A lightweight, self-heating aerostatic bearing spindle and a method of manufacturing the same

Abstract

This invention belongs to the field of air static pressure bearing technology, and particularly relates to a lightweight, uniformly heated air static pressure bearing mandrel and its manufacturing method. It is used in air static pressure spindles. The mandrel includes a mandrel body, which comprises an inner mandrel shaft and an outer mandrel shaft sleeved outside the inner shaft. A sealed hollow interlayer is formed between the inner and outer mandrel shafts. A wire mesh assembly is disposed within the hollow interlayer and is attached to the wall surface of the inner and / or outer mandrel shafts. Both ends of the mandrel body include side baffles. A filling pipe communicating with the hollow interlayer is disposed on one side baffle, through which a phase change heat transfer medium is filled into the hollow interlayer. This solution can achieve heat flow distribution and temperature field uniformity across the entire outer wall of the shell through the phase change heat transfer of the internal phase change heat transfer medium. This is beneficial for improving the strength, stiffness, and thermal stability of the air static pressure spindle, and effectively reducing the weight of the air static pressure spindle mandrel.

Description

Technical Field

[0001] This invention belongs to the field of air static pressure bearing technology, and particularly relates to a lightweight, uniformly heated air static pressure bearing mandrel and its preparation method, for use in air static pressure spindles. Background Technology

[0002] Air static pressure spindles are one of the main components of ultra-precision machine tools, and their performance directly affects the machining accuracy of the machine tool. Air static pressure electric spindles have advantages such as low friction characteristics, excellent high and low speed and high and low temperature performance, smooth movement, high rotational accuracy, low noise, low vibration, compact structure, short transmission chain, and high mechanical efficiency. They have been widely used in precision ultra-high speed light load cutting equipment. Air static pressure spindles utilize high pressure gas to form an air film between the shaft and the bearing, which has outstanding advantages such as low friction, high rotational accuracy, high speed, and low vibration. Therefore, they have been widely used in precision ultra-high speed light load cutting equipment, high precision machining mother machines and other fields.

[0003] When performing ultra-precision cutting, air hydrostatic spindles generally require high cutting speeds, and the spindle will operate at very high speeds. At high speeds, the spindle system generates temperature rise and complex temperature fields under the combined action of internal and external heat sources, which causes thermal expansion and thermal deformation of spindle components. This may cause bearings to seize during operation. The thermal characteristics and thermal deformation of bearings are one of the main reasons that limit the increase of their speed.

[0004] Currently, air static pressure spindles are usually directly driven by motors. During spindle operation, thermal deformation of the spindle occurs due to shear friction loss of the air film of the static pressure bearing and motor loss, which in turn affects the working performance of the spindle components. Sometimes, the bearing structure may even experience thermal expansion, causing the bearing to seize up. As the core rotating component, the mechanical properties and thermal stability of the spindle spindle directly determine the machining accuracy and reliability of the machine tool.

[0005] Existing technologies have seen some research and practice in the design of air hydrostatic spindle mandrels. For example, to meet the demands of ultra-high-speed operation, existing solutions utilize structures such as axial concentric holes, cylindrical magnets, and axial limiting sleeves inside the mandrel (e.g., CN202111436241.7) to optimize rotor mass distribution and enhance centrifugal force bearing capacity. Furthermore, some solutions employ a matching structure of positioning bars and positioning grooves (e.g., CN202323418046.9) to improve the installation stability of internal components, thereby ensuring the reliability of ultra-high-speed rotation. Regarding spindle thermal management, some existing technologies recognize that motor operation generates heat and attempt to address this by installing heat-conducting frames, flow channels, and external cooling devices on the spindle (e.g., CN202411675669.0). These devices utilize forced convection circulation of heat-conducting fluid to remove heat generated by the motor stator and rotor, preventing thermal deformation of the spindle due to temperature rise.

