CN217831896U

CN217831896U - Pre-tightening mechanism of electric spindle, electric spindle and numerical control machine tool

Info

Publication number: CN217831896U
Application number: CN202222286648.2U
Authority: CN
Inventors: 闫海鹏; 牛虎利; 常宏杰
Original assignee: Hebei University of Science and Technology
Current assignee: Hebei Ruihua Medical Instrument Co ltd
Priority date: 2022-08-26
Filing date: 2022-08-26
Publication date: 2022-11-18
Anticipated expiration: 2032-08-26

Abstract

The utility model provides a pretension mechanism, electric main shaft and digit control machine tool of electricity main shaft belongs to mechanical equipment technical field, including installing on the rear end cap of electricity main shaft, include: the pre-tightening disc is used for being connected to the rear end face of the rear bearing chamber of the electric spindle; and an actuating rod of the linear driving assembly is connected with the pre-tightening disc and is used for driving the pre-tightening disc to move back and forth along the axial direction of the electric spindle and adjusting the pre-tightening force of the front bearing and the rear bearing. The utility model provides a pretension mechanism of electricity main shaft, pretension mechanism install on the rear end face of the rear bearing room of electricity main shaft, through linear drive assembly drive pretension dish along the axial to the preceding a pair of bearing pretension of electricity main shaft, through the conductibility of power, the pretension is conducted forward to the preceding a pair of bearing of electricity main shaft along the main shaft on, accomplishes the pretension of two pairs of bearings around the electricity main shaft.

Description

Pre-tightening mechanism of electric spindle, electric spindle and numerical control machine tool

Technical Field

The utility model belongs to the technical field of mechanical equipment, concretely relates to pretension mechanism, electric main shaft and digit control machine tool of electric main shaft.

Background

The high-speed electric spindle is one of main parts of a numerical control machine tool, and adopts a structural design of integrating a machine tool spindle and a machine tool pre-tightening motor into a whole, so that the internal structure of the high-speed electric spindle is compact and complex, and the structural design of the inside of the electric spindle is particularly important for ensuring the stability and the convenience of work of the high-speed electric spindle. The motorized spindle is used as a core component of the numerical control machine tool, and the level and the performance of the motorized spindle determine the overall quality of the numerical control machine tool. The electric main shaft bearing pre-tightening technology is an important research content of an electric main shaft, and the proper pre-tightening force can enable the electric main shaft to obtain the advantages of stable performance, improvement of working efficiency, prolongation of the service life of the bearing and the like. Because the best pretightening force required by the bearing is different when the bearing rotates at different speeds, the current pretightening technology cannot perform self-adaptive pretightening adjustment aiming at different rotating speeds, and the problem of the current electric main shaft bearing pretightening needs to be further improved.

SUMMERY OF THE UTILITY MODEL

An embodiment of the utility model provides a pretension mechanism, electric main shaft and digit control machine tool of electric main shaft aims at solving the problem that the required pretightning force of electric main shaft bearing is different and the performance that leads to reduces when different rotational speeds.

In order to achieve the above object, the present invention adopts the following technical solutions: the utility model provides a pretension mechanism of electricity main shaft, install on the rear end cap of electricity main shaft, include: the pre-tightening disc is used for being connected to the rear end face of the rear bearing chamber of the electric spindle; and an actuating rod of the linear driving assembly is connected with the pre-tightening disc and is used for driving the pre-tightening disc to move back and forth along the axial direction of the electric spindle and adjusting the pre-tightening force of the front bearing and the rear bearing.

With reference to the first aspect, in a possible implementation manner, the front end surface of the pre-tightening disk is provided with a plurality of pre-tightening elastic pieces uniformly distributed in the circumferential direction, and the pre-tightening elastic pieces are connected with the rear end surface of the rear bearing chamber.

With reference to the first aspect, in one possible implementation manner, the pre-tightening elastic member is an extension spring.

With reference to the first aspect, in a possible implementation manner, the linear driving assembly includes a pre-tightening motor, a lead screw connected to the pre-tightening motor, a lead screw nut screwed with the lead screw, the actuating rod fixedly connected to the lead screw nut, and a sleeve sleeved on the lead screw, wherein a guide rail extending along an axis of the lead screw is disposed in the sleeve, and a guide groove in sliding fit with the guide rail is disposed on the lead screw nut; the pre-tightening motor is fixed at the rear end of the sleeve, and the actuating rod is provided with a central hole for the screw rod to reciprocate.

