Electric spindles and CNC machine tools

Abstract

This application relates to an electric spindle and a CNC machine tool. The electric spindle includes a spindle core; a bearing assembly including a bearing sleeved on the outer periphery of the spindle core, the bearing including an inner ring and a plurality of balls distributed within the inner ring; and a bearing housing for mounting the bearing assembly. The bearing housing includes a raceway sleeved on the outer periphery of the inner ring of the bearing. The inner ring rotates with the spindle core, causing the plurality of balls to roll relative to the raceway. By removing the outer ring of the bearing, and allowing the bearing balls to engage with the raceway of the bearing housing, the assembly accuracy of the electric spindle is improved.

Description

Technical Field

[0001] This application relates to the field of CNC machine tool technology, and in particular to an electric spindle and a CNC machine tool. Background Technology

[0002] An electric spindle is a new technology that integrates the machine tool spindle and spindle motor into one unit. The spindle is directly driven by the built-in motor, eliminating the gear, belt, or coupling transmission of traditional spindles. This reduces the transmission chain length of the machine tool spindle to zero, resulting in features such as compact structure, light weight, low inertia, low vibration, low noise, and fast response speed. It is widely used in the manufacturing of precision molds, automobiles, ships, aerospace, and other cutting-edge products. However, electric spindles have a complex structure and require high precision in parts and advanced assembly techniques.

[0003] Existing technologies typically employ various bearing configurations, such as two bearings at the front and two at the rear, to ensure high precision while maintaining high spindle speeds. Furthermore, to extend bearing life, oil and air circulation is usually used to clean and lubricate the bearing assembly.

[0004] With the technological iteration of high-precision and high-efficiency machining requirements, the industry has put forward the demand for higher speeds and higher precision for electric spindles. As the direct output end of the electric spindle, the structural precision and assembly precision of the front bearing housing and its matching bearing assembly have become bottleneck issues restricting the development of high-speed and high-precision electric spindles. Summary of the Invention

[0005] The purpose of this application is to provide an electric spindle and a CNC machine tool that can improve assembly accuracy.

[0006] In a first aspect, embodiments of this application provide an electric spindle, including a spindle core; a bearing assembly, including a bearing sleeved on the outer periphery of the spindle core, the bearing including an inner ring and a plurality of balls distributed within the inner ring; and a bearing housing, the bearing housing for mounting the bearing assembly, the bearing housing including a raceway, the raceway being sleeved on the outer periphery of the inner ring of the bearing, the inner ring rotating with the spindle core, causing the plurality of balls to roll relative to the raceway.

[0007] In one embodiment of this application, the bearing assembly includes a first bearing, an inner ring spacer, and a second bearing spaced axially. The first bearing includes a first inner ring, and the second bearing includes a second inner ring. The bearing housing is provided with a first raceway, a height calibration section, and a second raceway sequentially along the axial direction. The first raceway mates with a plurality of balls of the first inner ring, and the second raceway mates with a plurality of balls of the second inner ring. The height calibration section has a first plane extending radially. The axial height dimension H of the inner ring spacer must satisfy the following condition: H = L1 + (Q1 - Q2) + (M1 - ... M2)-(N1+N2); where L1 is the distance between the first plane and the lower end face of the second raceway, M1 is the distance between the center of the raceway arc surface of the first raceway and the lower end face of the first raceway, M2 is the distance between the center of the raceway arc surface of the second raceway and the lower end face of the second raceway, N1 is the distance between the center of the raceway arc surface of the first inner ring and the lower end face of the first inner ring, N2 is the distance between the center of the raceway arc surface of the second inner ring and the upper end face of the second inner ring, Q1 is the axial displacement of the first inner ring after pre-tightening the first bearing, and Q2 is the axial displacement of the second inner ring after pre-tightening the second bearing.

[0008] In one embodiment of this application, the height calibration segment is formed by an inward recess in the inner wall of the bearing housing. The height calibration segment has a first plane and a second plane in sequence along the axial direction. The second plane extends radially, and the first plane is located on the side of the second plane facing the first bearing.

[0009] In one embodiment of this application, the bearing housing is further provided with a first gas-liquid channel along the axial direction. The first gas-liquid channel includes: a first branch, one end of which is connected to the first gas-liquid channel and the other end of which is connected to the first bearing; and a second branch, one end of which is connected to the first gas-liquid channel and the other end of which is connected to the second bearing.

