Fluid bearing device for machine tool spindle

Abstract

The invention discloses a fluid bearing device for a machine tool spindle, which belongs to the technical field of fluid bearings and comprises a hydrostatic bearing mechanism, a spindle body is arranged in the hydrostatic bearing mechanism, and the hydrostatic bearing mechanism comprises a first shell and a second shell. A sealing cavity formed by the first shell and the second shell is internally provided with a lining cylinder and a step-by-step oil inlet mechanism, the inner wall and the outer wall of the lining cylinder are each provided with a first spiral groove and a plurality of oil inlet holes, and one side of the outer wall of the second shell is provided with a pre-alignment mechanism. The number of the oil inlet holes is increased to make up the response delay of the throttler and the hydraulic pump, oil is supplemented to an oil cavity in time to maintain the oil film pressure, meanwhile, different load requirements can be met, the number of the oil inlet holes is reduced when the load is small, oil waste can be avoided, and energy consumption increase caused by too high oil film pressure can be avoided; and oil film stability and operation economy are both considered.

Description

Technical Field

[0001] This invention belongs to the technical field of fluid bearings, and more specifically relates to a fluid bearing device for machine tool spindles. Background Technology

[0002] Fluid bearings are precision bearings that achieve support and lubrication through a "non-contact fluid film." Their core feature is the use of a fluid (lubricating oil, water, or compressed gas, etc.) between the bearing and the shaft to form a continuous pressure film, completely isolating the friction surfaces and transforming traditional solid friction into viscous friction between fluid molecules. Based on the fluid film formation mechanism, they can be divided into two categories: hydrodynamic bearings rely on the "fluid self-suction effect" when the shaft rotates, using structures such as wedge gaps and spiral grooves to bring the fluid into a narrow space, naturally compressing it to form the bearing pressure; hydrostatic bearings, on the other hand, actively inject fluid into the gap through an external high-pressure system to establish a pressure film and provide stable support. Compared with rolling bearings, fluid bearings have significant advantages such as high load-bearing capacity, high rotational accuracy, low vibration and noise, and near-zero wear due to the absence of metal contact.

[0003] In machine tool spindle systems, the oil film of the hydrostatic bearing is the core component for maintaining spindle rotation accuracy and bearing machining loads. When the machine tool spindle is running, the load end of the spindle needs to handle various situations. If the load end of the spindle increases, the oil film will be passively compressed under pressure, and its thickness will decrease significantly. At the same time, the pressure distribution of the oil film will change from "uniform bearing" to "local concentration". The stiffness of the oil film (its ability to resist deformation) is positively correlated with its thickness. The thinner the oil film, the lower the stiffness. When the load increases and the oil film becomes too thin, the oil film's buffering capacity for small disturbances decreases significantly, and "oil film vibration" is likely to occur. That is, the oil film pressure fluctuates at high frequency with disturbances, which cannot stably support the spindle. This causes the spindle and bearing surfaces to degenerate from "fluid friction" to "boundary friction" or "dry friction", reducing the spindle's machining accuracy on the workpiece.

[0004] Current hydrostatic bearing systems mainly achieve stable oil supply pressure output through the coordinated control of a throttling device and a hydraulic pump. The hydraulic pump provides the basic pressure source, while the throttling device dynamically adjusts the oil distribution according to load changes to maintain the balance between oil film pressure and load. This mechanism can effectively ensure oil film stability under normal load fluctuation scenarios. However, due to the complexity of the working environment, when encountering sudden heavy loads (such as cutting impacts) or continuous overload conditions, the system will expose obvious limitations: limited by the fixed structural parameters of the oil inlet (such as the number of holes and the flow area), the flow regulation by the throttling device alone cannot inject sufficient oil into the bearing oil cavity in a short time. This causes the oil film pressure replenishment to lag behind the load growth rate, which in turn leads to abnormal attenuation of oil film thickness, pressure imbalance, and even the risk of local oil film rupture. Summary of the Invention

