Novel permanent magnet synchronous double-shaft type grinding electric spindle

Abstract

The invention discloses a novel permanent magnet synchronous double-shaft type grinding electric spindle, which relates to the technical field of machining, and comprises a driving shaft and a driven shaft, the driving shaft is provided with a rear machine body, a stator assembly, a rotor assembly, an upper bearing assembly, an aluminum water jacket and a lower bearing gland, and the driven shaft is integrally arranged at the lower end of the driving shaft. The driven shaft comprises a front machine body, a coupler, a driven bearing assembly, a dustproof cover, a dustproof cap assembly and a grinding wheel assembly. According to the double-shaft type grinding electric spindle, the rigidity is improved by optimizing the bearing span, the double shafts are connected through the plum blossom type elastic coupler buffer pad, the deep hole grinding integrated forming technology is achieved, deep holes within 300 mm can be machined at a time, meanwhile, the efficiency and the power density are improved through the permanent magnet synchronous motor, the spindle is designed to be provided with a cooling liquid channel, and a cutter is cooled in real time; machining precision is improved, space and cost are saved, and the performance and the service life of the motorized spindle are comprehensively improved.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical processing, in particular to a novel permanent magnet synchronous double-axis grinding electric spindle. Background Art

[0002] With the development and application of new technologies, the efficiency, precision and processing range of grinding have been significantly improved in recent years. Grinding plays an extremely important role in the efficient and high-precision processing of difficult-to-process materials, and various new grinding technologies, new processes and finished products emerge in an endless stream. The grinding electric spindle is the core functional component of high-precision grinding equipment. The dynamic and static performance of the spindle axis directly determines the technical performance indicators of high-precision grinding equipment and is related to the final accuracy of manufacturing and processing.

[0003] In the prior art, the conventional grinding spindle often adopts an external motor, driven by a high-frequency motor, and uses a transmission mechanism to transmit the motor power to the spindle to achieve grinding. The introduction of the transmission mechanism in the precision grinding system will lead to a decrease in the efficiency of the whole machine, an extension of the system response time and a decrease in the processing accuracy of the whole machine; at the same time, the system integration of this method is relatively poor, the volume is relatively large, and a large number of matching errors are introduced in the manufacturing process, which is not conducive to the precision of high-precision grinding equipment; in addition, in the prior art, high-precision deep hole grinding, due to the long length of the deep hole spindle, when the internal circle is ground, the grinding wheel vibrates greatly, and the heat at the shaft end is transmitted to the grinding wheel, causing the bearing at the grinding wheel to be easily damaged, and it cannot meet long-term stable production; at the same time, during the rotation process of the spindle, the bearing needs to bear the radial load of the external body. Since the body is a circular ring structure, the radial stiffness of the spindle will drop sharply, which will cause the tool to let down and vibration during deep hole grinding, thereby reducing the grinding accuracy and failing to meet high-precision processing requirements. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a novel permanent magnet synchronous dual-axis grinding electric spindle, which solves the problems raised by the above-mentioned background technology.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a new type of permanent magnet synchronous dual-axis grinding electric spindle, including a driving shaft and a driven shaft, the driving shaft is provided with a rear body, a stator assembly, a rotor assembly, an upper bearing assembly, an aluminum water jacket and a lower bearing gland, the driven shaft is arranged as a whole at the lower end of the driving shaft, and the driven shaft includes a front body, a coupling, a driven bearing assembly, a dust cover, a dust cap assembly and a grinding wheel assembly.

[0006] Furthermore, a bearing chamber is provided at the lower part of the rear body of the driving shaft, an angular contact ball bearing in a DT combination is provided in the bearing chamber, and a lower bearing pressure cover for fixing the bearing is provided at the lower part of the angular contact ball bearing.

[0007] Furthermore, a receiving cavity is recessed in the middle of the rear body, the stator assembly is slidably fitted in the receiving cavity and fixed by machine screws; an upper bearing assembly is connected and fixed to the upper opening of the rear body, and an aluminum water jacket is fixed to the upper part of the upper bearing assembly.

[0008] Furthermore, a rotor assembly is arranged below the aluminum water jacket, and the rotor assembly passes through the middle through holes of the aluminum water jacket, the upper bearing assembly, the stator assembly, and the lower bearing gland.

