A method for assembling a liquid metal bearing

Abstract

The present invention discloses a method for assembling a liquid metal bearing, comprising the following steps: 1) placing the inner hole of the outer sleeve upward, injecting liquid metal into the inner hole, and inserting the lower end of the inner shaft into the inner hole of the outer sleeve; 2) both the end cover and the gasket are sleeved on the inner shaft, and the end cover and the gasket are fixed together by a fixing tool; 3) turning the outer sleeve and the inner shaft upside down, so that the inner hole of the outer sleeve is placed downward, and the end cover and the gasket are located below the outer sleeve and the annular boss; 4) injecting liquid metal into the cavity surrounded by the gasket and the inner shaft, pressing the outer sleeve, the gasket and the end cover together, and inserting the annular boss into the gasket; 5) fixing the outer sleeve, the gasket and the end cover together by fasteners. The assembly method of the liquid metal bearing of the present invention can ensure that the lubrication gaps on both sides of the annular boss are filled with liquid metal, so as to achieve good packaging of the liquid metal.

Description

Technical Field

[0001] The invention relates to an assembly method of a liquid metal bearing, belonging to the technical field of liquid metal bearings. Background Art

[0002] Gallium-based liquid alloys are widely used as lubricants for bearing systems. Since liquid gallium-based alloys have good fluidity, the bearing system can operate with less resistance and achieve high-speed movement, with a speed of up to 30,000 rpm. Since liquid gallium-based alloys have a very wide liquid phase range and evaporate less at high temperatures, they can be used for a long time at high temperatures. Since liquid gallium-based alloys have good thermal conductivity, they can transfer heat to loads with heat input and perform effective cooling. Therefore, gallium-based liquid metal bearings are widely used in rotating target disks and hard disks in industrial CT, medical CT, etc.

[0003] Gallium-based liquid metal has the following characteristics, which require the use of a high vacuum system or argon protection during packaging and use.

[0004] 1. Gallium-based metals are easily oxidized and form an oxide film on the surface.

[0005] 2. The oxide film will increase the apparent viscosity of the liquid metal gallium alloy, thereby increasing the bearing resistance.

[0006] 3. Liquid gallium metal easily absorbs water in a humid environment. Hydrogen atoms will dissolve in the liquid gallium metal alloy, and oxygen will combine with gallium to form gallium oxide. Under vacuum and high temperature conditions, the dissolved hydrogen atoms will aggregate and precipitate into hydrogen molecules and overflow in the form of gas, causing the vacuum system to be destroyed and the electron beam to ionize and discharge, affecting the normal operation of the CT light source.

[0007] At present, there are certain problems in accurately controlling the composition of gallium-indium-tin liquid alloy.

[0008] 1. Gallium is liquid at room temperature, while indium and tin are solid. There is an oxide layer on the surface of indium and tin ingots, which is not easy to remove. Therefore, when preparing gallium-indium-tin liquid alloy, there are oxides in the alloy liquid that need to be removed. During the oxide removal process, the composition is inevitably fluctuating.

[0009] 2. Gallium-indium-tin liquid alloy hopes to obtain the composition of the eutectic point to ensure that the liquid metal will not solidify and avoid damaging the bearing. However, it is not convenient to measure the composition during the actual alloy configuration process. Therefore, there is a slight deviation in the composition, and the deviation in the composition is likely to lead to an increase in the phase transition point and solidification of the liquid metal.

[0010] For example, the liquid metal bearing disclosed in Patent Document 1 (publication number CN117628054A) usually uses a friction pair assembled with inner and outer shafts to constrain the radial runout of the bearing, and an annular boss to constrain the axial movement, and an annular gasket (spacer) is arranged on the periphery of the annular boss. Such a liquid metal bearing has a simple structure and can greatly improve machining accuracy, finish, concentricity, etc., and improve grinding accuracy, but there are difficulties in encapsulating liquid metal.

[0011] 1. Gallium-indium-tin alloy has low viscosity and good fluidity; at the same time, it has a large surface tension of about 600N / m.

[0012] 2. Since the gap between the sliding contact surfaces of the bearings is only tens of microns, and the surface tension of the gallium-indium-tin alloy is large, a very large hydrostatic pressure is required to allow the liquid metal to fill the entire gap starting from one end of the bearing (for example, the liquid metal bearing filling tooling disclosed in the Chinese utility model patent publication number CN221033677U adopts this method).

