WO2022007366A1

WO2022007366A1 - Air-bearing motorized spindle and machine tool

Info

Publication number: WO2022007366A1
Application number: PCT/CN2020/141604
Authority: WO
Inventors: 赵聪; 龚展宏; 张翰乾; 黄俊治; 汤秀清
Original assignee: 广州市昊志机电股份有限公司
Priority date: 2020-07-07
Filing date: 2020-12-30
Publication date: 2022-01-13
Also published as: CN111940766B; CN111940766A

Abstract

An air-bearing motorized spindle and a machine tool. The air-bearing motorized spindle comprises: a machine body assembly; a spindle core assembly having a flying disc and being supported and suspended on the machine body assembly by means of a thrust bearing assembly and an air bearing assembly, with a first end of the spindle core assembly forming a power output end, and a second end of the spindle core assembly forming a power input end; and an electric motor assembly arranged at the power input end and comprising a stator and a copper squirrel cage, with the stator being connected to the machine body assembly, and the copper squirrel cage being combined with the spindle core assembly and forming a cylindrical surface which is coaxial with the spindle core assembly.

Description

Air-floating electric spindles and machine tools

This application claims the priority of the Chinese patent application with an application date of July 7, 2020 and an application number of 202010644467.5, the entire contents of which are incorporated herein by reference.

technical field

The present application relates to the field of mechanical processing, for example, to an air-floating electric spindle and a machine tool.

Background technique

In the 1950s, the precision machining level could reach 3-5 μm, and the machining accuracy that ultra-precision machining could achieve could reach 1 μm. In the late 1970s, the precision of precision machining can reach 1 μm, and the level of ultra-precision machining can reach 0.1 μm. In related technologies, the machining accuracy of precision and ultra-precision machining has been improved to the nanometer level.

Because of the error homogenization phenomenon of the air-floated electric spindle, as well as low friction and low loss, the air-floated electric spindle has become one of the best carriers for ultra-precision machining. The vibration of the air-flotation electric spindle has a huge impact on the machining accuracy. Excessive vibration may cause vibration and knife lines in the machining, which cannot guarantee the machining quality of ultra-precision machining.

SUMMARY OF THE INVENTION

The application provides an air-floating electric spindle and a machine tool, which can ensure that the spindle can still ensure extremely low vibration at high speed, and ensure the stability of the spindle during long-term and high-speed operation while ensuring nano-level processing. .

An embodiment provides an air-floating electric spindle, including: a body assembly; a shaft core assembly having a flying disc, the shaft core assembly is suspended on the body assembly by a thrust bearing assembly and an air bearing assembly, and the shaft core assembly is suspended on the body assembly. The first end of the shaft core assembly forms a power output end, the second end of the shaft core assembly forms a power input end; and a motor assembly is provided at the power input end, the motor assembly includes a stator and a copper squirrel cage, the stator and the The body assembly is connected, the copper squirrel cage is combined with the shaft core assembly, and forms a cylindrical surface coaxial with the shaft core assembly.

In one embodiment, the flying disc is located at a position where the shaft core assembly is close to the motor assembly, the thrust bearing assembly is located between the flying disc and the motor assembly, and the air bearing assembly is located on the flying disc On the side away from the motor assembly, the thrust bearing assembly has a first thrust surface matched with the flying disc, the first thrust surface is provided with a first axial air outlet, and the air bearing assembly There is a second thrust surface matched with the flying disc, the second thrust surface is provided with a second axial outlet hole, and the air bearing assembly has a support surface matched with the outer peripheral surface of the shaft core assembly The bearing surface is provided with radial air outlet holes, and the body assembly is provided with air passages connected with the first axial air outlet holes, the second axial air outlet holes and the radial air outlet holes.

In one embodiment, the air bearing assembly has a first bearing surface and a second bearing surface that cooperate with the outer peripheral surface of the shaft core assembly, and the first bearing surface and the second bearing surface extend along the power input end to The direction distribution of the power output end, the first support surface and the second support surface are both provided with radial air outlet holes, and the air flotation pressure generated by the radial air outlet holes on the second support surface is greater than that of the radial air outlet holes in the first support surface. Air flotation pressure generated by a bearing surface.

