CN112775447A

CN112775447A - Self-balancing electric spindle with automatic pre-tightening function

Info

Publication number: CN112775447A
Application number: CN202110008818.8A
Authority: CN
Inventors: 王展; 祁登红; 王子男; 张珂
Original assignee: Shenyang Jianzhu University
Current assignee: Shenyang Jianzhu University
Priority date: 2021-01-05
Filing date: 2021-01-05
Publication date: 2021-05-11

Abstract

The invention relates to a self-balancing electric spindle with automatic pre-tightening function, which consists of a spindle assembly, a shell assembly, an upper balance head assembly, a disc spring and lower balance head assembly, a bearing pre-tightening force automatic adjusting and bearing assembly, a cooling water system and a bearing lubricating system, wherein the upper balance head assembly is arranged on the shell assembly; the electric main shaft generates overheating and vibration phenomena along with the operation time, the load size, the cooling strength, the bearing abrasion and the change of the lubricating state, thereby influencing the processing precision and the product quality of mechanical equipment; the invention adopts the vibration sensor, the temperature sensor, the automatic bearing pretightening force adjusting mechanism, the upper balance head assembly, the lower balance head assembly, the spiral cable, the automatic controller, the cooling water system and the bearing lubricating system to cooperate to track and monitor the overheating and loosening states of the transmission part and automatically adjust the cooling intensity, the bearing pretightening force and the lubricating state, thereby prolonging the service life of the electric main shaft, avoiding the maintenance fault caused by stopping the operation of equipment and improving the product quality and the productivity.

Description

Self-balancing electric spindle with automatic pre-tightening function

Technical Field

The invention belongs to the technical field of electric spindles of machine tools, and particularly relates to a self-balancing electric spindle with automatic pre-tightening function.

Background

The electric spindle is a new technology for integrating a machine tool spindle and a spindle motor, and in recent years, more and more high-speed machine tools adopt the electric spindle to fully exert the advantages of compact structure, light weight, small inertia, low noise, fast response, high rotating speed, high power and the like.

The machining precision of the machine tool directly determines the machining quality of the part, so the running precision of the electric spindle must be ensured to ensure the machining quality of the part; the mass unbalance of the electric spindle is one of the most common faults, and the problem of the mass unbalance vibration of the electric spindle is solved by adopting a dynamic balance technology at present; the operation precision of the electric spindle is reduced due to the fact that the temperature of the electric spindle is increased during long-time high-speed operation, so that the machining precision of a machine tool is reduced, generally, the traditional adjusting pretightening force is only adjusted by a spring and needs to be stopped, overhauled and adjusted, and therefore not only is the machining quality influenced, but also the machining progress is influenced, and the productivity is reduced; in summary, how to ensure the normal operation of the electric spindle by using a way of automatically adjusting the pretightening force when the bearing of the electric spindle is deformed is a key problem to be solved.