[0009] Furthermore, the front body is a variable cross-section cylindrical structure and is T-shaped. The front body flange shaft is provided with a plurality of liquid inlets, which are interconnected with the radial liquid inlet holes and axial liquid holes of the front body and are connected to the water spray holes at the bottom of the dust cap.

[0010] Furthermore, the rear body is provided with a cooling mechanism, which consists of a water inlet, a water outlet and a cooling channel. The cooling channel includes a plurality of water channel holes and waist-shaped water channel grooves. The water channel holes and waist-shaped water channel grooves exist independently and are distributed in a ring shape.

[0011] Furthermore, the rotor assembly includes a shaft core and a rotor core. The shaft core shaft body has bearing locking threads on the upper and lower outer walls, a rotating shaft section is provided in the middle, and the rotor core is installed on the rotating shaft section. The outer wall of the rotor core is provided with a plurality of circular arc grooves, and permanent magnets are mounted on the circular arc grooves.

[0012] Furthermore, a bearing locking front nut and a bearing locking rear nut are provided on the upper and lower outer walls of the coupling shaft, a plum blossom groove structure is provided on the upper part of the coupling, and a plum blossom-shaped elastic buffer pad is provided in the plum blossom groove structure of the coupling.

[0013] Furthermore, the dust cap assembly and the dust cover together form a dustproof mechanism, the dust cap assembly includes a dust cap and an insert, the dust cap is provided with a concave mounting cavity just accommodating the insert, the insert is interference fit in the concave mounting cavity, and the lower part of the dust cap is provided with a plurality of evenly distributed water spray holes.

[0014] Furthermore, the grinding wheel assembly is arranged at the lower part of the coupling, including a grinding wheel frame, a grinding wheel, a pressure plate and a fixing nut. The grinding wheel is locked on the coupling through the fixing nut and rotates synchronously with the coupling.

[0015] The present invention provides a new type of permanent magnet synchronous dual-axis grinding electric spindle. Compared with the prior art, it has the following beneficial effects: 1. The front overhang has a great influence on the comprehensive stiffness of the spindle assembly, so the spindle structure design should be reduced as much as possible, while the span has a non-unidirectional influence on the comprehensive stiffness. If the span is too large or too small, the stiffness of the spindle will be reduced. Therefore, the optimal span that satisfies the minimum fine deflection condition of the front end of the spindle needs to be taken. The present invention uses finite element analysis software (such as Ansys) to analyze the material properties of the structure, and combines numerical analysis methods such as the transfer matrix method to calculate the frequency and vibration mode of each order of the electric spindle. The first-order natural frequency and vibration mode of the spindle modal inherent characteristic analysis are used as the objective function to optimize the bearing span of the spindle. The dual-axis shaft system structure designed by the present invention has a longer bearing span and stiffness.

[0016] 2. The double shafts are connected by a plum blossom-shaped elastic coupling buffer pad. The manufacturing material of the plum blossom-shaped elastic coupling buffer pad is polyurethane. This plum blossom-shaped elastic coupling buffer pad is installed in the coupling, which can play the role of connecting transmission and transmit power between the two couplings. It also has a certain rebound effect. When force acts on its petals, it can play a certain role in slowing down the rebound, so it also plays a buffering role. It can compensate for the relative offset of the two shafts and has the characteristics of no lubrication and easy maintenance. At the same time, the elastomer buffer pad made of polyurethane material also has a long service life, thereby increasing the service life of the main shaft system.

[0017] 3. With deep hole grinding integrated molding technology, the grinding depth of ordinary built-in grinding electric spindles is generally within 100mm, and it needs to be processed in multiple times. However, with the continuous improvement of modern processing technology, the ordinary grinding depth can no longer meet the processing requirements. Deep hole grinding with a depth of 100mm, 200mm, and 300mm or more has become a topic of current processing. And ordinary electric spindles cannot meet this processing requirement. The grinding depth of ordinary electric spindles is mainly determined by the size of the electric spindle shaft end plus the size of the grinding connecting rod. The dual-axis grinding electric spindle provided by this project has the technical feature of deep hole grinding integrated molding. By adding a grinding spindle extension structure, the processing depth of the grinding electric spindle can be extended, so that the grinding electric spindle can process deep holes within 300mm, and can achieve one-time processing without repeated clamping, saving processing time and cost.