In one embodiment, the number of radial air outlet holes of the second support surface is greater than the number of radial air outlet holes of the first support surface.

In one embodiment, the density of the radial outlet holes of the second bearing surface is greater than the density of the radial outlet holes of the first bearing surface.

In one embodiment, the first bearing surface and the second bearing surface are axially separated by a certain distance, and the portion of the inner wall surface of the air bearing assembly between the first bearing surface and the second bearing surface The shaft core assembly is left with a non-fit clearance.

In one embodiment, the air-floating electric spindle further comprises: a vibration sensor, configured to monitor the vibration of the shaft core assembly; and a processor, according to the signal of the vibration sensor, to control the motor assembly to stop the shaft core assembly. .

In one embodiment, the vibration sensor is integrated into the stator.

In one embodiment, the air-floating electric spindle further includes: a cylinder assembly configured to drive the shaft core assembly to enable the power output end to perform tool change.

An embodiment also provides a machine tool, including the above-mentioned air-floating electric spindle.

The motor assembly uses a copper squirrel cage as the rotor. The motor assembly is located at the end of the shaft core assembly and drives the copper squirrel cage to drive the shaft core assembly to rotate at high speed. The thrust bearing assembly and the air bearing assembly support the shaft core assembly to suspend.

Vibration has a huge impact on the machining accuracy. Excessive vibration may lead to vibrating knife lines in machining, which cannot guarantee the machining quality of ultra-precision machining. For the electric spindle, the maximum vibration position is located at the drive position, that is, the motor position. The copper squirrel cage, which is more tightly closed and can ensure the shape and position tolerance, is used as the shaft core rotor to ensure the stability of the entire shaft core. Secondly, the rear position of the motor assembly keeps the vibration source away from the tool end to ensure that the tool is affected by minimal vibration. The above The combination of the two settings can avoid the poor machining caused by vibration to the greatest extent, and also avoid the large vibration of the machining end caused by the single copper squirrel cage motor in the middle or the motor excitation caused by the poor machining of the cast aluminum rotor itself, so as to ensure the machining quality. The rear-mounted copper squirrel cage makes it possible for ultra-precision machining with a surface accuracy of less than 10nm.

Description of drawings

1 is a schematic structural diagram of an air-floating electric spindle provided by an embodiment of the present application;

FIG. 2 is a schematic structural diagram of the motor assembly shown in FIG. 1 according to an embodiment of the present application;

FIG. 3 is a schematic structural diagram of the air bearing assembly shown in FIG. 1 according to an embodiment of the present application;

FIG. 4 is a schematic diagram of a combined state of the vibration sensor shown in FIG. 1 and the stator according to an embodiment of the present application.

detailed description

In this application, if there is a description of directions (up, down, left, right, front and rear), it is only for the convenience of describing the technical solutions of this application, rather than indicating or implying that the technical features referred to must have a specific orientation , are constructed and operated in a specific orientation, and therefore should not be construed as limiting the application.

In this application, "several" means one or more, "multiple" means two or more, "greater than", "less than" and "exceeding" are understood as not including this number; "above", "below" and "within" " etc. are understood to include the original number. In the description of this application, if it is described that "first" and "second" are only used for the purpose of distinguishing technical features, it should not be understood as indicating or implying relative importance or implying the number of indicated technical features or Implicitly indicates the order of the indicated technical features.

In this application, unless otherwise expressly defined, words such as "arrangement", "installation" and "connection" should be understood in a broad sense. For example, it may be directly connected or indirectly connected through an intermediate medium; it may be a fixed connection or a The detachable connection can also be integrally formed; it can be a mechanical connection or an electrical connection or can communicate with each other; it can be the internal communication between the two elements or the interaction relationship between the two elements. Those skilled in the art can reasonably determine the specific meanings of the above words in this application in combination with the specific content of the technical solutions.

1 shows the reference direction coordinate system of the embodiment of the present application, and the following describes the embodiment of the present application with reference to the directions shown in FIG. 1 .