[0010] In one embodiment of this application, the first branch is independent of the engagement position of the second ball, and the second branches are all independent of the engagement position of the second ball.

[0011] In one embodiment of this application, the angle between the extension direction of the first branch and the axial direction is a1, the angle between the extension direction of the second branch and the axial direction is a2, the value of a1 is in the range of 0° < a1 < 30°, and the value of a2 is in the range of 0° < a2 < 30°.

[0012] In one embodiment of this application, the inner ring spacer includes: an axial section, one end of which abuts against the first inner ring and the other end of which abuts against the second inner ring; and a radial section, one end of which is connected to the axial section and the other end of which has a second gas-liquid channel.

[0013] In one embodiment of this application, the liquid level in the second gas-liquid channel is lower than the second plane.

[0014] In one embodiment of this application, the second gas-liquid channel includes: an axial oil hole, which is opened at one end of the radial section away from the shaft core, the axial oil hole being a blind hole, and the liquid level in the axial oil hole being lower than the second plane; and a radial oil hole, which is opened at one end of the radial section facing the first bearing, the radial oil hole communicating with the axial oil hole.

[0015] Secondly, embodiments of this application provide a CNC machine tool, including: an electric spindle as described in any of the first aspects.

[0016] This application provides an electric spindle, including a spindle core; a bearing assembly including a bearing sleeved on the outer periphery of the spindle core, the bearing including an inner ring and a plurality of balls distributed within the inner ring; and a bearing housing for mounting the bearing assembly, the bearing housing including a raceway, the raceway being sleeved on the outer periphery of the inner ring of the bearing, the inner ring rotating with the spindle core, causing the plurality of balls to roll relative to the raceway. The electric spindle provided in this application includes a spindle core, a bearing assembly, and a bearing housing. The bearing in the bearing assembly only has an inner ring sleeved on the spindle core and balls spaced apart within the inner ring. The rolling support of the balls is formed by the raceway on the inner wall of the bearing housing. This eliminates assembly errors between the outer ring of the bearing and the bearing housing, improves the installation accuracy of the bearing assembly, and also solves the problems of difficult bearing assembly installation and poor matching accuracy, thus improving the overall rigidity of the electric spindle. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In addition, in the drawings, the same parts use the same reference numerals, and the drawings are not drawn to scale.

[0018] Figure 1 This illustration shows a front view of a bearing housing for an electric spindle according to an embodiment of this application;

[0019] Figure 2 Based on Figure 1 Top view;

[0020] Figure 3 for Figure 2 A sectional view along the AA direction;

[0021] Figure 4 This illustration shows a front view of a first bearing of an electric spindle according to an embodiment of this application;

[0022] Figure 5 Based on Figure 4 Top view;

[0023] Figure 6 This illustration shows a front view of a second bearing of an electric spindle according to an embodiment of this application;

[0024] Figure 7 Based on Figure 6 Top view;

[0025] Figure 8 This illustration shows a front view of the inner ring spacer of an electric spindle according to an embodiment of this application;

[0026] Figure 9 Based on Figure 8 Top view;

[0027] Figure 10 for Figure 9 A sectional view along the BB direction;

[0028] Figure 11 This illustration shows a front view of the spindle core of an electric spindle according to an embodiment of this application;

[0029] Figure 12 This diagram illustrates the external structure of an electric spindle according to an embodiment of this application.

[0030] Figure 13 Based on Figure 12 Exploded view;

[0031] Figure 14 This image shows a cross-sectional view of an electric spindle provided in an embodiment of this application.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Shaft core; 11. Mounting position; 12. Thrust surface; 2. Bearing assembly; 21. First bearing; 211. First inner ring; 212. First ball; 213. First cage; 22. Second bearing; 221. Second inner ring; 222. Second ball; 223. Second cage; 23. Inner ring spacer; 231. Axial section; 232. Radial section; 2321. Second gas-liquid passage; 2322. Axial oil hole; 2323. Radial oil hole; 3. Bearing housing; 31. First raceway; 32. Second raceway; 33. Height calibration section; 331. First plane; 332. Second plane; 34. First gas-liquid passage; 341. First branch; 342. Second branch; 343. Oil and gas inlet; 344. Plug mounting hole. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] like Figures 1-14 As shown, this application embodiment provides an electric spindle, including a spindle core 1; a bearing assembly 2, including a bearing sleeved on the outer periphery of the spindle core 1, the bearing including an inner ring and a plurality of balls distributed in the inner ring; and a bearing housing 3, the bearing housing 3 being used to install the bearing assembly 2, the bearing housing 3 including a raceway, the raceway being sleeved on the outer periphery of the inner ring of the bearing, the inner ring rotating with the spindle core 1, causing the plurality of balls to roll relative to the raceway.

