WO2022036990A1

WO2022036990A1 - Air bearing spindle and grinding machine tool

Info

Publication number: WO2022036990A1
Application number: PCT/CN2020/141659
Authority: WO
Inventors: 朱胜利; 张翰乾; 汤丽君; 汤秀清
Original assignee: 广州市昊志机电股份有限公司
Priority date: 2020-08-18
Filing date: 2020-12-30
Publication date: 2022-02-24
Also published as: CN112059902A

Abstract

An air bearing spindle, comprising: a machine body (1) provided with a shaft hole, a shaft core (2), a motor assembly (7) used for driving the shaft core (2) to rotate, an air bearing (3), a thrust bearing (4), and an intake channel (6). The shaft core (2) is arranged in the shaft hole in a penetrating manner, and is provided with a thrust flying disc (21); the air bearing (3) is disposed in the shaft hole, and matches the outer circle bearing surface of the shaft core (2); the thrust bearing (4) comprises a front thrust bearing (41) and a rear thrust bearing (42), which respectively match the front and rear surfaces of the thrust flying disc (21); the intake channel (6) comprises a main intake channel (61), a first branch intake channel (62), and a second branch intake channel (63), the first and second branch intake channels (62, 63) are respectively connected to the front and rear thrust bearings (41, 42), and the apertures of the first and second branch intake channels (62, 63) are 0.8-1.0 mm. The air bearing spindle can effectively prevent the thrust bearing from generating air vibration, thereby greatly improving the rigidity and dynamic rotation precision of the spindle. Also provided is a grinding machine tool comprising the air bearing spindle.

Description

Air Float Spindles and Grinding Machines

This application claims the priority of the Chinese patent application with application number 202010833257.0 filed with the China Patent Office on August 18, 2020, the entire contents of which are incorporated herein by reference.

technical field

The present application is used in the field of electric spindles, for example, it relates to an air-floating electric spindle and a grinding machine tool.

Background technique

Modern manufacturing is developing in the direction of high speed, high precision and high efficiency. As the "heart" of high-performance machine tools, high-speed motorized spindles are the most important guarantee for the realization of the above functions. Compared with ball bearings, due to the low viscosity of air as a lubricating medium, aerostatic bearings have the advantages of low friction and wear, less heat generation, high and low temperature resistance, and long life. Rotation accuracy, these advantages can make the air static electric spindle achieve high running speed and rotation accuracy, so as to meet the conditions for high-speed and high-precision cutting.

There is a common technical difficulty in high-rigidity air-floating spindles: the thrust bearing is prone to static air vibration (or air hammer vibration), which brings great trouble to the rigidity of the spindle, and there is no effective solution so far.

SUMMARY OF THE INVENTION

The present application solves at least one of the technical problems existing in the related art, and provides an air-floating electric spindle and a grinding machine tool, which can effectively avoid the gas vibration of the thrust bearing and greatly improve the rigidity and dynamic rotation accuracy of the spindle.

The technical solution adopted by this application to solve its technical problems is:

In a first aspect, an air-floating electric spindle includes:

The body is provided with a shaft hole;

The shaft core is inserted into the shaft hole, and a thrust flying disc is arranged on the shaft core;

a motor assembly for driving the shaft to rotate;

an air bearing, which is arranged in the shaft hole and is matched with the outer circular bearing surface of the shaft core;

a thrust bearing, including a front thrust bearing and a rear thrust bearing, the front thrust bearing is matched with the front surface of the thrust flying disc, and the rear thrust bearing is matched with the rear surface of the thrust flying disc;

The intake channel includes a main intake channel, the main intake channel is branched into a branch intake channel, the branch intake channel includes a first branch intake channel and a second branch intake channel, and the first branch intake channel is divided into a branch intake channel. The air passage is connected to the front thrust bearing, the second branch air inlet passage is connected to the rear thrust bearing, and the apertures of the first branch air passage and the second branch air passage are 0.8-1.0 mm .

With reference to the first aspect, in some implementations of the first aspect, a plurality of the first branch air intake passages are distributed along the circumferential direction of the front thrust bearing, and each of the first branch air intake passages is along the front thrust bearing. The axial direction of the thrust bearing extends, and an air outlet is formed on the rear surface of the front thrust bearing; a plurality of the second branch air intake passages are distributed along the circumferential direction of the rear thrust bearing, and each of the second branches The air intake passage extends in the axial direction of the rear thrust bearing, and an air outlet is formed on the front surface of the rear thrust bearing.

In combination with the first aspect and the foregoing implementation manners, in some implementation manners of the first aspect, the motor assembly adopts a permanent magnet synchronous motor.

