A magnetic flux tensioner servo motor

Abstract

A kind of magnetic flux tensioner servo motor, including shaft, tension wheel, disc side end face slot stator, fixed plate rotor with magnet, plane bearing axial limiting sealing lubrication structure, temperature control self-adaptive air-cooled component, tail high-precision servo encoder;Rotor magnet and stator end face generate axial magnetic attraction, rely on front and rear end cap plane bearing to bear axial attraction, permanent lock stator rotor air gap, matched double-layer sealing ring closed lubricating grease;Adopt large outer diameter short axial axial magnetic flux structure, torque force arm is longer, magnetic circuit short iron loss is low, the high torque density of the present application, stable heat dissipation, bearing long service life, low energy consumption, low production cost, adapt to domestic, commercial full series of tension fitness equipment, with extremely high industrial value.

Description

Technical Field

[0001] This invention relates to a low-speed, high-torque servo drive motor suitable for use with pull-type fitness training machines, specifically to a flux puller servo motor with an axial flux structure that is adapted to human pulling loads. Background Technology

[0002] In strength training equipment, resistance training devices rely on motors to output resistance in the opposite direction to simulate weight training effects. The core drive unit needs to meet stringent requirements such as low speed, continuous high torque, smooth operation, stable heat dissipation under long-term low-speed, high-load conditions, and a compact structure suitable for the large body of fitness equipment. Currently, the industry entirely uses traditional radial cylindrical inner / outer rotor servo motors as the resistance source. Existing radial cylindrical motors have many unavoidable technical defects, such as torque increase relying on increased axial length, poor heat dissipation, and severe power loss. Radial large outer diameter and short body solutions suffer from low material utilization, high cost, and are prone to imbalance and wear failure under stress, among other problems.

[0003] Traditional radial motors have a stator and rotor arranged concentrically radially around the shaft, relying on axially lengthened core length and extended effective magnetic flux path to increase output torque. When fitness equipment requires high tensile resistance, the motor's axial dimension is forced to increase significantly. The core and windings are arranged along the axial depth, concentrating internal heat in the middle area of ​​the stator and rotor, making it difficult for heat to conduct outwards. Under low-speed, high-torque conditions, the temperature rises sharply, and winding copper losses and core iron losses continuously amplify, leading to a rapid decline in motor efficiency. Long-term use can easily result in overheating and power reduction, insulation aging, and magnet demagnetization, significantly shortening the equipment's lifespan. If the radial motor is made with a larger outer diameter and a shorter axial length to accommodate the short body requirements of fitness equipment, its permanent magnets and copper wire windings are still arranged on the inner circumference of the larger outer diameter, resulting in a limited effective magnetic flux area per unit volume. Under the same torque output, the consumption of copper wire, silicon steel sheets, and permanent magnets is large, resulting in high raw material costs, which does not meet the market demand for cost reduction in mass production of fitness equipment. Meanwhile, the excessively long magnetic circuit of the stator yoke of the large-diameter radial motor significantly increases core losses, further exacerbating the overheating problem under low-speed continuous load conditions.

[0004] Existing axial flux disc motors generally suffer from a strong axial magnetic attraction between the rotor permanent magnet and the stator end face. The rotor continuously attracts to the stator side, relying solely on the front and rear deep groove ball bearings to bear the axial tension. However, ball bearings can only withstand radial loads; continuous axial attraction causes unilateral compression of the steel balls and cage deformation. This leads to bearing wear, clearance misalignment, and motor jamming and abnormal noises even after a short period of operation, and in severe cases, complete seizure and shutdown. Such motors cannot meet the high-frequency, long-duration tension training conditions required for fitness equipment. Current industry solutions only alleviate the problem by thickening the bearings and increasing their number, failing to fundamentally stabilize the air gap between the stator and rotor, and thus the bearing wear problem remains unresolved.

[0005] Fitness resistance bands operate by being pulled slowly by human force, causing the motor to operate at low speed, high current, and high torque output for extended periods. This results in a winding heating rate far exceeding that of conventional high-speed motors. Existing disc motors rely solely on natural convection cooling from the casing, lacking active cooling and temperature-linked control mechanisms. Furthermore, there are no automatic cooling mechanisms when the temperature rises excessively. Sustained high temperatures can lead to irreversible demagnetization of the permanent magnets, damage to the winding insulation, frequent equipment failures, and high maintenance costs.

[0006] When a traditional radial motor drives a pull wheel, the driver relies solely on a common Hall sensor to acquire the rotor position. This results in low position detection accuracy, large fluctuations in motor resistance output during manual, uniform pulling, and inconsistent pulling force, leading to a clunky and unsmooth training experience. It also fails to achieve high-precision, linearly controllable resistance simulation, resulting in a poor fitness experience and making it difficult to meet the constant load requirements of professional strength training.

[0007] Under the same rated torque output conditions, traditional radial cylindrical motors use a huge amount of copper wire for windings, stator silicon steel sheets, and permanent magnets, resulting in a long and winding magnetic circuit, high core loss, and high overall energy consumption. With the trend of energy saving and low cost development in the fitness equipment industry, the existing motor structure cannot meet the product iteration requirements of lightweight, low material consumption, and low energy consumption.

[0008] When fitness equipment requires extremely high tensile resistance and the torque of a single-disc axial flux motor is insufficient, the existing dual-stator dual-rotor axial flux motors have no independent planar bearing limiters or lubricating oil sealing structures in the front and rear bearings. After long-term operation, the air gap shifts and lubricating grease is lost, resulting in a significant increase in the failure rate. The assembly process is cumbersome and mass production consistency is poor.