[0006] However, the existing technologies still have the following shortcomings: 1) Existing thermal management solutions mainly target the heat generated by friction between motor windings and bearings, while paying less attention to the "pneumatic heating" problem unique to air static pressure bearings. Local high-temperature and low-temperature areas will appear on the spindle wall. At the same time, during the operation of the air static pressure spindle, a large amount of non-uniformly distributed heat flow is easily generated, forming multiple local high-temperature areas on the spindle surface, i.e., the "hot spot" phenomenon. This non-uniform heat flow will cause a huge temperature gradient inside the spindle, which will then trigger local peak thermal stress. 2) The thermal conductivity and heat flow spreading capacity of the existing spindle structure are insufficient. Existing spindles are mostly made of stainless steel, which has a low thermal conductivity. Even if a hollow structure is used to reduce weight, its wall thickness is still large and its thermal inertia is high, making it difficult to quickly spread the heat from the local "hot spots" to the entire spindle. At the same time, relying on external pressurized gas or cooling medium to carry heat is not feasible because the gas has a small specific heat capacity and limited heat carrying capacity, and the flow path of the cooling medium is fixed. It cannot adaptively match the distribution characteristics of non-uniform heat flow, making it difficult to fundamentally solve the problem of local overheating.

[0007] In summary, how to effectively suppress hot spots and temperature gradients caused by non-uniform aerodynamic heating, achieve rapid homogenization of the spindle temperature field, and reduce system energy consumption while ensuring the spindle's lightweight and high strength is a technical problem that urgently needs to be solved in the current field of air hydrostatic spindle technology. Summary of the Invention

[0008] In view of this, the present invention aims to provide a lightweight and uniformly heated air hydrostatic bearing mandrel and its preparation method, so as to solve the problems of large internal temperature gradient, insufficient thermal conductivity and heat flow spreading capacity of existing mandrels.

[0009] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A lightweight, uniformly heated air static pressure bearing mandrel for use in air static pressure spindles includes a mandrel body, which comprises an inner mandrel and an outer mandrel sleeved outside the inner mandrel, forming a sealed hollow interlayer between the inner and outer mandrels; a wire mesh assembly is disposed within the hollow interlayer, the wire mesh assembly being attached to the wall surface of the inner and / or outer mandrels; both ends of the mandrel body include side baffles, and a filling pipe communicating with the hollow interlayer is disposed on one side baffle; a phase change heat transfer medium is filled into the hollow interlayer through the filling pipe.

[0010] Furthermore, the wire mesh assembly is a composite wire mesh structure arranged in zones. The wire mesh assembly includes at least two wire mesh groups, namely a high heat flux zone wire mesh group and a low heat flux zone wire mesh group. The high heat flux zone wire mesh group is applied to the high heat flux density region on the outer surface of the mandrel outer shaft that is subjected to non-uniform impact jets. The low heat flux zone wire mesh group is applied to the low heat flux density region on the outer surface of the mandrel outer shaft.

[0011] Furthermore, the mesh count of the wire mesh group in the high heat flux region is greater than that in the low heat flux region, and the porosity of the wire mesh group in the high heat flux region is less than that in the low heat flux region; the mesh count of the wire mesh group in the high heat flux region is 200-400 mesh, and the porosity is 40%-60%; the mesh count of the wire mesh group in the low heat flux region is 80-150 mesh, and the porosity is 60%-80%.

[0012] Furthermore, the wire mesh assembly has a zoned arrangement structure. Specifically, the wire mesh group in the high heat flux zone is set on the inner wall surface of the outer shaft of the mandrel and at the position of the air flotation hole; the wire mesh group in the low heat flux density zone is set in the gap position between the adjacent high heat flux density zones.

[0013] Furthermore, the phase change heat transfer medium is selected from one or more of water, methanol, ethanol, acetone, ammonia, and Freon, and the filling amount of the phase change heat transfer medium is 15% to 30% of the total internal volume of the hollow sandwich layer; the interior of the hollow sandwich layer is evacuated to 1.0 × 10⁻⁶ before filling. -3 Pa or above.

[0014] Furthermore, the maximum circumferential temperature difference of the outer surface of the spindle does not exceed 5℃, and the maximum axial temperature difference does not exceed 8℃; the air supply pressure range of the air static pressure spindle is 0.4MPa-0.8MPa.

