A gas bearing assembly and air floating motorized spindle having the same

Abstract

The application relates to the technical field of ultra-precision machining equipment, in particular to a gas bearing assembly and a gas-floating motorized spindle with the same, which comprises an outer shell and a radial gas bearing arranged in the outer shell, a ring-shaped air inlet groove is arranged on the inner wall of the outer shell and corresponds to the position of the radial gas bearing, a closed air inlet cavity is formed between the ring-shaped air inlet groove and the outer cylindrical surface of the radial gas bearing, a plurality of air inlet holes which are in communication with the air inlet cavity are circumferentially distributed on the outer cylindrical surface of the radial gas bearing, a throttling hole which is in communication with the air inlet hole is arranged on the inner cylindrical surface of the radial gas bearing, and a composite pressure equalizing structure which is in communication with the throttling hole; the composite pressure equalizing structure comprises at least one circumferential pressure equalizing groove and at least one axial pressure equalizing groove, and the circumferential pressure equalizing groove is a discontinuous structure which is discontinuous along the circumferential direction. The radial gas bearing is designed as a two-section type and an intermediate air outlet structure, the composite pressure equalizing groove which is combined with the circumferential discontinuous structure and the axial communication structure optimizes the pressure field distribution, suppresses the radial runout of the spindle rotor, and thus the supporting stiffness and the machining precision are improved.

Description

Technical Field

[0001] This invention relates to the field of ultra-precision machining equipment technology, and in particular to a gas bearing assembly and an air-bearing electric spindle having the same. Background Technology

[0002] Air-bearing electric spindles are widely used in ultra-precision machining fields such as wafer dicing, wafer thinning, and precision grinding due to their advantages of no mechanical contact, high speed, and high precision. Their core component is the gas bearing assembly, which enables contactless support and positioning of the spindle rotor.

[0003] Existing air-bearing electric spindles, especially those used in wafer dicing machines, still have the following technical problems under high-speed operating conditions: (1) The structural design of traditional radial gas bearings (such as the arrangement of pressure equalizing grooves) has limitations, resulting in insufficient support stiffness and difficulty in effectively suppressing the radial runout of the spindle rotor at high speeds, thus affecting the machining accuracy. Through research by the inventors, it has been found that some bearings use continuous circumferential pressure equalizing grooves. Although they can equalize the pressure, when the rotor is eccentric, the circumferential pressure difference will decrease, which will reduce the dynamic stiffness of the bearing.

[0004] (2) The improper assembly method of the bearing assembly and the housing can easily lead to coaxiality deviation. At the same time, the gas in the air supply system can easily enter the gap between the sleeve and the housing, generating eddies and vibrations, which seriously affect the stability of the spindle operation and shorten the bearing life.

[0005] (3) The design of the center of mass position of the main shaft rotor is unreasonable. If it deviates from the support center of the two radial gas bearings, it will generate an overturning moment under the action of gravity, causing the rotor to deflect and further reducing the rotation accuracy. Summary of the Invention

[0006] In order to address the technical deficiencies mentioned in the background art, the purpose of this invention is to provide a high-rigidity, high-precision gas bearing assembly and an air-floating electric spindle having the same, which can significantly improve rigidity, accuracy, and stability while reducing manufacturing costs.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A gas bearing assembly for supporting a main shaft rotor includes a housing and at least one radial gas bearing disposed within the housing. An annular inlet groove is formed on the inner wall of the housing corresponding to the position of the radial gas bearing, and the annular inlet groove and the outer cylindrical surface of the radial gas bearing form a sealed inlet cavity. Multiple inlet holes communicating with the inlet cavity are circumferentially distributed on the outer cylindrical surface of the radial gas bearing, so that a radial gas film is formed between the inner cylindrical surface of the radial gas bearing and the main shaft rotor. A throttling orifice communicating with the inlet holes and a composite pressure equalization structure communicating with the throttling orifice are provided on the inner cylindrical surface of the radial gas bearing. The composite pressure equalization structure includes at least one circumferential pressure equalization groove and at least one axial pressure equalization groove, wherein the circumferential pressure equalization groove is a discontinuous structure along the circumferential direction. The radial gas bearing includes two sub-bearing sections arranged axially, with an intermediate venting groove formed between the two sub-bearing sections; The axial pressure equalization groove is connected to multiple throttling orifices along the axial direction; and / or, the circumferential pressure equalization groove is disposed on both circumferential sides of the throttling orifice.

[0008] It also includes a sleeve, which is disposed on the axial outer side of the radial gas bearing, and the sleeve and the inner cylindrical surface of the housing are clearance fit.

[0009] Preferably, at least one annular groove is formed on the outer cylindrical surface of the sleeve, and an O-ring is installed in the annular groove, the O-ring being in contact with the inner cylindrical surface of the outer shell.

[0010] Preferably, it also includes two thrust gas bearings for axial positioning of the main shaft rotor; the two thrust gas bearings are axially disposed between the radial gas bearing and the sleeve, and a spacer ring is provided between the two thrust gas bearings.