[0009] In summary, existing radial cylindrical servo motors and conventional disc-type large-diameter cylindrical motors cannot meet the comprehensive working conditions of fitness resistance training machines, which require low speed, high torque, high frequency continuous load, smooth pulling force output, stable heat dissipation, and long service life. The industry urgently needs a new type of magnetic flux resistance servo motor with a specific structure that addresses the above-mentioned technical problems. Summary of the Invention

[0010] In view of the technical problems existing in the prior art, the present invention aims to provide a flux tensioner servo motor that can solve the problems of poor heat dissipation, efficiency reduction, and large power loss caused by traditional radial motors relying on increasing axial length to increase torque; axial magnetic attraction between stator and rotor in conventional disc-type axial flux motors; rapid wear of ball bearings under unidirectional force; inability to maintain a constant air gap; insufficient heat dissipation of motors under low-speed, high-torque conditions in fitness resistance bands; lack of adaptive active temperature control heat dissipation structure; high-temperature demagnetization; insulation damage; stuttering during tension output; poor resistance linearity; lack of smoothness of high-precision closed-loop position control; and high consumption of copper wire, silicon steel sheets, and magnets for motors with the same torque, resulting in high production costs and high energy consumption. The present invention can provide a standardized dual-stator, dual-rotor structure to meet the high torque requirements of ultra-large tension equipment, while ensuring stable lubrication, constant air gap, and adaptability to the large body space of fitness equipment. It achieves a short axial length, large outer diameter disc layout, and matches the tension wheel mounting structure and overall machine assembly requirements.

[0011] The flux-driven servo motor of the present invention is suitable for use in fitness resistance training machines. It belongs to the axial flux disc type servo motor category and includes two structures: a single-stator single-rotor structure and a double-stator double-rotor structure. It is equipped with a tension wheel, servo position detection, adaptive air-cooling heat dissipation, and an integrated structure for constant axial clearance, limiting lubrication, and sealing. The motor includes a shaft, tension wheel, front cover, rear cover, outer shell, rotor assembly, stator assembly, plane bearing, deep groove ball bearing, servo encoder, fan motor, fan motor mounting cover, sealing and lubrication assembly, fastener assembly, and limiting snap ring assembly. The rotor assembly includes a magnet fixing plate and a magnet; the stator assembly includes a stator and a shaft fixing sleeve (also known as a shaft fixing sleeve). An armature winding groove is opened on the side end face of the stator, a central circular hole is set in the inner hole of the stator, and a fixing tooth hole is opened on the back end face of the stator.

[0012] The sealing and lubrication assembly includes sealing rings and retaining ring washers; the limit retaining ring assembly includes bearing retaining rings and shaft retaining rings; the fasteners include bolts, screws (fixing screws), nylon nuts, and retaining pins; the servo detection assembly includes encoder sensing magnets and servo encoders; the air-cooling assembly includes a fan motor and a fan motor mounting cover; the mounting structure includes a square mounting base on the outer side of the front cover for fixing the entire machine to the fitness equipment mounting frame.

[0013] The shaft of the rotor axial magnetic flux rotation structure serves as the main rotating shaft. A magnet fixing plate (magnetic circular iron sheet) is fixed in the middle section of the shaft, and the magnet fixing plate is interference-locked to the shaft. A circle of magnets is evenly pasted around the circumference on one side of the magnet fixing plate to form axial magnetic lines of force. Deep groove ball bearings are respectively installed at both ends of the shaft. The deep groove ball bearings are axially limited by bearing retaining rings and shaft retaining rings to prevent axial movement of the bearings. A tension wheel is installed at the front end of the shaft. The tension wheel is fixed to the shaft by a pin. When a rope is pulled manually, the tension wheel, shaft, magnet fixing plate, and magnet rotate synchronously.

[0014] The stator with a slotted stator structure on the side end face is a disc-shaped silicon steel sheet stacked structure, formed by casting or precision casting. The stator has a central hollow circular hole in the inner hole, with an internal shaft fixing sleeve for the shaft to pass through. Unlike traditional radial motors where the armature winding slots are formed on the inner circular surface of the stator, the stator armature winding slots of this invention are formed on the side end face of the stator. The armature windings are arranged in the slots on the side of the stator, and the ends of the windings extend beyond the surface of the stator and the inner diameter of the inner hole. The back end face of the stator is integrally formed with multiple sets of fixing holes, which are locked and fixed to the front cover by fixing screws and fixing pins. The stator is fixed to the inner end face of the front cover. The side end face of the stator is axially aligned with the magnets on the magnet fixing plate, and a constant working air gap is reserved between them.

[0015] The stator core is a disc-type axial flux stator core. The stator as a whole has an annular disc structure and is integrally machined from silicon steel sheets or formed by powder metallurgy. The surface of the stator substrate is coated with a high-temperature resistant insulating coating. Several radially extending stator teeth are evenly distributed along the inner circumference of the annular structure. The stator teeth have a trapezoidal convex tooth structure, and the tooth portion is used for winding the excitation coil. A concave stator slot is formed between adjacent stator teeth to serve as a winding receiving space. Multiple axially penetrating mounting holes are evenly opened on the outer annular end face of the stator for locking and positioning the stator with the motor frame and rear end cover. The stator teeth are evenly distributed at equal angles along the circumference, and all stator teeth have uniform height and width. The end faces of the stator teeth are flat, forming an axial air gap with the end faces of the rotor magnets during operation, achieving axial flux coupling.