Referring to FIG. 1 , an embodiment of the present application provides an air-floating electric spindle, which includes a body assembly 1 , a shaft core assembly 2 and a motor assembly. The shaft core assembly 2 has a flying disc 21 , the shaft core assembly 2 is suspended on the body assembly 1 through the thrust bearing assembly 41 and the air bearing assembly 42 , the first end of the shaft core assembly 2 forms a power output end, and the second end of the shaft core assembly 2 form the power input. The power input end is located at the upper end of the shaft core assembly 2, the motor assembly is located at the power input end, the power output end is located at the lower end of the shaft core assembly 2, and the power output end is connected to the tool to realize the transmission of the power from the power input end to the machining tool.

Through the external air supply, the gas enters the air bearing assembly 42 and the thrust bearing assembly 41 in turn through the body assembly 1, and a pressure gas film is formed between the shaft core assembly 2 and the air bearing assembly 42 and the thrust bearing assembly 41 respectively, supporting the shaft core. The assembly 2 is in a suspended state, and the shaft core assembly 2 is driven by the motor assembly to rotate at a high speed.

2 , the motor assembly includes a stator 31 and a copper squirrel cage 32 . The stator 31 is connected to the body assembly 1 , and the copper squirrel cage 32 is combined with the shaft core assembly 2 to form a cylindrical surface coaxial with the shaft core assembly 2 . In other words, the copper squirrel cage 32 is integrated in the shaft core assembly 2, and together with the shaft core assembly 2 forms a perfect outer circular surface. The motor assembly uses a copper squirrel cage 32 as a rotor, and the motor assembly is located at the end of the shaft core assembly 2 to drive the shaft core assembly 2 to rotate at high speed by driving the copper squirrel cage 32 .

Vibration has a huge impact on the machining accuracy. Excessive vibration may lead to vibrating knife lines in machining, which cannot guarantee the quality of ultra-precision machining. For the electric spindle, the maximum vibration position is located at the drive position, that is, the motor position. First, use it to fit the shaft core. The copper squirrel cage 32, which is tighter and can guarantee the geometrical tolerance, is used as the shaft core rotor to ensure the stability of the entire shaft core. Secondly, the rear position of the motor assembly keeps the vibration source away from the tool end, so as to ensure that the tool is affected by the least degree of vibration. The combination of the two can avoid the poor machining caused by vibration to the greatest extent, and can also avoid the vibration of the machining end caused by the single copper squirrel cage motor in the middle. The motor is too large or the motor is excited by the poor processing of the cast aluminum rotor itself, so as to ensure the processing quality. The rear-mounted copper squirrel cage 32 makes it possible for the ultra-precision machining of the surface to be less than 10nm.

The embodiment of the present application uses the copper squirrel cage 32 rear structure rotor, combined with the high shape and position tolerance of the copper squirrel cage 32 and the small vibration characteristics of the rotor rear, so that the main shaft can still ensure extremely low vibration at high speed, ensuring that The nano-level surface milling also ensures the stability of the spindle during long-term, high-speed operation.

The flying disc 21 may be located at one end or the middle of the shaft core assembly 2 , and the flying disc 21 is arranged to carry the axial force generated by the shaft core assembly 2 during the tool machining process. Referring to FIG. 1 , in some embodiments, the flying disc 21 is located at the position of the shaft core assembly 2 close to the motor assembly, and the thrust bearing assembly 41 is located between the flying disc 21 and the motor assembly. The motor and Frisbee 21 are installed at the rear to eliminate temperature interference. In one embodiment, the motor assembly is located at the end of the shaft assembly 2 to drive the shaft assembly 2 to rotate at high speed, and the thrust bearing assembly 41 and the fly disc 21 of the shaft assembly 2 are located at the end of the spindle away from the tool. , The amount of heat generation has a great influence on the machining accuracy, so that the main heating part of the electric spindle is far away from the shaft core tool, which can avoid the thermal elongation of the shaft core caused by the heating of the internal structure to the greatest extent, and ensure the processing quality. The rear-mounted flying disc 21 and the rear-mounted motor structure make it possible to process the nanometer-level precision.