[0013] 3. Under the huge hydrostatic pressure, liquid metal can easily overflow from the assembly gap, resulting in inaccurate quality control of the metal liquid, and thus the metal liquid can easily fail to completely cover the lubrication surface of the friction pair.

[0014] 4. The two sides of the annular boss form two chambers (lubricating gaps) for accommodating liquid metal. When liquid metal is injected into one end of the outer shaft, it is difficult to fill both chambers with liquid metal, making it difficult to achieve encapsulation and even more difficult to accurately control the capacity of the encapsulated liquid metal. When the bearing runs at high temperature, there is a risk that the excess liquid metal will expand and overflow, damaging the bearing. Summary of the invention

[0015] In order to overcome the problems existing in the prior art, the present invention provides an assembly method of a liquid metal bearing, which is conducive to achieving good packaging of the liquid metal. The specific technical solution is as follows.

[0016] A method for assembling a liquid metal bearing, the liquid metal bearing comprising an outer sleeve, an inner shaft, an end cover and a gasket, one end of the inner shaft is located in the outer sleeve, the inner shaft is provided with an annular boss, the gasket is located at the periphery of the annular boss, and the gasket is fixed between the outer sleeve and the end cover;

[0017] The assembly method comprises the following steps:

[0018] 1) Place the inner hole of the outer sleeve upward, inject liquid metal into the inner hole, and insert the lower end of the inner shaft into the inner hole of the outer sleeve;

[0019] 2) The end cover and the gasket are both sleeved on the inner shaft, and the end cover and the gasket are fixed together by a fixing tool;

[0020] 3) Turn the outer sleeve and the inner shaft upside down so that the inner hole of the outer sleeve is placed downward, and the end cover and the gasket are located below the outer sleeve and the annular boss;

[0021] 4) Injecting liquid metal into the cavity formed by the gasket and the inner shaft, pressing the outer sleeve, gasket and end cover together, and inserting the annular boss into the gasket;

[0022] 5) Use fasteners to fix the outer sleeve, gasket and end cover together.

[0023] By adopting the above technical solution, the lubrication gap between the outer sleeve, the inner shaft and the annular boss is first filled with liquid metal, and the excess liquid metal will overflow from the gap between the outer sleeve and the annular boss. Then, the outer sleeve is turned upside down with the inner hole of the outer sleeve facing downward. At this time, the large surface tension of the liquid metal is creatively utilized, and the liquid metal will not flow out from the inner hole of the outer sleeve. Then, the lubrication gap between the gasket and the annular boss and the lubrication gap between the end cover and the inner shaft are filled with liquid metal. The present invention fills the lubrication gaps on both sides of the annular boss in two stages, and the amount of liquid metal filled is exactly the same as the volume of the bearing lubrication gap, ensuring good packaging of the liquid metal.

[0024] Preferably, each of the above assembly steps is completed in a vacuum environment or an oxygen-free inert gas protection environment. A vacuum environment or an inert gas environment can avoid the formation of an oxide layer in the liquid metal.

[0025] Furthermore, the above step 1) is carried out in a confined space, and the confined space is evacuated before the lower end of the inner shaft is inserted into the inner hole of the outer sleeve. After the confined space is evacuated, the inner shaft will fall under the action of gravity, and the lower end of the inner shaft will be inserted into the inner hole of the outer sleeve under vacuum and squeeze the injected liquid metal, so that the liquid metal fills the gap between the outer sleeve and the inner shaft. The advantage of this operation is that the gap between the outer sleeve and the inner shaft is completely filled with liquid metal, and there is no gas; at the same time, the subsequent inert gas will not enter the gap between the outer sleeve and the inner shaft. After the lower end of the inner shaft is inserted into the inner hole of the outer sleeve, the pressure applied by the press overcomes the hindrance of the capillary action of the liquid metal and fills the gap between the inner shaft and the outer sleeve. The process of applying pressure by the press can be carried out in a vacuum confined space, or it can be carried out in a confined space under the protection of an inert gas.

[0026] Furthermore, the outer peripheral surface of the gasket is provided with a groove; the fixing tool has two claws, one of which abuts against the outer end surface of the end cover, and the other claw abuts against the groove. By providing the groove, interference between the claw and the outer sleeve can be avoided.