[0015] Furthermore, both the inner and outer shafts of the mandrel are made of stainless steel, with the inner shaft having a thicker wall than the outer shaft. The inner shaft has a wall thickness of 3mm to 5mm, and the outer shaft has a wall thickness of 2mm to 4mm. The radial gap between the inner and outer shafts is 3mm to 8mm, which is used to accommodate the wire mesh assembly and the phase change heat transfer medium.

[0016] Furthermore, the side baffles are a left baffle and a right baffle, and the filling pipe is set on the left baffle or the right baffle. After the phase change heat transfer medium is filled, it is sealed by welding or riveting. Threaded positioning holes are provided on both the left baffle and the right baffle.

[0017] Furthermore, after the mandrel body is filled with and sealed with the phase change heat transfer medium, dynamic balancing is performed. The dynamic balancing is performed using a weight reduction method, which involves removing material from the non-sealed areas of the end face or circumference of the mandrel body by drilling, milling, or grinding. The amount of material removed is determined based on the measured initial imbalance. The weight reduction position must avoid the sealing areas of the left and right baffles and the sealing point of the filling tube, and the weight reduction depth must not exceed 80% of the outer shaft wall thickness of the mandrel.

[0018] A method for preparing a lightweight, uniformly heated air static pressure bearing mandrel includes the following steps: S1. Machin the inner shaft, outer shaft, and side baffle of the mandrel respectively, and reserve a filling tube on one side baffle. S2. Attach or sinter the wire mesh assembly to the outer surface of the inner shaft of the mandrel and / or the inner wall surface of the outer shaft of the mandrel; S3. Coaxially fit the inner shaft and outer shaft of the mandrel together, and seal and weld the side baffles on both sides to the two ends of the mandrel body to form a sealed hollow sandwich layer. S4. Vacuum the hollow sandwich layer through the filling pipe, and then fill it with a predetermined amount of phase change heat transfer medium. S5. Seal the filling tube by cold welding or fusion welding; S6. Perform dynamic balancing on the sealed mandrel body until it meets the accuracy requirements.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. This solution can achieve rapid spread of non-uniform heat flow, eliminate "hot spots", significantly improve the uniformity of the mandrel temperature field, reduce the overall operating temperature of the mandrel, reduce thermal inertia, reduce spindle temperature, achieve high spindle performance, improve thermal response speed, improve the thermal stability of the spindle system, and does not require external power to drive the heat transfer medium, sensors, or control algorithms. It is highly versatile, simple in structure, and easy to manufacture.

[0020] 2. This solution can achieve spindle lightweighting, improve spindle strength and rigidity, reduce rotational inertia, improve dynamic response performance, reduce the air supply pressure required for air static pressure bearings, reduce pump power loss of external cooling system, form a virtuous cycle, reduce air intake, reduce overall operating energy consumption, improve spindle rotation accuracy, avoid bearing jamming failure, and extend the life of spindle and bearings.

[0021] 3. Traditionally, mandrels typically have a temperature difference of around ±20℃. That is, where the intake gas of the hydrostatic spindle is compressed, the gas is compressed and the temperature increases, rising by 20℃ compared to the mainstream area. Where the gas expands, the temperature drops, with a decrease of up to -20℃. Due to the relatively poor thermal conductivity of the air-bearing spindle material, these two areas with large temperature differences will form a temperature field, leading to peak strain in the spindle. The air hydrostatic bearing mandrel in this solution can reduce the temperature difference to within ±1℃, ensuring that the mandrel is a homogeneous body and improving its performance and service life. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1A cross-sectional schematic diagram of the air hydrostatic bearing mandrel described in Embodiment 1 of the present invention; Figure 2 A top view of the air static pressure bearing mandrel described in Embodiment 1 of the present invention.

[0023] Reference numerals: 1. Inner spindle shaft; 2. Outer spindle shaft; 3. Threaded positioning hole; 4. Left side baffle; 5. Right side baffle; 6. Wire mesh assembly; 7. Filling tube. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, 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, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] The following will refer to the appendix. Figure 1-2 The invention will be described in detail with reference to the embodiments.

