WO2012163138A1

WO2012163138A1 - Air bearing, air floatation motion system and method for stabilizing the inner shaft of the air bearing

Info

Publication number: WO2012163138A1
Application number: PCT/CN2012/072573
Authority: WO
Inventors: 何继中
Original assignee: 无锡微焦科技有限公司
Priority date: 2011-05-30
Filing date: 2012-03-19
Publication date: 2012-12-06
Also published as: CN102252022A; CN203348321U

Abstract

Disclosed is an air bearing (100), which bearing (100) comprises an air bearing body (120) and a rotation shaft (140) located within the air bearing body (120), with the rotation shaft (140) containing a cylindrical shaft portion (142) and a flange portion (144) being perpendicular to the axis of the rotation shaft (140), and several gas-guiding holes (122) provided on the air bearing body (120). When the rotation shaft (140) is in a dynamic state, the gas flowing through the gas-guiding holes (122) forms a gas film between the rotation shaft (140) and the air bearing body (120); and when the rotation shaft (140) is in a static state, the gas flowing through the gas-guiding holes (122) provides an axial force to make part of the surface of the flange portion (144) contact closely with the air bearing body (120). When the rotation shaft of the air bearing in the present invention is in a static state, the rotation shaft closely contacts with the air bearing body by using air, such that the rotation shaft can be in a very stable state. At this time, either observation operations or other processing operations can achieve a good effect.

Description

Air bearing, air floating motion system and method for stabilizing inner shaft of air bearing

The present invention relates to an air bearing, and more particularly to the design of a moving part for use in an ultra-precision air-floating motion system.

Background technique

Air Bearing is one of the key components in ultra-precision air-floating motion systems included in equipment such as microscopes, lithography machines, and ultra-precision machining machines. Since the air bearing uses a gas film as a lubricant, it has many advantages such as high rigidity, cleanness and no friction, but it also has the disadvantage of poor stability in some application environments. The stability of the air bearing includes static stability and dynamic stability of the internal shaft at high speed rotation.

Common factors that restrict the static stability of air bearings include air hammer oscillations, micro-vibrations generated on air bearings when gas flows, self-excited resonance of air bearings, and squeeze film effects when carrying objects. For example, micro-vibration is due to the vibration generated by the unstable flow of gas in the airway; and the gas has a large compressibility, which can cause the object carried by the air bearing to be unstable in a certain equilibrium position, but to move in a sinusoidal manner. Self-excited resonance phenomenon. These factors may make the air bearing's stability in the static state worse, and can not meet the needs of the application. In actual use, the shaft in the air bearing is usually driven by a closed-loop control system including a permanent magnet motor, a gas supply device, and a programmable logic controller (PLC). The closed-loop control system is in accordance with a certain The predetermined logic drives the spindle to rotate such that the table connected to the spindle varies in different dynamics and statics. At this time, due to the pressure change between the rotating shaft and the gas film, the magnetic flux change of the permanent magnet motor and other factors further affect the static stability of the air bearing, so that the static stability of the existing air bearing can not meet the requirements of some applications. Claim. For example, a stage containing an air bearing in a microscope needs to be fixed at a specific position for observation. In this case, the air bearing is required to be static, but if the static stability of the air bearing used is poor, the observation may fail or the observation may be inaccurate. For example, a workbench containing an air bearing, such as a lithography machine or an ultra-precision tool, needs to be fixed at a specific position for continuous operation. Similarly, if the static stability of the air bearing is poor, the product will be made. The yield is reduced.

Therefore, it is necessary to provide a new air bearing to solve the above problems.

Summary of the invention

One of the objects of the present invention is to provide an air bearing which has better static stability. Another object of the present invention is to provide an ultra-precision air-floating motion system using the air bearing of the present invention having better static stability.

A third object of the present invention is to provide a method of stabilizing a rotating shaft of an air bearing, which method can provide better static stability of the rotating shaft.

