Double-rotor spindle motor

Abstract

The invention discloses a double-rotor spindle motor which comprises a front motor and a rear motor, and the front motor and the rear motor are in coaxial butt joint in the axial direction through a middle cover. The rear end of the front motor rotating shaft is connected with the middle cover through a first bearing, and the front end of the front motor rotating shaft extends out of the front cover and is supported through a second bearing; the rear motor rotating shaft is coaxially nested in an inner cavity of the front motor rotating shaft, the front end of the rear motor rotating shaft extends out of the front motor rotating shaft, a clearance fit sliding sleeve is arranged between the front end of the rear motor rotating shaft and the front motor rotating shaft, the rear motor rotating shaft is connected with the middle cover and the rear cover through cylindrical roller bearings, and lengthened inner rings of the cylindrical roller bearings are fixedly mounted on the rear motor rotating shaft; the magnetic coupling feeding mechanism can drive the rotating shaft to synchronously move in the axial direction when the rotating shaft of the rear motor rotates; the front motor and the rear motor can independently control the rotating speed and the rotating direction of the rotating shafts, combined machining is supported, and the feeding mechanism is simple, convenient and small in size.

Description

Technical Field

[0001] The present invention relates to the technical field of spindle motors, and particularly relates to a dual-rotor spindle motor. Background Art

[0002] A spindle motor is a special motor designed for high-precision and high-speed rotational motion, and is widely used in fields such as numerical control machine tools, precision machining, and semiconductor equipment. It is a direct drive or transmission device that converts electrical energy into high-speed rotational mechanical energy, and directly drives loads such as cutting tools and grinding wheels.

[0003] Conventional electric spindles and motors have fixed output shafts, with simple functions. In the field of composite machining, multiple spindle motors are required, resulting in a large machine structure and weight, and high manufacturing costs.

[0004] In the fields of machining and precision manufacturing, the axial feed mechanism of the spindle is the core module that determines the compactness, dynamic response, and cost-effectiveness of the equipment. The feed schemes of traditional mechanical spindles or electric spindles mainly use carriage lead screw mechanisms or bearing transition connection structures, and their technical frameworks have the following systematic bottlenecks: 1. Mechanical redundancy and space inefficiency: The carriage lead screw requires multiple layers of nested guide rails and support components, with redundant axial length (usually accounting for 30%-50% of the total spindle length), resulting in a bloated overall machine size; although the bearing transition structure can alleviate rigid impacts, additional connecting components such as couplings and flange plates need to be configured, further occupying mechanical space. 2. Limited dynamic performance: The friction loss and backlash problems of lead screw transmission are significant, and crawling phenomena are likely to occur during high-speed response (precision loss reaches ±5μm at the critical speed), and it has a strong dependence on lubrication and is prone to jamming under high-temperature conditions; the elastic deformation of the bearing transition mechanism will introduce phase delay, affecting the real-time performance of micron-level feeding. 3. Contradiction between cost and adaptability: The manufacturing costs of high-precision ball screws and customized bearing components account for up to 40%, but their drive sources are only compatible with rotary motors or hydraulic motors, and it is difficult to be compatible with new power forms such as pneumatic and linear motors, restricting the modular expansion ability of the equipment. Summary of the Invention

[0005] In order to overcome at least one of the technical problems existing in the prior art, the present invention provides a dual-rotor spindle motor. The front ends of the front motor shaft and the rear motor shaft can be simultaneously installed with tools for processing. The front motor and the rear motor can independently control the rotation speed and direction of their respective shafts, support composite machining, and the feed mechanism is simple and convenient, with a small volume.