Disclosure of Invention

A self-balancing electric main shaft with automatic pre-tightening function comprises a main shaft assembly, a shell assembly, an upper balance head assembly, a disc spring and lower balance head assembly, an automatic bearing pre-tightening force adjusting mechanism, a bearing assembly, an automatic balancing device, a cooling water system and a bearing lubricating system; the main shaft assembly comprises a main shaft, a first angular contact bearing, a second angular contact bearing, a bearing inner oil retainer ring, a bearing lubricating sleeve, an upper end cover, a switching sleeve, a bearing outer oil retainer ring, a rotor coil and a rotor fixing nut; installing a first angular contact bearing and a second angular contact bearing from the large-diameter end of a main shaft to a boss of the main shaft, wherein inner rings of the first angular contact bearing and the second angular contact bearing are in interference fit with the main shaft, outer rings of the first angular contact bearing and the second angular contact bearing are in interference fit with a first bearing fixing sleeve and a second bearing fixing sleeve, the first bearing fixing sleeve and the second bearing fixing sleeve are in interference fit with a transfer sleeve, an inner bearing oil retaining ring and a bearing lubricating sleeve are installed between the first angular contact bearing and the second angular contact bearing, an upper end cover and an outer bearing oil retaining ring are installed and fixed on the main shaft through screws, and then a rotor coil is installed on the main shaft from the other end of the main shaft and is fixed through a rotor fixing nut; the shell assembly comprises a shell, a switching sleeve, a first bearing fixing sleeve, a second bearing fixing sleeve, a stator-rotor oil slinger, a stator coil, a third bearing fixing sleeve and a fourth bearing fixing sleeve; installing a first bearing fixing sleeve and a second bearing fixing sleeve on the inner wall of the adapter sleeve, and installing a stator oil retainer ring, a rotor oil retainer ring, a third bearing fixing sleeve and a fourth bearing fixing sleeve on the inner wall of the shell; the upper balance head assembly comprises a main shaft assembly, a fastening screw and an upper balance head assembly, and the upper balance head assembly is fixedly connected with the end part of the main shaft by the fastening screw after the main shaft assembly is arranged in the shell assembly; the disc spring and lower balance head assembly comprises a disc spring, a disc spring fixing sleeve, a disc spring fastening screw, a lower balance head part fastening screw, an electric main shaft wiring port, a lower end cover and a main shaft; mounting a disc spring on a main shaft, fixedly mounting a disc spring fixing sleeve, a lower end cover and a lower end barrel opening of a shell by disc spring fastening screws, and arranging an electric main shaft wiring port on the lower end cover; the bearing pre-tightening force automatic adjusting and bearing assembly comprises a third corner contact bearing, a fourth corner contact bearing, a bearing inner oil retainer, a bearing lubricating sleeve, a spring, a piezoelectric ceramic column fixing seat, a piezoelectric ceramic column radial positioning disc, a first force transmission disc, a second force transmission disc, a temperature sensor and a bearing axial limiting nut; sequentially arranging a third angle contact bearing, an inner oil retainer ring of the bearing, a bearing lubricating sleeve and a fourth angle contact bearing between the main shaft and third and fourth bearing fixing sleeves, wherein the inner rings of the third angle contact bearing and the fourth angle contact bearing are in interference fit with the main shaft, the outer rings of the third angle contact bearing and the fourth angle contact bearing are in interference fit with the third and fourth bearing fixing sleeves, and sequentially arranging a temperature sensor, a second force transmission disc, a spring, a first force transmission disc, a piezoelectric ceramic column radial positioning disc and a piezoelectric ceramic column fixing seat between the main shaft and the third and fourth bearing fixing sleeves and connecting and limiting the temperature sensor, the second force transmission disc, the spring, the first force transmission disc, the piezoelectric; the piezoelectric ceramic column is arranged in a piezoelectric ceramic column fixing seat and is fixedly positioned by a piezoelectric ceramic column radial positioning disc, a spring is arranged between a first force transmission disc and a second force transmission disc in the bearing pre-tightening force automatic adjusting mechanism, one end of the piezoelectric ceramic column is in matched connection with a first force transmission disc hole shaft, the other end of the piezoelectric ceramic column penetrates through the piezoelectric ceramic column radial positioning disc provided with a piezoelectric ceramic column positioning hole to be in matched connection with a piezoelectric ceramic column fixing seat upper hole shaft, a temperature sensor is arranged on the second force transmission disc and is used for monitoring the temperature of a third and a fourth corner contact bearing in real time, the real-time monitored bearing temperature data is fed back to automatic control equipment, and then a control signal is output through the equipment to adjust the pre-tightening force; the number of the springs and the number of the piezoelectric ceramic columns are three, and the springs and the piezoelectric ceramic columns are uniformly distributed in the circumferential direction of the main shaft; the automatic balancing device consists of a vibration sensor, an automatic control device, an upper balancing head component and a lower balancing head component, wherein the vibration sensor is arranged at a position corresponding to a shell stator and rotor coil, the vibration sensor transmits the change of the vibration amplitude value to the automatic control device, and a monitoring device of the automatic balancing device starts a balancing head component and a lower balancing component of the automatic balancing device after receiving information to adjust the unbalance until the unbalance is balanced; the control instrument automatically controls the automatic pre-tightening and self-balancing of the electric spindle through electric connection; the cooling water system comprises a stator and rotor cooling water system and a bearing cooling water system, wherein the stator and rotor cooling water system consists of a stator and rotor cooling water channel, a stator and rotor cooling water channel annular groove outlet and a cooling water annular groove at the position, corresponding to the stator and rotor, of the inner wall of the shell, the stator and rotor cooling water channel is communicated with the stator and rotor cooling water annular groove, three cooling water annular grooves of the stator and rotor are provided with communicating channels, and the water supply strength of the stator and rotor cooling water system can be automatically adjusted through an external supply cooling system to carry out water cooling on the stator and rotor; the bearing cooling water system consists of a switching sleeve, a bearing cooling water channel, a cooling ring groove on a bearing fixing sleeve and a lower end cover, wherein the switching sleeve and the shell are provided with bearing cooling channels; a water inlet and a water outlet of a cooling water channel and a cooling water nozzle are arranged on the lower end cover; the bearing lubrication system comprises a switching sleeve, a shell, a first bearing lubrication slideway, a second bearing lubrication slideway, a first bearing lubrication sleeve and a second bearing lubrication sleeve, wherein the bearing lubrication slideways are arranged on the switching sleeve and the shell, a bearing lubrication channel on the switching sleeve directly reaches the positions of the first bearing lubrication sleeve and the second bearing lubrication sleeve, and a bearing lubrication channel on the shell directly reaches the position of the lubrication sleeve between a third bearing and a fourth bearing.