[0029] A lightweight, uniformly heated air hydrostatic bearing mandrel for use in air hydrostatic spindles, such as... Figure 1 , Figure 2 As shown, it includes a mandrel body, which includes an inner mandrel 1 and an outer mandrel 2 sleeved outside the inner mandrel 1. A sealed hollow sandwich is formed between the inner mandrel 1 and the outer mandrel 2. The hollow sandwich is as follows: Figure 1 As shown at point S, a wire mesh assembly 6 is provided inside the hollow sandwich layer. The wire mesh assembly 6 is attached to the wall surface of the inner shaft 1 and the outer shaft 2 of the mandrel. Both ends of the mandrel body include side baffles. A filling pipe 7 communicating with the hollow sandwich layer is provided on one side baffle. The phase change heat transfer medium is filled into the hollow sandwich layer through the filling pipe 7.

[0030] The side baffles are a left baffle 4 and a right baffle 5. The filling tube 7 is set on the left baffle 4 or the right baffle 5. In this embodiment, the filling tube 7 is set on the left baffle 4. After the phase change heat transfer medium is filled, it is sealed by welding or riveting. Both the left baffle 4 and the right baffle 5 are provided with threaded positioning holes 3. The threaded positioning holes 4 are used for the end threaded connection of the inner shaft 1 and the outer shaft 2 of the mandrel and the sealing of the hollow sandwich layer.

[0031] Both the inner shaft 1 and the outer shaft 2 of the mandrel are made of metal materials, preferably stainless steel or brass. The wall thickness of the inner shaft 1 and the outer shaft 2 of the mandrel is determined by finite element analysis. Under the same external load, the strength and stiffness of the hollow sandwich structure are guaranteed to be no less than the strength and stiffness of the original solid or hollow non-heat pipe structure mandrel. The external load includes air buoyancy support force and centrifugal force.

[0032] In this embodiment, both the inner shaft 1 and the outer shaft 2 are made of stainless steel. The wall thickness of the inner shaft 1 is greater than that of the outer shaft 2. The wall thickness of the inner shaft 1 is 3mm~5mm, and the wall thickness of the outer shaft 2 is 2mm~4mm. The radial gap between the inner shaft 1 and the outer shaft 2 is 3mm~8mm, which is used to accommodate the wire mesh assembly 6 and the phase change heat transfer medium. The wall thickness setting of the outer shaft 2 and the inner shaft 1, while ensuring rigidity and strength, can reduce the rotational inertia of the spindle and enhance the flexibility of the system. This setting allows for the highest... At the specified rotational speed, the maximum equivalent stress of the mandrel does not exceed 50% of the allowable stress of the stainless steel material, with a safety factor ≥2.0. Under the action of air buoyancy support force and cutting force, the maximum radial deformation of the mandrel does not exceed 10% of the air film gap. By controlling the wall thickness of the outer shaft 2 of the mandrel to 2mm~4mm, it can ensure that the thermal resistance from the outer surface of the mandrel to the phase change working fluid is low enough, and the heat pipe can respond quickly to non-uniform heat flow. By controlling the radial gap to 3mm~8mm, it can accommodate a wire mesh assembly structure of sufficient thickness and sufficient phase change working fluid, ensuring that the steam flow channel is not blocked.

[0033] The maximum circumferential temperature difference of the outer surface of the spindle 2 does not exceed 5℃, and the maximum axial temperature difference does not exceed 8℃. The air supply pressure range of the air static pressure spindle is 0.4MPa-0.8MPa. The temperature difference is reduced by 60%~75% compared with the non-heat pipe structure spindle. The temperature difference control and the reduction of air supply pressure form a positive feedback synergistic effect, making the spindle operation more stable, energy consumption lower, noise lower, and reliability higher.

[0034] The filling amount of the phase change heat transfer medium and the specifications of the wire mesh assembly 6 are configured to meet the conditions for heat pipe start-up and stable operation. Specifically, the heat pipe structure is started when the spindle body speed reaches 20%~30% of the rated speed, and the heat pipe structure does not experience heat transfer limit failure within the entire operating speed range from the start-up speed to the rated maximum speed of the spindle body. The criterion for judging heat transfer limit failure is that the circumferential temperature difference on the outer surface of the outer shaft 2 of the spindle continuously increases by more than ±1.0℃.