[0005] The present invention addresses the problem of overly simplistic solutions in existing technologies by providing a significantly different solution. The present invention primarily provides a fluid bearing device for machine tool spindles to solve the technical problem mentioned in the background art, which is prone to pressure imbalance and oil film rupture when encountering a sudden increase in load due to the complexity of the machine tool spindle's working environment.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: A fluid bearing device for a machine tool spindle includes a hydrostatic bearing mechanism. A spindle body is housed within the hydrostatic bearing mechanism. A fluid film composed of oil can be injected into the gap between the spindle body and the hydrostatic bearing mechanism. The hydrostatic bearing mechanism includes a first housing and a second housing, which are detachably connected. A sealed cavity formed by the first and second housings contains an inner liner with openings at both ends and a segmented oil inlet mechanism. The inner liner and the spindle body are rotatably connected. A transition cavity for oil flow is formed between the outer wall of the inner liner and the inner walls of the two housings. Both the inner and outer walls of the inner liner have first helical grooves with multiple oil inlets. The segmented oil inlet mechanism is located on one side of the outer wall of the inner liner and is used to adjust the flow of the oil inlets. A pre-alignment mechanism is located on one side of the outer wall of the second housing, and the spindle body passes through the pre-alignment mechanism.

[0007] Preferably, the plurality of oil inlet holes are grouped together, and each group of oil inlet holes is distributed at equal intervals along the direction of the first spiral groove.

[0008] Preferably, the inner liner is provided with a rotating component and a return torsion spring. The rotating component includes a spiral sealing plate, a receiving plate, and multiple stabilizing frames. The spiral sealing plate is engaged with a first spiral groove. Multiple adjustment ports are provided at equal intervals along the spiral direction on the spiral sealing plate. The receiving plate and stabilizing frames are located on the outside of the spiral sealing plate, and one end of the return torsion spring is connected to the interface at one end of the receiving plate.

[0009] Preferably, the graded oil inlet mechanism includes an arc-shaped cover and multiple arc-shaped oil grooves, with adjacent oil grooves tightly fitted together. Each oil groove is provided with an outlet hole and a transition hole, the transition hole connecting adjacent oil grooves. Each oil groove is provided with a trigger element, the trigger element and the corresponding oil groove are slidably connected, and the length of the trigger element increases progressively. The arc-shaped cover is located at the opening of one of the oil grooves, and the arc-shaped cover is provided with a first oil inlet pipe, the first oil inlet pipe passing through a circular hole on the first housing.

[0010] Preferably, the triggering element includes a trigger rod and a piston plate, the piston plate being located between the outlet hole and the transition hole of the corresponding oil groove, and a first reset spring being provided on the trigger rod.

[0011] Preferably, the pre-alignment mechanism includes a base, a rotating disk, and a top cover. The rotating disk rotates on the base. Multiple guide holes are arranged around the rotating disk at equal intervals. Multiple limiting holes are arranged around the top cover at equal intervals. The limiting holes and guide holes correspond one-to-one and form a set. Each set of limiting holes and guide holes is provided with a limiting component. The limiting component includes a limiting frame and multiple balls on the limiting frame.

[0012] Preferably, the base is provided with an oil inlet channel and an oil outlet hole, the end of the oil inlet channel is provided with a second return spring, and a pressure plate is provided at the outer edge of the rotating disk, and the pressure plate abuts against the front end of the second return spring.

[0013] Preferably, a shaft seal is provided between the rotating disk and the top cover, and a second oil inlet pipe is also provided on the top cover.

[0014] Preferably, an oil drain pipe is provided on one side of the outer wall of the first housing, and the oil drain pipe connects the gap between the main shaft body and the inner liner.