In order to attain the object of the present invention, in accordance with one aspect of the present invention, an air bearing includes an air bearing body and a rotating shaft located in the air bearing body, the rotating shaft including a rotating shaft portion and forming a plurality of air guiding holes formed on the air bearing body on the flange portion on the rotating shaft portion, and when the rotating shaft is dynamic, gas flowing through the air guiding hole is in the rotating shaft and the air bearing body A gas film is formed therebetween; and when the rotating shaft is at a static state, the gas flowing through the air guiding hole provides an axial force to bring a part of the surface of the flange portion into close contact with the air bearing body.

In a still further embodiment, the flange portion is located at a middle portion of the cylindrical shaft portion, and the flange portion has a rectangular shape, a fusiform shape, a circular shape, and a cross-sectional shape along an axis including the rotating shaft. One of the elliptical shapes, the air bearing body is formed with a plurality of pairs of air guiding holes that are perpendicular to the surface of the flange portion and are symmetrical.

In still another further embodiment, the flange portion includes a first flange portion located at an upper portion of the rotating shaft portion and a second flange portion located at a lower portion of the rotating shaft portion, the first flange portion and a second flange portion having a cross-sectional shape including an axis of the rotating shaft is one of a rectangular shape, a fusiform shape, a circular shape, and an elliptical shape, and the air bearing body is formed with a lower surface perpendicular to the first flange portion and A plurality of pairs of air guiding holes that are perpendicular to each other perpendicular to the upper surface of the second flange portion.

In a still further embodiment, the air bearing body includes air guiding holes with respect to upper and lower surfaces of the flange portion, when some or all of the air guiding holes are opposite to one surface of the flange portion Sustaining or accelerating the supply of gas, and the gas provides a perpendicular to the flange portion when a part or all of the air guiding holes of the other surface of the flange portion slows down the supply of the gas, does not supply the gas, or is in a vacuum state. The force of the surface causes the other surface of the flange portion to be in close contact with the air bearing body.

In a still further embodiment, the air bearing further includes a gas supply device connected to the air guiding hole, the gas supply device supplying air to each of the air guiding holes according to a predetermined logic.

In a still further embodiment, the air bearing further includes a driving device coupled to the rotating shaft portion, the driving device driving the rotating shaft portion to rotate according to a predetermined logic. In a still further embodiment, the drive device is a permanent magnet motor.

According to another aspect of the present invention, the present invention provides an ultra-precision air-floating motion system which employs the aforementioned air bearing.

According to still another aspect of the present invention, there is provided a method of stabilizing an inner shaft of an air bearing, the method comprising forming a flange portion on a rotating shaft of the air bearing body, and forming a body in the air bearing body with respect to the Air guiding hole of the flange portion;

When the rotating shaft needs to be changed from static to dynamic, a gas flowing between the rotating shaft and the air bearing body is formed by a gas flowing through an air guiding hole in the air bearing body, and the gas film is driven after the gas film is formed. Rotary shaft rotation;

When the rotating shaft needs to be dynamically changed to static, the rotating shaft is driven to decelerate to a standstill according to a predetermined logic acceleration, and then the gas flowing through the air guiding hole with respect to the flange portion is used to generate an axial direction along the rotating shaft. The force causes a part of the surface of the rotating shaft to come into contact with the air bearing body to be in a stable rest.

In still further embodiments, the air guiding holes with respect to the flange portion are respectively disposed at opposite positions of opposite surfaces of the flange portion, and will be opposite to a surface of the flange portion Continuously supplying gas or accelerating the supply gas in part or all of the air guiding holes, and decelerating the supply of gas, stopping the supply of the gas, or forming a vacuum with respect to the part or all of the air guiding holes of the other surface of the flange portion, so that the gas is supplied a force acting along the axial direction of the rotating shaft is given to the rotating shaft such that a part of the surface of the rotating shaft including the other surface of the flange portion is in contact with the air bearing body to be in a stable still state, wherein gas in each air guiding hole The supply rate and variation of the vacuum are controlled by predetermined logic.

Compared with the prior art, the air bearing of the present invention uses air to bring the rotating shaft into close contact with the air bearing body when the rotating shaft is at a static state, so that the rotating shaft can be in a very stable state. At this time, good results can be obtained regardless of the observation operation or other processing operations.