[0027] Furthermore, in step 1), a press is used to insert the lower end of the inner shaft into the inner hole of the outer sleeve, and the lower end of the inner shaft stops when it reaches the designed position. The process of applying pressure by the press can be carried out in a vacuum-sealed space, or can be carried out in a sealed space filled with inert gas protection.

[0028] Furthermore, in the step 5), excess liquid metal is removed before the fastener is locked.

[0029] Furthermore, the fastener is a bolt.

[0030] Furthermore, the liquid metal adopts a gallium-indium-tin ternary alloy, and the preparation method of the liquid metal includes the following steps:

[0031] S1. Referring to the designed gallium-indium-tin ternary eutectic alloy, when preparing the ingredients, the amount of Ga added should be greater than the designed gallium-indium-tin ternary eutectic alloy to form an alloy with excessive Ga;

[0032] S2. Melting the gallium-indium-tin ternary alloy with excess Ga in a vacuum container, heating it to 100 degrees above the melting temperature, mixing it evenly, cooling it in a vacuum container to 0.2-6 degrees above the eutectic point temperature, and removing the crystallized Ga particles floating on the metal liquid surface by filtering;

[0033] S3, continue cooling the gallium-indium-tin ternary alloy in the vacuum container until 90%-97% of the volume of the Ga-In-Sn alloy solidifies, and pour out the remaining liquid;

[0034] S4, repeat step S2 and step S3 at least once;

[0035] S5. Finally, the liquid metal in the vacuum container is heated to a temperature 10 to 20 degrees higher than the eutectic point, and the liquid metal melted at this temperature is obtained for bearing packaging.

[0036] Preferably, in step S2, the temperature is cooled in a vacuum container to a temperature 0.5-2 degrees higher than the eutectic point.

[0037] Preferably, in step S3, the gallium-indium-tin ternary alloy is cooled in a vacuum container until 94%-96% of the volume of the Ga—In—Sn alloy is solidified.

[0038] Preferably, in step S4, step S2 and step S3 are repeated twice.

[0039] Compared with the prior art, the assembly method of the liquid metal bearing of the present invention can ensure that the lubrication gaps on both sides of the annular boss are filled with liquid metal, thereby achieving good packaging of the liquid metal; at the same time, the purity of the gallium-indium-tin liquid alloy is improved by controlling the composition and process, thereby reducing its impurity content and moisture, and improving the high-temperature working performance of the liquid metal bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a cross-sectional view of the liquid metal bearing of the present invention;

[0041] Figure 2 is a cross-sectional view of the outer sleeve;

[0042] Figure 3 It is a cross-section of the inner shaft;

[0043] Figure 4 is a schematic diagram of injecting liquid metal into the outer sleeve;

[0044] Figure 5 It is a schematic diagram of inserting the inner shaft into the outer sleeve;

[0045] Figure 6 is a schematic diagram of injecting liquid metal into the cavity between the gasket and the inner shaft;

[0046] Figure 7 is a schematic diagram of inserting the annular boss into the inner cavity formed by the gasket and the end cover;

[0047] Figure 8 is a schematic diagram of fasteners used to secure the outer sleeve, gasket and end cover.

[0048] In the figure: outer sleeve 1, inner hole 1.1, inner shaft 2, annular boss 2.1, end cover 3, gasket 4, fixing tool 5, cavity 6, measuring tool 7, press 8. DETAILED DESCRIPTION

[0049] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0050] See also Figure 1-Figure 3The liquid metal bearing comprises an outer sleeve 1, an inner shaft 2, an end cover 3 and a gasket 4. One end of the inner shaft 2 is located in the outer sleeve 1. The inner shaft 2 is provided with an annular boss 2.1. The gasket 4 is located on the periphery of the annular boss 2.1. The gasket 4 is fixed between the outer sleeve 1 and the end cover 3. The end cover 3 is sleeved on the inner shaft 2. In the use state, the inner shaft 2 can rotate relative to the outer sleeve 1, the end cover 3 and the gasket 4. The liquid metal plays a lubricating role. The liquid metal is located in the gap between the outer sleeve 1 and the inner shaft 2, in the gap between the gasket 4 and the inner shaft 2, and in the gap between the end cover 3 and the inner shaft 2. A sealing structure is provided on the end cover 3. The sealing structure prevents the liquid metal from leaking from between the end cover 3 and the inner shaft 2. The sealing structure adopts the existing technology.