[0016] The rotor magnet and stator end face of the axial magnetic attraction cancellation limit and sealing lubrication structure have strong axial magnetic attraction, and the rotor continuously adheres to the stator side; a plane bearing is embedded in the inner hole of the front cover and the inner hole of the rear cover respectively, and a stop limit step is set on the shaft surface. One side of the plane bearing abuts against the shaft stop step, and the other side abuts against the inner wall of the end cover. The plane bearing bears all the axial magnetic attraction load of the rotor, isolates the impact of unidirectional attraction force on the deep groove ball bearing, permanently locks the air gap size between the stator and the rotor magnet, and ensures that the rotational clearance remains constant.

[0017] The operation of a planar bearing requires continuous lubrication with lubricating oil. Sealing rings are installed at both ends of the holes on the front and rear covers where the planar bearing is installed. The inner diameter of the sealing ring is in contact with the outer surface of the shaft, and the outer diameter of the sealing ring is in contact with the inner wall of the end cover. With the help of snap rings and washers, the sealing rings are limited to form a closed oil reservoir, preventing the lubricating oil from being diluted by high temperature and losing its flow, thus ensuring the smooth operation of the planar bearing for a long time.

[0018] The adaptive temperature-controlled air-cooling structure features a fan motor mounting cover fixed to the outside of the rear cover, with the fan motor housed inside. The servo driver incorporates a temperature monitoring module to collect real-time data on the stator winding and magnet temperatures. When the motor temperature rises to a set high-temperature threshold, the driver automatically starts the fan motor, which generates airflow to sweep the rear cover, outer casing, and outer stator end face, quickly removing heat from the disc stator and rotor. When the temperature drops to the energy-saving low-temperature threshold, the fan motor automatically stops, reducing no-load losses and extending its lifespan. The axial flux disc stator end face is completely exposed, providing a significantly larger heat dissipation contact area than traditional radial cylindrical motors, enabling stable temperature control under low-speed, high-torque conditions in conjunction with active air cooling.

[0019] The high-precision servo smooth tension control structure extends from the tail of the shaft to the outside of the rear cover. An encoder sensing magnet is fixed at the end of the shaft, and the servo encoder is fixed on the outside of the rear cover and axially aligned with the encoder sensing magnet. The servo encoder collects high-precision angle and speed position signals of the rotor in real time and transmits them to the driver. The driver outputs continuous linear torque based on the high-precision position signal. There is no torque fluctuation throughout the rotation of the tension wheel. When manually pulled, there is no jamming and the resistance is uniform and smooth, accurately simulating various load tension training curves.

[0020] The front cover has an integrally formed square mounting base with holes. The front cover, outer shell, and rear cover are locked together as a whole by bolts. The whole machine can be quickly assembled and fixed to the fitness training machine mounting frame through the square base of the front cover. The outer shell covers the stator and rotor body, which can play a role in dust protection. All assembly gaps are sealed by sealing rings, so the whole machine is dustproof and prevents grease leakage.

[0021] If the outer diameter space of the equipment is limited and the magnetic flux torque of a single disc cannot meet the requirements of ultra-high pulling force, ring magnets are attached to both ends of the rotor magnet fixing plate; an independent stator is fixed to the inner end face of the front cover and the inner end face of the rear cover, and the two stators are axially aligned with the magnets on both sides of the rotor; a set of plane bearings, matching sealing rings, and retaining ring washers are independently installed in the inner holes of the front and rear covers, and the two sets of plane bearings bear the bidirectional axial magnetic attraction load of the rotor, and the stators on both sides and the rotor magnets maintain a constant air gap; the front and rear stators are independently wired, and the two stators participate in magnetic flux coupling at the same time, doubling the effective magnetic flux area and greatly improving the torque density, making it suitable for ultra-high pulling force fitness equipment.

[0022] This invention features an axial flux disk-to-disc coupling structure. The permanent magnets and windings are distributed on the end face of a large-diameter disk, resulting in electromagnetic force farther from the axis. The torque calculation formula T=F×R significantly increases the lever arm R. Under the same outer diameter conditions, the torque of this invention is proportional to the cube of the outer diameter, while the torque of a traditional radial motor is only proportional to the square of the outer diameter, resulting in a huge increase in torque density. The magnetic lines of force pass through the thin air gap in a straight line along the axial direction, eliminating the circuitous magnetic path of the long iron core yoke in traditional radial motors. The magnetic path is short, the iron core loss is low, and a larger operating current can be passed under the same temperature rise conditions, continuously outputting high torque. The single / double-sided stator structure can multiply the effective air gap magnetic flux area, significantly enhancing the electromagnetic force per unit volume.

[0023] According to the present invention, at least the following beneficial effects are achieved: Due to the adoption of a large outer diameter, short axial disc-type axial flux structure, the torque is increased by increasing the radial outer diameter, and the axial length of the whole machine is greatly shortened. The stator and rotor are all arranged with disc end faces, and both end faces are fully exposed. The natural convection heat dissipation area is 3 to 5 times that of a radial cylindrical motor with the same torque. Heat is quickly dissipated under low speed and high torque conditions, the winding temperature rise is significantly reduced, the motor operating efficiency is stable, and there is no risk of power attenuation or magnet demagnetization. It is perfectly adapted to the continuous low-speed load conditions of fitness resistance bands.

[0024] The front and rear end caps have built-in flat bearings to bear all the unidirectional axial adsorption force of the rotor, while the deep groove ball bearings only bear the radial rotation load, eliminating the problem of unilateral extrusion and wear of the balls; combined with the shaft end stop limit structure to permanently lock the air gap between the stator and rotor, there is no gap offset or jamming noise during long-term operation, the service life of the motor bearing assembly is increased by more than 5 times, and the after-sales maintenance cost of fitness equipment is greatly reduced.

