] Meanwhile, the permanent magnet strips 14 embedded in the stator side slots 132 play a role in constraining radial lateral magnetic leakage. Since the magnetic field polarity of the side of the permanent magnet strip 14 facing the rotor is the same as that of the corresponding position of the rotor, according to the principle of mutual repulsion of magnetic fields of the same polarity, when the rotor flux attempts to overflow laterally from the inter-tooth space between the stator small teeth 131, it will be repelled by the permanent magnet strips 14 of the same polarity in the slots 132 and forced to converge towards the air gap coupling area between the stator and rotor teeth 241. This repulsion effect of the same polarity forms a local magnetic barrier in each slot 132, effectively suppressing radial lateral magnetic leakage.

[0027] The lateral leakage flux constraint on the stator side and the low-resistance axial flux conduction on the rotor side work together to gather the axial leakage flux to the rotor tooth 241 on the rotor side and gather the radial lateral leakage flux to the tooth tip coupling area on the stator side. This significantly increases the effective coupling flux between the stator and rotor tooth 241 without increasing the excitation current of the stator winding 30, thereby increasing the output torque of the motor. At the same time, the reduced leakage flux improves the flux utilization rate, and the excitation current can be reduced under the same output torque, thereby reducing iron loss and temperature rise. In the specific assembly, the permanent magnet strips 14 embedded in each slot 132 on the eight large poles 13 in the circumferential direction of the stator core 11 are all arranged with the same polarity throughout the entire range. The polarity of the permanent magnet strips 14 in the same large pole 13 and adjacent large poles 13 is consistent. In this embodiment, the same polarity throughout the entire range means that for a certain motor, the magnetic field polarity of the permanent magnet strips 14 in all slots 132 facing the rotor assembly 20 is all uniformly N pole or all uniformly S pole, and there is no polarity alternation between large poles 13 or between different slots 132 of the same large pole 13.

[0028] In this embodiment, the example is that the radial inner surface of all permanent magnet strips 14 is uniformly N pole: the permanent magnet strips 22 of the rotor assembly 20 are axially magnetized, and the corresponding position of one end of the axial direction is induced as N pole in the tooth of the rotor core 24, and the corresponding position of the other end of the axial direction is induced as S pole, or vice versa, depending on the magnetization direction.

[0029] Since all permanent magnet strips 14 on the stator side are N-poles, when the N-pole region on the left side of the rotor is directly opposite a large pole 13 of the stator, all permanent magnet strips 14 in the slots 132 of that large pole 13 are N-poles, and are of the same polarity as the corresponding region on the rotor. When the rotor rotates to the right S-pole region directly opposite the stator, the stator permanent magnet strips 14 are still N-poles, and are of opposite polarity to the corresponding region on the rotor. This uniform polarity arrangement means that the stator magnetic barrier does not change polarity with the rotor position, and always maintains a consistent repulsive characteristic.

[0030] The permanent magnet strip 14 is fixed in the tooth groove 132 by high-temperature resistant adhesive or mechanical clamping, ensuring that it fits the tooth groove 132 along its entire axial length. All the permanent magnet strips 14 on the large pole 13 are connected in the circumferential direction, and their radial inner surfaces together form a continuous isotropic magnetic barrier inside the stator core 11.

[0031] When the motor is running, the stator winding 30 is energized to generate a rotating magnetic field, and the rotor permanent magnet strip 22 generates axial magnetic flux. Since all permanent magnet strips 14 on the stator side are of the same polarity throughout, a continuous, circumferentially uninterrupted magnetic barrier of the same polarity is formed inside the stator core 11.

[0032] When the rotor rotates to a certain position, and the N pole of the rotor tooth 241 is directly opposite the small tooth 131 of a large pole 13 of the stator, the permanent magnet strips 14 in the stator tooth slot 132 are also N poles, and like poles repel each other. After the rotor flux is emitted from the rotor tooth 241, when it attempts to leak into the lateral space of the adjacent tooth slot 132, it is repelled by the like permanent magnet strips 14 in the slot and is forced back into the air gap coupling area between the small stator tooth 131 and the rotor tooth 241, and cannot escape laterally. Since all the tooth slots 132 of the large pole 13 are of the same polarity, this repulsive effect continuously covers the circumferential direction, forming a complete magnetic fence that confines the rotor flux within the coupling area of ​​each pair of stator and rotor teeth 241.