[0036] The electric spindle provided in this application includes a spindle core 1, a bearing assembly 2, and a bearing housing 3. The bearing assembly 2 has only an inner ring sleeved outside the spindle core 1 and balls spaced apart on the inner ring. The rolling support of the outer circumference of the balls is formed by the raceway on the inner wall of the bearing housing 3. In this way, the assembly error between the outer ring of the bearing and the bearing housing 3 is eliminated, the installation accuracy of the bearing assembly 2 is improved, and the problems of difficult installation and poor matching accuracy of the bearing assembly 2 are solved, thereby improving the overall rigidity of the electric spindle.

[0037] Furthermore, such as Figures 1-7 As shown, bearing assembly 2 includes a first bearing 21 and a second bearing 22. The first bearing 21 includes a first inner ring 211, a first cage 213, and a plurality of first balls 212 evenly distributed within the first cage 213. The second bearing 22 includes a second inner ring 221, a second cage 223, and a plurality of second balls 222 evenly distributed within the second cage 223. Both the first inner ring 211 and the second inner ring 221 are provided with inner ring spacers 23. Bearing housing 3 includes a first raceway 31 for supporting the rolling of the first balls 212. This raceway includes an arc-shaped edge and a straight edge. The first raceway 31 cooperates with the first balls 212 to ensure the normal operation of the first bearing 21. Similarly, bearing housing 3 includes a second raceway 32 for supporting the rolling of the second balls 222. This raceway includes an arc-shaped edge and a straight edge. The second raceway 32 cooperates with the second balls 222 to ensure the normal operation of the second bearing 22. During the use of bearing assembly 2, to better ensure load-bearing capacity, it is usually necessary to preload each bearing according to the actual working conditions.

[0038] The types of the first bearing 21 and the second bearing 22 need to be selected according to the actual operating conditions of the electric spindle. The types of the first bearing 21 and the second bearing 22 can be the same or different. In this embodiment, the same structure is selected for ease of description.

[0039] In addition, such as Figure 11 As shown, the shaft core 1 of this embodiment has a mounting position 11 for the bearing assembly 2 and a thrust surface 12. The mounting position 11 is used to mount the bearing assembly 2, and the thrust surface 12 is used to restrict the axial movement of the bearing assembly 2.

[0040] For details, please continue to refer to Figures 1-7 As shown, the bearing assembly 2 includes a first bearing 21, an inner ring spacer 23, and a second bearing 22 spaced apart along the axial direction. The first bearing 21 includes a first inner ring 211, and the second bearing 22 includes a second inner ring 221. The bearing housing 3 is provided with a first raceway 31, a height calibration section 33, and a second raceway 32 sequentially along the axial direction. The first raceway 31 is engaged with multiple balls of the first inner ring 211, and the second raceway 32 is engaged with multiple balls of the second inner ring 221. The height calibration section 33 has a first plane 331 extending radially. The axial height dimension H of the inner ring spacer 23 must satisfy the following condition: H = L1 + (Q1 - Q2) + (M1 - M2) + (Q ... 2)-(N1+N2); where L1 is the distance between the first plane 331 and the lower end face of the second raceway 32, M1 is the distance between the center of the raceway arc surface of the first raceway 31 and the lower end face of the first raceway 31, M2 is the distance between the center of the raceway arc surface of the second raceway 32 and the lower end face of the second raceway 32, N1 is the distance between the center of the raceway arc surface of the first inner ring 211 and the lower end face of the first inner ring 211, N2 is the distance between the center of the raceway arc surface of the second inner ring 221 and the upper end face of the second inner ring 221, Q1 is the axial displacement of the first inner ring 211 after pre-tightening the first bearing 21, and Q2 is the axial displacement of the second inner ring 221 after pre-tightening the second bearing 22.