Drawings

FIG. 1 is a schematic structural view of a self-balancing electric spindle with automatic pre-tightening function according to the present invention;

fig. 2 is a view showing an automatic adjusting mechanism for bearing pretightening force of a self-balancing electric spindle with automatic pretightening.

In the figure, 1 adapting sleeve, 2 bearing cooling channels, 3 bearing cooling ring grooves, 4 first and second bearing fixing sleeves, 5 upper end covers, 6 bearing outer oil retaining rings, 7 fastening screws, 8 balance head parts, 9 main shafts, 10 positioning screws, 11 first angular contact bearings, 12 bearing inner oil retaining rings, 13 first and second bearing lubricating sleeves, 14 first bearing lubricating slide, 15 second angular contact bearings, 16 rotor coils, 17 stator oil retaining rings, 18 stator coils, 19 vibration sensors, 20 shells, 21 stator cooling water ring groove outlets, 22 rotor fixing nuts, 23 third angular contact bearings, 24 fourth angular contact bearings, 25 springs, 26 piezoelectric ceramic columns, 27 bearing axial limiting nuts, 28 stator cooling water channels, 29 lower end covers, 30 disc springs, 31 disc spring fixing sleeves, 32 disc spring fastening screws, 33 lower balance fastening screws, 34 electric main shaft assembly terminal ports, 35 lower balance head assemblies, 36 piezoelectric ceramic column fixing seats, 37 piezoelectric ceramic column radial positioning disks, 38 first force transmission disks, 39 second force transmission disks, 40 temperature sensors, 41 third and four bearing fixing sleeves.

Detailed Description

The invention is described in further detail below with reference to the figures and the specific embodiments.