[0033] As the rotor continues to rotate, the area that was originally facing the rotor becomes the S pole, while the stator permanent magnet strip 14 remains the N pole. At this time, the rotor S pole and the stator N pole are opposite polarities, and theoretically there is an attraction. However, since the strip is located inside the slot 132 rather than at the tooth tip, the attraction between opposite polarities mainly acts in the direction of the slot bottom and will not pull the magnetic flux from the tooth tip coupling area to the side. At the same time, the main magnetic field established by the energization of the stator winding 30 in the air gap still drives the magnetic flux to close along the tooth tip. Therefore, the opposite polarity region will not destroy the overall magnetic concentration effect. The uniform polarity arrangement ensures that no matter the rotor position, there is always a uniform repulsive interface on the inside of the stator, and lateral leakage flux is always suppressed.

[0034] Furthermore, since all magnetic strips on the inner side of the stator have the same polarity, there is no source of torque fluctuation in the slot 132 with alternating N and S poles between adjacent large poles 13, which eliminates the additional slot torque component generated by the alternating polarity of the stator permanent magnet, making the motor run more smoothly and further reducing vibration and noise.

[0035] Reference Figure 6 Furthermore, the slot 132 has an inwardly recessed magnetic shielding step 133 formed at the slot opening. The magnetic shielding step 133 is made of non-magnetic material formed by the inward extension of the top of the slot walls on both sides of the slot 132. That is, in the area near the slot opening, the two side walls of the slot 132 protrude towards the center of the slot 132. The plane of the magnetic shielding step 133 is parallel to the radial direction of the stator core 11 and satisfies that the slot opening width is less than the internal width of the slot 132, forming a continuous ferromagnetic shielding wall between the slot 132 and the air gap of the rotor core 24.

[0036] It is worth noting that the permanent magnet strip 14 has an axially segmented structure with unequal thickness, and the thickness of the middle section along the axial direction is greater than that of the two ends. A non-magnetic insulating gap 134 is reserved between the permanent magnet strip 14 and the bottom of the groove 132.

[0037] After the permanent magnet strip 14 is embedded in the slot 132, a non-magnetic isolation gap 134 is reserved between its radially outer surface and the bottom of the slot 132. This non-magnetic isolation gap 134 is an air gap that isolates the permanent magnet strip 14 from the magnetically conductive material at the bottom of the slot, preventing the reverse demagnetizing magnetic field generated when the stator winding 30 is energized from acting on the permanent magnet strip 14 through the magnetically conductive material at the bottom of the slot. The magnetic isolation step 133 forms an inwardly recessed flange at the slot opening. This flange is made of magnetically conductive material and forms a continuous ferromagnetic shielding wall inside the stator core 11. When the rotor flux couples between the stator pinion 131 and the rotor tooth 241, some flux may attempt to overflow from the slot opening of the slot 132 into the outer region of the air gap. Due to the presence of the magnetic isolation step 133, the slot opening width is reduced, and the overflowing flux must bypass the magnetic isolation step 133 to leave the slot 132. As a magnetically conductive material, it can provide a high-permeability bypass for overflowing magnetic flux, redirecting the magnetic flux attempting to leak out to the stator yoke instead of allowing it to disperse into the air gap and cause leakage magnetic flux. At the same time, the magnetic isolation step 133 and the repulsive effect of the same-pole permanent magnet strip 14 in the slot are superimposed. The magnetic isolation step 133 narrows the slot opening from a physical structure perspective, limiting the magnetic flux overflow path. The like-pole repulsion effect of the permanent magnet strip 14 blocks the lateral escape of magnetic flux from the direction of the magnetic field. The two work together to further increase the magnetic flux density in the tooth tip coupling area.

[0038] The thickness of the axial middle section of the permanent magnet strip 14 is greater than that at both ends. Based on the magnetic flux distribution characteristics in the axial direction of the motor, in actual motor operation, the end effect of the stator winding 30 and the end leakage of the rotor axial magnetic flux make the leakage magnetic risk in the axial middle region of the slot 132 higher than that at both ends. Thickening the middle section of the strip makes the permanent magnet volume and magnetomotive force in the middle region larger, and the repulsive force of like poles stronger, which can specifically constrain the high-risk leakage magnetic flux in the axial middle section. On the other hand, thinning the two ends reduces the excessive constraint of the magnetic flux at both ends of the strip on the leakage magnetic flux at the rotor ends, avoiding local magnetic saturation or material waste due to excessive thickness of the strip. This unequal thickness structure with concentrated magnetism in the middle and weakened at both ends achieves a gradient distribution of leakage magnetic flux constraint capability in the axial direction, which matches the converging effect of the rotor side axial flow guiding structure, further improving the overall magnetic flux utilization rate.

