Liquid metal bearing with labyrinth-spiral combined seal

Abstract

This invention relates to the field of liquid metal bearing sealing technology, and discloses a liquid metal bearing with a labyrinth-spiral combined sealing structure, including a bearing sleeve and a support shaft. The bearing sleeve is rotatably connected to the support shaft. The support shaft has a shoulder on its outer side. The bearing sleeve has a flared opening on its outer right side. A sealing cover is provided on the outer right side of the shoulder. The sealing cover is fixedly connected to the outer right side of the bearing sleeve. A labyrinth seal is provided inside the sealing cover. A spiral return groove is provided on the outer right side of the support shaft, near the shoulder. The spiral return groove is located inside the first sealing groove of the labyrinth seal. By introducing the spiral return groove, the fluid dynamic pressure generated by the rotation of the shaft is used to reverse pump the leaking liquid metal, changing the traditional passive throttling to active return. When the reverse pumping flow rate is greater than the leakage flow rate, the leakage path can be cut off under dynamic operating conditions to achieve true zero leakage.

Description

Technical Field

[0001] This invention relates to the field of liquid metal bearing sealing technology, specifically to a liquid metal bearing with a labyrinth-spiral combined sealing structure. Background Technology

[0002] In modern high-end equipment manufacturing, such as aerospace vehicle rotating mechanisms, high-precision vacuum equipment, and specific high-temperature reaction devices, traditional greases or solid lubricants often fail to meet the demanding operating conditions. Liquid metals are gradually becoming ideal bearing lubrication media in these extreme environments, mainly due to their special physical properties: firstly, their extremely low saturated vapor pressure, which makes them less prone to volatilization under high vacuum; and secondly, their excellent thermal conductivity and thermal stability, which can quickly dissipate the heat generated by the high-speed operation of the bearing, thereby maintaining a good lubrication state of the system.

[0003] However, in practical engineering applications, liquid metal bearings have always faced a thorny bottleneck: they are extremely prone to leakage. Compared to conventional lubricating oils, liquid metals have extremely low kinematic viscosity and different surface tension characteristics. When the bearing is rotating at high speed, driven by centrifugal force and a slight vacuum pressure difference, the liquid metal easily leaks outward along the tiny gaps between the moving and stationary parts of the bearing. This irreversible loss directly leads to a continuous decrease in the effective lubricant dosage inside the bearing, thinning or even rupture of the lubricant film, which in turn causes dry friction between components, resulting in a sharp increase in frictional resistance, uncontrolled temperature rise during operation, and accelerated fatigue at the contact interfaces.

[0004] The hazards of leaks extend far beyond lubrication failure itself. Liquid metals typically possess extremely high permeability and chemical reactivity. Once they overflow from the bearing's working cavity and enter the surrounding vacuum environment or other precision structures, they readily react with the surrounding structural metals, causing liquid metal embrittlement and resulting in severe corrosion and adhesive wear at the contact interfaces. If leaked liquids drip onto nearby electronic components or sensors, they can also cause short circuits or electrochemical damage. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a liquid metal bearing with a labyrinth-spiral combined sealing structure, solving the problem of liquid metal easily leaking outwards along the tiny gaps between the moving and stationary parts of the bearing.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a liquid metal bearing with a labyrinth-spiral combined sealing structure, comprising a bearing sleeve and a support shaft, wherein the bearing sleeve is rotatably connected to the support shaft, the support shaft is provided with a shoulder on its outer side, the bearing sleeve is provided with an flared opening on its outer right side, a sealing cover is provided on the outer right side of the shoulder, the sealing cover is fixedly connected to the outer right side of the bearing sleeve, a labyrinth seal is provided inside the sealing cover, and a spiral reflux groove is provided on the outer right side of the support shaft near the shoulder.

[0007] Preferably, the spiral reflux groove is located inside the first sealing groove of the labyrinth seal.

[0008] Preferably, the radial gap between the inner wall surface of the sealing cap and the support shaft is in the range of 20-100 μm.

[0009] Preferably, one cycle of the spiral reflux groove consists of a groove and a ridge.

[0010] Preferably, the cross-section of the spiral reflux groove is a combination of one or more of the following cross-sections: rectangular, arc-shaped, trapezoidal, and triangular.

[0011] Preferably, the tooth shape of the labyrinth seal is a combination of one or more of the following shapes: rectangle, trapezoid, and triangle.

[0012] Preferably, the bearing sleeve and the sealing cover are fixedly connected by bolts.

[0013] Preferably, the left side of the shoulder abuts against the flared surface on the right side of the bearing sleeve.