[0025] Because the double sealing rings at the front and rear of the plane bearing installation position, together with the snap ring gasket, form a closed oil cavity, it isolates the high-temperature lubricating oil from evaporation and leakage. The entire machine does not need to be replenished with lubricating grease throughout its entire life cycle, making assembly and maintenance simple and ensuring high consistency in mass production.

[0026] Equipped with a temperature-linked automatic start / stop fan motor, it features automatic air cooling at high temperatures and energy saving by shutting down at low temperatures. The disc-type stator end face heat dissipation is combined with forced air cooling to solve the problem of high heat at low speeds and high torque, avoiding winding insulation aging and permanent magnet demagnetization at high temperatures. The equipment can work continuously without limitation, making it suitable for high-frequency commercial use scenarios in gyms. It features adaptive temperature control and active air cooling for precise temperature control and extended machine life.

[0027] The servo encoder at the tail end of the shaft provides a high-precision rotor position signal with millions of points. The driver adjusts the output torque linearly in real time. The resistance is constant and there are no sudden stops or jams when the pull wheel is pulled manually. The training feel is close to the real load. It can accurately realize a variety of professional training modes such as linear increase, constant resistance, and intermittent resistance, thereby enhancing the product's market competitiveness.

[0028] Due to the short magnetic circuit and low iron loss, the copper wire used in the winding can be reduced by about half under the same rated torque output conditions. The cost of stator silicon steel sheets and permanent magnets is also greatly reduced. The cost of raw material procurement is greatly reduced, the copper and iron losses of the motor are lower, and the energy consumption of the whole machine is reduced, which meets the requirements of low-carbon and low-cost mass production of fitness equipment.

[0029] The single-stator, single-rotor structure meets the needs of conventional home-use tensile training equipment, while the dual-stator, dual-rotor structure is suitable for commercial ultra-high tensile strength equipment. It retains standardized flat bearings, sealing lubrication, and limiting structures, eliminating the need to redesign assembly molds. It is compatible with the same shell, end cap, and fan components, resulting in a high degree of product modularity and reducing R&D and mold investment costs.

[0030] Because the square mounting base with holes on the outer side of the front cover can be directly locked onto the fitness machine frame, with a short axial dimension and a large radial outer diameter, it can perfectly match the large body space of the fitness equipment; all parts have standardized snap-fit ​​and bolt locking structures, explosive disassembly and assembly, simplifying the production and assembly process and improving the mass production efficiency of the whole machine.

[0031] The machine is sealed with multiple seals, and the internal lubricating oil and windings are not corroded by external dust and sweat. It can operate stably for a long time in the humid and dusty environment of the gym, and its protection level is superior to that of traditional radial servo motors. Attached Figure Description

[0032] Figure 1 To illustrate an axial sectional view of the overall structure of a flux tension servo motor (dual stator dual rotor structure) according to a specific embodiment of the present invention; Figure 2 This is an exploded view showing the disassembled assembly of components of a flux tension servo motor (dual stator dual rotor structure) according to an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures: 1-Pulley, 2-Pin, 3-Deep groove ball bearing, 4-Sealing ring, 5-Side bearing, 6-Front cover, 7-Front and rear cover bolts, 8-Stator fixing pin, 9-Stator fixing screw, 10-Snap ring washer, 11-Snap ring, 12-Housing shell, 13-Magnet fixing plate (forming the rotor with the magnet shaft), 14-Magnet, 15-Stator, 16-Rear cover, 17-Fan motor mounting cover, 18-Mounting cover bolt, 19-Bearing snap ring, 20-Encoder screw, 21-Servo encoder, 22-Fan motor, 23-Output line assembly, 24-Encoder sensing magnet, 25-Nylon nut, 26-Shaft fixing sleeve (shaft fixing sleeve), 27-Securing screw. Detailed Implementation

[0034] The technical solution of the present invention will now be described in complete and detailed manner with reference to the accompanying drawings and specific embodiments. Those skilled in the art will understand that this description is exemplary and that the present invention is not limited to the specific embodiments described herein.

[0035] Figure 1 To illustrate an axial sectional view of the overall structure of a flux tension servo motor (dual stator dual rotor structure) according to a specific embodiment of the present invention; Figure 2 Exploded views showing the disassembly and assembly of its components. Figure 1 The diagram shows the axial cross-sectional assembly relationship of the entire machine. A tension wheel 1 is mounted at the front end of the shaft and fixed circumferentially by pin 2. A magnet fixing plate 13 is fixed in the middle section of the shaft, and a magnet 14 is attached to the side end face of the magnet fixing plate 13. The stator 15 is locked to the front cover 6 by fixing pins 8 and fixing screws 9, with the side end face of the stator 15 axially opposite to the magnet 14. A plane bearing 5 and a deep groove ball bearing 3 are respectively mounted in the inner holes of the front cover 6 and the rear cover 16, along with bearing retaining rings 19 and shaft retaining rings for limiting the bearings. Sealing rings 4 are arranged on both sides of the plane bearings 5, and retaining ring washers 10 limit the sealing rings. The outer shell 12 encloses the stator and rotor body, and bolts are used to lock the front cover 6, outer shell 12, and rear cover 16. A fan motor mounting cover 17 and a fan motor 22 are installed on the outside of the rear cover 16. An encoder sensing magnet 24 is mounted at the tail end of the shaft, and a servo encoder 21 is fixed to the outside of the rear cover 16. Nylon nuts 25 are used to lock the tail components.