[0035] The wire mesh assembly 6 is a composite wire mesh structure arranged in zones. The wire mesh assembly 6 includes at least two wire mesh groups: a high heat flux zone wire mesh group and a low heat flux zone wire mesh group. The mesh size of the high heat flux zone wire mesh group is 100-200 mesh, and the mesh size of the low heat flux zone wire mesh group is 200-400 mesh. The porosity of the high heat flux zone wire mesh group and the low heat flux zone wire mesh group is 60%-85%. The high heat flux zone wire mesh group is set close to the wall of the mandrel body, and the low heat flux zone wire mesh group is set away from the wall of the mandrel body. The high heat flux zone wire mesh group is applied to the high heat flux density area on the outer surface of the outer shaft 2 of the mandrel under non-uniform impact jet, and is set at the position corresponding to the stator pores. The low heat flux zone wire mesh group is applied to the low heat flux density area on the outer surface of the outer shaft 2 of the mandrel. The high heat flux zone wire mesh group is used for the seepage return of liquid working fluid for replenishment, and the low heat flux zone wire mesh group is used to generate capillary force and motive steam.

[0036] The wire mesh assembly 6 has a zoned arrangement structure. Specifically, the high heat flux zone wire mesh is set on the inner wall of the outer shaft 2 of the mandrel and at the position of the air flotation hole, that is, at the position of the air flotation hole corresponding to the external gas of the static pressure air flotation main shaft, which can enhance the liquid return capacity. The low heat flux zone wire mesh is set in the gap position of the adjacent high heat flux density zone, which can enhance the ability to generate power steam. In this embodiment, the setting of the high heat flux zone wire mesh and the low heat flux zone wire mesh can allow the liquid working fluid to remain in the wire mesh layer, and will not affect the dynamic balance of the main shaft due to the larger eccentric torque generated by the high speed rotation of the main shaft rotor. It can avoid the occurrence of instability due to changes in the stability and stiffness of the main shaft.

[0037] The phase change heat transfer medium is selected from one or more of water, methanol, ethanol, acetone, ammonia, and Freon. The filling amount of the phase change heat transfer medium is 15% to 30% of the total internal volume of the hollow sandwich layer. The interior of the hollow sandwich layer is evacuated to 1.0 × 10⁻⁶ before filling. -A pressure of 3 Pa or higher can reduce the impact of non-condensable gases on phase change heat transfer performance. The smaller the non-condensable gas content, the smaller the internal absolute pressure value, and the better the heat dissipation performance of the spindle.

[0038] After the mandrel body is filled with and sealed with the phase change heat transfer medium, dynamic balancing is performed. The dynamic balancing is performed by weight reduction, that is, material is removed from the non-sealed area of ​​the end face or circumference of the mandrel body by drilling, milling or grinding. The amount of material removed is determined by the initial imbalance measured. The weight reduction position should avoid the sealing area of ​​the left baffle 4 and the right baffle 5 and the sealing point of the filling tube, and the weight reduction depth should not exceed 80% of the outer shaft wall thickness of the mandrel.

[0039] In this embodiment, the distance between the weight reduction position and the weld seam of the left baffle 4 and the right baffle 5 is ≥ 5mm, and the distance from the filling tube seal is ≥ 5mm, to avoid damaging the vacuum seal. Weight reduction processing is avoided in stress concentration areas such as steps, grooves, and threads on the outer shaft of the mandrel. The weight reduction depth does not exceed 80% of the outer shaft wall thickness to ensure that the hollow interlayer is not penetrated. In this embodiment, the outer shaft wall thickness is 2mm~4mm, so the weight reduction depth is ≤ 1.6mm~3.2mm. At the same time, the weight reduction position should be convenient for tool processing to avoid interference. This setting can meet the accuracy requirements of dynamic balance, comply with the allowable value of eccentric torque, and will not damage the vacuum of the hollow interlayer or affect the connection.

[0040] A method for preparing a lightweight, uniformly heated air static pressure bearing mandrel includes the following steps: S1. Machining the inner shaft 1, outer shaft 2, and side baffle of the mandrel respectively, and pre-reserving a filling tube 7 on one side baffle. The inner diameter of the filling tube 7 is 3mm-6mm, the wall thickness is 0.5mm~2.0mm, and the length is 20mm~40mm.