[0011] Preferably, it further includes a wave spring for applying axial preload to the radial gas bearing, the wave spring being disposed between the sleeve and the radial gas bearing; and / or disposed at the end of the radial gas bearing, and the elastic force of the wave spring being greater than the maximum axial thrust generated when the two thrust gas bearings are in operation.

[0012] The present invention also provides an air-bearing electric spindle, including the gas bearing assembly as described above, and a spindle rotor supported by the gas bearing assembly. The gas bearing assembly is coaxially arranged with the spindle rotor and sleeved on the outside of the spindle rotor. The spindle rotor is provided with a center of mass adjustment hole for adjusting the center of mass position of the spindle rotor.

[0013] Preferably, the main shaft rotor includes a spindle and a thrust plate disposed in the middle of the spindle. The spindle has a pneumatic lock pin hole, and a locking component is connected in the pneumatic lock pin hole. The thrust plate is located between two thrust gas bearings, and the two end faces of the thrust plate form an axial gas film with the corresponding thrust gas bearings.

[0014] Preferably, it further includes an air tube assembly, a motor assembly, and a cutter head assembly; the air tube assembly is disposed on the housing and communicates with the air inlet chamber of the radial gas bearing; the motor assembly is disposed at one end of the main spindle rotor for driving the main spindle rotor to rotate and is connected to the main spindle rotor in a transmission connection; the cutter head assembly is disposed at the other end of the main spindle rotor for mounting the dicing cutter and is coaxially fixedly connected to the main spindle rotor.

[0015] In summary, the beneficial effects of the present invention are as follows: 1. This invention achieves efficient sealing by opening an annular air inlet groove on the inner wall of the outer shell, which forms a sealed air inlet cavity with the outer cylindrical surface of the radial gas bearing, without the need for additional sealing elements; at the same time, multiple air inlets connected to the air inlet cavity are distributed circumferentially on the outer cylindrical surface of the radial gas bearing, so that high-pressure gas can enter the throttling orifice evenly, ensuring the consistency of the radial gas film pressure distribution and improving the static stiffness and stability of the gas bearing.

[0016] 2. This invention, by setting up a composite pressure equalization structure, that is, at least one axial pressure equalization groove and at least one circumferential pressure equalization groove work together. The axial pressure equalization groove connects multiple throttling holes along the axial direction, which expands the coverage of the high-pressure zone and avoids local pressure being too high or too low. Combined with the circumferential discontinuous pressure equalization groove, the pressure field distribution of the entire inner cylindrical surface of the bearing is optimized, thereby improving the load-bearing capacity and anti-interference capability of the gas bearing.

[0017] 3. The present invention adopts a discontinuous structure of circumferential pressure equalizing groove, which is not continuous along the circumference. Compared with the traditional continuous pressure equalizing groove, it can maintain a large circumferential pressure difference when the spindle rotor is eccentric, thereby effectively suppressing the radial runout of the rotor and significantly improving the dynamic stiffness of the radial gas bearing. It is particularly suitable for ultra-precision machining under high speed conditions.

[0018] 4. By opening a center of gravity adjustment hole on the main spindle rotor, the position of the rotor's center of gravity can be easily adjusted to make it as close as possible to the support center of the two radial gas bearings. This avoids the overturning moment caused by gravity causing the rotor to deflect, further ensuring the rotational accuracy of the main spindle, reducing the difficulty of assembly and debugging, and at the same time, the structure is simple and does not require additional complex adjustment structures, thus reducing manufacturing costs.

[0019] 5. The gas bearing assembly of the present invention has a compact overall structure and simple assembly process. The modular design reduces manufacturing costs and maintenance difficulty, and is suitable for the stringent requirements of wafer dicing machines for high speed, high precision and high stability. Attached Figure Description

[0020] Figure 1 This is a three-dimensional sectional view of the gas bearing assembly of the present invention, with arrows indicating the direction of gas flow; Figure 2This is an exploded view of the gas bearing assembly of the present invention; Figure 3 This is a half-sectional view of the gas bearing assembly of the present invention; Figure 4 This is a schematic diagram of the radial gas bearing in Embodiment 1 of the present invention; Figure 5 This is a cross-sectional view of the radial gas bearing in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the radial gas bearing in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the radial gas bearing in Embodiment 3 of the present invention; Figure 8 This is a schematic diagram of the radial gas bearing in Embodiment 4 of the present invention; Figure 9 This is a schematic diagram of the thrust gas bearing in Embodiment 1 of the present invention; Figure 10 This is a schematic diagram of the thrust gas bearing in Embodiment 5 of the present invention; Figure 11 This is the overall assembly drawing of the air-bearing electric spindle of the present invention; Figure 12 This is a top view of the air-bearing electric spindle of the present invention; Figure 13 yes Figure 12 A cross-sectional view of the AA plane; Figure 14 This is a schematic diagram of the main shaft rotor in this invention.