[0036] Figure 2 In the design, the shaft assembly consists of a tension wheel 1, a pin 2, a deep groove ball bearing 3, a sealing ring 4, and a flat bearing 5 assembled sequentially. The front cover 6 secures the stator 15 via a stator fixing pin 8 and a stator fixing screw 9. The rotor, consisting of a magnet fixing plate 13 and a magnet 14, is fitted onto the shaft body. The outer casing 12 connects the front cover 6 and the rear cover 16 via front and rear cover bolts 7. The fan motor mounting cover 17 and the fan motor 22 are mounted on the outside of the rear cover 16, and the mounting cover bolts 18 lock the mounting cover in place. The encoder sensing magnet 24 and the servo encoder 21 are assembled sequentially at the tail of the shaft, with the encoder screw 20 securing the encoder and the nylon nut 25 locking the tail. Snap ring washers 10, snap rings 11, and bearing snap rings 19 are used for axial positioning of the entire shaft system. The stator winding power supply line is led out from the outlet line group 23.

[0037] like Figure 1-2As shown, the magnetic flux tension servo motor of the present invention includes a shaft, a tension wheel 1, a front cover 6, a rear cover 16, a housing 12, a rotor assembly, a stator assembly, a plane bearing 5, a deep groove ball bearing 3, a servo encoder 21, a fan motor 22, a fan motor mounting cover 17, a sealing and lubrication assembly, a limit snap ring assembly, and a fastener assembly. The rotor assembly includes a magnet fixing plate 13 and a magnet 14. The magnet fixing plate 13 is fixedly fitted onto the middle section of the shaft, and an annular magnet 14 is attached to the side end face of the magnet fixing plate 13. The stator assembly is a disc silicon steel sheet stator 15. An armature winding groove is provided on the side end face of the stator 15 as a winding receiving space. The inner hole of the stator 15 has a central hollow circular hole, and a fixing tooth hole is provided on the back end face (outer annular end face) of the stator 15 for locking and positioning the stator as a whole with the motor base and the rear end cover. The stator 15 is provided with a shaft fixing sleeve 26. The core of the stator 15 is a disc-shaped axial flux stator core. The stator 15 has an overall annular disc structure. Several radially extending stator teeth (not shown) are evenly distributed along the inner circumference of the annulus. The stator teeth have a trapezoidal convex tooth structure, and the tooth part is used for winding the excitation coil. A concave stator slot (armature winding slot) is formed between two adjacent stator teeth. The stator teeth are evenly distributed at equal angles along the circumference, and all stator teeth have uniform height and tooth width dimensions. The end face of the stator teeth is flat, and during operation, it forms an axial air gap with the end face of the rotor magnet to achieve axial flux coupling.

[0038] The stator 15 is locked and fixed to the inner end face of the front cover 6 by fasteners (locking screws 27). The stator side end face is axially opposite to the magnet and has a reserved working air gap. The front end of the shaft extends outward and is equipped with a tension wheel 1. The tension wheel 1 is fixed to the shaft circumferentially by a pin. Deep groove ball bearings 3 are respectively installed at both ends of the shaft. The limiting snap ring assembly includes a bearing snap ring 19 and a shaft snap ring 11 to limit the axial movement of the deep groove ball bearings 3. The inner holes of the front cover 6 and the rear cover 16 are both equipped with plane bearings 5. A stop limiting step is set on the shaft surface. The plane bearing 5 abuts against the stop step to bear the axial magnetic attraction load between the rotor magnet 14 and the stator 15, and constantly locks the air gap between the stator 15 and the magnet 14. The sealing and lubrication assembly includes a sealing ring 4 and a snap ring washer 10. The front and rear ends of the mounting hole of the plane bearing 5 are equipped with a sealing ring. The inner diameter of the sealing ring 4 fits the shaft surface, and the outer diameter fits the inner hole of the end cover. It forms a closed oil storage cavity with the snap ring washer 10. The fan motor mounting cover 17 is fixed on the outside of the rear cover 16. The fan motor 22 is assembled inside the fan motor mounting cover 17. The servo driver (not shown) has a built-in temperature monitoring module. When the temperature rises to the threshold, the fan motor will automatically start to cool down. When the temperature drops to the energy-saving threshold, the fan motor will stop. The tail of the shaft extends to the outside of the rear cover. The encoder sensing magnet 24 is fixed at the end of the shaft. The servo encoder 21 is fixed on the outside of the rear cover 16 and aligned with the encoder sensing magnet 24. The servo encoder 21 collects the rotor position signal and transmits it to the driver to realize linear torque output. The front cover 6 has an integrally formed square mounting base with holes. The whole machine is fixed to the fitness equipment mounting frame through the square base.

[0039] The fastener assembly includes bolts 7, locking screws 27, nylon nuts 25, and retaining pins 8. The front and rear covers 6 and 16 are secured to the outer shell by bolts. The stator is secured to the front cover 6 by retaining pins 8 and screws 27. The shaft tail end is secured to the servo encoder 21 and encoder sensing magnet 24 by nylon nuts 25. The armature winding of the stator 15 is arranged in the winding slot (not shown) on the side end face of the stator. The winding end extends beyond the surface of the stator 15 and the inner diameter of the stator 15 inner hole. The winding leads form an outlet wire group 23 to connect to an external servo driver (a conventional stand-alone device, not shown). Magnetic lines pass through the stator 15, air gap, magnet 14, and magnet fixing plate in a straight axial direction to form an axial magnetic flux loop. The motor torque is proportional to the cube of the outer diameter of the whole machine. Under the same outer diameter, the torque density is higher than that of a traditional radial cylindrical motor. Under single stator and single rotor conditions, with the same rated torque output, the amount of copper wire used in the stator winding is reduced by half compared to traditional radial servo motors, and the consumption of stator silicon steel sheets and permanent magnets is reduced by 30%.