[0014] Preferably, the spiral angle of the spiral reflux groove is in the range of 15°-45°.

[0015] Preferably, the width ratio of the groove to the ridge is 0.8-1.2.

[0016] Preferably, the gap between the bearing sleeve and the support shaft is filled with a gallium indium tin liquid alloy.

[0017] This invention provides a liquid metal bearing with a labyrinth-spiral combined sealing structure. It possesses the following advantages: This invention introduces a spiral reflux groove, utilizing the hydrodynamic pressure generated by the rotating shaft to reverse-pump the leaking liquid metal, transforming the traditional passive throttling into active reflux. When the reverse pumping flow rate exceeds the leakage flow rate, the external leakage path can be completely cut off under dynamic operating conditions, achieving true zero leakage. This structure fundamentally solves the problems of dry friction and equipment corrosion caused by lubricant loss, improving the service life and long-term reliability of liquid metal bearings under extreme conditions such as high vacuum and high speed. Attached Figure Description

[0018] Figure 1 This is a perspective view of the present invention; Figure 2 A schematic diagram illustrating the support shaft structure of the present invention; Figure 3 A schematic diagram illustrating the spiral reflux groove structure of the present invention; Figure 4 A schematic diagram illustrating the sealing cap structure of the present invention; Figure 5 A plan view illustrating the support shaft structure of the present invention; Figure 6 This is a schematic diagram showing the circumferential unfolding of the spiral reflux groove of the present invention.

[0019] Figure 7 The schematic diagram of Embodiment 2 of the present invention is shown in the figure.

[0020] Figure 8 A schematic diagram of the sealing cap structure in Embodiment 2 of the present invention is shown.

[0021] Figure 9 The schematic diagram of Embodiment 3 of the present invention is shown in the figure.

[0022] Figure 10 A schematic diagram of the sealing cap structure in Embodiment 3 of the present invention is shown.

[0023] Among them, 1. bearing sleeve; 2. support shaft; 3. sealing cover; 4. shaft shoulder; 5. spiral reflux groove; 6. labyrinth seal; 7. raised ridge; 8. groove; 9. spiral groove. Detailed Implementation

[0024] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0025] Please see the appendix Figure 1 -Appendix Figure 6This invention provides a liquid metal bearing with a labyrinth-spiral combined sealing structure, including a bearing sleeve 1 and a support shaft 2. The bearing sleeve 1 and the support shaft 2 are rotatably connected. The support shaft 2 has a shoulder 4 on its outer side. The bearing sleeve 1 has an flared opening on its outer right side. The shoulder 4 has a sealing cover 3 on its outer right side. The sealing cover 3 is fixedly connected to the outer right side of the bearing sleeve 1. The sealing cover has a labyrinth seal inside. The support shaft has a spiral return groove on its outer right side near the shoulder.

[0026] Under actual operating conditions, as the rotational speed of the support shaft 2 gradually increases, the liquid metal filling the bearing gap not only serves the functions of lubrication and heat conduction, but also inevitably tends to leak outward along the axial direction due to the centrifugal force and the volume expansion caused by the temperature rise during operation. When the liquid metal fluid carrying a certain dynamic pressure flows through the mating gap between the moving and stationary parts and passes through the physical barrier at the left end of the shaft shoulder 4, it will penetrate through the tiny tooth gaps at the front end of the labyrinth seal 6 to the outer surface of the support shaft 2, and then be sent into the control area of ​​the spiral return groove 5.

[0027] At this time, driven directly by the high-speed rotation of the support shaft 2, the ridges 7 on the surface of the spiral reflux groove 5 tightly cooperate with the inner sealing wall of the sealing cover 3, applying physical shearing force to the liquid metal entering this area. The fluid is guided into the groove 8, and with the axial movement of the shaft, this shearing force is quickly converted into a fluid dynamic pressure gradient along the axial direction and pointing towards the inside of the bearing. Based on the above complex flow field changes, the reverse pumping volume flow rate generated by the spiral reflux groove 5 at the current rotation speed must be strictly greater than the axial leakage flow rate attempting to penetrate the labyrinth seal 6 due to the slight pressure difference inside and outside the sealing cover 3 and the centrifugal force. In actual operation, as long as the operating parameters of the equipment can cross and maintain this dynamic flow balance point, the outward leakage kinetic energy will be completely suppressed and offset by the inward pumping kinetic energy, thus achieving the goal of zero leakage of liquid metal steadily and persistently under harsh high temperature and high vacuum rotation environment.