With reference to the first aspect and the above implementations, in some implementations of the first aspect, the motor assembly includes a stator and a rotor, the rotor is connected to the shaft core, the stator is connected to the body, and the The inner circular surface of the stator is provided with inclined grooves, a plurality of the inclined grooves are distributed along the circumferential direction of the inner circular surface of the stator, the inclined grooves extend along the axis of the rotor, and form an included angle with the axis of the rotor.

In combination with the first aspect and the above implementations, in some implementations of the first aspect, the output end of the shaft core is connected to a grinding wheel.

In combination with the first aspect and the above implementations, in some implementations of the first aspect, the output end of the shaft core is provided with an outer tapered surface, and the grinding wheel has an inner tapered hole matched with the outer tapered surface, so The grinding wheel is sleeved on the output end of the shaft core and locked by an axial locking structure.

In combination with the first aspect and the above implementations, in some implementations of the first aspect, the end face of the output end of the shaft core is provided with a threaded hole, and the grinding wheel is provided with a screw hole at the bottom of the inner tapered hole , the grinding wheel is locked by a screw connected to the threaded hole.

In combination with the first aspect and the above implementations, in some implementations of the first aspect, the inner tapered hole and the threaded hole are both coincident with the axis of the shaft core, and the shaft core is provided with the same shaft on the outside of the threaded hole. A shaft positioning hole, the screw has a coaxial positioning section matched with the coaxial positioning hole.

In combination with the first aspect and the above implementations, in some implementations of the first aspect, a blind hole is provided at the front end of the grinding wheel, and the screw is located in the blind hole.

In a second aspect, a grinding machine tool includes the air-floating electric spindle described in any one of the implementations of the first aspect.

One of the above technical solutions has at least one of the following advantages or beneficial effects: In order to solve the problem caused by static air vibration to increase the rigidity of the main shaft, the embodiment of the present application finally determined that the diameter of the branch air intake cross-section was 0.8~ When the range is 1.0mm, the thrust direction frequency of the thrust bearing can be avoided from the shafting frequency, and the gas vibration of the thrust bearing can be effectively avoided. After the implementation of this scheme, the rigidity of the spindle has been greatly improved, the dynamic rotation accuracy of the spindle has reached within 0.05μm, and the processing data has reached the same level in foreign countries.

Additional aspects and advantages of the present application will be set forth, in part, from the following description, and in part will become apparent from the following description, or may be learned by practice of the present application.

Description of drawings

The above and/or additional aspects and advantages of the present application will become apparent and readily understood from the following description of embodiments in conjunction with the accompanying drawings, wherein:

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

Fig. 2 is a partial enlarged view at A in Fig. 1;

FIG. 3 is a schematic diagram of the stator structure of the motor assembly of one embodiment shown in FIG. 1;

FIG. 4 is a graph showing the thrust direction frequency f1 and the shafting frequency f2 corresponding to the apertures of different branch intake passages.

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 specific characteristics Orientation, construction and operation in a particular orientation, and therefore should not be construed as a limitation of the present 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 and 2 show the reference direction coordinate system of the embodiments of the present application, and the embodiments of the present application will be described below with reference to the directions shown in FIGS. 1 and 2 .

Referring to FIG. 1 , an embodiment of the present application provides an air-floating electric spindle, including a body 1, a shaft core 2, a motor assembly 7, an air bearing 3, a thrust bearing 4 and an air intake channel 6, and the body 1 is an assembly spindle The carrier is provided with cooling axial water channels. The body 1 is provided with a shaft hole, the front end of the air bearing 3 is fixed by screws, the inner hole of the rear end is equipped with a motor assembly 7, and the rear end is connected to the back cover by screws. The shaft core 2 of the component is inserted through the shaft hole, and the shaft core 2 is provided with a thrust flying disc 21 . The air bearing 3 is arranged in the shaft hole and is matched with the outer circular bearing surface of the shaft core 2. The thrust bearing 4 includes a front thrust bearing 41 and a rear thrust bearing 42. The front thrust bearing 41 is matched with the front surface of the thrust flying disc 21, and the rear thrust bearing 42 is matched with the rear surface of the thrust flying disc 21. The distance between the bearing 41 and the rear thrust bearing 42 is adjusted with the thrust fly disc 21 through the clearance plate 43 . The outer side of the front thrust bearing 41 is provided with a protective cover 5 .

Referring to FIGS. 1 and 2 , the intake passage 6 includes a main intake passage 61 , and one or more main intake passages 61 may be provided. The main intake passage 61 is branched into a branch intake passage 6 , and the branch intake passage 6 includes a first intake passage 61 . A branched air intake passage 62 and a second branched air intake passage 63 , and the first branched air intake passage 62 is connected to the front thrust bearing 41 to form an air film gap between the front thrust bearing 41 and the thrust flywheel 21 . Correspondingly, the second branch air intake passage 63 is connected to the rear thrust bearing 42 to form an air film gap between the front thrust bearing 41 and the thrust flywheel 21 .