With reference to the first aspect, in a possible implementation manner, a limiting end cover is arranged at the front end of the sleeve, and the limiting end cover constitutes a stroke limit of the lead screw nut.

With reference to the first aspect, in a possible implementation manner, a step surface is arranged on the outer circumferential surface of the lead screw nut, and the rear end of the actuating rod is connected to the step surface.

The utility model provides a pretension mechanism of electricity main shaft compares with prior art, and beneficial effect lies in: the pre-tightening mechanism is installed on the rear end face of a rear bearing chamber of the electric spindle, the pre-tightening disc is driven by the linear driving assembly to pre-tighten the rear pair of bearings of the electric spindle, and the pre-tightening force is transmitted to the front pair of bearings of the electric spindle along the spindle through force conductivity to complete pre-tightening of the two pairs of bearings of the electric spindle.

The pre-tightening mechanism provided by the embodiment is simple in structure, and the pre-tightening disc is driven by the execution rod to axially extrude the rear bearing or pull the rear bearing backwards, so that the pre-tightening force is adjusted. After the linear driving assembly is in signal connection with a driving pre-tightening motor of the electric spindle, the linear driving assembly can drive the pre-tightening disc to adaptively extrude the rear bearing forwards or pull the rear bearing backwards according to the change of the rotating speed of the electric spindle, so that the self-adaptive adjustment of the pre-tightening force of the bearing to the optimal value required by the current rotating speed is realized, the working stability of the electric spindle is improved, the working efficiency of the electric spindle is improved, and the service life of the bearing is prolonged.

In a second aspect, the embodiment of the present invention further provides an electric spindle, including an electric spindle body and the pre-tightening mechanism, wherein, the pre-tightening plate of the pre-tightening mechanism is fixed on the rear end face of the rear bearing chamber of the electric spindle body, the actuating rod of the pre-tightening mechanism passes the rear end cap of the electric spindle body and the pre-tightening plate is connected.

With reference to the second aspect, in a possible implementation manner, the electric spindle body includes a housing, a cooling water jacket disposed in the housing, a stator disposed in the cooling water jacket, a rotor disposed in the stator, a spindle in interference fit with the rotor, a front bearing chamber and a front bearing mounted at a front end of the spindle, a rear bearing chamber and a rear bearing mounted at a rear end of the spindle, a steel ball sleeve and steel balls mounted between the housing and the rear bearing chamber, and a front end cover and a rear end cover mounted at front and rear ends of the housing; the end cover is provided with a cooling water inlet, a cooling water outlet, a lubricating oil inlet and a lubricating oil outlet, the shell is provided with a circulating water channel communicated with the cooling water inlet and the cooling water outlet, the shell is further provided with a lubricating channel communicated with the lubricating oil inlet and the lubricating oil outlet, and the lubricating channel is communicated with the front bearing chamber and the rear bearing chamber.

With reference to the second aspect, in a possible implementation manner, a limit groove connected with the pre-tightening elastic piece of the pre-tightening mechanism is formed in the rear end cover.

In a third aspect, the embodiment of the present invention further provides a numerically-controlled machine tool, including the electric spindle.

The application provides an electricity main shaft and digit control machine tool owing to adopted foretell pretension mechanism, can promote the stability ability of electricity main shaft work, improves the work efficiency of electricity main shaft, prolongs the life of bearing.

Drawings

Fig. 1 is a schematic cross-sectional structural view of an electric spindle according to an embodiment of the present invention;

fig. 2 is a schematic view of an appearance three-dimensional structure of an electric spindle according to an embodiment of the present invention;

fig. 3 is a schematic perspective view of a rear bearing chamber of an electric spindle according to an embodiment of the present invention;

fig. 4 is a schematic view of an appearance three-dimensional structure of a pre-tightening mechanism of an electric spindle according to an embodiment of the present invention;

fig. 5 is a schematic view of an appearance front view structure of a pre-tightening mechanism of an electric spindle according to an embodiment of the present invention;

FIG. 6 isbase:Sub>A sectional view taken along line A-A of FIG. 5;

FIG. 7 is a sectional view taken along line B-B of FIG. 5;

description of reference numerals:

1. a pre-tightening mechanism; 101. pre-tightening the motor; 102. an extension spring; 103. a coupling; 104. a sleeve; 105. a guide rail; 106. a lead screw; 107. a lead screw nut; 108. an actuating lever; 109. a limiting end cover; 110. pre-tightening the disc; 2. a shaft sleeve; 3. a rear end cap; 4. steel ball sleeve; 5. a back nut; 6. a rear bearing chamber; 7. steel balls; 8. a compression spring; 9. a cooling water jacket; 10. a rotor; 11. a stator; 12. a main shaft; 13. a housing; 14. a front bearing chamber; 15. a space ring; 16. a front bearing; 17. a front nut; 18. a front end cover; 19. a limiting groove; 20. a circulating water channel; 21. a lubrication channel.