[0006] A dual-rotor spindle motor includes a front motor and a rear motor. Both the front motor and the rear motor include a stator, a front cover installed at the front end of the front motor, and a rear cover installed at the rear end of the rear motor. The front motor and the rear motor are axially and coaxially butted through a middle cover to form a dual-rotor independent drive structure. The front motor shaft is a hollow shaft body and axially penetrates. Its rear end is connected to the middle cover through a first bearing, and its front end extends outside the front cover and is supported by a second bearing. The rear motor shaft is coaxially nested in the inner cavity of the front motor shaft. Its front end extends outside the front motor shaft and a clearance fit sliding sleeve is provided between it and the front motor shaft. The rear motor shaft is connected to the middle cover and the rear cover through cylindrical roller bearings, and the extended inner ring of the cylindrical roller bearing is fixedly installed on the rear motor shaft. Tool clamping seats can be installed at the front ends of both the front motor shaft and the rear motor shaft at the same time. The front motor and the rear motor can independently control the rotation speed and direction of their respective shafts. It also includes a magnetic coupling feeding mechanism that can drive the rear motor shaft to move axially synchronously when the rear motor shaft rotates. The magnetic coupling feeding mechanism includes a feeding shaft coaxially arranged with the rear motor shaft. Ball grooves are correspondingly opened on the end faces of the rear motor shaft and the feeding shaft close to each other, and spheres are placed in each ball groove. Compression covers are sleeved on the outer walls of the rear motor shaft and the feeding shaft close to each other, and the two compression covers are kept in a non-contact state. Axially penetrating ball holes are opened on each compression cover, and the positions of the ball holes correspond to those of the ball grooves. The compression cover restricts the spheres in the area between the ball grooves and the ball holes, and part of the outer walls of the two spheres protrude outside the ball holes and contact each other. Opposite-pole magnetic steels are installed at the close ends of the two compression covers, and the two magnetic steels are kept in a non-contact state.

[0007] In some embodiments, axially protruding socket shafts are correspondingly provided on the adjacent end faces of the two tool clamping seats, and an axially telescopic bellows is sleeved between the two socket shafts. The socket shafts and the bellows are rotatably connected. The axial pre-compression amount of the bellows is 8%-12% of the total length, and the axial tension is maintained by the elastic restoring force.

[0008] In some embodiments, screw threads for threaded connection with the compression cover are provided on the outer walls of the rear motor shaft and the feeding shaft close to each other. At least one fastener is installed on the outer wall of the compression cover, and the fastener fixes the two compression covers corresponding to the rear motor shaft and the feeding shaft in the radial direction.

[0009] In some embodiments, the magnetic steel is in a ring shape, and axially protruding positioning shafts are provided on the end faces of the two compression covers. The magnetic steel is sleeved on the positioning shafts. It also includes at least two regularly distributed locking parts, and the locking parts fix the two magnetic steels corresponding to the rear motor shaft and the feeding shaft in the axial direction.

[0010] In some embodiments, a flange is installed on the periphery of the magnetic coupling feeding mechanism. One end of it is coaxially connected to the rear cover, and the other end is coaxially connected to a cylinder. The cylinder is used to drive the feeding shaft to move axially back and forth.

[0011] In some embodiments, the outer wall of the sliding sleeve is in interference fit with the inner wall of the front motor rotating shaft, and the sliding sleeve is slidably sleeved on the rear motor rotating shaft; the extended inner rings of the cylindrical roller bearings extend axially and are in interference fit with the rear motor rotating shaft. The axial length of the extended inner ring is at least twice the axial length of the outer ring. The extended inner ring can provide a longer rolling surface for the rollers, enabling the rear motor rotating shaft to effectively support and perform sliding feed within the feed stroke range.

[0012] Additional aspects and advantages of the present invention will be given in the following description. Some will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0014] Figure 1 is the front perspective structural schematic diagram of the present application;

[0015] Figure 2 is the rear perspective structural schematic diagram of the present application;

[0016] Figure 3 is the front structural schematic diagram of the present application;

[0017] Figure 4 is Figure 3 the sectional structural schematic diagram of

[0018] Figure 5 is Figure 4 the enlarged view at A in

[0019] Figure 6 is Figure 4 the enlarged view at B in

[0020] Figure 7 is the front structural schematic diagram of the magnetic coupling feed mechanism;

[0021] Figure 8 is Figure 7 the sectional structural schematic diagram of

[0022] Figure 9 is Figure 7 the structural schematic diagram of

[0023] Figure 10 is the three-dimensional structural schematic diagram of the magnetic coupling feed mechanism;

[0024] Figure 11 is the sectional structural schematic diagram of the cylindrical roller bearing and the rear motor rotating shaft;

[0025] Figure 12It is a three-dimensional structural schematic diagram of a cylindrical roller bearing and the rear motor rotating shaft.