Referring to FIG. 1 , the air bearing assembly 42 is located on the side of the flying disc 21 away from the motor assembly, the thrust bearing assembly 41 has a first thrust surface that cooperates with the flying disc 21 , and the first thrust surface is provided with a first axial air outlet 43 , the air bearing assembly 42 has a second thrust surface that cooperates with the flying disc 21, the second thrust surface is provided with a second axial air outlet 44, and the air bearing assembly 42 has a support that cooperates with the outer peripheral surface of the shaft core assembly The support surface is provided with radial air outlet holes 45 , and the body assembly 1 is provided with air passages connected to the first axial air outlet holes 43 , the second axial air outlet holes 44 and the radial air outlet holes 45 . Through the external air supply, the gas enters the air bearing assembly 42 and the thrust bearing assembly 41 in turn through the air passage of the body assembly 1, between the shaft core assembly 2 and the air bearing assembly 42 and between the shaft core assembly 2 and the thrust bearing assembly 41 A pressure gas film is formed therebetween, the supporting shaft core assembly 2 is in a suspended state, and the shaft core assembly 2 is driven by the motor assembly to rotate at a high speed.

In some embodiments, referring to FIGS. 1 and 3 , the air bearing assembly 42 has a first bearing surface 46 and a second bearing surface 47 that cooperate with the outer peripheral surface of the shaft core assembly 2 . The first bearing surface 46 and the second bearing surface The surfaces 47 are distributed along the direction from the power input end to the power output end, that is, the first support surface 46 is located above the second support surface 47 , and the second support surface 47 is closer to the power output end than the first support surface 46 . The first supporting surface 46 and the second supporting surface 47 are provided with radial air outlet holes 45 , and the air flotation pressure generated by the radial air outlet holes 45 on the second supporting surface 47 is greater than the air generated by the radial air outlet holes 45 on the first supporting surface 46 . float pressure. In other words, a non-uniform pressure air bearing is formed inside the air bearing assembly 42, and the high-pressure gas enters from the body assembly 1, enters the gap between the air bearing assembly 42 and the body assembly 1 through the air passage, and passes through the diameter of the radial air outlet 45. The shaft core assembly 2 is suspended toward the damping plug 49 . In the state of high speed, the ultra-precision spindle is prone to vibration excitation, column vortex, cone vortex and other phenomena, which eventually lead to the rotational vibration of the spindle or the large swing of the shaft core or even lock. In order to avoid such phenomena, the application uses an internal non-uniform pressure air bearing, that is, the air flotation pressure generated by the radial air outlet 45 on the second bearing surface 47 is greater than that of the radial outlet 45 on the first bearing surface 46. The generated air flotation pressure causes differences in the stiffness of the air film at different positions inside the spindle. The above settings make the entire shaft core achieve a force balance, maximize the comprehensive stiffness of the entire shaft system, ensure the optimal overall radial stiffness of the application, and ensure extremely high rotational accuracy requirements and rotational stability at high rotational speeds. .

The embodiment of the present application uses a brand-new internal non-uniform pressure air bearing, and through rigorous calculation, the rigidity of the entire shaft system of the main shaft is guaranteed, and the extremely high rotational accuracy requirements can still be met under the state of ultra-high rotation speed. It makes ultra-precision machining of high-speed small-diameter tools possible.

Among them, in order to make the air flotation pressure generated by the radial air outlet holes 45 on the second supporting surface 47 greater than the air flotation pressure generated by the radial air outlet holes 45 on the first supporting surface 46, various technical means can be used. The radial outlet holes 45 of the bearing surface 47 are fed with a higher pressure high-pressure gas. Alternatively, for example, in the embodiment shown in FIG. 3 , the number of the radial air outlet holes 45 of the second bearing surface 47 is greater than the number of the radial air outlet holes 45 of the first bearing surface 46 . Alternatively, the density of the radial air outlet holes 45 of the second support surface 47 is greater than the density of the radial air outlet holes 45 of the first support surface 46 . That is, by adjusting the distance and quantity of the radial damping plugs 49 in the air bearing, the air film stiffness at different positions inside the main shaft is different.