[0015] Preferably, a second helical groove is provided at the journal position on the main spindle body.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention, through the first housing, oil drain pipe, second housing, inner liner, first spiral groove, oil inlet, rotating part, reset torsion spring, oil groove, arc cover, outlet hole, transition hole, triggering part, first oil inlet pipe and first reset spring, realizes the linkage adjustment of the number of oil inlet openings by oil pressure changes, achieves rapid response to load change scenarios, and can increase the number of oil inlet openings instantly by relying on oil pressure when the load suddenly increases. This design can effectively make up for the response delay problem that exists when only relying on throttle and hydraulic pump adjustment. At the moment of load change, the total oil inlet volume is directly increased by increasing the number of oil inlets, so that the oil can be quickly injected into the bearing oil cavity, replenish the oil film pressure in time, and avoid the risk of sudden reduction of oil film thickness and local rupture caused by insufficient oil film pressure. Thus, it significantly improves the dynamic adaptability of hydrostatic bearing to load change and ensures the stability of oil film during load fluctuation. Adapting to different load requirements and improving operational economy: This structure can dynamically adjust the number of oil inlets open according to the load size. When the load is large, multiple oil inlets provide sufficient oil volume to meet the oil film bearing requirements. When the load is small, the number of oil inlets is reduced to avoid excessive oil film pressure caused by excessive oil volume. This on-demand adjustment method can accurately match the oil demand under different loads and prevent problems such as increased energy consumption caused by excessive oil film pressure. On the other hand, it can reduce unnecessary oil delivery and reduce the continuous output energy consumption of the hydraulic pump. While ensuring the operational stability of the hydrostatic bearing, it can improve oil utilization efficiency and operational economy.

[0017] (2) By setting up a base, oil inlet channel, oil outlet hole, rotating disk, top cover, second oil inlet pipe, limiting component and shaft seal, the present invention enables the existing oil conveying equipment to use oil pressure to drive the limiting component to position the main shaft body on the central axis of the fluid bearing before the main shaft body is started, ensuring that the gap between the main shaft and the inner wall of the bearing is uniform, effectively avoiding the chain problem of "main shaft offset-impact collision-rigid friction" during traditional start-up, reducing scratches, pits and other damage to the contact surface between the main shaft journal and the inner side of the bearing, and significantly extending the service life of the high-precision friction pair; Furthermore, in the initial alignment state, the oil cavity clearance within the bearing is uniform, providing suitable conditions for the rapid formation of a stable oil film pressure field. This avoids localized thinning or rupture of the oil film due to uneven clearance. Once the spindle has stabilized and rotated, it can separate from the spindle under the action of the second return spring. This not only avoids interfering with the dynamic characteristics of the oil film during normal operation but also lays the foundation for oil film stability through early alignment, reducing vibration and noise during the startup phase. This allows the spindle to reach its rated speed more quickly and is particularly suitable for large precision machine tools and other scenarios with extremely high requirements for startup smoothness.

[0018] (3) By designing spiral grooves on the journal of the main shaft body and the inner wall of the inner liner, the present invention enables the oil to quickly fill the gap between the main shaft and the inner liner in the initial state with the help of the guiding effect of the spiral grooves, avoiding the problem of uneven oil distribution in the traditional structure and accelerating the formation of the initial oil film. At the same time, when the main shaft starts to rotate, the spiral grooves can use the "pumping effect" generated by the relative motion to push the oil to gather in the bearing area, and a certain initial oil film pressure can be established at low speed, effectively reducing the rigid friction that may be caused by the initial alignment deviation or instantaneous impact between the main shaft and the inner wall of the bearing. In addition, the symmetrical structure of the spiral grooves can guide the oil to be evenly distributed, assisting the main shaft to quickly achieve coaxial positioning with the bearing in the start-up stage, further improving the positioning effect and laying the foundation for subsequent stable operation.

[0019] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0020] Figure 1 This is a physical model drawing of the present invention; Figure 2 This is a schematic diagram of the overall structure of the present invention; Figure 3 This is an exploded view of the overall structure of the present invention; Figure 4 This is a schematic diagram of the inner bushing connection of the present invention; Figure 5 This is a schematic diagram of the inner and outer structures of the inner liner of the present invention; Figure 6 This is a schematic diagram of the rotating component structure of the present invention; Figure 7 This is an exploded view of the graded oil inlet mechanism of the present invention; Figure 8 This is an exploded view of the pre-alignment mechanism of the present invention; Figure 9 This is a schematic diagram of the base structure of the present invention; Figure 10 This is a schematic diagram of the rotating disk structure of the present invention; Figure 11 This is a schematic diagram of the top cover structure of the present invention; Figure 12 This is a schematic diagram of the main shaft body structure of the present invention.