[0039] Example 2: Figures 1-8As shown, it also includes a non-magnetic pad 15 that is slidably installed in the tooth groove 132. The non-magnetic pad 15 is made of a non-magnetic material, specifically polyimide or phosphor bronze, which are non-magnetic materials with good mechanical strength and heat resistance. This ensures that the pad will not form a magnetic short circuit between the magnetic strip and the bottom of the groove. The non-magnetic pad 15 is a long strip of thin plate and is arranged along the axial direction of the stator core 11. The side of the non-magnetic pad 15 near the groove opening of the tooth groove 132 has an integrally formed snap-fit ​​groove 151. The permanent magnet strip 14 is correspondingly provided with a snap-fit ​​end 141. The permanent magnet strip 14 and the non-magnetic pad 15 are fixedly connected through snap-fit, so that the permanent magnet strip 14 and the non-magnetic pad 15 constitute a modular unit that can be completely removed and installed.

[0040] Furthermore, the non-magnetic pad 15 has several strip-shaped through holes 152 extending axially along the stator core 11. Each strip-shaped through hole 152 is evenly distributed along the width direction of the non-magnetic pad 15. The wall of the strip-shaped through hole 152 is provided with a heat-conducting layer 153. The heat-conducting layer 153 is thermally coupled to the surface of the permanent magnet strip 14 to conduct the heat generated by the permanent magnet strip 14 during operation.

[0041] In the assembly process, the non-magnetic pad 15 first slides axially from one end of the stator core 11 into the bottom of the tooth groove 132, and its radial outer surface fits against the bottom of the tooth groove 132; then the snap-fit ​​end 141 of the permanent magnet strip 14 is inserted axially into the snap-fit ​​groove 151 of the non-magnetic pad 15, and the magnetic strip and the pad form an integral module.

[0042] The magnetic isolation step 133 is located at the groove opening, which guides and limits the axial sliding of the non-magnetic pad 15 and the permanent magnet strip 14. The fit between the non-magnetic pad 15 and the bottom of the toothed groove 132 is a sliding fit, which allows the pad to slide in and out freely along the axial direction without producing obvious radial shaking.

[0043] When the permanent magnet strip 14 is attached to the non-magnetic pad 15, the gap between the magnetic strip and the bottom of the groove is the thickness of the pad, which is independent of the assembly operation and ensures that the magnetic isolation gap of each magnetic strip is consistent.

[0044] Reference Figure 2A non-magnetic shielding sleeve 16 is provided between the inner wall of the motor housing and the outer circumference of the stator core 11. Its inner diameter is interference-fitted with the outer circumference of the stator core 11, and its outer diameter is fitted with the inner wall of the housing. The main function of the non-magnetic shielding sleeve 16 is to isolate the eddy current loss of the housing and provide an outer circumferential positioning reference for the stator core 11. The non-magnetic shielding sleeve 16 has guide holes 161 at the positions of the two ends of the axial outlet of the strip-shaped through hole 152. The guide holes 161 penetrate the wall thickness of the non-magnetic shielding sleeve 16. One end of the guide hole 161 is aligned and connected with the axial outlet of the strip-shaped through hole 152, and the other end is connected to the external cooling flow path, such as the cooling fan, cooling water pipe or heat dissipation fin channel outside the housing. Thus, the strip-shaped through hole 152, the guide hole 161 and the external cooling flow path together form a through heat dissipation channel from the inside of the stator slot 132 to the outside of the housing.

[0045] Reference Figure 7 and Figure 8 The non-magnetic pad 15 has a hollow structure inside, and an elastic cantilever clip 154 ​​is rotatably installed inside it. In this embodiment, the number of elastic cantilever clips 154 is preferably two, and they are symmetrically arranged. An opening 155 is opened on the non-magnetic pad 15, which is in communication with the interior. A clip 156 is slidably installed in the opening 155, and a push rod 157 is fixedly installed on the clip 156. The elastic cantilever clip 154 ​​is hinged to the end of the push rod 157. When the clip 156 slides in the opening 155, the push rod 157 moves linearly, pushing the elastic cantilever clip 154 ​​to swing around the rotation center, so that the end of the elastic cantilever clip 154 ​​extends out or retracts from the groove 159.