[0026] Reference numerals:

[0027] Front motor 1, rear motor 2, stator 3, middle cover 4, front motor rotating shaft 5,

[0028] First bearing 6, second bearing 7, rear motor rotating shaft 8, sliding sleeve 9, cylindrical roller

[0029] bearing 10, extended inner ring 100, outer ring 101, roller 102, front cover 11,

[0030] tool clamping seat 12, magnetic coupling feeding mechanism 13, feeding shaft 14, ball groove

[0031] 15, sphere 16, gland 17, ball hole 18, magnet 19, socket shaft 20, wave

[0032] corrugated pipe 21, rear cover 22, thread 23, fastener 24, positioning shaft 25, locking

[0033] member 26, flange 27, cylinder 28. Detailed implementation manners

[0034] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0035] In the description of the present invention, it should be understood that for the orientation description, such as the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0036] In the description of the present invention, the meaning of "several" is one or more, the meaning of "multiple" is two or more, and the understanding of "greater than", "less than", "exceeding", etc. does not include the present number, and the understanding of "above", "below", "within", etc. includes the present number. If the first and second are described only for the purpose of distinguishing technical features, they should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0037] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Referring to Figures 1 - 12 , a dual-rotor spindle motor includes a front motor 1 and a rear motor 2. Both the front motor 1 and the rear motor 2 include a stator 3, a front cover 11 installed at the front end of the front motor 1, and a rear cover 22 installed at the rear end of the rear motor 2. The front motor 1 and the rear motor 2 are axially coaxially docked through a middle cover 4 to form a dual-rotor independent drive structure; the front motor shaft 5 is a hollow shaft body and axially penetrates. Its rear end is connected to the middle cover 4 through a first bearing 6, and its front end extends outside the front cover 11 and is supported by a second bearing 7. The first bearing 6 and the second bearing 7 can be deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings, etc.; the rear motor shaft 8 is coaxially nested in the inner cavity of the front motor shaft 5. Its front end extends outside the front motor shaft 5 and a clearance fit sliding sleeve 9 is provided between it and the front motor shaft 5. The rear motor shaft 8 is connected to the middle cover 4 and the rear cover 22 through a cylindrical roller bearing 10, and the extended inner ring 100 of the cylindrical roller bearing 10 is fixedly installed on the rear motor shaft 8; tool holders 12 can be installed at the front ends of both the front motor shaft 5 and the rear motor shaft 8, and the front motor 1 and the rear motor 2 can independently control the rotation speed and direction of their respective shafts; it further includes a magnetic coupling feeding mechanism 13, which can drive the rear motor shaft 8 to move axially synchronously when the rear motor shaft 8 rotates; the magnetic coupling feeding mechanism 13 includes a feeding shaft 14 coaxially arranged with the rear motor shaft 8. Ball grooves 15 are correspondingly formed on the end faces of the rear motor shaft 8 and the feeding shaft 14 near the ends, and spheres 16 are placed in each ball groove 15; gland plates 17 are sleeved on the outer walls of the rear motor shaft 8 and the feeding shaft 14 near the ends, and the two gland plates 17 are kept in a non-contact state; through holes 18 axially penetrating are formed on each gland plate 17, and the positions of the through holes 18 correspond to those of the ball grooves 15. The gland plates 17 limit the spheres 16 in the area between the ball grooves 15 and the through holes 18, and a part of the outer walls of the two spheres 16 protrude outside the through holes 18 and are in contact with each other; the double-ball contact forms a physical limit, suppressing the radial offset of the magnet 19 caused by vibration, eliminating the response lag of the magnetic coupling, achieving zero delay in power transmission, and the contact friction damping absorbs high-frequency vibration energy, enabling power transmission to be maintained through sphere contact even if the magnet 19 is accidentally demagnetized; opposite-pole magnets 19 are installed at the near ends of the two gland plates 17, and the two magnets 19 are kept in a non-contact state.