DRAWINGS

The invention will be more readily understood by reference to the appended drawings and the detailed description in which <RTIgt;

Figure 1 is a schematic cross-sectional view showing an air bearing in an embodiment of the present invention;

Figure 2 is a schematic view showing the principle of an air bearing in an embodiment of the present invention;

Figure 3 is a perspective view of the rotating shaft of the present invention in another embodiment;

Figure 4 is a perspective view showing the rotating shaft of the present invention in still another embodiment; Figure 5 is a perspective view showing the rotating shaft of the present invention in still another embodiment;

Figure 6 is a schematic view showing the structure of an ultra-precision air-floating motion system in an embodiment of the present invention; and Figure 7 is a flow chart showing the method of stabilizing an air bearing center shaft in one embodiment of the present invention.

detailed description

The above described objects, features and advantages of the present invention will become more apparent from the aspects of the appended claims.

Referring to Figure 1, there is shown a cross-sectional schematic view of an air bearing of the present invention in an embodiment 100. The air bearing 100 includes an air bearing body 120 and a rotating shaft 140 located within the air bearing body 120.

The rotating shaft 140 includes a cylindrical rotating shaft portion 142 and a flange portion 144 formed perpendicular to the axis of the rotating shaft, and the flange portion 144 is located at a middle portion of the cylindrical rotating shaft portion 142, and the The cross section of the flange portion 144 on the section including the axis of the rotating shaft (that is, the cross section shown in the figure) has a rectangular shape. The air bearing body 120 is formed with a plurality of air guiding holes 122, which are generally present in pairs and are relatively perpendicular to the surface of the flange portion 144.

When the rotating shaft 140 is dynamic, that is, when the rotating shaft 140 rotates, the gas flowing through the air guiding hole 122 forms a gas film between the rotating shaft 140 and the air bearing body 120. With the above structure, the basic functions of the air bearing are realized. In particular, when the rotating shaft 140 is rotated to a certain position and needs to be rotated to be static, the prior art stops the rotating shaft 140 from rotating at a certain acceleration or stops driving the rotating shaft 140 to rotate, thereby stopping the rotating shaft 140 at a predetermined position. stand still. In the embodiment, after the rotating shaft 140 is static in the prior art, the gas flowing through the air guiding hole 122 further provides an axial force to make the upper surface or the lower surface of the flange portion 144 and the The air bearing body 120 is in close contact. That is, after the rotating shaft 140 is static, the air guiding hole 122 located above the upper surface of the flange portion 144 may be used to continue the air conduction, and the air guiding hole 122 located below the lower surface of the flange portion 144 is stopped. Air, suction, or in a vacuum form to generate a negative pressure, generating an axial and downward force such that the lower surface of the flange portion 144 is in close contact with the air bearing body 120 such that the flange portion 144 The local portion of the air bearing body 120 produces a close fit effect similar to "vacuum suction." Obviously, when the lower surface of the flange portion 144 is in close contact with the air bearing body 120, factors such as air flow and the static stability of the rotating shaft 140 will be minimized. At this time, the rotating shaft 140 maintains a good static stability. The specific principle can be seen in Figure 2. Need to pay attention In other words, the air guiding hole in the air bearing body 120 with respect to the surface of the rotating shaft portion of the rotating shaft 140 should continue to stably supply the gas to maintain the force balance of the rotating shaft 140 in the radial direction.

When the rotating shaft 140 is in a static state and needs to be changed to dynamic, it is necessary to first conduct the air guiding holes 122 above and below the upper surface of the flange portion 144 to continue to conduct air, in the rotating shaft 140 and the air bearing. The air film is reformed between the bodies 120, and then the driving device that drives the rotation of the rotating shaft 140 generates a driving force, so that the rotating shaft 140 starts to rotate.