[0041] In this embodiment, the bearing housing 3 has a height calibration section 33 between the corresponding first raceway 31 and second raceway 32. This structure allows for height measurement, enabling precise and convenient calibration of the axial positions of the first bearing 21 and the second bearing 22. This solves the problems of difficult installation and poor matching accuracy of the bearing assembly 2 in the prior art. Based on the structural characteristics of each part and their corresponding assembly relationships, the relevant expressions for the preload of the bearing assembly 2 are summarized as follows:

[0042] The center distance between the first raceway 31 and the second raceway 32 is (L1+M1-M2).

[0043] The center distance between the inner rings of the first ball 212 and the inner rings of the second ball 222 in the free state is (N1+N2+H).

[0044] Axial preload is applied to bearing assembly 2, with the load applied at the lower end face of the second bearing 22. Both the first inner ring 211 and the second inner ring 221 of bearing assembly 2 undergo axial movement. The axial preload amount is related by the following equation:

[0045] (L1+M1-M2)=Q2+(N1+N2+H)-Q1;

[0046] It can be deduced that the axial height H of the inner ring spacer 23 must meet the following conditions:

[0047] H=L1+(Q1-Q2)+(M1-M2)-(N1+N2).

[0048] Further analysis shows that M1, M2, N1, N2, Q1, and Q2 are determined by the actual bearing model used. In order to accurately control the axial preload of bearing assembly 2, the thickness H1 of the inner ring spacer 23 can be adjusted according to the actual value of the distance L1 from the upper end face of the height calibration section 33 to the lower end face of the second raceway 32.

[0049] Please continue to refer to this. Figure 1 and Figure 14 As shown, the height calibration section 33 is formed by an inward indentation of the inner wall of the bearing housing 3. The height calibration section 33 has a first plane 331 and a second plane 332 sequentially along the axial direction. The second plane 332 extends radially, and the first plane 331 is located on the side of the second plane 332 facing the first bearing 21. The first plane 331 and the second plane 332 of the height calibration section 33 facilitate the measurement of the height of this structure, thereby solving the problems of difficult bearing assembly and poor matching accuracy of the bearing assembly 2 in the prior art.

[0050] Additionally, please continue to refer to Figures 1-3 as well as Figure 14 As shown, the bearing housing 3 also has a first gas-liquid channel 34 along the axial direction. The first gas-liquid channel 34 includes: a first branch 341, one end of which is connected to the first gas-liquid channel 34, and the other end of which is connected to the first bearing 21; and a second branch 342, one end of which is connected to the first gas-liquid channel 34, and the other end of which is connected to the second bearing 22. The first gas-liquid channel 34 directly connects to the first bearing 21 and the second bearing 22 of the bearing housing 3, allowing for thorough lubrication and cleaning of the first bearing 21 and the second bearing 22, shortening the flow path transmission chain, and improving the cleaning and lubrication effect of the bearing assembly 2.

[0051] Furthermore, the first branch 341 is independent of the engagement position of the second ball 222, and the second branch 342 is also independent of the engagement position of the second ball 222, thereby avoiding adverse effects on the operation of the first bearing 21 and the second bearing 22.

[0052] Specifically, in order to ensure sufficient lubrication of the bearings under high speed and high torque conditions, the angle between the extension direction of the first branch 341 and the axial direction is a1, and the angle between the extension direction of the second branch 342 and the axial direction is a2. The value of a1 is in the range of 0° < a1 < 30°, and the value of a2 is in the range of 0° < a2 < 30°. When both a1 and a2 are less than 30°, it can be ensured that the lubricating oil or clean gas-liquid in the first gas-liquid channel 34 can fully enter the first bearing 21 and the second bearing 22, ensuring sufficient cleaning and lubrication.

[0053] In addition, it also includes an oil and gas inlet 343 and two plug mounting holes. Given the shape of the bearing housing 3, the first gas-liquid channel 34 is L-shaped, which includes a first channel and a second channel that are perpendicular to each other and connected. The oil and gas inlet 343 is arranged axially and communicates with the first channel that extends radially. In order to facilitate the processing of the first channel and the second channel, both the first channel and the second channel pass through the bearing housing 3. In order to prevent leakage, the first channel and the second channel are blocked by the two plug mounting holes respectively.