[0028] The spiral reflux groove 5 is located inside the first sealing groove of the labyrinth seal 6, which prevents a large amount of liquid metal from flowing into the labyrinth seal 6 and reduces the pressure load on the overall sealing structure.

[0029] The radial clearance between the inner wall of the sealing cover 3 and the support shaft 2 is controlled within the range of 20-100μm. This clearance size is an optimal value after comprehensive consideration of thermodynamics and fluid mechanics: if the clearance is less than 20μm, the bearing is prone to seizure due to the thermal expansion of the metal parts during high-temperature and high-speed operation; if the clearance is greater than 100μm, the capillary force and shear force of the liquid metal in the clearance will be significantly reduced, resulting in the reverse pumping volume of the spiral reflux groove 5 being insufficient to resist the outward leakage pressure of the liquid metal.

[0030] One cycle of the spiral reflux channel 5 consists of a groove 8 and a ridge 7. A complete cycle of the spiral reflux channel 5 along the axial direction consists of alternating recessed grooves 8 and raised ridges 7. The grooves 8 are used to contain and guide the liquid metal, while the ridges 7 apply shear force to the fluid to establish a pressure gradient.

[0031] The cross-section of the spiral reflux channel 5 is a combination of one or more of the following shapes: rectangular, arc, trapezoidal, and triangular. The geometric shape of the cross-section directly determines the shear rate and pressure gradient of the liquid metal in the channel. The spiral reflux channel 5, with its cross-section being a combination of one or more of the following shapes, can adapt to the fluid dynamic pressure under different working conditions. The tooth shape of the labyrinth seal 6 is a combination of one or more of the following shapes: rectangular, trapezoidal, and triangular.

[0032] The bearing sleeve 1 and the sealing cover 3 are connected by bolts or laser welding. The sealing cover 3 is connected to the outer right side of the bearing sleeve 1 by bolt fastening. The use of bolt fastening or laser welding ensures the structural rigidity and tightness of the mating surface after assembly, preventing the possibility of secondary leakage from the static mating surface, and also facilitates the disassembly, inspection and maintenance of the internal sealing components in the later stage.

[0033] The left side of the shoulder 4 abuts against the flared surface on the right side of the bearing sleeve 1. The left end face of the shoulder 4 abuts against the flared surface. This design not only reliably limits the axial movement of the support shaft 2 and prevents axial movement, but also forms the first mechanical barrier layer for liquid metal leakage, which can reduce the kinetic energy of the fluid flowing towards the sealing area.

[0034] The spiral angle of the spiral reflux groove 5 is in the range of 15°-45°, and the width ratio of the groove 8 to the ridge 7 is 0.8-1.2. The groove-ridge ratio is set between 0.8 and 1.2. If the groove 8 is too narrow, the volume of medium in a single reflux will be limited. If the ridge 7 is too narrow, sufficient pumping back pressure cannot be established. At the same time, the spiral angle of the spiral reflux groove 5 is set in the range of 15°-45°. Within this angle range, the circumferential linear velocity generated by the rotation of the shaft can be converted into the axial component velocity that drives the liquid metal to reflux into the bearing cavity with maximum efficiency, thus achieving true zero leakage.

[0035] The gap between bearing sleeve 1 and support shaft 2 is filled with a liquid alloy. This liquid metal alloy is chosen to replace traditional organic lubricants or solid greases for several reasons. First, gallium indium tin alloy maintains good fluidity at room temperature and even over a wider temperature range, and possesses extremely low saturated vapor pressure. This indicates that in aerospace deep space exploration or high-precision vacuum equipment, it will not vaporize, evaporate, or degrade like conventional lubricants, fundamentally solving the vacuum contamination and loss caused by phase change of the lubricating medium. Second, when support shaft 2 rotates at high speed within bearing sleeve 1, the gallium indium tin alloy filled in the gap can establish a hydrodynamic pressure effect through the viscous shearing action of the fluid. This hydrodynamic pressure forms a continuous and dense liquid metal lubricating film with extremely high load-bearing stiffness, completely physically isolating the dynamic and static metal surfaces of the bearing, reducing operating resistance, and avoiding adhesive wear and fatigue spalling caused by direct contact.