A self-balancing electric spindle with automatic pre-tightening function comprises a spindle assembly, a shell assembly, an upper balance head assembly, a disc spring and lower balance head assembly, a bearing pre-tightening force automatic adjusting and bearing assembly, an automatic balancing device, a cooling water system and a bearing lubricating system; as shown in fig. 1, the spindle assembly includes a spindle 9, a first angular contact bearing 11, a second angular contact bearing 15, a bearing inner oil retainer 12, a bearing lubricating sleeve 13, an upper end cover 5, an adapter sleeve 1, a bearing outer oil retainer 6, a rotor coil 16, and a rotor fixing nut 22; installing a first angular contact bearing 11 and a second angular contact bearing 15 from the large-diameter end of a main shaft 9 to a boss of the main shaft 9, wherein inner rings of the first angular contact bearing 11 and the second angular contact bearing 15 are in over-hard interference fit with the main shaft 9, outer rings of the first angular contact bearing 11 and the second angular contact bearing 15 are in interference fit with a first bearing fixing sleeve 4 and a second bearing fixing sleeve 4, the first bearing fixing sleeve 4 and the second bearing fixing sleeve 4 are in interference fit with a switching sleeve 1, an inner bearing oil retainer ring 12 and a bearing lubricating sleeve 13 are installed between the first angular contact bearing 11 and the second angular contact bearing 15, an upper end cover 5 and an outer bearing oil retainer ring 6 are installed and fixed on the main shaft 9 through screws 10, and then a rotor coil 16 is installed on the main shaft 9 from the other end of the main shaft 9 and is fixed through a rotor fixing nut 22; the shell component comprises a shell 20, a switching sleeve 1, a first bearing fixing sleeve 4, a second bearing fixing sleeve 4, a stator oil slinger 17, a rotor oil slinger, a stator coil 18, a third bearing fixing sleeve 41 and a fourth bearing fixing sleeve 41; installing a first bearing fixing sleeve 4 and a second bearing fixing sleeve 4 on the inner wall of the adapter sleeve 1, sequentially installing a stator-rotor oil slinger 17 and a stator coil 18 on the inner wall of a shell 20, and then installing a third bearing fixing sleeve 41 and a fourth bearing fixing sleeve 41 on the inner wall of the shell 20; the upper balance head assembly comprises a main shaft assembly, a fastening screw 7 and an upper balance head assembly 8, the main shaft assembly is installed in the shell assembly, the upper balance head assembly is fixedly connected with the end part of the main shaft 9 through the fastening screw 7, and the disc spring and lower balance head assembly comprises a disc spring 30, a disc spring fixing sleeve 31, a disc spring fastening screw 32, a lower balance head assembly 35, a lower balance head assembly fastening screw 33, an electric main shaft wiring port 34, a lower end cover 29 and the main shaft 9; a disc spring 30 is arranged on the main shaft 9, a disc spring fixing sleeve 31, a lower end cover 29 and a lower end cylinder opening of the shell 20 are fixedly arranged by a disc spring fastening screw 32, and an electric main shaft wiring port 34 is arranged on the lower end cover 29; the bearing pre-tightening force automatic adjustment and bearing assembly comprises a third corner contact bearing 23, a fourth corner contact bearing 24, a bearing inner oil retainer ring 12, a bearing lubricating sleeve 13, a spring 25, a piezoelectric ceramic column 26, a piezoelectric ceramic column fixing seat 36, a piezoelectric ceramic column radial positioning disc 37, a first force transmission disc 38, a second force transmission disc 39, a temperature sensor 40 and a bearing axial limiting nut 27; sequentially arranging a third contact bearing 23, a bearing inner oil retainer ring 12, a bearing lubricating sleeve 13 and a fourth contact bearing 24 between a main shaft 9 and third and fourth bearing fixing sleeves 41, wherein the inner rings of the third contact bearing 23 and the fourth contact bearing 24 are in interference fit with the main shaft 9, the outer rings of the third contact bearing 23 and the fourth contact bearing 24 are in interference fit with the third and fourth bearing fixing sleeves 41, and the third contact bearing 23 and the fourth contact bearing 24 are made of wear-resistant, high-temperature-resistant and corrosion-resistant ceramic bearings; as shown in fig. 2, a temperature sensor 40, a second force transmission disc 39, a spring 25, a first force transmission disc 38, a piezoelectric ceramic column radial positioning disc 37 and a piezoelectric ceramic column fixing seat 36 are sequentially arranged between the main shaft 9 and a third and a fourth bearing fixing sleeves 41, and are connected and limited with the main shaft 9 by a bearing axial limiting nut 27; the piezoelectric ceramic column 26 is arranged in a piezoelectric ceramic column fixing seat 36 and is fixedly positioned by a piezoelectric ceramic column radial positioning disc 37, a spring 25 is arranged between a first force transmission disc 38 and a second force transmission