[0046] A spherical air cushion 158 is fixedly installed between the locking block 156 and the side wall of the opening 155 of the non-magnetic pad 15. The spherical air cushion 158 is filled with inert gas. When the locking block 156 slides into the opening 155, the spherical air cushion 158 is compressed and stores elastic potential energy. When the external pressure is released, the spherical air cushion 158 expands and pushes the locking block 156 to reset outward. The spherical air cushion 158 provides the driving force for the automatic reset of the locking block 156, and at the same time provides a continuous radial clamping force for the locked state.

[0047] Reference Figure 7 A boss 135 is provided on the inner side wall of the tooth groove 132, and a groove 159 is provided on the non-magnetic pad 15. The groove 159 communicates with the internal cavity. When the elastic cantilever card 154 is in the extended state, the elastic cantilever card 154 passes through the groove 159 and is inserted into the corresponding insertion hole on the boss 135, thereby realizing the radial and axial locking of the non-magnetic pad 15 in the tooth groove 132.

[0048] Traditional stepper motors rely mainly on natural convection or conduction on the surface of the housing for stator heat dissipation. Heat inside the tooth groove 132 is difficult to transfer to the outside. However, in this embodiment, when the motor is running, the external cooling flow path drives the cooling medium to flow. The cooling medium enters from the guide hole 161 of the non-magnetic shielding sleeve 16 and is directly aligned with the axial outlet of the strip-shaped through hole 152. Since the strip-shaped through hole 152 passes through the non-magnetic pad 15 axially, the cooling medium flows in from the guide hole 161 and flows along the entire axial length of the strip-shaped through hole 152, fully exchanging heat with the heat-conducting layer 153 of the hole wall, absorbing the heat generated by the permanent magnet strip 14, and finally being discharged from the outlet at the other end of the strip-shaped through hole 152 through the corresponding guide hole 161 to the external cooling flow path. At the same time, the non-magnetic shielding sleeve 16 itself is not magnetic and will not generate an additional magnetic short circuit between the stator core 11 and the external housing, ensuring the integrity of the main magnetic circuit.

[0049] After the non-magnetic pad 15, together with the permanent magnet strip 14, slides axially into the toothed groove 132 to the predetermined position, the locking block 156 is pushed manually or with a tool to slide into the opening 155, compressing the spherical air cushion 158. The locking block 156 drives the push rod 157 to move inward, and the push rod 157 pushes the elastic cantilever lock 154 to swing around the rotation center, so that its end extends out of the groove 159 and is inserted into the insertion hole of the boss 135 on the side wall of the toothed groove 132. At this time, the end of the elastic cantilever lock 154 forms mechanical interference with the boss 135, preventing the non-magnetic pad 15 from moving axially or jumping radially, thus achieving reliable fixation of the pad and the magnetic strip.

[0050] When the magnetic strip needs to be replaced or removed, continue pressing the locking block 156. The spherical air cushion 158 is further compressed, and the elastic cantilever lock 154 continues to swing until it is fully retracted into the groove 159 and disengaged from the insertion hole of the boss 135. At this time, the non-magnetic pad 15 is released and can be pulled out axially from the toothed groove 132. It can be taken out as a whole along with the permanent magnet strip 14. After releasing the locking block 156, the spherical air cushion 158 expands and resets, pushing the locking block 156 to slide outward. The push rod 157 drives the elastic cantilever lock 154 back to the initial position, ready for the next locking.

[0051] Furthermore, if the polarity of the non-magnetic pad 15 and the permanent magnet strip 14 are reversed, only one end of the axial ends of the pad is provided with a groove 159 and an elastic locking mechanism, while the boss 135 of the toothed groove 132 is only provided at one end. When reversed, the locking mechanism cannot be aligned with the boss 135 and cannot be locked, thus ensuring that the polarity condition of like poles repelling each other is not destroyed.