In summary, the air bearing uses air to form a lubricating gas film on the one hand when its internal rotating shaft is dynamic or rotating; on the other hand, when its internal rotating shaft is static, the rotating shaft and the air bearing are used by air. The bodies are tightly pressed together to increase the static stability of the air bearing. For details not disclosed in FIG. 1, such as the shape, number and position of the air vents, the structure of the air supply passage, various implementation structures of the air bearing body, etc., are well known and easily implemented by those skilled in the art. Repeatedly. It is easy to understand that those skilled in the art can also use more improved details to achieve better static stability. For example, controlling the rotating shaft, in particular, a gap of a reasonable width between the flange portion on the rotating shaft and the air bearing body to cause a radial error as small as possible when the rotating shaft moves in the axial direction; The rotating shaft, in particular, the surface of the flange portion on the rotating shaft and the air bearing body should have a shape that fits as much as possible; for example, the rotating shaft and the air bearing body should be selected to have appropriate hardness, plasticity and The wear-resistant material is made to avoid abrasion, dust, and the like when the shaft and the air bearing body are attached.

Although the cross-sectional shape of the flange portion 144 shown in FIG. 1 is rectangular, it is easy to be considered that the flange portion 144 may be located at any position of the rotating shaft portion 142, and the cross section of the flange portion 144 may be The shape may also be other shapes, and the flange portion 344 in the rotating shaft 340 as shown in FIG. 3 has a cross-sectional shape of a shuttle shape and is located at the upper middle portion of the rotating shaft portion 342; and a rotating shaft 440 as shown in FIG. The flange portion 444 has a substantially elliptical cross-sectional shape and is located at a lower middle portion of the rotating shaft portion 442. Further, the rotating shaft 540 shown in FIG. 5 includes two flange portions including the rotating shaft portion 542. An upper first flange portion 544 and a second flange portion 546 located at a lower portion of the rotating shaft portion 542, and the first flange portion 544 and the second flange portion 546 have a sectional shape along an axis including the rotating shaft Semicircular. Regardless of the specific location of the flange portion and the shape of the specific shape, one of the important points and points of the present invention is to provide an axial force through the air such that a certain portion or surface of the shaft is tightly attached to the air bearing body. Contact, so that the shaft can be static and has good stability.

Please continue to refer to FIG. 6, which illustrates an ultra-precision air-floating motion system in the present invention in one embodiment. Schematic diagram of the structure in 600. The ultra-precision air-floating motion system 600 includes an air bearing 620, a gas supply device 640 connected to an air guiding hole in the air bearing 620, a driving device 660 connected to a rotating shaft in the air bearing 620, and a control device 680.

The air bearing 620 includes an air bearing body 622 and a rotating shaft 624, and the air bearing body 622 includes air guiding holes therein. The air bearing 620 has a structure substantially similar to the air bearing shown in Fig. 1. The air bearing 620 is capable of bringing a portion of the rotating shaft 624 into close contact with the air bearing body 622 with air when the rotating shaft 624 is stationary. One end of the rotating shaft 624 is connected to the table 628, and the other end of the rotating shaft 624 is connected to the driving device 660.

The air supply device 640 includes a gas supply module 641, a filter 642, a flow dividing head 643, and a gas pipe connected to the air guiding hole. The air pipe 644 includes a controllable wide door 645. The air pump 641 and the controllable wide door 645 are coupled to the control unit 680. In one embodiment, the gas supply module 641 includes one or more of a gas treatment device such as an air pump, an inert gas source, a vacuum pump, a compressor, and a dryer to provide a certain pressure gas or vacuum to the chamber. The trachea 644 is described. The controllable wide gate 645 can be controlled by the control device 680 using a control technique such as Pulse Width Modulation (PWM) technology, and is respectively in an open state, a closed state, or in a predetermined state according to predetermined logic at different time periods. Flow control status, etc.

The drive unit 660 can be a permanent magnet motor 660 that is coupled to the shaft 624 of the air bearing 620 and that drives the shaft 624 to rotate or rest. The permanent magnet motor 660 is also coupled to the control device 680.

The control device 680 can be a PLC programmable control system including a grating sensor 682 and a single-chip microcomputer 684, and the grating sensor 682 can detect a displacement change on the table 626, and transmit the detection result to the single-chip microcomputer. 684. The single chip microcomputer 684 can generate control logic according to the detection result and a user input, and control the switch or flow of the controllable wide door 645 by using the control logic, and control a rotation angle of the permanent magnet motor 662. And speed.

With the above construction, a closed loop control system can be formed which generates predetermined control logic for controlling the positional change of the rotary shaft 624 and the table 628 connected thereto in accordance with the user's input.