disc 39 in the bearing pre-tightening force automatic adjusting mechanism, and in order to eliminate vibration generated in the running process of the electric main shaft, the spring 25 is endowed with certain load in the installation state, so that the connection tightness and reliability of the bearing are enhanced; one end of the piezoelectric ceramic column 26 is in fit connection with a hole shaft of the first force transmission disc 38, the other end of the piezoelectric ceramic column 26 penetrates through a piezoelectric ceramic column radial positioning disc 37 provided with a piezoelectric ceramic column positioning hole to be in fit connection with a hole shaft on a piezoelectric ceramic column fixing seat 36, a temperature sensor 40 is mounted on the second force transmission disc 39 and used for monitoring the temperature of a third and a fourth corner contact bearing in real time, feeding back the real-time monitored bearing temperature data to automatic control equipment, and outputting a control signal through the equipment to adjust the pretightening force; the number of the springs 25 and the number of the piezoelectric ceramic columns 26 are three, and the springs and the piezoelectric ceramic columns are uniformly distributed in the circumferential direction of the main shaft 9; the automatic balancing device consists of a vibration sensor 19, an automatic control device, an upper balancing head part 8, a lower balancing head part 35, a main shaft 9 and a spiral cable; the main shaft 9 is of a hollow structure and is used for mounting an upper balance head component 8, a lower balance head component 35 and a spiral cable, and two ends of the spiral cable are respectively in threaded connection with the upper balance head component 8 and the lower balance head component 35; a vibration sensor 19 is arranged at a position corresponding to a stator coil and a rotor coil of the shell 20, the vibration sensor 19 transmits the change of the vibration amplitude to automatic control equipment, and monitoring equipment of the automatic balancing device starts a balancing head assembly 8 and a lower balancing assembly 35 of the automatic balancing device after receiving information to adjust the unbalance until the unbalance is balanced; the control instrument automatically controls the automatic pre-tightening and self-balancing of the electric spindle through electric connection; the cooling water system comprises a stator and rotor cooling water system and a bearing cooling water system, wherein the stator and rotor cooling water system consists of a stator and rotor cooling water channel 28, a stator and rotor cooling water channel annular groove outlet 21 and a cooling water annular groove 3 at the position, corresponding to the stator and rotor, of the inner wall of the shell 20, the stator and rotor cooling water channel 28 is communicated with the stator and rotor cooling water annular groove 3, three cooling water annular grooves 3 of the stator and rotor are provided with communicating channels, and the water supply strength of the stator and rotor cooling water system can be automatically adjusted through an external supply cooling system to carry out water cooling on the stator and rotor; the bearing cooling water system consists of a transfer sleeve 1, a bearing cooling water channel 2, cooling ring grooves 3 on bearing fixing sleeves 4 and 41 and a lower end cover 29, wherein the transfer sleeve 1 and a shell 20 are provided with bearing cooling channels 2, the peripheries of a first bearing fixing sleeve 4, a second bearing fixing sleeve 4, a third bearing fixing sleeve 41 and a fourth bearing fixing sleeve 41 are provided with the bearing cooling ring grooves 3, the bearing cooling channels 2 on the transfer sleeve 1 are communicated with the cooling ring grooves 3 on the first bearing fixing sleeve 4 and the second bearing fixing sleeve 4, the bearing cooling channels 2 on the shell 20 are communicated with the bearing cooling ring grooves 3 on the third bearing fixing sleeve 41 and the fourth bearing fixing sleeve 41, the cooling ring grooves 3 on the bearing fixing sleeves 4 and 41 are provided with communicating channels, and the water supply strength of the bearing cooling water system can be automatically adjusted through an external supply; a water inlet and a water outlet of a cooling water channel and a cooling water nozzle are arranged on the lower end cover 29; the bearing lubrication system comprises a switching sleeve 1, a shell 20, a first bearing lubrication way 14, a second bearing lubrication way 14, a first bearing lubrication sleeve 13 and a second bearing lubrication sleeve 13, wherein the bearing lubrication ways 14 are arranged on the switching sleeve 1 and the shell 20, the bearing lubrication ways 14 on the switching sleeve 1 directly reach the positions of the first bearing lubrication way 13 and the second bearing lubrication way 13, the bearing lubrication ways 14 on the shell 20 directly reach the position of the lubrication sleeves between a third bearing and a fourth bearing, and the bearings are well lubricated and can effectively reduce heat generation.