[0021] In the diagram: 1. Hydrostatic bearing mechanism; 11. First housing; 111. Oil drain pipe; 12. Second housing; 13. Inner liner; 131. First spiral groove; 132. Oil inlet; 14. Rotating component; 141. Spiral sealing plate; 142. Support plate; 143. Stabilizer; 144. Adjustment port; 15. Return torsion spring; 2. Divided oil inlet mechanism; 21. Oil trough; 22. Arc-shaped cover; 23. Outlet hole; 24. Transition hole; 25. Trigger element; 251. Trigger rod; 252. Piston plate; 26. First oil inlet pipe; 27. First return spring; 3. Pre-alignment mechanism; 31. Base; 311. Oil inlet channel; 312. Oil outlet; 32. Rotary disc; 321. Guide hole; 322. Pressure plate; 33. Top cover; 331. Limiting hole; 332. Second oil inlet pipe; 34. Limiting component; 341. Limiting bracket; 342. Ball bearing; 35. Shaft seal; 36. Second return spring; 4. Main spindle body; 41. Second spiral groove. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the present invention. However, the present invention can be implemented in different forms and is not limited to the embodiments described in the text. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete.

[0023] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly associated with those skilled in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] Example 1, please refer to the appendix for details. Figure 1-12 As shown, a fluid bearing device for a machine tool spindle includes a hydrostatic bearing mechanism 1. A spindle body 4 is disposed within the hydrostatic bearing mechanism 1. A fluid film composed of oil can be injected into the gap between the spindle body 4 and the hydrostatic bearing mechanism 1. The hydrostatic bearing mechanism 1 includes a first housing 11 and a second housing 12, which are detachably connected. An inner liner 13 with openings at both ends and a segmented oil inlet mechanism 2 are disposed within the sealed cavity formed by the first housing 11 and the second housing 12. The inner liner 13 and the main shaft body 4 are rotatably connected. The outer wall of the inner liner 13 and the inner walls of the two housings form a transition cavity for oil flow. The inner wall and outer wall of the inner liner 13 are provided with a first spiral groove 131. Multiple oil inlet holes 132 are provided in the first spiral groove 131. The graded oil inlet mechanism 2 is located on one side of the outer wall of the inner liner 13 and is used to adjust the opening and closing of the oil inlet holes 132. A pre-alignment mechanism 3 is provided on one side of the outer wall of the second housing 12, and the main shaft body 4 passes through the pre-alignment mechanism 3.

[0026] Through the above structure, the number of oil inlet holes 132 can be adjusted in conjunction with changes in oil pressure. When the load is large, the number of oil inlet holes 132 is increased to improve the total oil intake. When the load is small, the number of oil inlet holes 132 is reduced to avoid excessive oil film pressure. This allows for a rapid response to sudden load changes. The increased number of oil inlet holes 132 compensates for the response delay of the throttle and hydraulic pump, and timely replenishes oil to the oil chamber to maintain oil film pressure. At the same time, it can match different load requirements. When the load is small, reducing the number of oil inlet holes 132 can avoid oil waste and increased energy consumption caused by excessive oil film pressure, thus balancing oil film stability and operating economy. In addition, it can also reduce the problem of rigid friction between the spindle and bearing caused by instantaneous impact force during initial operation, which can damage the contact surface and hinder oil film formation.