[0021] Explanation of the reference numerals in the figure: 1. Outer shell; 11. Front end cover; 12. Rear end cover; 13. End face seal ring; 2. Radial gas bearing; 2a. First radial gas bearing; 2b. Second radial gas bearing; 21. Sub-bearing section; 22. Intermediate vent groove; 23. Throttling orifice; 24. Composite pressure equalization structure; 241. Circumferential pressure equalization groove; 242. Axial pressure equalization groove; 25. Intermediate vent hole; 26. Inlet hole; 27. End face vent groove; 3. Sleeve; 31. Annular groove; 32. O-ring; 4. Thrust gas bearing; 4a. First thrust gas bearing; 4b. Second thrust gas bearing; 41. Spacer ring; 42. O-ring seal; 5. Wave spring; 6. Main spindle rotor; 61. Mandrel; 62. Thrust disc; 63. Center of gravity adjustment hole; 64. Pneumatic lock pin hole; 7. Locking component; 8. Air pipe assembly; 81. Air inlet connector; 82. Air outlet connector; 83. Diverter air path; 84. Air inlet plug; 85. Air outlet plug; 9. Motor assembly; 91. Motor housing; 92. Motor stator; 93. Motor mover; 10. Cutter head assembly; 101. Cutter head; 102. Blade. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0023] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0024] In the description of this invention, the use of terms such as "a number" means one or more, with "more than" meaning two or more. Terms like "greater than," "less than," and "exceeding" are understood to exclude the stated number, while terms like "above," "below," and "within" are understood to include the stated number. The use of terms like "first," "second," and "third" is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, the number of indicated technical features, or the sequential relationship between indicated technical features.

[0025] The following is in conjunction with the appendix Figure 1-14 The present invention will be further described in detail with respect to an embodiment of a gas bearing assembly and an air-floating electric spindle having the same.

[0026] Example 1 A gas bearing assembly for supporting the main shaft rotor 6, such as Figure 1 , 2 As shown in Figure 9, the device includes a housing 1 and at least one radial gas bearing 2 disposed within the housing 1. An annular air inlet groove is provided on the inner wall of the housing 1 at the position corresponding to the radial gas bearing 2. The annular air inlet groove and the outer cylindrical surface of the radial gas bearing 2 form a sealed air inlet cavity. Multiple air inlets 26 communicating with the air inlet cavity are distributed circumferentially on the outer cylindrical surface of the radial gas bearing 2, so that a radial air film is formed between the inner cylindrical surface of the radial gas bearing 2 and the main shaft rotor 6.

[0027] Furthermore, the outer shell 1 is made of high-strength stainless steel, possessing excellent rigidity, wear resistance, and corrosion resistance. The inner cylindrical surface of the outer shell 1 serves as the mounting reference surface for the radial gas bearing 2 and the sleeve 3, with its cylindricity tolerance controlled within 0.002 mm to ensure the coaxiality requirements of each bearing. In this embodiment, two radial gas bearings 2 are preferably present, namely a first radial gas bearing 2a and a second radial gas bearing 2b. The structures of the first radial gas bearing 2a and the second radial gas bearing 2b are basically the same, and the outer cylindrical surfaces of the first radial gas bearing 2a and the second radial gas bearing 2b are both interference-fitted with the inner cylindrical surface of the outer shell 1. The interference fit not only ensures the high coaxiality between the radial gas bearing 2 and the outer shell 1 but also avoids the eccentricity problem caused by assembly clearance.

[0028] It should be noted that although the two radial gas bearings 2 are interference-fitted with the housing 1, in order to reduce the deformation of the inner cylindrical surface of the radial gas bearing 2 and thus improve the accuracy of the air-bearing electric spindle, the interference needs to be as small as possible. At the same time, it is also necessary to ensure that the air intake chamber of the radial gas bearing 2 has no leakage or minimal leakage, so as to avoid affecting the performance of the gas bearing and thus the accuracy of the air-bearing electric spindle.

[0029] In this embodiment, as Figure 1 , 2 As shown, the gas bearing assembly also includes a front cover 11 and a rear cover 12 disposed at the front and rear ends of the housing 1, respectively. The front cover 11 and the rear cover 12 are fixed to the end face of the housing 1 by screws. At the same time, one side of the front cover 11 and the rear cover 12 respectively abuts against the end face of the radial gas bearing 2, and an end face sealing ring 13 is provided at the abutment surface.

[0030] Furthermore, the end face seal ring 13 adopts a non-contact labyrinth seal structure, that is, the end face seal ring 13 maintains a small gap with the spindle rotor 6, forming an air resistance effect when the spindle rotates at high speed, effectively preventing external dust and coolant from entering the bearing, and improving the axial damping of the spindle, reducing the transmission of vibration of the motor housing to the radial gas bearing 2 or housing 1, thereby reducing the vibration of the entire air-bearing electric spindle housing, thereby improving the accuracy and stability of the spindle rotor 6.

[0031] In this embodiment, as Figure 4 , 5 As shown, the radial gas bearing 2 includes two sub-bearing sections 21 arranged symmetrically along the axial direction. Each sub-bearing section 21 has multiple rows of throttling holes 23 connected to the air inlet 26 on its inner cylindrical surface. The throttling holes 23 are evenly distributed circumferentially, and the number of throttling holes 23 in each row is 6-12 to ensure sufficient throttling effect.