[0054] Therefore, the bearing housing 3 is provided with a first gas-liquid channel 34, a first branch 341, a second branch 342, and an oil-gas branch. The angle between the extension direction of the first branch 341 and the axial direction is a1, and the angle between the extension direction of the second branch 342 and the axial direction is a2, both a1 and a2 being controlled within 30°. The first branch 341 and the second branch 342 directly reach the first raceway 31 and the second raceway 32 of the bearing housing 3. Furthermore, the first branch 341 and the second branch 342 must avoid the meshing position of the first ball 212 and the second ball 222 to prevent adverse effects on the operation of the first bearing 21 and the second bearing 22. Oil and gas enter from the oil-gas inlet 343 of the bearing housing 3, and flow along the first gas-liquid channel 34 into the first branch 341 and the second branch 342 respectively, then fully lubricate and clean the first ball 212 and the second ball 222 of the first bearing 21 and the second bearing 22, shortening the flow path transmission chain and improving the bearing lubrication effect.

[0055] like Figures 8-10As shown, the inner ring spacer 23 includes: an axial section 231, one end of which abuts against the first inner ring 211, and the other end of which abuts against the second inner ring 221; and a radial section 232, one end of which is connected to the axial section 231, and the other end of which has a second gas-liquid channel 2321. The inner ring spacer 23 is used to separate the first bearing 21 and the second bearing 22, and provides preload force to the first bearing 21 during preload. The height h of the inner ring spacer 23 can be adjusted according to the actual operating conditions of the electric spindle.

[0056] In this embodiment, the liquid level in the second gas-liquid channel 2321 is lower than the second plane 332. As a result, during rotation, the gas and liquid in the second gas-liquid channel 2321 will be sprayed onto the second plane 332 to flush it, thus preventing oil and gas from being deposited and precipitated on the step surface for a long time, forming impurities that affect the performance and life of the bearing assembly 2.

[0057] Specifically, the second gas-liquid channel 2321 includes: an axial oil hole 2322, which is opened at one end of the radial section 232 away from the shaft core 1. The axial oil hole 2322 is a blind hole to prevent oil and other fluids from directly entering between the first bearing 21 and the second bearing 22 through the axial oil hole 2322. The liquid level in the axial oil hole 2322 is lower than the second plane 332; and a radial oil hole 2323, which is opened at one end of the radial section 232 facing the first bearing 21. The radial oil hole 2323 communicates with the axial oil hole 2322.

[0058] In this embodiment, the inner ring spacer 23 has a flange-like structure and is provided with multiple radial oil holes 2323 and multiple axial oil holes 2322. The radial oil holes 2323 and the axial oil holes 2322 are connected to form a second gas-liquid channel 2321. After the oil and gas lubricate the first bearing 21 along the first branch 341, they eventually settle downwards due to gravity and other factors. Some of the oil and gas hits the side or end face of the inner ring spacer 23 and enters the axial oil hole 2322. Since the inner ring spacer 23 rotates at high speed along with the electric spindle sub-spindle 1, the lubricating oil on the side and end face is thrown against the bearing chamber wall of the front bearing seat 3 under the action of centrifugal force, cleaning the bearing seat 3. The lubricating oil entering the axial oil hole 2322 flows into the radial oil hole 2323 along the flow channel. Through the control of the overall structural dimensions, the lower liquid level of the radial oil hole 2323 is lower than the lower end face of the height calibration section 33 of the bearing housing 3. The lubricating oil entering the radial oil hole 2323 is thrown towards the lower end face of the height calibration section 33 of the bearing housing 3 under the action of centrifugal force, and this area is flushed to avoid long-term deposition and sedimentation of oil and gas on the step surface, which would form impurities and affect the performance and life of the bearing assembly 2.

[0059] like Figures 12-14As shown, the assembly sequence of the electric spindle in this embodiment is as follows: First, the first bearing 21 is press-fitted onto the bearing assembly 2 mounting position 11 of the spindle core 1 through the center hole of its first inner ring 211. The thrust surface 12 of the spindle core 1 serves to axially limit the first bearing 21. Next, the inner ring spacer 23 is installed onto the bearing assembly 2 mounting position 11 of the spindle core 1 through the center hole of its axial section 231. The center hole of the axial section 231 and the spindle core 1 are in clearance fit. Then, the second bearing 22 is press-fitted onto the bearing assembly 2 mounting position 11 of the spindle core 1 through the center hole of its second inner ring 221. Finally, the assembled components are press-fitted into the bearing chamber structure (i.e., the inner wall of the bearing housing 3) of the bearing seat 3.