[0027] The specific operation is as follows: First, connect the oil drain pipe 111, the first oil inlet pipe 26, and the second oil inlet pipe 332 to the external throttle and hydraulic pump (the throttle and hydraulic pump are existing equipment and are not shown in the figure) to form a closed circuit. Turn on the hydraulic pump, and the oil will enter the oil inlet channel 311 through the second oil inlet pipe 332. Then, it will abut against the pressure plate 322, pushing the pressure plate 322 to move along the oil inlet channel 311. The second return spring 36 will be compressed until the pressure plate 322 moves to the position of the oil outlet 312. The oil will then enter the oil outlet channel 311 formed by the inner liner 13 and the hydraulic pump. The two housings form a transition cavity through which the oil flows. At the same time, the rotating disk 32 rotates, and with the cooperation of the limiting hole 331 and the guide hole 321, each limiting member 34 moves towards the central axis of the rotating disk 32. The ball 342 contacts the main shaft body 4 and positions the main shaft body 4 on the central axis. In addition, the first oil inlet pipe 26 in another oil circuit also introduces the oil into the oil tank 21. Then the oil enters the transition cavity from the outlet hole 23. The oil in the transition cavity will enter the gap between the inner liner 13 and the main shaft body 4 from the oil inlet hole 132. Then the spindle body 4 rotates. When the spindle body 4 rotates smoothly, the second oil inlet pipe 332 is cut off by the throttle. Under the action of the second return spring 36, the pressure plate 322 is reset. At the same time, the rotating disk 32 rotates. With the cooperation of the limiting hole 331 and the guide hole 321, the limiting part 34 is reset and the ball 342 is disengaged from the spindle body 4. When the output end of the spindle body 4 suddenly encounters a large load, the oil pressure increases under the control of the throttle and hydraulic pump. Consequently, the oil rapidly pushes the trigger 25 in the oil groove 21, and the piston plate 252 passes over the corresponding transition hole 24. Then, the oil enters the next oil groove 21 and flows out from the outlet hole 23 on that oil groove 21. This process continues, with the increase in oil pressure, oil enters the next oil groove 21 sequentially. Since the length of the trigger 25 increases progressively, each additional trigger 25 pushed causes a greater deflection of the receiving plate 142 that the trigger rod 251 contacts. This results in the spiral sealing plate 141 moving along... The greater the movement of the first spiral groove 131, the more oil inlet holes 132 are covered by the adjustment port 144. This achieves the goal of opening more oil inlet holes 132 when the load increases, ensuring a rapid increase in oil intake in a short period of time. At this time, the reset torsion spring 15 and the corresponding first reset spring 27 deform. When the load is small, the reset torsion spring 15 and the first reset spring 27 cause the spiral sealing plate 141 and the trigger 25 to reset, thereby reducing the oil inlet holes 132 and the oil intake, achieving the purpose of adjustment. At the same time, the oil drain pipe 111 discharges the high-temperature oil generated by the rotational friction, ensuring dynamic circulation.

[0028] Example 2, please refer to the appendix for details. Figure 4 , Figure 5 , Figure 6 and Figure 7As shown, multiple oil inlet holes 132 are grouped together, and each group of oil inlet holes 132 is evenly distributed along the direction of the first spiral groove 131. The inner liner 13 is provided with a rotating component 14 and a return torsion spring 15. The rotating component 14 includes a spiral sealing plate 141, a receiving plate 142, and multiple stabilizers 143. The spiral sealing plate 141 cooperates with the first spiral groove 131. Multiple adjusting ports 144 are evenly distributed along the spiral direction on the spiral sealing plate 141. The moving range of the spiral sealing plate 141 is one group of oil inlets. The greater the distance between holes 132, the more adjustment ports 144 cover each group of oil inlet holes 132, the greater the oil inlet volume. The receiving plate 142 and the stabilizer 143 are located on the outside of the spiral sealing plate 141, ensuring the stability of the spiral sealing plate 141. One end of the reset torsion spring 15 is connected to the interface at one end of the receiving plate 142. When the oil pressure drops, it pushes the rotating component 14 to rotate and reset. The segmented oil inlet mechanism 2 includes an arc-shaped cover 22 and multiple arc-shaped oil grooves 21, with adjacent oil grooves 21 tightly fitted together. Each of the oil grooves 2... Each of the oil tanks 21 is provided with an outlet hole 23 and a transition hole 24. The transition hole 24 connects to adjacent oil tanks 21. Each oil tank 21 is provided with a trigger 25. The trigger 25 and the corresponding oil tank 21 are slidably connected, and the length of the trigger 25 increases sequentially. During the process of increasing oil pressure, the trigger 25 will be pushed open one by one, so that the oil will enter the next oil tank 21 through the transition hole 24 in sequence, thereby contacting the receiving plate 142 in sequence, and gradually increasing the movement range of the rotating part 14. The arc-shaped cover 22 is located in one of the oil tanks. At the opening of 21, the arc-shaped cover 22 is provided with a first oil inlet pipe 26. The first oil inlet pipe 26 passes through the round hole on the first housing 11, and external oil is introduced through the first oil inlet pipe 26. The trigger 25 includes a trigger rod 251 and a piston plate 252. The piston plate 252 is located between the outlet hole 23 and the transition hole 24 of the corresponding oil groove 21. The trigger rod 251 is provided with a first return spring 27. The first return spring 27 enables the trigger 25 to return to its original position when the oil pressure drops.