[0036] In addition, gallium indium tin alloy has the ultra-high thermal conductivity of traditional organic lubricants. When bearings are subjected to high-speed friction or long-term external high-temperature heat radiation, heat is easily generated inside. This liquid metal not only performs the lubrication function, but also transfers and dissipates the heat of the working area to the external structure, preventing thermal expansion deformation or seizing failure caused by local overheating of components, and ensuring the stability of clearance dimensions and the safety of bearing operation under high-temperature conditions. Example 2:

[0037] Unlike Embodiment 1, in this embodiment, the spiral reflux groove 5 is disposed on the inner wall surface of the sealing cover 3, and the labyrinth seal 6 is disposed on the outside of the support shaft 2 and on the right side near the shaft shoulder 4. This structure can still achieve multi-stage throttling through the labyrinth seal, and use the spiral reflux groove 5 on the inner surface of the sealing cover 3 to return liquid metal to the bearing cavity, which is suitable for situations where the outer surface of the support shaft is more convenient for machining labyrinth tooth profiles. Example 3:

[0038] Unlike Embodiment 1, this embodiment features a spiral groove 9 on the inner wall of the sealing cap 3 and a spiral return groove 5 on the right side of the support shaft 2, near the shoulder 4. The spiral groove 9 can be single-headed or double-headed to extend the leakage path of the liquid metal and enhance the leakage prevention effect; the spiral return groove 5 on the surface of the support shaft 2 continues to perform the active return function. This embodiment balances structural compactness and ease of manufacturing.

[0039] Working Principle: During operation, when the liquid metal bearing is running, the liquid metal also flows inside the bearing. When the liquid metal flows to the left end of the shaft shoulder 4, it passes through the front tooth gap of the labyrinth seal 6 and reaches the shaft surface, entering the spiral return groove 5. Driven by the high-speed rotation of the bearing, the spiral return groove 5 generates hydrodynamic pressure. This hydrodynamic pressure gradient drives the fluid to flow back to the bearing cavity in the opposite direction. Therefore, the sealing condition of this sealing structure can be described as follows: the reverse pumping volume flow rate generated by the spiral return groove 5 per unit time must be greater than the axial leakage flow rate of the labyrinth seal 6. When this condition is met, the goal of zero leakage of liquid metal can be achieved dynamically.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A liquid metal bearing with a labyrinth-spiral combined sealing structure, comprising a bearing sleeve (1) and a support shaft (2), characterized in that, The bearing sleeve (1) is rotatably connected to the support shaft (2). The support shaft (2) has a shoulder (4) on its outside. The bearing sleeve (1) has an opening on its outer right side. The shoulder (4) has a sealing cover (3) on its outer right side. The sealing cover (3) is fixedly connected to the outer right side of the bearing sleeve (1). The sealing cover (3) has a labyrinth seal (6) inside. The support shaft (2) has a spiral reflux groove (5) on its outer right side near the shoulder (4).

2. The liquid metal bearing with a labyrinth-spiral combined sealing structure according to claim 1, characterized in that, The spiral reflux groove (5) is located inside the first sealing groove of the labyrinth seal (6), and the tooth shape of the labyrinth seal (6) is a combination of one or more shapes among rectangle, trapezoid and triangle.

3. The liquid metal bearing with a labyrinth-spiral combined sealing structure according to claim 1, characterized in that, The radial gap between the inner wall of the sealing cap (3) and the support shaft (2) is 20-100 μm.

4. A liquid metal bearing with a labyrinth-spiral combined sealing structure according to claim 1, characterized in that, One cycle of the spiral reflux groove (5) consists of a groove (8) and a ridge (7).

5. A liquid metal bearing with a labyrinth-spiral combined sealing structure according to claim 1, characterized in that, The cross-section of the spiral reflux groove (5) is a combination of one or more of the following cross-sections: rectangular, arc-shaped, trapezoidal, and triangular.

6. A liquid metal bearing with a labyrinth-spiral combined sealing structure according to claim 1, characterized in that, The bearing sleeve (1) and the sealing cap (3) are fixedly connected by bolts or by laser welding.

7. A liquid metal bearing with a labyrinth-spiral combined sealing structure according to claim 1, characterized in that, The left side of the shoulder (4) abuts against the flared surface on the right side of the bearing sleeve (1).

8. A liquid metal bearing with a labyrinth-spiral combined sealing structure according to claim 1, characterized in that, The spiral angle of the spiral reflux groove (5) ranges from 15° to 45°.

9. A liquid metal bearing with a labyrinth-spiral combined sealing structure according to claim 4, characterized in that, The width ratio of the groove (8) to the ridge (7) is 0.8-1.

2.

10. A liquid metal bearing with a labyrinth-spiral combined axial sealing structure according to claim 1, characterized in that, The gap between the bearing sleeve (1) and the support shaft (2) is filled with liquid alloy.

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