[0018] 4. Use permanent magnet synchronous motor: Using permanent magnets to provide excitation makes the motor structure simpler, reduces processing and assembly costs, and eliminates collector rings and brushes that are prone to problems, thereby improving the reliability of motor operation. Because no excitation current is required and there is no excitation loss, the efficiency and power density of the motor are improved.

[0019] 5. The coolant of the spindle is provided by the coolant channel of the spindle itself when it is working. The coolant is transported to the center of the grinding head from the rear end of the spindle, instead of adding external cooling equipment. This design can not only cool the tool in real time when the spindle is working, improve the processing accuracy and extend the service life of the grinding head; at the same time, it can reduce the installation space, save processing costs and improve economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a cross-sectional view of the overall internal structure of the present invention.

[0021] Figure 2 It is a schematic diagram of the axonometric measurement of the rear body of the present invention.

[0022] Figure 3 It is a schematic diagram of the axonometric measurement of the front body of the present invention.

[0023] Figure 4 This is an axonometric schematic diagram of the rotor structure of the present invention.

[0024] Figure 5 It is an axonometric schematic diagram of the dust cap assembly of the present invention.

[0025] Figure 6 It is a cross-sectional view of the internal structure of the dust cap assembly of the present invention.

[0026] In the figure: 1. driving shaft; 2. driven shaft; 3. rear body; 4. stator assembly; 5. rotor assembly; 6. upper bearing assembly; 7. aluminum water jacket; 8. lower bearing gland; 9. angular contact ball bearing; 10. machine screw; 11. front body; 12. coupling; 13. driven bearing assembly; 14. dust cover; 15. dust cap assembly; 16. grinding wheel assembly; 17. radial liquid inlet hole; 18. axial liquid hole; 19. water spray hole; 20. water inlet; 21. water outlet; 22. cooling channel; 23. water channel hole; 24. waist-shaped water channel groove; 25. water channel gasket; 26. core base; 27. insulator Edge plate; 28. Coil winding; 29. ​​Shaft core; 30. Rotor core; 31. Shaft core front nut; 32. Shaft core rear nut; 33. Plum blossom groove structure; 34. Bearing locking front nut; 35. Bearing locking rear nut; 36. Plum blossom elastic buffer pad; 37. Cylindrical petal; 38. Bearing seat; 39. Bottom plate; 40. Upper bearing spacer; 41. Dustproof mechanism; 42. Dustproof cap; 43. Insert; 44. Concave mounting cavity; 45. Diverter groove; 46. Axial air inlet hole; 47. Radial air hole; 48. Water spray hole; 49. Grinding wheel frame; 50. Grinding wheel; 51. Pressure plate; 52. Fixing nut. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] See also Figure 1-4 The present invention provides a technical solution: a new type of permanent magnet synchronous double-axis grinding electric spindle, including a driving shaft 1 and a driven shaft 2, wherein the driving shaft 1 includes a rear body 3, a stator assembly 4, a rotor assembly 5, an upper bearing assembly 6, an aluminum water jacket 7, and a lower bearing cover 8. A bearing chamber is provided at the lower part of the rear body 3, and an angular contact ball bearing 9 in a DT combination is provided in the bearing chamber. A lower bearing cover 8 for fixing the bearing is provided at the lower part of the angular contact ball bearing 9. An accommodating cavity is concavely provided at the middle part of the rear body 3, and the stator assembly 4 is slidably fitted in the accommodating cavity and fixed by a machine screw 10. An upper bearing assembly 6 is connected and fixed at the upper opening of the rear body 3, and an aluminum water jacket 7 is fixed at the upper part of the upper bearing assembly 6. A rotor assembly 5 is provided below the aluminum water jacket 7, and the rotor assembly 5 passes through the middle through holes of the aluminum water jacket 7, the upper bearing assembly 6, the stator assembly 4, and the lower bearing cover 8.

[0029] The driven shaft 2 is integrally arranged at the lower end of the driving shaft 1. The driven shaft 2 includes a front body 11, a coupling 12, a driven bearing assembly 13, a dust cover 14, a dust cap assembly 15 and a grinding wheel assembly 16. The flange end of the front body 11 is fixedly connected to the rear body 3 by screws. The lower end ring surface and the upper end ring surface of the front body 11 are both provided with a driven bearing assembly 13. The lower end of the front body 11 is provided with a dust cover 14, a dust cap assembly 15 and a grinding wheel assembly 16 in sequence. The coupling 12 is passed through the middle through hole of each of the front body 11, the driven bearing assembly 13, the dust cover 14 and the dust cap assembly 15.