When the rotating shaft 624 and the table 628 connected thereto are dynamic, the control device 680 controls the controllable wide door 645 to be in an on state, and an air film is formed between the air bearing body 622 and the rotating shaft 624. The air bearing 620 can rotate normally.

When the rotating shaft 624 and the table 628 connected thereto are about to rotate or be displaced to a specific position In response, the control device 680 controls the permanent magnet motor 662 to decelerate at a certain acceleration such that the table 628 is just stopped when rotated to the particular position, and the error is corrected based on feedback from the grating sensor 682.

When the table 628 is static at the specific position, the control device 680 controls some of the controllable wide doors 645 to be in a closed state such that the air bearing body 622 and the partial surface of the rotating shaft 624 The intimate contact is made so that the table can be stably located at the specific position, facilitating other operations such as monitoring, machining, cutting, and the like.

Obviously, for better control effect, the control device can also control the air outlet amount of the air pump and other factors; the control device can also adopt better control logic to control the amount of air entering each air guiding hole, and the like. . Because such technical details are not related to the substance of the invention on the one hand, and are also readily achievable by those skilled in the art on the other hand, the detailed disclosure is not continued herein.

With continued reference to Figure 7, there is shown a flow chart of a method of stabilizing an air bearing center shaft in an embodiment 700 of the present invention. The method of stabilizing the intermediate shaft of the air bearing requires that a flange portion is formed in advance in the shaft portion of the air bearing, and an air guiding hole with respect to the flange portion is formed in the air bearing body. The method 700 of stabilizing an air bearing center shaft includes:

Step 701, since the initial state, all the air guiding holes may be non-conductive. First, it is necessary to supply air to the air bearing such that a stable air film is formed between the rotating shaft and the air bearing, and the rotating shaft is at a static state.

Step 702, after a stable air film is formed between the rotating shaft and the air bearing, the rotating shaft is driven to rotate by a driving device such as a permanent magnet motor, so that the rotating shaft is dynamic. The rotating shaft is dynamic including the rotating shaft rotating at a constant acceleration according to a predetermined control logic, or rotating at a constant speed, or rotating at a certain variable acceleration.

Step 703, when the rotating shaft needs to change from dynamic to static, the rotating shaft may be driven to rotate at a negative acceleration until decelerating until the speed is zero, and then remain static, or other driving and stopping the rotating shaft may be adopted to make the rotating shaft Stop rotating and stay in a predetermined position.

Step 704, when the rotating shaft becomes static, generating a force along the axial direction of the rotating shaft by using the gas flowing through the air guiding hole with respect to the flange portion, so that a part of the surface of the rotating shaft and the air bearing The body is in contact and is in a stable static state. It is foreseen that the force acting in the axial direction of the rotating shaft by the gas flowing through the air guiding holes with respect to the flange portion can be employed in various ways. For example, the air guiding holes with respect to the flange portion may be respectively disposed at opposite positions of upper and lower surfaces of the flange portion Providing that gas is continuously supplied or accelerated in a part or all of the air guiding holes of the upper surface of the flange portion, and gas is decelerated in a part or all of the air guiding holes of the lower surface of the flange portion, Stop supplying a gas or forming a vacuum such that the gas provides a force in the axial direction of the rotating shaft to the rotating shaft such that a part of the surface of the rotating shaft including the other surface of the flange portion is in contact with the air bearing body It is stable and still. However, the stability of the shaft in the radial direction should be maintained, and only the axial force is generated on the shaft.

At the same time, reasonable gas supply control should be taken to maintain a smoother process when the shaft moves in the axial direction. That is, in the process of contacting the rotating shaft with the surface of the air bearing body, the two surfaces are brought into contact as gently as possible, and then the pressure is gradually increased so that the rotating shaft is close to the air bearing body. fit. Instead of using a relatively sudden or rushing manner, it is avoided that the rotating shaft collides with the air bearing body to cause damage and dust.

Step 705, when the rotating shaft needs to be re-dynamic, the axial force generated by the gas is gradually canceled, so that a stable gas film is formed between the rotating shaft and the air bearing body, and the The shaft is static.