[0032] Furthermore, after the high-pressure gas enters the intake port 26 from the intake chamber, it flows into the gap between the main shaft rotor 6 and the radial gas bearing 2 through the throttling orifice 23 to form a gas film. At the same time, an intermediate exhaust groove 22 is formed between the two sub-bearing sections 21 of the radial gas bearing 2; the intermediate exhaust groove 22 is used to collect the gas discharged from the two sub-bearing sections 21, and an intermediate exhaust port 25 communicating with the intermediate exhaust groove 22 is correspondingly provided on the outer cylindrical surface of the radial gas bearing 2, so that the gas can be discharged to the outside of the outer casing 1.

[0033] In this embodiment, as Figure 4 , 5 As shown, each sub-bearing section 21 of the radial gas bearing 2 is also provided with a composite pressure equalization structure 24 that communicates with the throttling orifice 23. The composite pressure equalization structure 24 is provided at the outlet end of the throttling orifice 23 and includes a circumferential pressure equalization groove 241 and an axial pressure equalization groove 242. The circumferential pressure equalization groove 241 is a discontinuous structure along the circumferential direction. The discontinuous structure refers to the structure that is divided into multiple independent groove segments by a solid part in the circumferential direction.

[0034] Furthermore, each sub-bearing segment 21 is provided with 2-4 circumferential pressure equalizing grooves 241, each circumferential pressure equalizing groove 241 consisting of 3-6 arc segments, with adjacent arc segments separated by solid parts. The central angle of the arc segments is 30-60 degrees, and the central angle of the solid parts between adjacent arc segments is 10-20 degrees. The axial pressure equalizing groove 242 extends axially, connecting multiple throttling holes 23 at the same circumferential position, forming an axial pressure equalization channel. The length of the axial pressure equalizing groove 242 covers the axial length of a single sub-bearing segment 21. This composite structure of circumferential discontinuity and axial connectivity not only ensures circumferential pressure non-uniformity to improve dynamic stiffness, but also expands the high-pressure distribution area at the outlet of each throttling hole 23 through axial connectivity, increasing the pressure difference between different areas in the circumferential direction of the entire cylindrical surface, thereby improving dynamic stiffness. It also avoids excessively high or low local pressure, optimizing the pressure field distribution on the entire radial gas bearing 2 surface.

[0035] In this embodiment, as Figure 1-5 As shown, the gas bearing assembly also includes a sleeve 3, which is located on the axial outer side of the two radial gas bearings 2 for axial positioning and auxiliary support; and the inner diameter of the sleeve 3 is larger than the outer diameter of the main shaft rotor 6, forming an exhaust space between them; at the same time, two annular grooves 31 are machined on the outer cylindrical surface of the sleeve 3, and an O-ring 32 is installed in each annular groove 31.

[0036] Furthermore, the sleeve 3 and the inner cylindrical surface of the outer shell 1 are in clearance fit, with a clearance of 0.01-0.05mm. This small clearance fit ensures that the sleeve 3 can be smoothly assembled while restricting the space for gas flow. The O-ring 32 is made of fluororubber or perfluoroether rubber, and the O-ring 32 forms elastic contact with the inner cylindrical surface of the outer shell 1, producing a dual effect: first, a sealing effect, preventing external gas from entering the bearing area through the gap between the sleeve 3 and the outer shell 1, avoiding the generation of eddies and vibrations; second, a damping effect, utilizing the viscoelastic properties of the rubber material to absorb the airflow pulsation inside the bearing and the vibration energy transmitted from the outside, significantly improving the operating stability of the spindle.

[0037] In this embodiment, as Figure 1 , 9 As shown, the gas bearing assembly also includes a first thrust gas bearing 4a and a second thrust gas bearing 4b for axial positioning of the main shaft rotor 6; the first thrust gas bearing 4a and the second thrust gas bearing 4b are axially arranged between two radial gas bearings 2, and a spacer ring 41 is provided between the first thrust gas bearing 4a and the second thrust gas bearing 4b.

[0038] Furthermore, one end face of the first thrust gas bearing 4a is close to the end face of the first radial gas bearing 2a with the exhaust groove, and the interference fit surface of the first thrust gas bearing 4a and the inner cylindrical surface of the gas bearing assembly housing 1 are interference-fitted; thus forming the air intake chamber of the first thrust gas bearing 4a and ensuring the coaxiality between the second thrust gas bearing 4b and the housing 1. The second thrust gas bearing 4b and the housing 1 are also interference-fitted, and the axial positioning and clamping of the second thrust gas bearing 4b are achieved by pressing the sleeve 3 towards the front end cover 11. The spacer ring 41 is used to control the micron-level gap between the first thrust gas bearing 4a and the second thrust gas bearing 4b and the bearing surfaces on both sides of the thrust disc 62 of the main shaft rotor 6, respectively. The spacer ring 41 and the housing 1 are radially positioned by a small clearance fit, and axially positioned and clamped by the first thrust gas bearing 4a and the second thrust gas bearing 4b on both sides.

[0039] It should be noted that the high-pressure gas enters the two thrust gas bearings 4 through their respective gas passages and forms an axial gas film on their bearing surfaces to achieve axial positioning of the main shaft rotor 6. At the same time, the exhaust paths of the two thrust gas bearings 4 are carefully designed, and are discharged into the rear exhaust gas passage of the housing 1 through the exhaust holes of the spacer ring 41 and the end face exhaust grooves 27 of the two radial gas bearings 2, respectively.