[0030] The front body 11 is a variable cross-section cylindrical structure and is T-shaped. The flange shaft of the front body 11 is provided with a plurality of liquid inlets, which are connected to the radial liquid inlet holes 17 and the axial liquid through holes 18 of the front body 11, and are connected to the water spray holes 19 at the bottom of the dust cap.

[0031] The rear body 3 is provided with a cooling mechanism, which is composed of a water inlet 20, a water outlet 21 and a cooling channel 22. The cooling channel 22 includes a plurality of water channel holes 23 and a waist-shaped water channel groove 24. The water channel holes 23 and the waist-shaped water channel groove 24 exist independently and are distributed in a ring shape. The cooling water channel holes 23 are interconnected through the waist-shaped water channel groove 24 to form a circulating cooling system. The circulating water channel sealing at both ends of the rear body 3 is achieved by providing a water channel gasket 25 in the waist-shaped water channel groove 24. The cross-sectional shape of the water channel gasket 25 is consistent with that of the waist-shaped water channel groove 24. The water channel gasket 25 is fixed by evenly applying AB glue to ensure that the coolant does not overflow when the spindle is working.

[0032] The stator assembly 4 is positioned through the positioning holes of the rear housing 3 and the external screws 10, limiting its axial and radial movement space. The stator assembly 4 is composed of a cylindrical iron core base 26, insulating plates 27 respectively arranged at both ends of the iron core base 26, and coil windings 28 connected to both ends of the insulating plates. The iron core base 26 is formed by laminating a number of silicon steel sheets of equal thickness, and its inner cavity is provided with slot wedges distributed in an annular array. The winding is wound by a number of enameled wires of equal diameter and embedded in the slot wedges. A PTC-130 thermistor capable of detecting temperature is also embedded in the stator winding part.

[0033] The rotor assembly 5 includes a shaft core 29 and a rotor core 30. The shaft core 29 has a bearing locking thread on the upper and lower sides of the shaft body. The locking thread is provided with a shaft core front nut 31 and a shaft core rear nut 32. The shaft core front nut 31 and the shaft core rear nut 32 lock the angular contact ball bearing 9 through threads. A rotating shaft section is provided in the middle, and the rotor core 30 is installed on the rotating shaft section. The rotor assembly 5 is provided with excitation by a permanent magnet. The outer wall of the rotor core 30 is provided with a plurality of arc grooves. A groove rib is provided between two adjacent arc grooves. The arc groove is equipped with a permanent magnet. The inner and outer walls of the permanent magnet are both arcs. The thickness of the permanent magnet gradually decreases from the middle to the two sides. An outer protective sleeve is interference-fitted on the outer arc of the permanent magnet, and an insulating coating is provided on the outer arc of the permanent magnet. The inner arc of the permanent magnet is the same shape as the arc groove of the rotor core. One or more permanent magnets are installed in each arc groove of the rotor core 30. A plum blossom groove structure 33 is provided at the lower part of the shaft core 29.

[0034] The outer wall of the shaft of the coupling 12 is provided with a front bearing locking nut 34 and a rear bearing locking nut 35, which can be used to tighten the bearing. The upper part of the coupling 12 is provided with a plum blossom groove structure 33, and a plum blossom elastic buffer pad 36 is arranged in the coupling plum blossom groove structure 33. The plum blossom elastic buffer pad 36 includes a cylinder and a cylindrical petal 37 arranged along the cylinder in an annular manner. The cylindrical petal 37 and the cylinder are formed as a whole by casting. The manufacturing material of the plum blossom elastic plum blossom elastic buffer pad 36 is polyurethane. The coupling 12 is matched with the shaft core 29 through the plum blossom groove structure 33 and rotates synchronously with the shaft core 29.

[0035] The upper bearing assembly 6 includes a bearing seat 38, a bottom plate 39, an upper bearing spacer 40, and a plurality of angular contact ball bearings 9 stacked on each other in the inner cavity of the bearing seat. The bearing seat 38 and the bottom plate 39 are fixed by screws. This combined structure makes processing easy, loading and unloading convenient, and can better adjust the axial stability of the spindle.