[0039] The hollow front motor shaft 5 and the rear motor shaft 8 achieve dynamic coupling through a sliding sleeve 9. The hollow shaft nested structure compresses the axial dimension by more than 40%, making it suitable for installation in narrow spaces. The two shafts can rotate independently at different speeds and in different directions, or rotate at the same speed and in the same direction. The front motor 1 can drive a high-torque grinding wheel through the front motor shaft 5 for rough machining. The rear motor shaft 8 of the rear motor 2 can synchronously drive a precision polishing wheel for fine finishing. The reverse thermal deformation generated by the differential speed of the double rotors can offset more than 60% of the axial elongation. The bellows 21 is used for sealing and preventing chips, ensuring synchronous operation of the double tools. The service life of the magnetic coupling mechanism reaches 2 million cycles, which is 5 times higher than that of the ball screw.

[0040] The feed shaft 14 can use any mechanism that can move axially forward and backward, such as a cylinder, a hydraulic cylinder, an electric device, a lead screw, etc., as the driving source, and it can rotate or not. Two spheres are correspondingly installed at the central position, and two gland covers correspondingly fix the two spheres on the rear motor shaft 8 and the feed shaft 14. Partial areas of the two spheres abut against each other, which can reduce the friction area and the rotational resistance of the rear motor shaft 8. The magnetic steel has strong magnetic force. The end faces of the two magnetic steels do not contact and maintain a small distance, and the magnetic polarities are opposite, which can ensure propulsion during the rotation of the rear motor shaft 8. When the feed shaft 14 moves forward, the rear motor shaft 8 moves forward synchronously; when the feed shaft 14 moves backward, the rear motor shaft 8 moves backward synchronously. The structural design of the two spheres and the two magnetic steels with opposite polarities can ensure that the rear motor shaft 8 retreats synchronously and moves forward and backward seamlessly during rotation.

[0041] This application solves the problems that a single motor cannot complete composite machining synchronously. For example, rough grinding and fine grinding need to be carried out step by step; it eliminates the repeated positioning error caused by multi-process switching, actively compensates for thermal deformation through the differential rotation of the double rotors, and the magnetic coupling feed mechanism realizes high-precision axial displacement, replacing the traditional ball screw.

[0042] In some embodiments, axially protruding socket shafts 20 are correspondingly provided on the adjacent end faces of the two tool holders 12. A bellows 21 that can axially expand and contract is sleeved between the two socket shafts 20. The socket shafts 20 and the bellows 21 are rotatably connected. The axial pre-compression amount of the bellows 21 is 8%-12% of the total length, and the elastic restoring force is used to maintain axial tension. The composite structure of the metal layer (such as 304 stainless steel) and the rubber layer (such as fluororubber) of the bellows 21 has good dynamic sealing performance. The 8%-12% pre-compression amount can balance the attenuation of the elastic force.

[0043] In some embodiments, screw threads 23 for threaded connection with the gland 17 are provided on the outer walls of the near ends of the rear motor rotating shaft 8 and the feed shaft 14; at least one fastener 24, preferably a set screw, is installed on the outer wall of the gland 17. The fastener 24 fixes the two glands 17 corresponding to the rear motor rotating shaft 8 and the feed shaft 14 radially to prevent loosening and plays a role in strengthening the fixation; the gland 17 is axially pre-tightened with the rotating shaft 8 and the feed shaft 14 through the screw threads 23. The fastener 24 applies a locking force of >500 N radially to eliminate the risk of thread loosening. The screw threads 23 bear 70% of the axial force, and the fastener 24 bears 30% of the radial force, optimizing the stress distribution. The gland 17 can be replaced only by loosening the fastener 24.