The working process of a certain embodiment is described. The air bearing 3 and the thrust bearing 4 support the suspended state of the shaft core 2, and then connect the main shaft and the inlet and outlet pipes of the cooling equipment, and finally connect the variable frequency driver and the main shaft motor, and the motor drives the shaft. Core 2 operates at high speed.

In order to solve the problem caused by static air vibration to the increase of the rigidity of the main shaft, in the embodiment of the present application, it is finally determined that the apertures of the first branch intake passage 62 and the second branch intake passage 63 are 0.8-1.0 mm after many experiments. 4. When the diameter of the branch inlet section is 0.8 to 1.0 mm, the frequency of the thrust direction of the thrust bearing 4 can be avoided from the frequency of the shaft system, effectively avoiding the gas vibration of the thrust bearing 4, and solving the problem of the high rigidity of the thrust bearing 4 is easy. The problem of generating static air vibration, the experimental conclusion has been verified and effective in a variety of air flotation spindles, which has the significance of public promotion. After the implementation of this scheme, the rigidity of the spindle has been greatly improved, the dynamic rotation accuracy of the spindle has reached within 0.05μm, and the processing data has reached the same level in foreign countries.

Referring to FIG. 2 , a plurality of first branch air intake passages 62 are distributed along the circumferential direction of the front thrust bearing 41 , and each of the first branch air intake passages 62 extends along the axial direction of the front thrust bearing 41 and extends in the front thrust bearing 41 . An air outlet is formed on the rear surface of the rear thrust bearing 41 to form a uniform air film gap on the front side of the thrust flying disc 21; a plurality of second branch air intake passages 63 are distributed along the circumferential direction of the rear thrust bearing 42, and each second branch enters the air gap 41. The air passage 63 extends in the axial direction of the rear thrust bearing 42 and forms an air outlet on the front surface of the rear thrust bearing 42 to form a uniform air film gap on the rear side of the thrust flywheel 21 .

The motor assembly 7 is used to drive the shaft core 2 to rotate at a high speed. In some embodiments, the motor assembly 7 adopts a permanent magnet synchronous motor. Compared with an asynchronous motor, the permanent magnet synchronous motor has lower loss and lower temperature rise due to no current in the rotor. It is beneficial to the spindle to obtain better rotation accuracy, high power factor and high efficiency. The motor of the same size can output more power, as well as better dynamic response characteristics and running stability. The driving accuracy of the spindle motor is greatly improved, which is conducive to the improvement of processing quality.

Further, referring to FIGS. 1 and 3, the motor assembly 7 includes a stator 71 and a rotor 72, the rotor 72 is connected to the shaft core 2, the stator 71 is connected to the body 1, and the inner circular surface of the stator 71 is provided with inclined grooves 73, a plurality of The inclined grooves 73 are distributed along the circumference of the inner circular surface of the stator 71 . The inclined grooves 73 extend along the axis of the rotor 72 and form an included angle with the axis of the rotor 72 . By adopting the iron core inclined slot 73 technology, the vibration frequency of the cogging is changed to avoid the influence on the spindle speed range. Attenuate the high frequency harmonic vibration of stator 71, effectively solve the impact of motor cogging vibration on the vibration of the main shaft, realize no vibration peak in the full speed range of the main shaft, more stable high-speed performance and less vibration.

In some embodiments, referring to FIG. 1 and FIG. 2 , the output end of the shaft core 2 is connected to the grinding wheel 8 to form an electric spindle for air flotation grinding, which can be used for grinding the inner hole and the inner taper hole of the core component, for example, the fuel injection nozzle. Machining, polishing and grinding of superhard materials to achieve higher surface quality, shape and dimensional accuracy, and have the performance characteristics of high rigidity, low vibration and low elongation.

The poor installation of the grinding wheel 8 causes excessive vibration of the main shaft and poor processing quality, which are common phenomena in the industry. Referring to Figure 2, the output end of the shaft core 2 is provided with an outer tapered surface 22, and the grinding wheel 8 has an inner tapered hole that cooperates with the outer tapered surface 22. The taper of the inner tapered hole and the outer tapered surface 22 can be a small angle long taper (1:20 taper). The grinding wheel 8 is sleeved on the output end of the shaft core 2 and locked by the axial locking structure. The tapered surfaces 22 cooperate with each other to automatically achieve centering and ensure repeatable assembly accuracy within 1 μm. This embodiment innovatively adopts the self-centering locking structure of the replacement tool, which effectively reduces the mass eccentricity caused by the installation of the grinding wheel 8, does not require rebalancing and correction, achieves higher rotation accuracy and low vibration performance characteristics, and significantly improves the processing quality.