Detailed Description

In order to make the technical problem, technical solution and advantageous effects to be solved by the present invention more clearly understood, the following description is given in conjunction with the accompanying drawings and embodiments to illustrate the present invention in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1 to 7, a pre-tightening mechanism for an electric spindle according to the present invention will be described. The pre-tightening mechanism of the electric spindle comprises a rear end cover 3 arranged on the electric spindle and comprises: the pre-tightening disc 110 is used for being connected to the rear end face of the rear bearing chamber 6 of the electric spindle; an actuating rod 108 of the linear driving assembly is connected with a pre-tightening disc 110 and is used for driving the pre-tightening disc 110 to move back and forth along the axial direction of the electric spindle so as to adjust the pre-tightening force of the front bearing 16 and the rear bearing.

The utility model provides a pretension mechanism 1 of electricity main shaft's beneficial effect lies in: the pre-tightening mechanism 1 is installed on the rear end face of the rear bearing chamber of the electric spindle, the pre-tightening disc 110 is driven by the linear driving assembly to pre-tighten the rear pair of bearings of the electric spindle along the axial direction, and the pre-tightening force is transmitted to the front pair of bearings of the electric spindle along the front direction of the main shaft 12 through force conductivity, so that pre-tightening of the front pair of bearings and the rear pair of bearings of the electric spindle is completed.

The pre-tightening mechanism 1 provided by the embodiment has a simple structure, the execution rod 108 drives the pre-tightening disc 110 to axially extrude the rear bearing or pull the rear bearing backwards, the pre-tightening force of the front pair of bearings and the rear pair of bearings is adjusted through force transmission, and the adjustment is simple and convenient. After the linear driving assembly is in signal connection with the driving pre-tightening motor 101 of the electric spindle, the size of the pre-tightening force can be changed according to the rotating speed of the electric spindle, the self-adaptive adjustment of the pre-tightening force of the bearing to the optimal value required by the current rotating speed can be realized, the working stability of the electric spindle is improved, the working efficiency of the electric spindle is improved, and the service life of the bearing is prolonged; the problem of performance reduction caused by different required pretightening forces of the electric main shaft bearing at different rotating speeds is solved, and self-adaptive adjustment of the pretightening force between the electric main shaft bearing can be realized within the range of the working rotating speed of the electric main shaft.

The pretensioning mechanism 1 provided by the embodiment is suitable for a structural form that an internal motor is installed between a front bearing and a rear bearing, and the structural form can enable the electric spindle to obtain better rigidity and higher power.

In some embodiments, referring to fig. 4, the front end surface of the pre-tightening disk 110 is provided with a plurality of pre-tightening elastic members uniformly distributed in the circumferential direction, and the pre-tightening elastic members are connected with the rear end surface of the rear bearing chamber. The pretightening force is elastically exerted by the pretightening elastic piece, and the radially moving execution rod 108 stretches or relaxes the spring to realize the adaptive control of the pretightening force, so that when the rotating speed is changed, the pretightening force can be adaptively adjusted to the optimal value required by the current rotating speed.

In some embodiments, as shown in fig. 1 and 4, the pre-tensioned elastic element is a tension spring 102. The pre-tightening mechanism 1 of the motorized spindle has a simple structure, pre-tightening force is applied through the extension spring 102, and the radially moving actuating rod 108 stretches or releases the spring to realize self-adaptive control of the pre-tightening force, so that when the rotating speed is changed, the pre-tightening force can be self-adaptively adjusted to the optimal value required by the current rotating speed. After the tension spring 102 is installed in the pre-tightening mechanism 1, adjusting initial pre-tightening force for the electric main shaft bearing according to the pre-tightening standards of light, medium and heavy; after the integral assembly of the electric main shaft is completed, the power supply of the pre-tightening mechanism 1 is switched on, and the self-adaptive adjustment of the pre-tightening force between the bearings can be realized during the work of the electric main shaft.