[0029] Example 3, please refer to the appendix for details. Figure 3 , Figure 8 , Figure 9 , Figure 10 , Figure 11 and Figure 12As shown, the pre-alignment mechanism 3 includes a base 31, a rotating disk 32, and a top cover 33. The rotating disk 32 rotates on the base 31. The groove on the back of the base 31 engages with one end of the return torsion spring 15. Multiple guide holes 321 are evenly spaced around the rotating disk 32, and multiple limiting holes 331 are evenly spaced around the top cover 33. The limiting holes 331 and guide holes 321 correspond one-to-one, forming a set. Each set of limiting holes 331 and guide holes 321 is provided with a limiting element 34. The limiting element 34 includes a limiting frame 341 and multiple balls 342 on the limiting frame 341. Through the base 31, rotating disk 32, top cover 33, and limiting element 34, the spindle body 4 is positioned at the central axis of the inner liner 13. The base 31 is provided with an oil inlet channel 311 and an oil outlet hole 312. A second return spring 36 is provided at the end of the oil inlet channel 311. A pressure plate 322 is provided on the outer edge of the rotating disk 32, and the pressure plate 322 abuts against the front end of the second return spring 36. Through the second return spring 36, the oil in the second oil inlet pipe 332 is cut off after the main shaft body 4 rotates stably, pushing the pressure plate 322 to return to its original position, thereby causing the limiting member 34 to separate and return to its original position from the main shaft body 4. A shaft seal 35 is provided between the rotating disk 32 and the top cover 33. The top cover 33 is also provided with a second oil inlet pipe 332. Through the shaft seal 35, the problem of oil leakage in the oil inlet channel 311 is avoided. An oil drain pipe 111 is provided on one side of the outer wall of the first housing 11, and the oil drain pipe 111 connects the gap between the main shaft body 4 and the inner liner 13. Through the oil drain pipe 111, the high temperature oil is discharged to facilitate the circulation of the oil. A second spiral groove 41 is provided at the journal position on the main shaft body 4, which is conducive to accelerating the formation of the initial oil film.

[0030] The present invention has been described by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvement made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, shall be within the protection scope of the present invention.

Claims

1. A fluid bearing device for a machine tool spindle, comprising a hydrostatic bearing mechanism (1), wherein a spindle body (4) is disposed within the hydrostatic bearing mechanism (1), and a fluid film composed of oil can be injected into the gap between the spindle body (4) and the hydrostatic bearing mechanism (1), wherein the hydrostatic bearing mechanism (1) comprises a first housing (11) and a second housing (12), and the first housing (11) and the second housing (12) are detachably connected, characterized in that... The sealed cavity formed by the first housing (11) and the second housing (12) is provided with an inner liner (13) with openings at both ends and a graded oil inlet mechanism (2). The inner liner (13) and the main shaft body (4) are rotatably connected. The outer wall of the inner liner (13) and the inner walls of the two housings form a transition cavity for oil flow. The inner wall and outer wall of the inner liner (13) are provided with a first spiral groove (131). The first spiral groove (131) is provided with multiple oil inlets (132). The graded oil inlet mechanism (2) is located on one side of the outer wall of the inner liner (13) and is used to adjust the opening and closing of the oil inlets (132). The outer wall of the second housing (12) is provided with a pre-alignment mechanism (3). The main shaft body (4) passes through the pre-alignment mechanism (3).