[0040] To precisely control the equal film gap between the two thrust gas bearings 4, in this embodiment, the spacer ring 41 has a film thickness twice as large as the axial length of the thrust plate 62 of the main shaft rotor 6. The spacer ring 41 precisely limits the distance between the bearing surfaces of the two thrust gas bearings 4, which is twice the film thickness larger than the axial length of the thrust plate 62 of the thrust gas bearing 4. After the spacer ring 41, the two thrust gas bearings 4, and the main shaft rotor 6 are assembled, air is supplied to the thrust gas bearings 4 and the radial gas bearings 2 respectively, causing the main shaft rotor 6 to levitate under the action of airflow. Since the thrust is different when the film thickness is different, in order to achieve axial force balance of the main shaft rotor 6, the thrust on both sides will automatically adjust to be equal, thereby automatically adjusting the film thickness on both sides to be equal.

[0041] In this embodiment, as Figure 1 , 2 As shown, the gas bearing assembly also includes a wave spring 5 for applying axial preload to the radial gas bearing 2 and the thrust gas bearing 4; the wave spring 5 is disposed between the sleeve 3 and the radial gas bearing 2, or at the end of the radial gas bearing 2, and the elastic force of the wave spring 5 is greater than the maximum axial thrust generated when the two thrust gas bearings 4 are working.

[0042] Furthermore, the wave spring 5 is pressed between the rear end cover 12 and the end face of the second radial gas bearing 2b, providing a continuous, rightward axial preload force that presses the second radial gas bearing 2b, the second thrust gas bearing 4b, the spacer ring 41, the first thrust gas bearing 4a, the sleeve 3, and the first radial gas bearing 2a to the right against the front end cover 11. The design magnitude of this preload force must be greater than the maximum axial thrust that the two thrust gas bearings 4 may generate during operation, within the tolerance range. The axial thrust of the thrust gas bearing 4 can be estimated using gas lubrication theory formulas.

[0043] Ps is the gas supply pressure (unit: Pa), which is set by the gas source system; A represents the effective bearing area (unit: m²), which depends on the thrust disc diameter and the bearing throttling orifice distribution. It is a pressure coefficient, which is related to the thickness of the gas film, the diameter of the throttling orifice, the pressure equalization groove, the number of grooves, and the exhaust method, and is usually calibrated through fluid simulation or experiments.

[0044] Since the thrust gas bearing 4 achieves axial positioning of the main shaft rotor 6 through a gas film, its thrust is directly related to the gas film pressure distribution. The spring force of the wave spring 5 is greater than the thrust of the thrust gas bearing 4, ensuring that the entire gas bearing assembly will not experience axial movement under any operating condition, thus guaranteeing absolute accuracy of axial positioning.

[0045] In addition, there are two situations regarding the axial force generated by the interference fit between the radial gas bearing 2 and the housing 1 and the thrust of the thrust gas bearing 4: When the axial force generated by the interference deformation between the radial gas bearing 2 and the housing 1 is less than the thrust of the thrust gas bearing 4, the entire air bearing system is axially compressed by the wave spring 5.

[0046] When the axial force generated by the interference fit between the radial gas bearing 2 and the housing 1 is greater than the thrust of the thrust gas bearing 4, the two thrust gas bearings 4 and the spacer ring 41 can be pressed together by the axial force generated by the interference fit between the radial gas bearing 2 and the housing 1, thereby ensuring the gas film thickness of the thrust gas bearing 4. However, under the action of long-term vibration or temperature changes, there is a possibility of slight loosening of the interference fit between the radial gas bearing 2 and the housing 1. When there is slight loosening of the interference fit between the radial gas bearing 2 and the housing 1, the axial force generated by the interference fit will be less than the thrust of the thrust gas bearing 4. At this time, the wave spring 5 and the front cover 11 are required to ensure that all parts between the two radial gas bearings 2 remain pressed together and in the same position, thereby ensuring the high precision, high stability and long service life of the entire air-bearing electric spindle.

[0047] It should be noted that during actual processing, there are machining errors in the lengths of the outer shell 1, radial gas bearing 2, sleeve 3, thrust gas bearing 4, and spacer ring 41. This makes it difficult to ensure that the two thrust gas bearings 4 are pressed tightly against the spacer ring 41, and consequently, to guarantee the gas film thickness and thrust of the thrust gas bearing 4. Therefore, the wave spring 5 in this embodiment can be installed between the second radial gas bearing 2b and the sleeve 3, such as... Figure 3 As shown, the rear end cover 12 directly presses against the end face of the second radial gas bearing 2b, making the elastic force of the wave spring 5 greater than the thrust of the thrust gas bearing 4, thereby pressing the two thrust gas bearings 4 and the spacer ring 41 together to ensure the thickness of the gas film and thus ensure the accuracy of the air-float electric spindle.

[0048] This embodiment also provides an air-bearing electric spindle that utilizes the above-described gas bearing assembly, such as... Figure 10-14 As shown, it includes a main shaft rotor 6 supported by the aforementioned gas bearing assembly, the gas bearing assembly being coaxially arranged with the main shaft rotor 6 and sleeved on its outer side; the main shaft rotor 6 is provided with a center of mass adjustment hole 63 for adjusting its center of mass position.