In some embodiments, referring to fig. 4 to 7, the linear driving assembly includes a pre-tightening motor 101, a lead screw 106 connected to the pre-tightening motor 101, a lead screw nut 107 screwed with the lead screw 106, an actuating rod 108 fixedly connected to the lead screw nut 107, and a sleeve 104 sleeved on the lead screw 106, wherein a guide rail 105 extending along an axis of the lead screw 106 is disposed in the sleeve 104, and a guide groove slidably engaged with the guide rail 105 is disposed on the lead screw nut 107; the pre-tightening motor 101 is fixed at the rear end of the sleeve 104, and the actuating rod 108 is provided with a central hole for the screw 106 to reciprocate.

The pre-tightening motor 101 provided by the application can be started, stopped and rotated positively and negatively as a power source, and the force transmission component adopts the trapezoidal thread lead screw 106, so that the continuous operation can be well realized; the self-adaptive adjustment of the pre-tightening force between the electric main shaft bearings can be realized within the range of the working rotating speed of the electric main shaft by combining the drive of the extension spring 102 and the actuating rod 108.

The preferred linear driving assembly of this embodiment is an electric lead screw 106 mechanism, which is a screw transmission mechanism that can convert the rotary motion of the pre-tightening motor 101 into radial motion, and has good self-locking property, and can ensure the reliability of the position adjustment of the actuating rod 108. Alternatively, the linear drive assembly may also employ actuators such as hydraulic, pneumatic, etc.

The lead screw 106 is connected with the pretensioning motor 101 through the coupler 103.

In some embodiments, referring to fig. 4-6, the front end of the sleeve 104 is provided with a limit end cap 109, and the limit end cap 109 constitutes a travel limit for the lead screw nut 107. The lead screw nut 107 is limited in the sleeve 104 through a limiting end cover 109 at the front end of the sleeve 104; and the bolt connection of the limiting end cover 109 and the sleeve 104 is also convenient for the lead screw nut 107 to be arranged in the sleeve 104 after being disassembled.

In some embodiments, referring to fig. 6, a step surface is provided on the outer circumferential surface of the lead screw nut 107, the rear end of the actuating rod 108 is connected to the step surface, and the lead screw nut 107 reliably limits the actuating rod 108.

In the above embodiments, the description of each embodiment has its own emphasis, and reference may be made to the related description of other embodiments for parts that are not described or recited in any embodiment.

Based on the same inventive concept, the embodiment of the present application further provides an electric spindle, as shown in fig. 1 to fig. 3, including an electric spindle body and the pre-tightening mechanism 1, wherein a pre-tightening disc 110 of the pre-tightening mechanism 1 is fixed on a rear end surface of a rear bearing chamber of the electric spindle body, and an actuating rod 108 of the pre-tightening mechanism 1 penetrates through a rear end cover 3 of the electric spindle body to be connected with the pre-tightening disc 110.

Based on the electric spindle provided by the embodiment, the electric spindle is in signal connection or circuit connection with the linear driving assembly of the pre-tightening mechanism 1, a proper controller is selected, and the electric spindle is integrated on a master control system of a numerical control machine tool, and the pre-tightening force among bearings can be adjusted in real time according to different factors such as the rotating speed, the temperature, the rigidity and the precision of the electric spindle, so that the electric spindle is ensured to be kept in a high-performance working state under different working parameters. The electric spindle with the self-adaptive pre-tightening mechanism 1 can deal with various working conditions, is suitable for the working environment of a numerical control machine tool, can reduce the production cost greatly and reduce the resource waste due to the popularization and the use of the self-adaptive pre-tightening electric spindle under the condition of facing various working conditions.

The pre-tightening technology among the bearings of the high-speed electric main shaft is an important technology for realizing high performance of the electric main shaft, improving the rigidity and the critical rotating speed of the main shaft 12, prolonging the service life of the bearings and improving the processing precision. Under the condition of low rotating speed, the bearing is fully preloaded, so that the rigidity of the bearing is ensured; and under the high-speed condition, a small amount of pre-pressure is adopted, so that the surface treatment performance of the workpiece is improved. The pre-tightening mechanism 1 is additionally arranged on the electric main shaft body, so that the self-adaptability adjustment of the pre-tightening force of the bearing along with the difference of the rotating speed can be realized, the working stability of the electric main shaft can be improved, the working efficiency of the electric main shaft is improved, and the service life of the bearing is prolonged.