[0036] A step is provided at the lower part of the aluminum water jacket 7, which can be just embedded in the upper part of the inner cavity of the bearing seat 38. The upper end face of the aluminum water jacket 7 is provided with a cooling interface and a power main line interface for cooling. The aluminum water jacket 7 is an aluminum structure and has undergone a hard anodizing process, so it has a good anti-oxidation and anti-corrosion effect.

[0037] The dustproof mechanism 41 includes a dustproof cap assembly 15 and a dustproof cover 14. The lower part of the dustproof cover 14 is provided with a labyrinth structure that cooperates with the bearing locking front nut 34. The dustproof cap assembly 15 includes a dustproof cap 42 and an insert 43. The dustproof cap 42 is provided with a concave mounting cavity 44 that just accommodates the insert. The insert 43 is interference-fitted in the concave mounting cavity 44 and assembled together by laser welding. The insert 43 is provided with an annular confluence groove on one side that cooperates with the concave mounting cavity 44, and a plurality of diverter grooves 45 that are evenly distributed and extend radially along the inner wall thereof are provided on the other side. The diverter grooves 45 all extend to the annular confluence groove and are connected thereto. The confluence grooves are connected to the axial air inlet 46 and the radial air through hole 47 of the dustproof cap. The lower part of the dustproof cap 42 is provided with a plurality of evenly distributed water spray holes 48. The water spray holes 48 spray coolant in a parabolic shape to cool the processing tool in real time, and have a good cooling effect.

[0038] The grinding wheel assembly 16 is arranged at the lower part of the coupling 12 , and the grinding wheel assembly 16 includes a grinding wheel frame 49 , a grinding wheel 50 , a pressure plate 51 and a fixing nut 52 . The grinding wheel 50 is locked on the coupling 12 through the fixing nut 52 and rotates synchronously with the coupling 12 .

[0039] Working principle of the present invention: When three-phase alternating current is supplied to the stator assembly 4 of the permanent magnet synchronous motor, the rotating armature magnetomotive force and the armature magnetic field generated by the three-phase alternating current cut the stator coil winding 28 and generate an induced electromotive force in the stator coil winding 28 on the one hand; on the other hand, the electromagnetic force drags the rotor assembly 5 to rotate at the synchronous speed. The armature current also generates a stator winding leakage flux that only interlinks with the stator coil winding 28, and generates an induced leakage electromotive force in the stator coil winding 28. In addition, the magnetic field generated by the rotor permanent magnet also cuts the stator winding at the synchronous speed. Thereby generating a no-load electromotive force.

[0040] When the present invention is working, the front dust-proof air curtain air source is opened, and the compressed air that meets the requirements is connected from the air inlet of the aluminum water jacket 7, enters the dust cap 42 and maintains positive pressure, thereby preventing sewage, cutting chips, etc. outside the body from entering the main shaft 1, thereby greatly reducing the failure rate of the main shaft 1 during operation.

[0041] When the present invention is working, the coolant is introduced from the water inlet of the aluminum water jacket 7, the coolant enters the rear body 3 through the upper bearing assembly 6, and returns to the upper bearing assembly 6 after circulating around the rear body 3, and then flows out from the water outlet of the aluminum water jacket 7, taking away the heat generated by the friction when the motor is working and the bearing runs at high speed, thereby improving the processing accuracy and extending the service life of the main shaft 1.

[0042] When the present invention is working, a plurality of coolant inlets on the flange of the front body 11 are opened, and the coolant flows to the water spray hole at the bottom of the dust cap 42 through the axial liquid inlet hole and the radial liquid hole of the front body 11, and sprays out the coolant in a parabolic shape, so as to cool the processing tool in real time, have a good cooling effect, improve the processing accuracy, and extend the service life of the grinding head.