[0041] S2. Attach or sinter the wire mesh assembly 6 to the outer surface of the inner shaft 1 and the inner wall of the outer shaft 2 of the mandrel.

[0042] S3. Coaxially fit the inner shaft 1 and the outer shaft 2 of the mandrel together, and seal and weld the side baffles on both sides to the two ends of the mandrel body to form a sealed hollow sandwich layer.

[0043] S4. Vacuum the hollow jacket through filling pipe 7, and then fill it with a predetermined amount of phase change heat transfer medium.

[0044] S5. Seal the filling tube 7 by cold welding or fusion welding.

[0045] S6. Perform dynamic balancing on the sealed mandrel body until it meets the accuracy requirements.

[0046] Working principle: When the air static pressure spindle is running, the high-pressure gas ejected from the stator vent impacts the outer surface of the outer shaft 2 of the mandrel at high speed. Due to the shearing of the gas film and viscous dissipation, a local high heat flux density, as well as local high temperature and low temperature zones, are generated at the position directly opposite the vent, forming a "hot spot". This non-uniform heat flux passes through the wall of the outer shaft 2 of the mandrel and acts on the phase change heat transfer medium in the hollow sandwich structure. In the hot spot area (i.e., the high heat flux area), the medium absorbs heat and evaporates rapidly into steam. Since the inside of the heat pipe is a vacuum state, the steam flows and transfers to the low heat flux area (i.e., the low temperature area) with a very small pressure drop. When the steam encounters the cooler wall surface in the low temperature area, it releases latent heat and condenses into liquid. The condensed liquid relies on the capillary force provided by the wire mesh assembly 6 to flow back to the hot spot area along the wire mesh assembly, completing an evaporation-condensation-recirculation cycle.

[0047] In this embodiment, the heat from local hot spots is rapidly "transported" to the entire mandrel body surface through the latent heat of the working fluid, rather than relying solely on the slow diffusion of heat through metal conduction. As the heat is rapidly spread and ultimately carried away by the external cooling system of the spindle, the overall operating temperature of the mandrel body decreases. In this embodiment, the highest operating temperature of the outer surface of the outer shaft 2 of the mandrel is 5°C lower than that of the non-heat pipe structure mandrel under the same operating conditions. The hollow sandwich structure itself achieves weight reduction, while the efficient heat transfer of the heat pipe allows for further thinning of the wall thickness without sacrificing thermal performance. In this embodiment, the total mass of the mandrel is reduced by more than 50% compared to the original mandrel, reducing the moment of inertia and starting difficulty.

[0048] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0049] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A lightweight, uniformly heated air hydrostatic bearing mandrel for use in air hydrostatic spindles, characterized in that: The mandrel body includes an inner mandrel (1) and an outer mandrel (2) sleeved outside the inner mandrel (1). A closed hollow interlayer is formed between the inner mandrel (1) and the outer mandrel (2). A wire mesh assembly (6) is provided inside the hollow interlayer. The wire mesh assembly (6) is attached to the wall surface of the inner mandrel (1) and / or the outer mandrel (2). Both ends of the mandrel body include side baffles. A filling pipe (7) communicating with the hollow interlayer is provided on one side baffle. A phase change heat transfer medium is filled into the hollow interlayer through the filling pipe (7).

2. The lightweight, uniformly heated air hydrostatic bearing mandrel according to claim 1, characterized in that: The wire mesh assembly (6) is a composite wire mesh structure arranged in zones. The wire mesh assembly (6) includes at least two wire mesh groups, namely a high heat flux region wire mesh group and a low heat flux region wire mesh group. The high heat flux region wire mesh group is applied to the high heat flux density region of the outer surface of the mandrel outer shaft (2) subjected to non-uniform impact jet. The low heat flux region wire mesh group is applied to the low heat flux density region of the outer surface of the mandrel outer shaft (2).