As an embodiment of the electric spindle provided in this embodiment, referring to fig. 1 to 3, an electric spindle body includes a housing 13, a cooling water jacket 9 built in the housing 13, a stator 11 built in the cooling water jacket 9, a rotor 10 built in the stator 11, a spindle 12 in interference fit with the rotor 10, a front bearing chamber 14 and a front bearing 16 mounted at a front end of the spindle 12, a rear bearing chamber 6 and a rear bearing mounted at a rear end of the spindle 12, steel balls 7 and a steel ball 7 mounted between the housing 13 and the rear bearing chamber 6, a front end cover 18 and a rear end cover 3 mounted at front and rear ends of the housing 13; wherein, the end cover is provided with a cooling water inlet, a cooling water outlet, a lubricating oil inlet and a lubricating oil outlet, the shell 13 is provided with a circulating water channel 20 communicating the cooling water inlet and the cooling water outlet, the shell 13 is also provided with a lubricating channel 21 communicating the lubricating oil inlet and the lubricating oil outlet, and the lubricating channel 21 is communicated with the front bearing 16 chamber and the rear bearing chamber 6.

Wherein, a space ring 15 is arranged between two adjacent bearings, and a compression spring 8 is also arranged between the rear bearing chamber and the front end of the steel ball sleeve 4. The front end of the main shaft 12 is also provided with a front nut 17 for limiting a front bearing; the rear end of the main shaft 12 is provided with a rear nut 5 for limiting a rear bearing.

In the electric spindle provided by the embodiment, the built-in motor is arranged between the front bearing and the rear bearing. The high-speed electric spindle is a key part of CNC (numerical control machine tool), and the high-speed cutting technology thereof is also a key technology thereof. The high speed electric spindle is very different from the ordinary machine tool spindle, and the spindle 12 and the built-in motor are combined by the built-in motor. The system has the outstanding characteristics of light weight, small inertia, good dynamic performance, compact structure and the like, and enables the built-in motor and the machine tool spindle to have zero transmission. The electric spindle comprises a built-in motor, a spindle 12, a bearing, an electric spindle sleeve 2 barrel 104, a driving assembly, a spindle 12 cooling assembly, a bearing lubricating assembly and the like. The rotor 10 and the rotating shaft of the built-in motor are made into a whole by adopting a press-fit process, are supported by a front bearing and a rear bearing, the speed of the main shaft 12 is controlled by a transmission assembly, and a cooling system is used for limiting the temperature of the main shaft.

In order to meet the requirements of high rotating speed and high precision of the electric spindle, strict requirements are imposed on the internal structure and the part structure of the electric spindle, and the reasonable structural design is a premise for ensuring the normal work of the designed electric spindle. Meanwhile, a cooling system and a lubricating system of the electric spindle are also important contents for ensuring the stable work of the electric spindle.

The lubrication of the bearing can reduce the abrasion and friction of the bearing, keep good running and have a certain heat dissipation effect.

In the running process of the electric spindle, the main factors of heating are temperature rise of a built-in motor of the electric spindle due to electromagnetism and friction heating of a bearing. Because the oil-gas lubrication system of the bearing lubricates the bearing to reduce friction and simultaneously takes away part of heat generated on the friction of the bearing through the circulation of oil gas, a set of cooling system needs to be designed for the electric spindle pre-tightening motor 101 in order to prevent the heating condition of the electric spindle from influencing the normal work of the electric spindle. The cooling method of the application is that a cooling water jacket 9 is arranged on the outer side of a stator 11 of the built-in motor of the electric main shaft, and the cooling method can be water cooling, oil-water cooling or oil-water cooling.

As an embodiment of the electric spindle according to the present embodiment, referring to fig. 1 and 3, a limiting groove 19 connected to the pre-tightening elastic member of the pre-tightening mechanism 1 is provided on the rear end cap 3. The aim of self-adaptive pre-tightening force adjustment of the rotating speed of the self-adaptive main shaft 12 can be achieved by applying pre-tightening force through the pre-tightening motor 101 or the extension spring 102; the cooperation of the extension spring 102 and the pre-tightening motor 101 can realize the preliminary pre-tightening of the front and rear bearings through the pre-tightening motor 101, and the extension spring 102 can realize the automatic fine adjustment of the pre-tightening force of the front and rear bearings in the working process of the main shaft 12, because the bearings can extrude the extension spring 102 or extend the extension spring 102 to realize the adjustment under the influence of temperature and rotating speed; the tension spring 102 and the radially moving actuator rod 108 stretch or relax the spring to achieve adaptive control of the preload force, and when the rotating speed changes, the preload force can be adaptively adjusted to the optimal value required by the current rotating speed.