[0040] In this dual-stator dual-rotor structure, annular magnets 14 are attached to both the front and rear end faces of the magnet fixing plate 13. A set of stators 15 is fixed to the inner side of the front cover 6 and the inner side of the rear cover 16, respectively. The two sets of stators 15 are axially aligned with the magnets 14 on both sides of the rotor. A set of planar bearings 5, sealing rings 4, and retaining ring washers 10 are independently assembled in the inner holes of the front cover 6 and the rear cover 16. The two sets of planar bearings bidirectionally cancel the axial magnetic attraction of the rotor, and the two stators 15 synchronously participate in magnetic flux coupling to increase torque. The fan motor 22, servo encoder 21, housing 12, and end cover components of the dual-stator dual-rotor structure are the same as those of the single-stator single-rotor structure, and the design is modular and compatible.

[0041] According to the present invention, the planar bearing 5 fully bears the unidirectional axial adsorption force of the rotor, while the deep groove ball bearing 3 only bears the rotational radial load, thus eliminating the fault of unilateral extrusion wear of the balls. The whole machine has a short axial, large outer diameter disc layout, with both ends of the stator completely exposed. Combined with forced air cooling by a fan motor, it is suitable for the low-speed, continuous high-torque heat generation conditions of fitness resistance bands. The servo encoder collects high-precision rotor angle and speed signals in real time, and the driver outputs continuous linear resistance torque based on position closed loop, ensuring smooth rotation of the resistance wheel and uniform resistance output.

[0042] It should be pointed out that, although Figure 1-2 The description is based on a dual-rotor dual-stator structure, but the present invention is not limited to this dual-rotor dual-stator structure. It is compatible with the single-stator single-rotor structure and features a modular and compatible design. Therefore, to save space, the accompanying drawings of the single-stator single-rotor structure are not provided. However, the following will provide specific embodiments 1 and 2 for the single-stator single-rotor and dual-stator dual-rotor cases, respectively, to provide a more detailed description of the present invention.

[0043] Example 1: Single-stator, single-rotor basic flux tension servo motor (compatible with conventional home fitness tension equipment) Although no accompanying drawings are provided for this embodiment 1, it is obvious that they can also be referred to. Figure 1 and 2The following description uses the same reference numerals to denote the corresponding components, as most parts are interchangeable. In this embodiment 1, the spindle is pre-processed, with two stop-limiting steps machined on the spindle surface, corresponding to the installation positions of the front cover plane bearing and the rear cover plane bearing, respectively. A pin hole is opened at the front end of the spindle, an interference fit cylindrical surface is machined in the middle section of the spindle for pressing the magnet fixing plate 13, and a threaded section is machined at the tail end of the spindle for assembling the nylon nut 25. The front end of the spindle is sequentially fitted with a sealing ring 4, a plane bearing 5, and a deep groove ball bearing 3, and the bearing retainer 19 and the shaft retainer 11 are installed to complete the axial limiting of the front bearing. The tension wheel 1 is fitted onto the front end of the spindle, and the pin 2 is driven into the aligned pin hole to achieve synchronous rotation of the tension wheel and the spindle in the circumferential direction. The stator 15 is a stacked disc of silicon steel sheets. Multiple sets of armature winding slots are evenly opened on the side end face of the stator. The windings are embedded in the slots on the side end face, and the winding leads are led out from the inner hole of the stator to form the outlet wire group 23. The back end face of the stator has a pre-reserved threaded hole. The stator 15 is locked and fixed to the inner end face of the front cover 6 by the stator fixing pin 8 and the stator fixing screw 9. The magnet fixing plate 13 is press-fitted into the middle section of the shaft. The annular permanent magnet 14 is evenly pasted along the circumference on one side end face of the magnet fixing plate. The magnet is axially aligned with the side end face of the stator 15, and a constant working air gap of 0.2~0.5mm is reserved. Install the front cover 6, stator 15, and rotor shaft assembly into the front end of the outer casing 12. Align the rear end of the outer casing 12 with the rear cover 16. Use front and rear cover bolts 7 to lock the front cover, outer casing, and rear cover to form a closed housing for the whole machine. Install sealing rings 4, snap ring washers 10, and snap rings 11 on both sides of the mounting holes of the front and rear cover plane bearings, respectively. Add high-temperature grease into the plane bearing cavity. The sealing rings seal the oil storage cavity to prevent grease loss.

[0044] A fan motor mounting cover 17 is installed on the outer side of the rear cover 16. The mounting cover is secured with bolts 18, and the fan motor 22 is embedded inside the mounting cover. The shaft end passes through the center hole of the rear cover and is fitted with an encoder sensing magnet 24. The servo encoder 21 is fixed to the outer side of the rear cover by encoder screws 20. The encoder sensing magnet 24 and the sensing face of the servo encoder 21 are aligned. Finally, the nylon nut 25 is tightened on the threaded section of the shaft end to complete the locking of all parts at the shaft end. The entire machine is mounted on the square mounting base with holes on the outer side of the front cover 6 and secured to the frame of the fitness resistance training machine with bolts. The outlet cable group 23 is connected to the external servo drive, completing the assembly of the entire machine.