In one embodiment, the air bearing assembly 42 has two or more air inlet areas matched with the outer peripheral surface of the shaft core assembly 2 , so as to provide multi-point support for the shaft core assembly 2 .

The first support surface 46 and the second support surface 47 may be distributed continuously or at intervals. For example, in the embodiment shown in FIG. 1 and FIG. 3 , the first bearing surface 46 and the second bearing surface 47 are separated by a certain distance in the axial direction, and the first bearing surface 46 and the second bearing surface 47 are matched with the shaft core assembly 2 , provides two-point support for the shaft core assembly 2 in the radial direction, and is more stable for the positioning of the shaft core assembly 2 . At the same time, a part of the inner wall surface of the air bearing assembly 42 located between the first bearing surface 46 and the second bearing surface 47 leaves a non-fit gap 48 with the shaft core assembly 2. In other words, the first bearing surface 46 and the second bearing surface The part between 47 does not provide radial support for the shaft core assembly 2, so that it is not necessary to perform high-precision machining on the part between the first bearing surface 46 and the second bearing surface 47, and only the first bearing surface 46 and the second bearing surface 47 can be processed with high precision, so that the processing cost of the air bearing assembly 42 can be greatly reduced.

In some embodiments, referring to FIG. 1 and FIG. 4 , the air-floating electric spindle further includes a vibration sensor 5 and a processor (not shown in the figure). The signal from the sensor 5 controls the motor assembly to stop the shaft assembly 2 . The stability and safety of the ultra-precision spindle are ensured by setting the spindle vibration monitoring device. When the vibration of the shaft core assembly 2 exceeds the allowable value inside the main shaft, the vibration sensor 5 will forcibly terminate the operation of the main shaft to prevent damage to the main shaft or cause serious accidents. Ultra-precision spindles have extremely high requirements on the environment during operation. Small temperature changes or changes in air source air pressure may cause the spindle to become unstable and lock up. However, the air-floating spindle will not lock instantly due to the dynamic pressure effect. The process of locking can often be reflected in the change of vibration. The detection of temperature and air pressure cannot fully reflect whether the spindle has the risk of locking. Therefore, the vibration sensor 5 is used to detect the vibration of the position of the spindle motor, which can save processing costs and reduce the risk of spindle locking. , The vibration sensor 5 integrated in the spindle motor ensures that the spindle will not be locked due to unstable operation, and the spindle will be forcibly stopped at the moment of unstable operation, which ensures the life of the spindle and the safety of the operator.

Wherein, the processor controls the motor assembly to stop or provides a reverse driving force to stop the shaft core assembly 2 according to the signal of the vibration sensor 5 .

For the electro-spindle, the maximum vibration position is located at the drive position, that is, the motor position. Therefore, in some embodiments, referring to FIG. 4 , the vibration sensor 5 is integrated in the stator 31 . The vibration sensor 5 determines the vibration state of the shaft core assembly 2 by monitoring the vibration state of the stator 31, and the structure is more concise, and the vibration sensor 5 integrated in the stator 31 can not only monitor the vibration amplitude, but also monitor the acceleration of vibration and many other vibrations. parameters to further ensure the life of the spindle and the safety of the operator.

The embodiment of the present application uses the vibration monitoring device integrated inside the motor for the first time to ensure that the spindle can "brake" in time when an external abnormality occurs and is about to lock up, thereby ensuring the life of the spindle and the safety of processing operators.

In some embodiments, referring to FIG. 1 , the top of the body assembly 1 is connected to the top cover assembly 6 , and the coolant enters the thrust bearing assembly 41 from the body assembly 1 and the top cover assembly 6 to the upper half of the air bearing assembly 42 and the thrust bearing assembly 41 , the flange assembly 7 and the motor are cooled. A cylinder assembly 8 is connected to the top cover assembly 6, and the cylinder assembly 8 is used to drive the shaft core assembly 2 to make the power output end perform tool change.