Optionally, a shaft sleeve 2 is further disposed on the through hole of the rear end cover 3, and the sleeve 104 of the pre-tightening mechanism 1 is in interference fit with the shaft sleeve 2.

Based on the same inventive concept, the embodiment of the utility model also provides a numerical control machine tool, include electric main shaft.

The application provides an electricity main shaft and digit control machine tool owing to adopted foretell pretension mechanism 1, can promote the stability ability of electricity main shaft work, improves the work efficiency of electricity main shaft, prolongs the life of bearing.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

1. The utility model provides a pretension mechanism of electricity main shaft, installs on the rear end cap (3) of electricity main shaft, its characterized in that includes:

the pre-tightening disc (110) is connected to the rear end face of the rear bearing chamber (6) of the electric spindle;

and the actuating rod (108) of the linear driving assembly is connected with the pre-tightening disc (110) and is used for driving the pre-tightening disc (110) to move back and forth along the axial direction of the electric spindle to adjust the pre-tightening force of the front bearing (16) and the rear bearing.

2. The pretensioning mechanism for an electric spindle according to claim 1, wherein the pretensioning disk (110) is provided at its front end face with a plurality of pretensioning elastic elements which are uniformly distributed in the circumferential direction and are connected to the rear end face of the rear bearing chamber (6).

3. The pretensioning mechanism for an electric spindle according to claim 2, characterized in that the pretensioning elastic member is a tension spring (102).

4. The pre-tightening mechanism of the electric spindle according to claim 1, characterized in that the linear driving assembly comprises a pre-tightening motor (101), a lead screw (106) connected with the pre-tightening motor (101), a lead screw nut (107) screwed with the lead screw (106), the actuating rod (108) fixedly connected with the lead screw nut (107), and a sleeve (104) sleeved on the lead screw (106), wherein a guide rail (105) extending along the axis of the lead screw (106) is arranged in the sleeve (104), and a guide groove in sliding fit with the guide rail (105) is arranged on the lead screw nut (107); the pre-tightening motor (101) is fixed at the rear end of the sleeve (104), and the actuating rod (108) is provided with a central hole for the screw rod (106) to reciprocate.

5. The pretensioning mechanism for an electric spindle according to claim 4, wherein a limit end cap (109) is provided at the front end of the sleeve (104), and the limit end cap (109) constitutes a travel limit for the lead screw nut (107).

6. The pre-tightening mechanism for the electric spindle according to claim 4, characterized in that a step surface is arranged on the outer circumferential surface of the lead screw nut (107), and the rear end of the actuating rod (108) is connected to the step surface.

7. An electric spindle, characterized by comprising an electric spindle body and a pretensioning mechanism (1) according to any one of claims 1-6, wherein a pretensioning disc (110) of the pretensioning mechanism (1) is fixed on a rear end face of a rear bearing chamber (6) of the electric spindle body (12), and an actuating rod (108) of the pretensioning mechanism (1) penetrates through a rear end cover (3) of the electric spindle body to be connected with the pretensioning disc (110).

8. The electric spindle of claim 7, characterized in that the electric spindle body comprises a housing (13), a cooling water jacket (9) built in the housing (13), a stator (11) built in the cooling water jacket (9), a rotor (10) built in the stator (11), a spindle (12) in interference fit with the rotor, a front bearing chamber (14) and a front bearing (16) mounted at the front end of the spindle (12), a rear bearing chamber (6) and a rear bearing mounted at the rear end of the spindle (12), a steel ball sleeve (4) and a steel ball (7) mounted between the housing (13) and the rear bearing chamber (6), and a front end cover (18) and a rear end cover (3) mounted at the front and rear ends of the housing (13); the rear end cover (3) is provided with a cooling water inlet, a cooling water outlet, a lubricating oil inlet and a lubricating oil outlet, the shell (13) is provided with a circulating water channel (20) communicated with the cooling water inlet and the cooling water outlet, the shell (13) is further provided with a lubricating channel (21) communicated with the lubricating oil inlet and the lubricating oil outlet, and the lubricating channel (21) is communicated with the front bearing chamber (14) and the rear bearing chamber (6).

9. Electric spindle according to claim 8, characterized in that the rear end cap (3) is provided with a limiting groove (19) to which the pre-tensioning elastic element of the pre-tensioning mechanism (1) is connected.

10. A numerically controlled machine tool comprising an electric spindle according to any one of claims 7 to 9.