[0045] The rotor magnet 14 and the end face of the stator 15 generate a continuous axial attraction force, and the rotor always tends to move towards the stator side of the front cover; the abutment step on the shaft surface abuts against the plane bearing 5, the plane bearing 5 bears all the axial magnetic attraction load, the deep groove ball bearing 3 only bears the rotational radial force, and the steel balls do not have unilateral extrusion wear; the inner diameter of the sealing rings 4 on both sides of the plane bearing fits the outer circle of the shaft, and the outer diameter fits the inner hole of the end cover, and with the cooperation of the snap ring washer 10, the grease cavity is sealed, so the grease will not be diluted and leaked under high temperature conditions, the plane bearing rotates with low friction for a long time, and the air gap between the stator and rotor maintains the design value throughout the process, without deviation or friction.

[0046] The driver supplies three-phase alternating current to the armature winding on the stator side end face, and the winding generates an axial alternating magnetic field. The magnetic field on the stator 15 end face is axially coupled with the permanent magnet magnetic field of the rotor magnet 14. The magnetic lines of force pass perpendicularly through the air gap between the stator and rotor to form a complete axial magnetic flux loop. The interaction of the magnetic fields generates a circumferential tangential torque, which drives the shaft and the tension wheel 1 to rotate synchronously. When the tension wheel rope is pulled manually, the shaft rotates in the opposite direction to cut the axial magnetic flux, and the motor outputs a reverse resistance torque to simulate a load training load.

[0047] This embodiment features a large-diameter disc structure with permanent magnets and windings distributed on the edge of the disc far from the axis. The torque arm R is much larger than that of a radial cylindrical motor of the same volume. The magnetic circuit only passes through the stator, thin air gap, rotor magnet, and magnetic disk, without a long-distance detour path through the iron core yoke. Iron loss is extremely low, and the iron core heating is significantly reduced under low-speed, high-current conditions. The torque output is 2.5 to 3 times that of a traditional radial motor with the same outer diameter.

[0048] The servo driver (using a conventional driver) has a built-in NTC temperature detection module (not shown). The temperature probe is attached to the stator winding end face to collect the internal temperature of the motor in real time. When the detected temperature is ≥75℃ (high temperature threshold), the driver outputs a power supply signal to start the fan motor 22. The fan generates axial airflow to continuously blow on the rear cover 16, the outer shell 12, and the outer disc end face of the stator 15, quickly removing the heat from the stator winding and magnets. The two end faces of the disc stator are completely exposed, and the airflow directly contacts the heat dissipation surface, resulting in a heat dissipation efficiency far exceeding that of a cylindrical motor. When the detected temperature drops to 45℃ (energy-saving low temperature threshold), the driver cuts off the power supply to the fan motor, and the fan stops, reducing no-load energy consumption and extending the service life of the fan motor. During continuous tensile training, the temperature fluctuates, and the fan automatically starts and stops in a cycle to control the temperature. The overall temperature rise is stably controlled within the insulation tolerance range, avoiding demagnetization of permanent magnets and aging of windings.

[0049] The encoder magnet 24 at the tail end of the shaft rotates synchronously with the rotor. The servo encoder 21 collects high-precision position signals of rotor angle and speed in real time and transmits them to the servo driver. Based on the position signals of millions of subdivisions, the driver adjusts the output current of the three-phase winding in real time through closed loop, and outputs resistance torque linearly and continuously. When the pull wheel is pulled at a constant speed by hand, the torque output is without sudden changes or pulse jamming, and the pulling force feels uniform and smooth. The driver can preset various resistance curves through the program to realize professional training modes such as constant pulling force, incremental pulling force, and intermittent resistance, which can be adapted to different fitness training needs.

[0050] Under the same rated output torque of 30 N·m, the amount of copper wire used in the stator winding in this embodiment is reduced by 50% compared with the traditional radial servo motor, and the consumption of stator silicon steel sheets and permanent magnets is reduced by 30%. The magnetic circuit is short and the iron loss and copper loss are low. Under the same tensile load, the power consumption of the whole machine is reduced by 28%. Long-term commercial use will save a lot of energy and significantly reduce the cost of raw material procurement, which is conducive to the mass production of fitness equipment.

[0051] Example 2: Dual-stator, dual-rotor high-torque flux tension servo motor (suitable for commercial ultra-high tension fitness equipment) When fitness equipment requires extremely high tensile force, the torque of a single stator and single rotor structure cannot meet the requirements, and the radial outer diameter space of the equipment cannot be further increased, the structure of this embodiment is adopted.

[0052] Annular magnets 14 are circumferentially attached to both the front and rear end faces of the magnet fixing plate 13, forming an axial permanent magnet magnetic field on both sides of the rotor. A complete set of stators 15 is independently assembled on the inner end face of the front cover 6 and the inner end face of the rear cover 16. The two sets of stators are axially aligned with the magnets on the front and rear sides of the rotor, respectively. The two sets of stators independently lead out the outlet wire group 23, and synchronously pass in alternating current, with double-sided magnetic flux coupling, doubling the effective magnetic flux area. A set of planar bearings 5, sealing rings 4, retaining ring washers 16, and retaining rings 11 are independently assembled in the inner holes of the front cover 6 and the rear cover 16, respectively. The front planar bearing bears the magnetic attraction force of the rotor towards the rear cover, and the rear planar bearing bears the magnetic attraction force of the rotor towards the front cover, thus canceling the axial attraction force in both directions. The air gap between the stator and rotor on both sides permanently maintains a constant size. Both sets of planar bearings are equipped with independent sealed oil storage chambers, so that the grease does not interfere with each other and provides long-term lubrication. The structure of the fan motor 22 on the outer side of the rear cover 16 and the servo encoder 21 at the tail of the shaft are completely universal with those of Embodiment 1, and the modular parts are universal. With double-sided stator and double-sided magnetic flux coupling, the torque density is increased by more than 90% compared with the single stator structure under the same outer diameter, which can meet the needs of commercial training equipment with ultra-large tensile force of more than 100 N·m, while retaining all the advantages of short axial direction, easy heat dissipation, low material consumption and long bearing life.