[0043] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Technical personnel in this industry can make some deformation and modifications under the inspiration of this technical solution. Any modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A new type of permanent magnet synchronous double-axis grinding electric spindle, characterized in that: The invention comprises a driving shaft (1) and a driven shaft (2), wherein the driving shaft (1) is provided with a rear body (3), a stator assembly (4), a rotor assembly (5), an upper bearing assembly (6), an aluminum water jacket (7) and a lower bearing gland (8), and the driven shaft (2) is integrally arranged at the lower end of the driving shaft (1), and the driven shaft (2) comprises a front body (11), a coupling (12), a driven bearing assembly (13), a dust cover (14), a dust cap assembly (15) and a grinding wheel assembly (16).

2. According to claim 1, a new type of permanent magnet synchronous dual-axis grinding electric spindle is characterized in that: A bearing chamber is provided at the lower part of the rear body (3) of the driving shaft (1), an angular contact ball bearing (9) in a DT combination is provided in the bearing chamber, and a lower bearing pressure cover (8) for fixing the bearing is provided at the lower part of the angular contact ball bearing (9).

3. A new type of permanent magnet synchronous dual-axis grinding electric spindle according to claim 1, characterized in that: The middle part of the rear body (3) is provided with a receiving cavity, the stator assembly (4) is slidably fitted in the receiving cavity and fixed by means of screws (10); an upper bearing assembly (6) is connected and fixed to the upper opening of the rear body (3), and an aluminum water jacket (7) is fixed to the upper part of the upper bearing assembly (6).

4. A new type of permanent magnet synchronous dual-axis grinding electric spindle according to claim 1, characterized in that: A rotor assembly (5) is disposed below the aluminum water jacket (7), and the rotor assembly (5) passes through the middle through holes of the aluminum water jacket (7), the upper bearing assembly (6), the stator assembly (4), and the lower bearing gland (8).

5. The novel permanent magnet synchronous dual-axis grinding electric spindle according to claim 1 is characterized in that: The front body (11) is a variable cross-section cylindrical structure in a T-shape. The flange shaft of the front body (11) is provided with a plurality of liquid inlets, the liquid inlets are connected to the radial liquid inlet holes (17) and the axial liquid holes (18) of the front body (11), and are connected to the water spray holes (19) at the bottom of the dust cap (42).

6. The novel permanent magnet synchronous dual-axis grinding electric spindle according to claim 1 is characterized in that: The rear body (3) is provided with a cooling mechanism, the cooling mechanism comprising a water inlet (20), a water outlet (21) and a cooling channel (22), the cooling channel (22) comprising a plurality of water channel holes (23) and waist-shaped water channel grooves (24), the water channel holes (23) and waist-shaped water channel grooves (24) existing independently and distributed in a ring shape.

7. A new type of permanent magnet synchronous dual-axis grinding electric spindle according to claim 4, characterized in that: The rotor assembly (5) comprises a shaft core (29) and a rotor core (30); the shaft core (29) is provided with bearing locking threads on the upper and lower outer walls of the shaft body, a rotating shaft section is provided in the middle, the rotor core (30) is mounted on the rotating shaft section, and the outer wall of the rotor core (30) is provided with a plurality of circular arc grooves, on which permanent magnets are mounted.

8. The novel permanent magnet synchronous dual-axis grinding electric spindle according to claim 1 is characterized in that: A bearing locking front nut (34) and a bearing locking rear nut (35) are provided on the upper and lower sides of the shaft outer wall of the coupling (12); a plum blossom groove structure (33) is provided on the upper part of the coupling (12); and a plum blossom-shaped elastic buffer pad (36) is provided in the plum blossom groove structure (33) of the coupling.

9. The novel permanent magnet synchronous dual-axis grinding electric spindle according to claim 1 is characterized in that: The dust cap assembly (15) and the dust cover (14) together form a dust protection mechanism (41). The dust cap assembly (15) comprises a dust cap (42) and an insert (43). The dust cap (42) is provided with a concave mounting cavity (44) that just accommodates the insert (43). The insert (43) is interference fit in the concave mounting cavity (44). A plurality of evenly distributed water spray holes (48) are provided at the bottom of the dust cap (42).

10. A new type of permanent magnet synchronous dual-axis grinding electric spindle according to claim 1, characterized in that: The grinding wheel assembly (16) is arranged at the lower part of the coupling (12), and comprises a grinding wheel frame (49), a grinding wheel (50), a pressure plate (51) and a fixing nut (52). The grinding wheel (50) is locked on the coupling (12) through the fixing nut (52) and rotates synchronously with the coupling (12).

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