[0049] Furthermore, the center of gravity adjustment hole 63 on the spindle rotor 6, through precise calculation and machining, can accurately adjust the center of gravity of the entire spindle rotor 6 to the axial midpoint of the two radial gas bearings 2. This can minimize the influence of gravity on the rotor's motion trajectory, prevent the rotor from tilting due to gravity, and thus improve the rotational accuracy of the spindle.

[0050] In this embodiment, as Figure 14 As shown, the main shaft rotor 6 includes a spindle 61 and a thrust plate 62 disposed in the middle of the spindle 61. The spindle 61 has a plurality of pneumatic locking pin holes 64, preferably four in this embodiment. The thrust plate 62 is located between two thrust gas bearings 4, and the two end faces of the thrust plate 62 form an axial gas film with the thrust gas bearings 4 on the corresponding sides.

[0051] Furthermore, the pneumatic locking pin holes 64 are evenly distributed around the outer side of the spindle 61, and a locking component 7 is connected inside the pneumatic locking pin holes 64. The locking component 7 adopts a locking pin, which extends out and inserts into the pneumatic locking pin holes 64 of the spindle rotor 6 under the action of the air source, thereby realizing the axial and circumferential locking and positioning of the spindle rotor 6 to facilitate operations such as tool changing.

[0052] In this embodiment, as Figure 11-13 As shown, the air-bearing electric spindle also includes an air pipe assembly 8 disposed on the housing 1, a motor assembly 9 for driving the spindle rotor 6 to rotate, and a cutter head assembly 10 for mounting the dicing cutter. The air pipe assembly 8 is connected to the air inlet chamber of the radial gas bearing 2. The motor assembly 9 is disposed at one end of the spindle rotor 6 and is connected to the spindle rotor 6 in a transmission manner. The cutter head assembly 10 is disposed at the other end of the spindle rotor 6 and is coaxially fixedly connected to the spindle rotor 6.

[0053] Furthermore, the air pipe assembly 8 includes an inlet connector 81, an outlet connector 82, a diversion air passage 83, an inlet plug 84, and an outlet plug 85. The inlet connector 81 is located on the radial side wall of the housing 1 and uses a quick-connect type for easy connection to an external air source. The outlet connector 82 is located on the radial side wall of the motor assembly 9 and also uses a quick-connect type for easy connection to an external vacuum recovery system or exhaust pipe. The diversion air passage 83 connects to the inlet chamber as an inlet pipe, and the outlet plug 85 connects to the outlet pipe as an exhaust pipe. The inlet and exhaust pipes are sealed by the inlet plug 84 and outlet plug 85, respectively. The same inlet passage or inlet chamber supplies air to each radial gas bearing 2 and thrust gas bearing 4, thereby avoiding deviations in the bearing capacity of the gas bearing assembly due to unequal inlet pressures.

[0054] It should be noted that the intake plug 84 is a process hole plug for machining the intake pipe, and the exhaust plug 85 is a process hole plug for machining the exhaust pipe. The intake pipe and the exhaust pipe are independent, and the intake pipe is located in the middle, while the exhaust pipe is located on the side to avoid the intake pipe.

[0055] like Figure 11-13 As shown, the air intake and exhaust processes of the gas bearing assembly are as follows (solid arrows indicate the intake path, and dashed arrows indicate the exhaust path; the intake and exhaust paths are separate and independent): During intake, high-pressure gas enters the distribution air passage 83 inside the housing 1 through the intake connector 81, and is evenly distributed by the distribution air passage 83 to the intake chambers of the first radial gas bearing 2a and the second radial gas bearing 2b, as well as the intake chambers of the two thrust gas bearings 4. After the high-pressure gas is throttled and depressurized through the throttling orifice 23 on each bearing, a radial gas film is formed between the inner cylindrical surface of the bearing and the outer cylindrical surface of the main shaft rotor 6, and an axial gas film is formed between the end face of the thrust plate 62 and the bearing surface of the thrust gas bearing 4.

[0056] During exhaust, part of the gas in the radial gas bearing 2 is discharged from the end face exhaust groove 27 at the bearing end, part is collected from the middle exhaust groove 22 through the middle exhaust hole 25 to the rear exhaust pipe, part is discharged from the front labyrinth seal, and part is finally collected from the motor side to the exhaust connector 82; while the exhaust from the outer circumferential surface of the thrust gas bearing 4 is collected into the rear exhaust pipe through the exhaust hole on the spacer ring 41, and the exhaust from the inner circumferential surface of one side of the thrust gas bearing 4 is collected from the sleeve 3 through the end face exhaust groove of one radial gas bearing 2 to the exhaust connector 82; the exhaust from the inner circumferential surface of the other side is discharged through the end face exhaust groove of the other radial gas bearing 2 to the external vacuum recovery system or exhaust pipe through the exhaust connector 82.