The self-balancing electric spindle with the automatic pre-tightening function has the advantages that the electric spindle generates heating and vibration phenomena along with the running time of equipment, the load of the spindle, the change of cooling strength, the abrasion of a bearing and the change of a lubricating state; the invention automatically monitors the running environment of the bearing and the stator and the rotor of the electric main shaft through the temperature sensor and the vibration sensor, automatically controls the cooling water system, the lubricating system, the self-balancing device and the automatic adjustment of the bearing pretightening force by connecting external automatic control equipment through the wiring port of the electric main shaft, automatically adjusts the size of the cooling strength, automatically adjusts the bearing pretightening force and automatically adjusts the lubricating state, prolongs the service life of the electric main shaft, avoids the maintenance fault caused by the running of the stop equipment, and improves the product quality and the productivity.

Claims

1. A self-balancing electric spindle with automatic pre-tightening function comprises a spindle assembly, a shell assembly, an upper balance head assembly, a disc spring and lower balance head assembly, a bearing pre-tightening force automatic adjusting and bearing assembly, an automatic balancing device, a cooling water system and a bearing lubricating system; the main shaft assembly comprises a main shaft (9), a first angular contact bearing (11), a second angular contact bearing (15), a bearing inner oil retainer ring (12), a bearing lubricating sleeve (13), an upper end cover (5), a switching sleeve (1), a bearing outer oil retainer ring (6), a rotor coil (16) and a rotor fixing nut (22); the shell assembly comprises a shell (20), a switching sleeve (1), a first bearing fixing sleeve, a second bearing fixing sleeve, a third bearing fixing sleeve and a fourth bearing fixing sleeve (41); the upper balance head assembly comprises a main shaft assembly, a fastening screw (7) and an upper balance head assembly (8); the disc spring and lower balance head assembly comprises a disc spring (30), a disc spring fixing sleeve (31), a disc spring fastening screw (32), a lower balance head assembly fastening screw (33), an electric main shaft wiring port (34), a lower end cover (29) and a main shaft (9); the bearing pre-tightening force automatic adjustment and bearing assembly comprises a third corner contact bearing (23), a fourth corner contact bearing (24), a bearing inner oil retainer ring (12), a bearing lubricating sleeve (13), a spring (25), a piezoelectric ceramic column (26), a piezoelectric ceramic column fixing seat (36), a piezoelectric ceramic column radial positioning disc (37), a first force transmission disc (38), a second force transmission disc (39), a temperature sensor (40) and a bearing axial limiting nut (27); the automatic balancing device consists of a vibration sensor (19), automatic control equipment, an upper balancing head component (8), a lower balancing head component (35) and a spiral cable; the cooling water system comprises a switching sleeve (1), a bearing cooling channel (2), a bearing cooling annular groove (3), a stator and rotor cooling water channel (28), a stator and rotor cooling water channel outlet (21) and a lower end cover (29); the cooling water system comprises a stator cooling water channel (28), a rotor cooling water channel annular groove outlet (21) and a cooling water annular groove (3) at the position, corresponding to the stator and the rotor, of the inner wall of the shell (20), and is divided into a stator cooling water channel and a rotor cooling water channel and a bearing cooling water channel, wherein the bearing cooling water system comprises a switching sleeve (1), a bearing cooling water channel (2), a cooling annular groove (3) on a bearing fixing sleeve (4) and a bearing fixing sleeve (41) and a lower end cover (29); the bearing lubricating system comprises a switching sleeve (1), a shell (20), a first bearing lubricating slideway, a second bearing lubricating slideway (14), a first bearing lubricating sleeve and a second bearing lubricating sleeve (13).

2. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: the main shaft assembly is characterized in that a first angular contact bearing (11) and a second angular contact bearing (15) are installed to a boss of a main shaft (9) from a large-diameter end of the main shaft (9), inner rings of the first angular contact bearing (11) and the second angular contact bearing (15) are in interference fit with the main shaft (9), outer rings of the first angular contact bearing (11) and the second angular contact bearing (15) are in interference fit with a first bearing fixing sleeve and a second bearing fixing sleeve (4), the first bearing fixing sleeve and the second bearing fixing sleeve (4) are in interference fit with a switching sleeve (1), an inner bearing oil retaining ring (12) and a bearing lubricating sleeve (13) are installed between the first angular contact bearing (11) and the second angular contact bearing (15), an upper end cover (5) and a bearing outer oil retaining ring (6) are installed and fixed on the main shaft (9) through screws (10), and a rotor coil (16) is installed on the main shaft (9) from the other end of the main shaft (9), and is fixed by a rotor fixing nut (22).

3. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: the shell assembly is characterized in that the first bearing fixing sleeve (4) and the second bearing fixing sleeve (4) are installed on the inner wall of the adapter sleeve (1), the stator and rotor oil retainer (17) and the stator coil (18) are installed on the inner wall of the shell (20), and the third bearing fixing sleeve (41) and the fourth bearing fixing sleeve (41) are installed on the inner wall of the shell (20).

4. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: after the main shaft assembly is arranged in the shell assembly, the upper balance head assembly is fixedly connected with the end part of the main shaft (9) through a fastening screw (7).

5. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: and after the main shaft assembly is arranged in the shell assembly, the upper balance head assembly is fixedly connected with the end part of the main shaft 9 by a fastening screw (7).

6. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: the disc spring and lower balance head assembly is characterized in that a disc spring (30) is arranged on a main shaft (9), a disc spring fixing sleeve (31), a lower end cover (29) and a lower end barrel opening of a shell (20) are fixedly arranged through a disc spring fastening screw (32), an electric main shaft wiring port (34) is formed in the lower end cover (29), and a controller is electrically connected.

7. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: the bearing pre-tightening force automatic adjustment and bearing assembly is characterized in that a third angle contact bearing (23), a bearing inner oil retainer ring (12), a bearing lubricating sleeve (13) and a fourth angle contact bearing (24) are sequentially arranged between a main shaft (9) and a third and fourth bearing fixing sleeve (41), inner rings of the third angle contact bearing (23) and the fourth angle contact bearing (24) are in interference fit with the main shaft (9), outer rings of the third angle contact bearing (23) and the fourth angle contact bearing (24) are in interference fit with the third and fourth bearing fixing sleeves (41), and the third angle contact bearing (23) and the fourth angle contact bearing (24) are ceramic bearings; a temperature sensor (40), a second force transmission disc (39), a spring (25), a first force transmission disc (38), a piezoelectric ceramic column radial positioning disc (37) and a piezoelectric ceramic column fixing seat (36) are sequentially arranged between a main shaft (9) and a third and fourth bearing fixing sleeves (41) and are connected and limited with the main shaft (9) through a bearing axial limiting nut (27); a spring (25) is arranged between a first force transmission disc (38) and a second force transmission disc (39) in the bearing pre-tightening force automatic adjusting mechanism, one end of a piezoelectric ceramic column (26) is connected with a shaft hole of the first force transmission disc (38) in a matched manner, the other end of the piezoelectric ceramic column (26) penetrates through a piezoelectric ceramic column radial positioning disc (37) provided with a piezoelectric ceramic column positioning hole to be connected with a through hole in a piezoelectric ceramic column fixing seat (36) in a matched manner, a temperature sensor (40) is arranged on the second force transmission disc (39) and used for monitoring the temperature of the bearing in real time, feeding the monitored temperature data of the bearing back to equipment automatic control equipment, and outputting a control signal through the equipment to adjust the pre-tightening force; the number of the springs (25) and the number of the piezoelectric ceramic columns (26) are three, and the springs and the piezoelectric ceramic columns are uniformly distributed in the circumferential direction of the main shaft (9).

8. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: the main shaft (9) of the automatic balancing device is of a hollow structure and is used for mounting an upper balancing head component (8), a lower balancing head component (35) and a spiral cable, one end of the spiral cable is in threaded connection with the upper balancing head component (8), and the other end of the spiral cable is in threaded connection with the lower balancing head component (35); the vibration sensor (19) is installed at a position corresponding to a stator coil and a rotor coil of the shell (20), the vibration sensor (19) transmits the change of the vibration amplitude value to the automatic control equipment, the monitoring equipment of the automatic balancing device receives information and then starts the upper balancing head assembly (8) and the lower balancing assembly (35) of the automatic balancing device to adjust the unbalance until the unbalance is balanced, and the controller automatically controls the self-balance of the electric spindle through electric connection.

9. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: the stator and rotor cooling water system is provided with stator and rotor cooling water channels (28) communicated with the stator and rotor cooling water annular grooves (3), three cooling water annular grooves (3) of the stator and the rotor are provided with communicating channels, and the water supply strength of the stator and rotor cooling water system can be automatically adjusted by an external supply cooling system to carry out water cooling on the stator and the rotor; bearing cooling channels (2) are arranged on the adapter sleeve (1) and the shell (20), bearing cooling ring grooves (3) are formed in the peripheries of the first and second bearing fixing sleeves (4) and the third and fourth bearing fixing sleeves (41), the bearing cooling channels (2) on the adapter sleeve (1) are communicated with the cooling ring grooves (3) on the first and second bearing fixing sleeves (4), the bearing cooling channels (2) on the shell (20) are communicated with the bearing cooling ring grooves (3) on the third and fourth bearing fixing sleeves (41), the cooling ring grooves (3) on the bearing fixing sleeves (4) and (41) are provided with communicating channels, and water cooling can be performed on the bearings by automatically adjusting the water supply strength of a bearing cooling water system through an external supply cooling system; the lower end cover (29) is provided with a cooling water channel water inlet, a cooling water channel water outlet and a cooling water connecting nozzle.

10. The self-balancing electric spindle with automatic pre-tightening function as claimed in claim 1, wherein: the bearing lubrication system is characterized in that bearing lubrication grooves (14) are formed in the adapter sleeve (1) and the shell (20), the bearing lubrication grooves (14) on the adapter sleeve (1) directly reach the positions of the first bearing lubrication sleeve and the second bearing lubrication sleeve (13), and the bearing lubrication grooves (14) on the shell (20) directly reach the position of a lubrication sleeve between the third bearing and the fourth bearing.