[0044] In some embodiments, the magnet steel 19 is in a circular ring shape. Axially protruding positioning shafts 25 are provided on the end faces of the two glands 17, and the magnet steel 19 is sleeved on the positioning shafts 25; further included are at least two regularly distributed locking members 26, preferably set screws. The locking members 26 fix the two magnet steels 19 corresponding to the rear motor rotating shaft 8 and the feed shaft 14 axially. The feed shaft 14 is the driving part, which can be driven to move axially by a cylinder 28, a linear motor, a hydraulic cylinder or a manual screw, etc.; the rear motor rotating shaft 8 is the driven part and is passively followed through the attracting force of the opposite poles (N-S poles) of the magnet steel 19; the positioning shafts 25 undertake radial positioning, and the locking members 26 solve axial displacement, improving the reliability compared with a single fixing method. At a rotational speed of 20,000 rpm, the radial runout of the magnet steel 19 is controlled within 0.005 mm, and the dynamic balance is good. The magnet steel 19 and the positioning shafts 25 form a standardized unit, supporting rapid adaptation to different power models.

[0045] In some embodiments, a flange 27 is installed on the periphery of the magnetic coupling feed mechanism 13. One end of the flange 27 is coaxially connected to the rear cover 22, and the other end is coaxially connected to the cylinder 28. The cylinder 28 is used to drive the feed shaft 14 to move axially back and forth. Driven by the cylinder 28, its pneumatic transmission response time <10 ms, which is 5-10 times faster than that of a servo motor; it has an anti-pollution ability, and its axial length is 40% shorter than that of a ball screw module, being more compact. It is directly coaxially integrated through the flange 27, saving lateral space.

[0046] In some embodiments, the outer wall of the sliding sleeve 9 is in interference fit with the inner wall of the front motor rotating shaft 5, and the sliding sleeve 9 is slidably sleeved on the rear motor rotating shaft 8; the extended inner rings 100 of the two cylindrical roller bearings 10 extend axially, and are in interference fit with the rear motor rotating shaft 8. The axial length of the extended inner ring 100 is at least twice the axial length of the outer ring 101. The extended inner ring 100 can provide a longer rolling surface for the rollers 102; the extended inner ring 100 is equivalent to a sliding sleeve, and the extended inner ring 100 and the motor rotating shaft 8 assembly can axially move and rotate relative to the rollers 102, enabling effective support and sliding feed of the rear motor rotating shaft within the feed stroke range.

[0047] The outer wall of the sliding sleeve 9 and the inner wall of the front motor rotating shaft 5 are in interference fit to form a rigid torque transmission interface, avoiding energy loss caused by relative sliding; the sliding sleeve 9 is slidably sleeved with the rear motor rotating shaft 8, allowing axial thermal expansion displacement, and at the same time realizing radial precise positioning through the extended inner ring 100 of the cylindrical roller bearing 10; the extended inner ring 100 (length ≥ 2 times the outer ring 101) provides an extended rolling surface for the rollers 102, reducing the risk of roller skew (especially at high speeds), and suppressing the radial vibration of the rear motor rotating shaft 8 through interference fit; the sliding sleeve design compensates for the axial thermal expansion difference during motor operation, and the interference-fitted bearing inner ring absorbs radial thermal stress through metal elastic deformation; solving the problems that traditional equal-length inner ring bearings are prone to generate gyroscopic effects due to short-range guidance of rollers at high speeds (>8000 rpm), resulting in vibration exceeding the standard, etc.

[0048] In some embodiments, the ball groove 15 is circular and concave, the sphere 16 is made of quenched alloy steel, and the magnet 19 is a neodymium iron boron permanent magnet; the circular and concave ball groove 15 can better fit the shape of the sphere 16, and the hardness of the quenched alloy steel material reaches 60-65 HRC (Rockwell hardness), which is 3 times higher than that of untreated steel, with the characteristics of ultra-high hardness, significantly extended fatigue life, and outstanding compressive strength. The neodymium iron boron magnet 19 (N52 grade) generates a 1.4T magnetic field, enhancing the axial pressure through the attraction of opposite poles; the sliding sleeve 9 is a copper sleeve, which has the advantages of self-lubrication, low friction, corrosion resistance, good thermal conductivity, vibration reduction and noise reduction; the extended inner ring is a steel sleeve, which has the advantages of high strength, wear resistance, low cost, strong load-bearing capacity, etc.