[0057] In this embodiment, as Figure 12 As shown, the motor assembly 9 is located at the tail end of the housing 1, and includes a motor housing 91, a motor stator 92, and a motor rotor 93. The motor stator 92 is fixedly connected to the motor housing 91, and the motor rotor 93 is fixedly connected to the main shaft rotor 6. An air gap is provided between the motor stator 92 and the motor rotor 93. When energized, it generates electromagnetic driving force to drive the main shaft rotor 6 to rotate at high speed. The motor housing 91 and the gas bearing assembly housing are positioned by a cylindrical surface stop and fixedly connected by screws to ensure the coaxiality of the motor assembly 9 and the gas bearing assembly.

[0058] Furthermore, the motor housing 91 is made of high-strength stainless steel or aluminum alloy with an anodized surface, ensuring both structural strength and excellent heat dissipation. The motor stator 92 adopts a coreless design, effectively reducing cogging torque and eddy current losses, improving the motor's operational smoothness and efficiency, making it particularly suitable for the stringent requirements of high speed and low vibration in wafer dicing machines. The motor mover 93 adopts a permanent magnet synchronous motor structure, with permanent magnets embedded in the outer cylindrical surface of the main shaft rotor 6, forming an integrated design with the main shaft rotor 6. This structure reduces rotational inertia, facilitating higher acceleration and more precise speed control. The permanent magnets are made of neodymium iron boron material, possessing high magnetic energy product and good temperature stability, ensuring that the motor maintains stable output characteristics under different operating temperatures.

[0059] In this embodiment, as Figure 14As shown, the cutter head assembly 10 includes a cutter head 101 and a blade 102. The blade 102 is clamped in the cutter head 101. The cutter head 101 and the front end of the spindle rotor 6 are connected in a high-precision coaxial manner through a tapered surface fit.

[0060] Furthermore, the cutter head 101 has a tapered hole at its center that matches the tapered shaft at the front end of the spindle rotor 6. The tapered surface fit has a self-centering characteristic, which can automatically eliminate assembly gaps and ensure that the coaxiality of the cutter head 101 and the spindle rotor 6 reaches the micron level. At the same time, the end face of the cutter head 101 has multiple evenly distributed blade 102 mounting slots. Each mounting slot is fixed with a diamond blade 102 by a precision screw. The extension of the blade 102 can be precisely adjusted by a fine-tuning shim to meet the process requirements of different cutting depths.

[0061] The working principle of the air-bearing electric spindle of this invention: When the air-float electric spindle starts, the high-pressure air source first supplies air to each radial gas bearing 2 and thrust gas bearing 4. After throttling, the high-pressure gas forms uniform and stable radial and axial air films, respectively, which float the spindle rotor 6, ensuring that the spindle rotor 6 and the gas bearing assembly are completely non-contact. Subsequently, the motor assembly 9 is energized, and the electromagnetic drive force drives the spindle rotor 6 to rotate at high speed, simultaneously driving the blade 102 to complete the cutting and processing of wafers and other workpieces. During the rotation of the spindle rotor 6, the center of gravity adjustment hole 63 adjusts the center of gravity of the spindle rotor to the middle of the two radial gas bearings 2, reducing the impact of gravity skew on rotational accuracy. The axial force balance mechanism automatically ensures that the axial air film thickness formed by the thrust gas bearings 4 on both sides is equal. The pre-tensioned structure of the wave spring 5 avoids axial movement of parts due to fluctuations in working conditions or long-term use, always maintaining the positioning accuracy of each part. When a tool change operation is required, the external air source drives the locking pin to extend and insert into the pneumatic locking pin hole 64 of the spindle rotor 6, realizing the axial and circumferential locking of the spindle rotor 6, thus completing the tool change operation.

[0062] Example 2 The main difference between this embodiment and Embodiment 1 lies in the different composite pressure equalization structure 24 of the radial gas bearing 2. For example... Figure 6 As shown, the radial gas bearing 2 in this embodiment only has a throttling orifice 23 and a circumferential pressure equalizing groove 241, but no axial pressure equalizing groove 242, and the circumferential pressure equalizing groove 241 is a continuous structure. Compared with the composite pressure equalizing structure 24 of Embodiment 1, the structure of this embodiment has the lowest structural stiffness, but the processing cost is also relatively low. This structure can also achieve the inventive objective of this invention and falls within the protection scope of this invention.

[0063] Example 3 The main difference between this embodiment and Embodiment 1 lies in the different composite pressure equalization structure 24 of the radial gas bearing 2. For example... Figure 7As shown, in this embodiment, the radial gas bearing 2 has an additional circumferential pressure equalizing groove on the axial pressure equalizing groove 242. Compared with the composite pressure equalizing structure 24 of Embodiment 1, the structure of this embodiment can slightly increase the bearing's support stiffness, but correspondingly, the processing cost is also increased. This structure can also achieve the inventive objective of this invention and falls within the protection scope of this invention.

[0064] Example 4 The main difference between this embodiment and Embodiment 1 lies in the different composite pressure equalization structure 24 of the radial gas bearing 2. For example... Figure 8 As shown, the radial gas bearing 2 in this embodiment has a circumferential pressure equalizing groove 241 on the axial pressure equalizing groove 242, which is different from that in Embodiment 1. This circumferential pressure equalizing groove 241 has a continuous structure. Compared with the composite pressure equalizing structure 24 in Embodiment 1, the structural stiffness of this embodiment is slightly reduced. This structure can still achieve the inventive objective of this invention and falls within the protection scope of this invention.