Step 706, returning to step 702, after a stable air film is formed between the rotating shaft and the air bearing, the rotating shaft is driven to rotate by a driving device such as a permanent magnet motor, so that the rotating shaft is dynamic.

Obviously, repeating some of the steps in the above process can cause the shaft to transition between dynamic, static and stable static. The entire process can achieve closed-loop control through the corresponding control logic, resulting in a more stable and efficient system, improving the static stability of air bearings in some application scenarios.

The above description has fully disclosed the specific embodiments of the present invention. It is to be understood that any changes to the specific embodiments of the invention may be made by those skilled in the art without departing from the scope of the invention. Accordingly, the scope of the claims of the invention is not limited to the specific embodiments.

Claims

Claim

An air bearing, characterized in that it comprises:

An air bearing body and a rotating shaft located in the air bearing body, the rotating shaft includes a rotating shaft portion and a flange portion formed on the rotating shaft portion, and the air bearing body is formed with a plurality of air guiding holes

When the rotating shaft is dynamic, gas flowing through the air guiding hole forms a gas film between the rotating shaft and the air bearing body; and

When the rotating shaft is at a static state, the gas flowing through the air guiding hole provides an axial force to bring a part of the surface of the flange portion into close contact with the air bearing body.

2. The air bearing according to claim 1, wherein the flange portion is located at a middle portion of the cylindrical shaft portion, and the flange portion has a rectangular shape along a cross-sectional shape including an axis of the rotating shaft. And one of a fusiform shape, a circular shape and an elliptical shape, wherein the air bearing body is formed with a plurality of pairs of air guiding holes which are perpendicular to the surface of the flange portion and are symmetrical.

The air bearing according to claim 1, wherein the flange portion includes a first flange portion located at an upper portion of the rotating shaft portion and a second flange portion located at a lower portion of the rotating shaft portion, The cross-sectional shape of the first flange portion and the second flange portion along the axis including the rotating shaft is one of a rectangular shape, a fusiform shape, a circular shape, and an elliptical shape, and the air bearing body is formed to be perpendicular to the first portion a flange lower surface and a plurality of pairs of air guiding holes that are perpendicular to each other perpendicular to the upper surface of the second flange portion.

The air bearing according to any one of claims 1 to 3, wherein the air bearing body includes air guiding holes with respect to upper and lower surfaces of the flange portion, when relative to the convex Part or all of the air guiding holes of one surface of the edge portion continue or accelerate the supply of gas, and when some or all of the air guiding holes of the other surface of the flange portion slow down the supply of the gas, do not supply the gas, or are in a vacuum state, The gas provides a force perpendicular to one surface of the flange portion such that the other surface of the flange portion is in close contact with the air bearing body.

The air bearing according to claim 4, wherein the air bearing further comprises a gas supply device connected to the air guiding hole, wherein the air supply device supplies gas or vacuum to each air guiding hole according to a predetermined logic. .

The air bearing according to claim 4, wherein the air bearing further includes a driving device connected to the rotating shaft portion, and the driving device drives the rotating shaft portion to rotate according to a predetermined logic.

7. The air bearing according to claim 6, wherein the driving device is a permanent magnet motor.

An ultra-precision air-floating motion system, characterized in that it comprises the air bearing according to any one of claims 1 to 7.

9. A method of stabilizing an inner shaft of an air bearing, characterized in that it comprises:

Forming a flange portion on a rotating shaft of the air bearing body, and forming an air guiding hole with respect to the flange portion in the air bearing body;

10. The method of stabilizing an inner shaft of an air bearing according to claim 9, wherein said air guiding holes with respect to said flange portion are respectively disposed on opposite sides of said flange portion Location,

The gas is continuously supplied or accelerated in a part or all of the air guiding holes of one surface of the flange portion, and the gas is decelerated and stopped in a part or all of the air guiding holes of the other surface of the flange portion. Supplying a gas or forming a vacuum such that the gas provides a force in the axial direction of the rotating shaft to the rotating shaft such that a part of the surface of the rotating shaft including the other surface of the flange portion is in contact with the air bearing body In a stable still state,

Wherein, the supply rate and variation of gas and vacuum in each of the air guiding holes are controlled by predetermined logic.