Claims

1. A stator-embedded permanent magnet hybrid stepper motor, comprising a stator assembly (10), a rotor assembly (20), and a stator winding (30), characterized in that: The stator assembly (10) includes a stator core (11), on which a plurality of large poles (13) are evenly arranged in the circumferential direction. Each of the large poles (13) has a plurality of small teeth (131) evenly distributed on the side near the rotor assembly (20). A tooth groove (132) is formed between adjacent small teeth (131). A permanent magnet strip (14) is embedded in each tooth groove (132). The magnetic field polarity of the side of the permanent magnet strip (14) facing the rotor assembly (20) is the same as the magnetic field polarity of the rotor assembly (20) at the corresponding position. The rotor assembly (20) includes a coaxially assembled shaft (21) and a permanent magnet strip (22). The permanent magnet strip (22) is axially magnetized and fixed in the middle of the shaft (21). A magnetic conductor (23) is attached to both axial end faces of the permanent magnet strip (22). A rotor core (24) is provided on the outer side of the magnetic conductor (23). Among them, the magnetic conductor (23) and the rotor core (24) on the same side are independent separate parts, and the two form an overlapping area with axial projection in the radial direction, which constitutes a soft magnetic low resistance bypass from the permanent magnet strip (22) through the magnetic conductor (23) to the teeth of the rotor core (24).

2. A stator-embedded permanent magnet hybrid stepper motor according to claim 1, characterized in that: The permanent magnet strips (14) of the tooth groove (132) are arranged with the same polarity throughout the entire area. The permanent magnet strips (14) of the same large pole (13) and adjacent large poles (13) have the same polarity, forming a continuous magnetic barrier with the same polarity inside the stator core (11).

3. A stator-embedded permanent magnet hybrid stepper motor according to claim 2, characterized in that: The slot (132) has an inwardly recessed magnetic shielding step (133) formed at the slot opening. The magnetic shielding step (133) is formed by the inwardly protruding extension of the top of the slot walls on both sides of the slot (132). The plane of the magnetic shielding step (133) is parallel to the radial direction of the stator core (11) and satisfies that the slot opening width is less than the internal width of the slot (132), forming a continuous ferromagnetic shielding wall between the slot (132) and the air gap of the rotor core (24).

4. A stator-embedded permanent magnet hybrid stepper motor according to claim 1, characterized in that: The permanent magnet strip (14) has an axially segmented structure with unequal thickness. The thickness of the middle section along the axial direction is greater than the thickness of both ends. A non-magnetic gap (134) is reserved between the permanent magnet strip (14) and the bottom of the groove (132).

5. A stator-embedded permanent magnet hybrid stepper motor according to claim 1, characterized in that: It also includes a non-magnetic pad (15) that is slidably installed in the tooth groove (132). The non-magnetic pad (15) is a long strip of thin plate and is arranged along the axial direction of the stator core (11). The non-magnetic pad (15) has an integrally formed snap-fit ​​groove (151) on the side of the non-magnetic pad (15) near the groove opening of the tooth groove (132). The permanent magnet strip (14) is provided with a corresponding snap-fit ​​end (141). The non-magnetic pad (15) has several strip-shaped through holes (152) extending along the axial direction of the stator core (11). Each strip-shaped through hole (152) is evenly distributed along the width direction of the non-magnetic pad (15), and the wall of the strip-shaped through hole (152) is provided with a heat-conducting layer (153).

6. A stator-embedded permanent magnet hybrid stepper motor according to claim 5, characterized in that: A non-magnetic shielding sleeve (16) is provided between the inner wall of the motor housing and the outer circumference of the stator core (11). The non-magnetic shielding sleeve (16) is provided with a guide hole (161) at the position of the outlet of the two ends of the strip-shaped through hole (152) in the axial direction. The guide hole (161) is connected to the external cooling flow path.

7. A stator-embedded permanent magnet hybrid stepper motor according to claim 5, characterized in that: The non-magnetic pad (15) has a hollow structure inside, and an elastic cantilever clamp (154) is rotatably installed inside it. The non-magnetic pad (15) has an opening (155) that communicates with the interior. A clamping block (156) is slidably installed in the opening (155). A push rod (157) is fixedly installed on the clamping block (156). The elastic cantilever clamp (154) is hinged to the end of the push rod (157). A spherical air cushion (158) is fixedly installed between the card block (156) and the side wall of the opening (155) of the non-magnetic pad (15).

8. A stator-embedded permanent magnet hybrid stepper motor according to claim 7, characterized in that: A boss (135) is provided on the inner side wall of the groove (132), and a groove (159) is provided on the non-magnetic pad (15). The elastic cantilever card (154) passes through the groove (159) and is embedded in the corresponding insertion hole on the boss (135).

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