[0060] Secondly, embodiments of this application provide a CNC machine tool, including: an electric spindle as described in any of the first aspects.

[0061] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0062] It should be readily understood that the terms “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on top of something” but also “on top of something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0063] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation other than those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0064] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An electric spindle, characterized in that, include: Shaft core; A bearing assembly includes a bearing fitted onto the outer periphery of the shaft core, the bearing comprising an inner ring and a plurality of balls distributed within the inner ring; and A bearing housing for mounting the bearing assembly, the bearing housing including a raceway, the raceway being fitted around the outer periphery of the inner ring of the bearing, the inner ring rotating with the shaft core, causing the plurality of balls to roll relative to the raceway; The bearing assembly includes a first bearing, an inner ring spacer, and a second bearing distributed axially at intervals. The first bearing includes a first inner ring, and the second bearing includes a second inner ring. The bearing housing is provided with a first raceway, a height calibration section and a second raceway in sequence along the axial direction. The first raceway is engaged with a plurality of balls of the first inner ring, and the second raceway is engaged with a plurality of balls of the second inner ring. The height calibration section has a first plane extending radially. The axial height H of the inner spacer ring must meet the following conditions: H=L1+(Q1-Q2)+(M1-M2)-(N1+N2); Wherein, L1 is the distance between the first plane and the lower end face of the second raceway, M1 is the distance between the center of the raceway arc surface of the first raceway and the lower end face of the first raceway, M2 is the distance between the center of the raceway arc surface of the second raceway and the lower end face of the second raceway, N1 is the distance between the center of the raceway arc surface of the first inner ring and the lower end face of the first inner ring, N2 is the distance between the center of the raceway arc surface of the second inner ring and the upper end face of the second inner ring, Q1 is the axial displacement of the first inner ring after pre-tightening the first bearing, and Q2 is the axial displacement of the second inner ring after pre-tightening the second bearing.

2. The electric spindle according to claim 1, characterized in that, The height calibration section is formed by an inward indentation of the inner wall of the bearing housing. The height calibration section has a first plane and a second plane in sequence along the axial direction. The second plane extends radially, and the first plane is located on the side of the second plane facing the first bearing.

3. The electric spindle according to claim 1 or 2, characterized in that, The bearing housing also has a first gas-liquid channel along the axial direction, the first gas-liquid channel comprising: The first branch, one end of which is connected to the first gas-liquid channel, and the other end of which is connected to the first bearing; and The second branch has one end connected to the first gas-liquid channel and the other end connected to the second bearing.

4. The electric spindle according to claim 3, characterized in that, The balls in the first raceway are first balls, and the first branch is independent of the engagement position of the first ball; the balls in the second raceway are second balls, and the second branch is independent of the engagement position of the second ball.

5. The electric spindle according to claim 3, characterized in that, The angle between the extension direction of the first branch and the axial direction is a1, and the angle between the extension direction of the second branch and the axial direction is a2. The value of a1 is in the range of 0° < a1 < 30°, and the value of a2 is in the range of 0° < a2 < 30°.

6. The electric spindle according to claim 2, characterized in that, The inner ring spacer includes: An axial segment, with one end abutting against the first inner ring and the other end abutting against the second inner ring; and The radial section is connected at one end to the axial section, and a second gas-liquid channel is provided at the other end.

7. The electric spindle according to claim 6, characterized in that, The liquid level in the second gas-liquid channel is lower than the second plane.

8. The electric spindle according to claim 6 or 7, characterized in that, The second gas-liquid channel includes: An axial oil hole is formed at the end of the radial section opposite to the shaft core. The axial oil hole is a blind hole, and the liquid level inside the axial oil hole is lower than the second plane. A radial oil hole is provided at one end of the radial segment facing the first bearing, and the radial oil hole communicates with the axial oil hole.

9. A CNC machine tool, characterized in that, include: The electric spindle as described in any one of claims 1 to 8.

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