3. The lightweight, uniformly heated air hydrostatic bearing mandrel according to claim 2, characterized in that: The high heat flux zone wire mesh is used for the seepage return of the liquid working fluid, and the mesh size of the high heat flux zone wire mesh is 100-200 mesh; the low heat flux zone wire mesh is used to generate capillary force and motive steam, and the mesh size of the low heat flux zone wire mesh is 200-400; the porosity of the high heat flux zone wire mesh and the low heat flux zone wire mesh is 60%-85%.

4. The lightweight, uniformly heated air hydrostatic bearing mandrel according to claim 3, characterized in that: The wire mesh assembly (6) has a partitioned arrangement structure. Specifically, the wire mesh assembly in the high heat flux region is set on the inner wall surface of the outer shaft (2) of the mandrel and at the position of the air flotation hole; the wire mesh assembly in the low heat flux density region is set in the gap position of the adjacent high heat flux density region.

5. The lightweight, uniformly heated air hydrostatic bearing mandrel according to claim 1, characterized in that: The phase change heat transfer medium is selected from one or more of water, methanol, ethanol, acetone, ammonia, and Freon. The filling amount of the phase change heat transfer medium is 15% to 30% of the total internal volume of the hollow sandwich layer. The hollow sandwich layer is evacuated to 1.0 × 10⁻⁶ before filling. -3 Pa or above.

6. The lightweight, uniformly heated air hydrostatic bearing mandrel according to claim 1, characterized in that: The maximum circumferential temperature difference of the outer surface of the spindle (2) does not exceed 5℃, and the maximum axial temperature difference does not exceed 8℃; the air supply pressure range of the air static pressure spindle is 0.4MPa-0.8MPa.

7. The lightweight, uniformly heated air hydrostatic bearing mandrel according to claim 1, characterized in that: The inner shaft (1) and outer shaft (2) of the mandrel are both made of stainless steel. The wall thickness of the inner shaft (1) is greater than that of the outer shaft (2). The wall thickness of the inner shaft (1) is 3mm~5mm, and the wall thickness of the outer shaft (2) is 2mm~4mm. The radial gap between the inner shaft (1) and the outer shaft (2) is 3mm~8mm, which is used to accommodate the wire mesh assembly (6) and the phase change heat transfer medium.

8. The lightweight, uniformly heated air hydrostatic bearing mandrel according to claim 1, characterized in that: The side baffles are a left baffle (4) and a right baffle (5). The filling tube (7) is set on the left baffle (4) or the right baffle (5). After the phase change heat transfer medium is filled, it is sealed by welding or riveting. The left baffle (4) and the right baffle (5) are both provided with threaded positioning holes (3).

9. The lightweight, uniformly heated air hydrostatic bearing mandrel according to claim 8, characterized in that: After the mandrel body is filled with phase change heat transfer medium and sealed, dynamic balance correction is performed. The dynamic balance correction adopts the weight reduction method, that is, the material is removed by drilling, milling or grinding in the non-sealed area of ​​the end face or circumference of the mandrel body. The amount of material removed is determined by the initial imbalance measured. The weight reduction position should avoid the sealing area of ​​the left baffle (4) and the right baffle (5) and the sealing of the filling tube, and the weight reduction depth should not exceed 80% of the wall thickness of the outer shaft (2) of the mandrel.

10. A method for preparing a lightweight, uniformly heated air static pressure bearing mandrel, comprising preparing the lightweight, uniformly heated air static pressure bearing mandrel according to any one of claims 1-9, characterized in that: Includes the following steps: S1. Machining the inner shaft (1), outer shaft (2), and side baffle respectively, and pre-reserving a filling tube (7) on one side baffle. S2. Attach or sinter the wire mesh assembly (6) to the outer surface of the inner shaft (1) of the mandrel and / or the inner wall surface of the outer shaft (2) of the mandrel; S3. Coaxially fit the inner shaft (1) and outer shaft (2) of the mandrel, and seal and weld the side baffles on both sides to the two ends of the mandrel body to form a sealed hollow sandwich layer. S4. Vacuum the hollow sandwich layer through the filling tube (7) and then fill it with a predetermined amount of phase change heat transfer medium. S5. The filling tube (7) is sealed by cold welding or fusion welding; S6. Perform dynamic balancing on the sealed mandrel body until it meets the accuracy requirements.

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