The axial locking structure can be a buckle, a screw, a pull stud, etc. For example, in some embodiments, referring to FIG. 2 , the end face of the output end of the shaft core 2 is provided with a threaded hole, and the grinding wheel 8 is provided with a bottom hole of the inner tapered hole. There are screw holes, and the grinding wheel 8 is locked by screws 9 connected to the threaded holes. Thread locking ensures that the thread locking force is transmitted to the tool in a straight line to achieve the purpose of locking, without affecting the accuracy of tool assembly, improving processing quality and reducing spindle vibration.

The inner taper hole and the threaded hole are both coincident with the axis of the shaft core 2 , the shaft core 2 is provided with a coaxial positioning hole 23 outside the threaded hole, and the screw 9 has a coaxial positioning section 91 matched with the coaxial positioning hole 23 . The coaxial locating hole 23 and the coaxial locating section 91 cooperate with each other to achieve locking. While achieving the purpose of locking, the tool assembly accuracy is not affected, and the processing quality is improved and the spindle low vibration is achieved.

In order to prevent the screw from affecting the grinding of the grinding wheel 8 and to prevent the screw from being damaged during grinding, the front end of the grinding wheel 8 is provided with a blind hole 81, and the screw is located in the blind hole for concealment.

A grinding machine tool includes the air-floating electric spindle of any of the above embodiments. It can achieve higher machining accuracy, higher efficiency machining, and meet the new needs of the market.

In the description of this specification, a description with reference to the terms "example", "embodiment" or "some embodiments" etc. means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one of the present application in one embodiment or example. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Claims

An air-floating electric spindle, comprising:

The body is provided with a shaft hole;

The shaft core is inserted into the shaft hole, and a thrust flying disc is arranged on the shaft core;

a motor assembly for driving the shaft to rotate;

an air bearing, which is arranged in the shaft hole and is matched with the outer circular bearing surface of the shaft core;

a thrust bearing, including a front thrust bearing and a rear thrust bearing, the front thrust bearing is matched with the front surface of the thrust flying disc, and the rear thrust bearing is matched with the rear surface of the thrust flying disc;

The intake channel includes a main intake channel, the main intake channel is branched into a branch intake channel, the branch intake channel includes a first branch intake channel and a second branch intake channel, and the first branch intake channel is divided into a branch intake channel. The air passage is connected to the front thrust bearing, the second branch air inlet passage is connected to the rear thrust bearing, and the apertures of the first branch air passage and the second branch air passage are 0.8-1.0 mm .
The air-floating electric spindle according to claim 1, wherein a plurality of the first branch air intake passages are distributed along the circumferential direction of the front thrust bearing, and each of the first branch air intake passages is along the front thrust bearing. The axial direction of the bearing extends, and an air outlet is formed on the rear surface of the front thrust bearing; a plurality of the second branch air intake passages are distributed along the circumferential direction of the rear thrust bearing, and each second branch air intake A channel extends in the axial direction of the rear thrust bearing and forms an air outlet on the front surface of the rear thrust bearing.
The air-floated electric spindle according to claim 1, wherein the motor assembly adopts a permanent magnet synchronous motor.
The air-floating electric spindle according to claim 3, wherein the motor assembly comprises a stator and a rotor, the rotor is connected with the shaft core, the stator is connected with the body, and the inner circular surface of the stator is There are inclined slots, a plurality of the inclined slots are distributed along the circumference of the inner circular surface of the stator, the inclined slots extend along the axis of the rotor, and form an included angle with the axis of the rotor.
The air-floating electric spindle according to claim 1, wherein the output end of the shaft core is connected to the grinding wheel.
The air-floating electric spindle according to claim 5, wherein the output end of the shaft core is provided with an outer tapered surface, the grinding wheel has an inner tapered hole matched with the outer tapered surface, and the grinding wheel is sleeved on the The output end of the shaft core is locked by the axial locking structure.
The air-floating electric spindle according to claim 6, wherein the end surface of the output end of the shaft core is provided with a threaded hole, the grinding wheel is provided with a screw hole at the bottom of the inner taper hole, and the grinding wheel is connected by Tighten the screws in the threaded holes.
The air-floating electric spindle according to claim 7, wherein the inner tapered hole and the threaded hole are both coincident with the axis of the shaft core, the shaft core is provided with a coaxial positioning hole on the outer side of the threaded hole, and the The screw has a coaxial positioning segment matched with the coaxial positioning hole.
The air-floating electric spindle according to claim 7, wherein the front end of the grinding wheel is provided with a blind hole, and the screw is located in the blind hole.
A grinding machine tool comprising the air-floated electric spindle according to any one of claims 1 to 9.