[0049] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should be considered as the scope described in this specification. Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A dual-rotor spindle motor, comprising a front motor and a rear motor, wherein the front motor and the rear motor both comprise a stator, a front cover mounted at the front end of the front motor, and a rear cover mounted at the rear end of the rear motor, wherein: The front motor and the rear motor are coaxially connected along the axial direction through the middle cover to form a dual-rotor independent drive structure; the front motor shaft is a hollow shaft body and axially through, its rear end is connected to the middle cover through the first bearing, and the front end extends to the outside of the front cover and is supported by the second bearing; the rear motor shaft is coaxially nested in the inner cavity of the front motor shaft, its front end extends to the outside of the front motor shaft and a clearance fitting sleeve is set between the front motor shaft, the rear motor shaft is connected to the middle cover and the rear cover through a cylindrical roller bearing, and the extended inner ring of the cylindrical roller bearing is fixedly installed on the rear motor shaft; the front ends of the front motor shaft and the rear motor shaft can be installed with a tool clamp at the same time, and the front motor and the rear motor can independently control the speed and direction of their respective shafts; it also includes a magnetic The coupling feed mechanism can drive the shaft to move synchronously along the axial direction when the rear motor shaft rotates; the magnetic coupling feed mechanism includes a feed shaft coaxially arranged with the rear motor shaft, and ball grooves are correspondingly opened on the end faces of the rear motor shaft and the feed shaft near the end, and a ball is placed in each ball groove; a pressure cover is sleeved on the outer wall of the rear motor shaft and the feed shaft near the end, and the two pressure covers are kept in a non-contact state; each pressure cover is opened with a ball hole that passes through in the axial direction, and the position of the ball hole corresponds to the ball groove, and the pressure cover restricts the ball to the area between the ball groove and the ball hole, and part of the outer walls of the two spheres protrude out of the ball hole and contact each other; magnets with different poles are installed at the near ends of the two pressure covers, and the two magnets are kept in a non-contact state.

2. The dual-rotor spindle motor according to claim 1, characterized in that: Axially protruding sleeve shafts are correspondingly arranged on the adjacent end faces of the two tool clamping seats, and an axially retractable bellows is sleeved between the two sleeve shafts. The sleeve shaft and the bellows are rotationally connected. The axial pre-compression of the bellows is 8%-12% of the total length, and the axial tension is maintained by using elastic restoring force.

3. The dual-rotor spindle motor according to claim 1 or 2, characterized in that: The outer walls of the rear motor shaft and the feed shaft near the end are both provided with screw threads for threaded connection with the gland; at least one fastener is installed on the outer wall of the gland, and the fastener fixes the two glands to the rear motor shaft and the feed shaft in the radial direction.

4. The dual-rotor spindle motor according to claim 3, characterized in that: The magnet is in the shape of a circular ring, and an axially protruding positioning shaft is provided on the end faces of the two pressure covers, and the magnet is sleeved on the positioning shaft; it also includes at least two regularly distributed locking parts, which axially fix the two magnets to the rear motor shaft and the feed shaft.

5. The dual-rotor spindle motor according to claim 4, characterized in that: A flange is installed on the periphery of the magnetic coupling feeding mechanism, one end of which is coaxially connected to the rear cover, and the other end is coaxially connected to the cylinder. The cylinder is used to drive the feeding shaft to move forward and backward along the axial direction.

6. The dual-rotor spindle motor according to claim 1 or 2, characterized in that: The outer wall of the sleeve is interference fit with the inner wall of the front motor shaft, and the sleeve is slidingly sleeved with the rear motor shaft; the extended inner ring of each cylindrical roller bearing extends axially and is interference fit with the rear motor shaft, and the axial length of the extended inner ring is at least twice the axial length of the outer ring. The extended inner ring can provide a longer rolling surface for the roller, so that the rear motor shaft can be effectively supported and slidably fed within the feed stroke range.

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