[0053] The present invention has been described in detail above through specific embodiments. However, this description is exemplary and various modifications and changes can be made. As long as they do not depart from the spirit and purpose of the present invention, all such modifications and changes should fall within the protection scope of the present invention, which is defined by the appended claims.

Claims

1. A flux tension servo motor, adapted for use in fitness tension training machines, characterized in that, Includes shaft, tension wheel, front cover, rear cover, housing, rotor assembly, stator assembly, plane bearing, deep groove ball bearing, servo encoder, fan motor, fan motor mounting cover, sealing and lubrication assembly, limit snap ring assembly, and fastener assembly; The rotor assembly includes a magnet fixing plate and a magnet. The magnet fixing plate is fixedly fitted onto the middle section of the shaft, and a ring magnet is attached to the side end face of the magnet fixing plate. The stator assembly includes a disc silicon steel sheet stator, an armature winding groove is provided on the side end face of the stator, a central hollow circular hole is provided in the inner hole of the stator, and a fixing tooth hole is provided on the back end face of the stator. The stator winding leads are connected to an external servo driver. The stator is locked and fixed to the inner end face of the front cover by fasteners. The side end face of the stator is axially opposite to the magnet and a working air gap is reserved. The front end of the shaft extends outward and is equipped with a tension wheel, which is fixed to the shaft circumferentially by a pin; deep groove ball bearings are respectively installed at both ends of the shaft, and the limiting snap ring assembly includes a bearing snap ring and a shaft snap ring, which are used to limit the axial movement of the deep groove ball bearings; The inner holes of the front cover and the rear cover are both equipped with plane bearings. A stop limit step is set on the shaft surface. The plane bearing abuts against the stop step to bear the axial magnetic attraction load between the rotor magnet and the stator, and constantly locks the air gap between the stator and the magnet. The sealing and lubrication assembly includes a sealing ring and a snap ring washer. The sealing ring is installed at both ends of the mounting hole of the plane bearing. The inner diameter of the sealing ring fits the shaft surface and the outer diameter fits the inner hole of the end cover. Together with the snap ring washer, it forms a closed oil storage cavity. The fan motor mounting cover is fixed to the outside of the rear cover, and the fan motor is assembled inside the fan motor mounting cover. The servo driver has a built-in temperature monitoring module. When the temperature rises to a threshold, the fan motor is automatically started to cool down, and when the temperature drops to an energy-saving threshold, the fan motor stops. The shaft extends to the outside of the rear cover, and an encoder sensing magnet is fixed at the end of the shaft. The servo encoder is fixed to the outside of the rear cover and aligned with the encoder sensing magnet. The servo encoder collects the rotor position signal and transmits it to the servo driver to achieve linear torque output.

2. The flux tension servo motor according to claim 1, characterized in that, The fastener assembly includes bolts, screws, nylon nuts, and retaining pins; the front and rear covers are locked to the outer shell by bolts, the stator is locked to the front cover by retaining pins and screws, and the servo encoder and encoder sensing magnet are locked to the shaft tail end by nylon nuts.

3. A flux tensioner servo motor according to claim 1 or 2, characterized in that, The armature winding of the stator is arranged in the winding slot on the side end face of the stator, and the end of the winding extends beyond the surface of the stator and the inner diameter of the stator inner hole. The winding leads form an outlet wire group to connect to an external servo driver.

4. A flux tension servo motor according to claim 3, characterized in that, The magnetic lines of force pass through the stator, air gap, magnet, and magnet fixing plate in a straight axial direction to form an axial magnetic flux loop. The motor torque is proportional to the cube of the outer diameter of the whole machine.

5. A flux tension servo motor according to claim 4, characterized in that, It has a dual-stator, dual-rotor structure.

6. A flux tension servo motor according to claim 5, characterized in that, The magnet fixing plate has ring magnets pasted on both the front and rear end faces. A set of stators is fixed on the inner side of the front cover and the inner side of the rear cover respectively. The two sets of stators are axially aligned with the magnets on both sides of the rotor. A set of plane bearings, sealing rings and retaining ring washers are independently assembled in the inner holes of the front cover and the rear cover. The two sets of plane bearings bidirectionally cancel the axial magnetic attraction of the rotor, and the stators on both sides synchronously participate in magnetic flux coupling to increase torque.

7. A flux tension servo motor according to claim 1 or 6, characterized in that, The planar bearing fully bears the unidirectional axial adsorption force of the rotor, while the deep groove ball bearing only bears the rotational radial load.

8. A flux tensioner servo motor according to claim 1 or 7, characterized in that, The front cover has an integrally formed square mounting base with holes, and the whole machine is fixed to the fitness equipment mounting frame through the square base.

9. A flux tension servo motor according to claim 1 or 8, characterized in that, The servo encoder acquires rotor angle and speed signals in real time, and the driver outputs continuous linear resistance torque based on position closed loop.

10. A flux tension servo motor according to claim 5, characterized in that, The fan motor, servo encoder, housing, end cover components are interchangeable with the single stator and single rotor structure.

Images