The air-floating electric spindle of the embodiment of the present application can be applied to the fields of lamp mold processing, aerospace and other fields, and has the characteristics of high precision, high speed, automatic tool change, etc., the milling surface roughness can reach 20nm, the speed can reach 9W, and the automatic tool change When using the HSK tool holder. Compared with the processing in the related art, it can replace the grinding process or shorten the grinding process time. Compared with other ultra-precision spindles, it has a higher speed and has an HSK automatic tool change mechanism, which can greatly improve the work efficiency.

The embodiments of the present application provide a machine tool, including the air-floating electric spindle of any of the above embodiments. The machine tool has the following characteristics: the copper squirrel cage 32 is used as the rotor and the copper squirrel cage 32 is placed behind to ensure the vibration stability and processing reliability of the spindle. The spindle still maintains the rotation accuracy below 50nm at high speed. The unique spindle vibration detection and alarm device ensures that the spindle is always monitored for abnormality during the rotation of the spindle, and the spindle can be stopped at any time to ensure that the spindle will not be locked due to external factors. The automatic tool change function greatly improves the spindle Processing efficiency, the spindle milling surface accuracy can reach below 20nm.

Claims

An air-floating electric spindle, comprising:

body components;

The shaft core assembly has a flying disc, the shaft core assembly is carried and suspended on the body assembly through a thrust bearing assembly and an air bearing assembly, the first end of the shaft core assembly forms a power output end, and the second end of the shaft core assembly is formed. terminal forms a power input terminal; and

A motor assembly is provided at the power input end, the motor assembly includes a stator and a copper squirrel cage, the stator is connected with the body assembly, the copper squirrel cage is combined with the shaft core assembly, and is formed with the The coaxial cylindrical surface of the shaft core assembly.
The air-floating electric spindle according to claim 1, wherein the flying disc is located at a position where the shaft core assembly is close to the motor assembly, the thrust bearing assembly is located between the flying disc and the motor assembly, and the The air bearing assembly is located on the side of the flying disc away from the motor assembly, the thrust bearing assembly has a first thrust surface matched with the flying disc, and the first thrust surface is provided with a first axial outlet. an air hole, the air bearing assembly has a second thrust surface matched with the flying disc, the second thrust surface is provided with a second axial outlet hole, the air bearing assembly has a The outer peripheral surface of the assembly is matched with the supporting surface, the supporting surface is provided with radial air outlet holes, and the body assembly is provided with the first axial air outlet hole, the second axial air outlet hole and the radial air outlet hole. open air channel.
The air-floating electric spindle according to claim 2, wherein the air-floating bearing assembly has a first bearing surface and a second bearing surface that cooperate with the outer peripheral surface of the shaft core assembly, the first bearing surface and the second bearing surface The two supporting surfaces are distributed along the direction from the power input end to the power output end. The first supporting surface and the second supporting surface are both provided with radial air outlet holes, and the air flotation pressure generated by the radial air outlet holes on the second supporting surface is greater than The air flotation pressure generated by the radial air outlet holes on the first bearing surface.
The air-floating electric spindle according to claim 3, wherein the number of the radial air outlet holes of the second support surface is greater than the number of the radial air outlet holes of the first support surface.
The air-bearing electric spindle according to claim 3 or 4, wherein the density of the radial air outlet holes of the second supporting surface is greater than the density of the radial air outlet holes of the first supporting surface.
The air-floating electric spindle according to claim 3, wherein the first bearing surface and the second bearing surface are separated by a certain distance in the axial direction, and the inner wall of the air bearing assembly is in contact with the first bearing surface and the second bearing surface. The part between the two bearing surfaces and the shaft core assembly leave a non-matching clearance.
The air-floating electric spindle according to claim 1, further comprising:

Vibration sensors for monitoring the vibration of the shaft core assembly; and

The processor controls the motor assembly to stop the shaft core assembly according to the signal of the vibration sensor.
The air-floated electric spindle of claim 7, wherein the vibration sensor is integrated in the stator.
The air-floating electric spindle according to claim 1, further comprising: a cylinder assembly configured to drive the shaft core assembly to enable the power output end to perform tool change.
A machine tool, comprising the air-floating electric spindle according to any one of claims 1 to 9.