[0065] The above embodiments 1-4 provide multiple implementations of the composite pressure equalization structure 24. A comprehensive comparison of the stiffness and processing cost of each embodiment shows that: Embodiment 3 has the highest stiffness but also the highest cost; Embodiment 2 has the lowest stiffness and also the lowest cost; Embodiment 4 has a slightly lower stiffness than Embodiment 1; Embodiment 1 achieves a good balance between stiffness and processing cost and is currently the preferred implementation. Those skilled in the art can select a suitable composite pressure equalization structure 24 based on the performance requirements and cost budget of specific application scenarios.

[0066] Example 5 The main difference between this embodiment and Embodiment 1 lies in the sealing structure of the thrust gas bearing 4. For example... Figure 10 As shown, in this embodiment, the thrust gas bearing 4 and the housing are sealed with an O-ring 42. Compared with the interference seal used in Embodiment 1, the overall precision is slightly lower, but the cost is lower in the process of processing, assembly and disassembly. This structure can also achieve the purpose of the invention and is within the scope of protection of the invention.

[0067] In summary, the air-bearing electric spindle provided in this embodiment achieves the comprehensive performance indicators of high speed, high precision, low vibration and long life required for wafer dicing through modular design of gas bearing assembly, optimized layout of air path and precise configuration of center of mass adjustment. It is particularly suitable for the high reliability cutting requirements of ultra-thin wafers and hard and brittle materials in the semiconductor manufacturing field.

[0068] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A gas bearing assembly for supporting a main shaft rotor, characterized in that, The device includes a housing and at least one radial gas bearing disposed within the housing. An annular inlet groove is formed on the inner wall of the housing corresponding to the position of the radial gas bearing, and the annular inlet groove and the outer cylindrical surface of the radial gas bearing form a sealed inlet cavity. Multiple inlet holes communicating with the inlet cavity are circumferentially distributed on the outer cylindrical surface of the radial gas bearing, so that a radial gas film is formed between the inner cylindrical surface of the radial gas bearing and the main shaft rotor. A throttling orifice communicating with the inlet holes and a composite pressure equalization structure communicating with the throttling orifice are provided on the inner cylindrical surface of the radial gas bearing. The composite pressure equalization structure includes at least one circumferential pressure equalization groove and at least one axial pressure equalization groove, wherein the circumferential pressure equalization groove is a discontinuous structure along the circumferential direction. The radial gas bearing includes two sub-bearing sections arranged axially, with an intermediate vent groove formed between the two sub-bearing sections; The axial pressure equalization groove is connected to multiple throttling orifices along the axial direction; and / or, the circumferential pressure equalization groove is disposed on both circumferential sides of the throttling orifice; It also includes a sleeve, which is disposed on the axial outer side of the radial gas bearing, and the sleeve and the inner cylindrical surface of the housing are in clearance fit.

2. The gas bearing assembly according to claim 1, characterized in that, At least one annular groove is formed on the outer cylindrical surface of the sleeve, and an O-ring is installed in the annular groove. The O-ring is in contact with the inner cylindrical surface of the outer shell.

3. The gas bearing assembly according to claim 1, characterized in that, It also includes two thrust gas bearings for axial positioning of the main shaft rotor; the two thrust gas bearings are axially arranged between the radial gas bearing and the sleeve, and a spacer ring is provided between the two thrust gas bearings.

4. The gas bearing assembly according to claim 3, characterized in that, It also includes a wave spring for applying axial preload to the radial gas bearing, the wave spring being disposed between the sleeve and the radial gas bearing; and / or disposed at the end of the radial gas bearing, and the elastic force of the wave spring being greater than the maximum axial thrust generated when the two thrust gas bearings are in operation.

5. An air-bearing electric spindle, characterized in that, The invention includes a gas bearing assembly as described in any one of claims 1-4, and a main shaft rotor supported by the gas bearing assembly, wherein the gas bearing assembly is coaxially arranged with the main shaft rotor and sleeved on the outside of the main shaft rotor; the main shaft rotor is provided with a center of mass adjustment hole for adjusting the center of mass position of the main shaft rotor.

6. The air-bearing electric spindle according to claim 5, characterized in that, The main shaft rotor includes a spindle and a thrust plate disposed in the middle of the spindle. A pneumatic lock pin hole is provided on the spindle, and a locking component is connected in the pneumatic lock pin hole. The thrust plate is located between two thrust gas bearings, and the two end faces of the thrust plate form an axial gas film with the corresponding thrust gas bearings.

7. The air-bearing electric spindle according to claim 6, characterized in that, It also includes an air tube assembly, a motor assembly, and a cutter head assembly; the air tube assembly is disposed on the housing and communicates with the air inlet chamber of the radial gas bearing; the motor assembly is disposed at one end of the main spindle rotor, used to drive the main spindle rotor to rotate, and is connected to the main spindle rotor in a transmission connection; the cutter head assembly is disposed at the other end of the main spindle rotor, used to install the dicing cutter, and is coaxially and fixedly connected to the main spindle rotor.

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