2. The fluid bearing device for a machine tool spindle according to claim 1, characterized in that, The multiple oil inlet holes (132) are grouped together, and each group of oil inlet holes (132) is distributed at equal intervals along the direction of the first spiral groove (131).

3. A fluid bearing device for a machine tool spindle according to claim 1, characterized in that, The inner liner (13) is provided with a rotating component (14) and a reset torsion spring (15). The rotating component (14) includes a spiral sealing plate (141), a receiving plate (142) and multiple stabilizers (143). The spiral sealing plate (141) and the first spiral groove (131) cooperate. Multiple adjustment ports (144) are provided at equal intervals along the spiral direction on the spiral sealing plate (141). The receiving plate (142) and the stabilizers (143) are located on the outside of the spiral sealing plate (141), and one end of the reset torsion spring (15) is connected to the interface of one end of the receiving plate (142).

4. A fluid bearing device for a machine tool spindle according to claim 1, characterized in that, The graded oil inlet mechanism (2) includes an arc-shaped cover (22) and multiple arc-shaped oil grooves (21), and the adjacent oil grooves (21) are closely fitted together. Each oil groove (21) is provided with an outlet hole (23) and a transition hole (24). The transition hole (24) connects to the adjacent oil groove (21). Each oil groove (21) is provided with a trigger (25). The trigger (25) and the corresponding oil groove (21) are slidably connected. The length of the trigger (25) increases one by one. The arc-shaped cover (22) is located at the opening of one of the oil grooves (21). The arc-shaped cover (22) is provided with a first oil inlet pipe (26). The first oil inlet pipe (26) passes through the round hole on the first housing (11).

5. A fluid bearing device for a machine tool spindle according to claim 4, characterized in that, The trigger (25) includes a trigger rod (251) and a piston plate (252). The piston plate (252) is located between the outlet hole (23) and the transition hole (24) of the corresponding oil groove (21). A first reset spring (27) is provided on the trigger rod (251).

6. A fluid bearing device for a machine tool spindle according to claim 1, characterized in that, The pre-alignment mechanism (3) includes a base (31), a rotating disk (32), and a top cover (33). The rotating disk (32) rotates on the base (31). Multiple guide holes (321) are arranged around the rotating disk (32) at equal intervals. Multiple limiting holes (331) are arranged around the top cover (33) at equal intervals. The limiting holes (331) and guide holes (321) correspond one-to-one and form a set. Each set of limiting holes (331) and guide holes (321) is provided with a limiting component (34). The limiting component (34) includes a limiting frame (341) and multiple balls (342) on the limiting frame (341).

7. A fluid bearing device for a machine tool spindle according to claim 6, characterized in that, The base (31) is provided with an oil inlet channel (311) and an oil outlet hole (312). A second return spring (36) is provided at the end of the oil inlet channel (311). A pressure plate (322) is provided at the outer edge of the rotating disk (32), and the pressure plate (322) abuts against the front end of the second return spring (36).

8. A fluid bearing device for a machine tool spindle according to claim 7, characterized in that, A shaft seal (35) is provided between the rotating disk (32) and the top cover (33), and a second oil inlet pipe (332) is also provided on the top cover (33).

9. A fluid bearing device for a machine tool spindle according to claim 1, characterized in that, An oil drain pipe (111) is provided on one side of the outer wall of the first housing (11), and the oil drain pipe (111) connects the gap between the main shaft body (4) and the inner liner (13).

10. A fluid bearing device for a machine tool spindle according to claim 9, characterized in that, The journal position on the main shaft body (4) is provided with a second helical groove (41).

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