[0051] See also Figure 1-Figure 8 , the assembly method of the liquid metal bearing comprises the following steps:

[0052] 1) If Figure 4-Figure 5 As shown, the inner hole 1.1 of the outer sleeve 1 is placed upward, and an excessive amount of liquid metal (the volume of the injected liquid metal is greater than the volume of the lubrication gap between the outer sleeve and the inner shaft) (the red part) is injected into the inner hole 1.1 using a container or a measuring tool 7. Before the lower end of the inner shaft 2 is inserted into the inner hole 1.1 of the outer sleeve 1, the closed space is evacuated, and the outer sleeve 1 and the inner shaft 2 are assembled in the closed space. After the closed space is evacuated, the inner shaft 2 is allowed to fall under the action of gravity, and the lower end of the inner shaft 2 is inserted into the inner hole 1.1 of the outer sleeve 1 under a vacuum state and squeezes the injected gallium-indium-tin liquid metal, so that the liquid metal fills the gap between the outer sleeve 1 and the inner shaft 2. After the lower end of the inner shaft 2 is inserted into the inner hole 1.1 of the outer sleeve 1, the pressure applied by the press overcomes the hindrance of the capillary action of the liquid metal and fills the gap between the inner shaft 2 and the outer sleeve 1. The process of applying pressure by the press can be carried out in a vacuum-sealed space, or in a sealed space filled with inert gas protection;

[0053] 2) If Figure 4 , Figure 5 As shown, the end cover 3 and the gasket 4 are both sleeved on the upper end of the inner shaft 2, and the end cover 3 and the gasket 4 are fixed together by a fixing fixture 5. Since the contact surface between the end cover 3 and the gasket 4 has a high degree of smoothness and straightness, the gap between the two will not leak liquid metal; preferably, the outer peripheral surface of the gasket 4 is provided with a groove (not shown); the fixing fixture 5 has two claws, one of which abuts against the outer end surface of the end cover 3, and the other abuts against the groove. By providing the groove, interference between the claws and the outer sleeve 1 can be avoided;

[0054] 3) If Figure 6As shown, the outer sleeve 1 and the inner shaft 2 are turned upside down so that the inner hole 1.1 of the outer sleeve 1 is placed downward. Due to the large surface tension of the liquid metal, the liquid metal packaged in the outer sleeve 1 will not flow out; the end cover 3 and the gasket 4 are located below the outer sleeve 1 and the annular boss 2.1;

[0055] 4) Figure 6-Figure 7 As shown, an excess amount of liquid metal (the volume of the injected liquid metal is greater than the volume of the lubrication gap between the inner shaft, the gasket and the end cover) is injected into the cavity 6 surrounded by the gasket 4 and the inner shaft 2, the outer sleeve 1, the gasket 4 and the end cover 3 are pressed together, and the annular boss 2.1 is inserted into the gasket 4;

[0056] 5) If Figure 8 As shown, the outer sleeve 1, the washer 4 and the end cover 3 are fixedly connected together by fasteners (preferably bolts), and the fixing tool 5 is removed.

[0057] By adopting the above technical solution, the lubrication gap between the outer sleeve 1, the inner shaft 2 and the annular boss 2.1 is first filled with liquid metal, and the excess liquid metal will overflow from the gap between the outer sleeve 1 and the annular boss 2.1. Then, the outer sleeve 1 is turned upside down, with the inner hole 1.1 of the outer sleeve 1 facing downward. At this time, the large surface tension of the liquid metal is creatively utilized, and the liquid metal will not flow out from the inner hole 1.1 of the outer sleeve 1. Then, the lubrication gap between the gasket 4 and the annular boss 2.1 and the lubrication gap between the end cover 3 and the inner shaft 2 are filled with liquid metal. The present invention fills the lubrication gaps on both sides of the annular boss 2.1 in two stages to ensure good packaging of the liquid metal.

[0058] In one embodiment, each step of the above assembly is completed in a vacuum environment with a vacuum degree of 0.01Pa to 0.0001Pa or in a high-purity Ar inert gas (purity of 99.995) protection environment. A vacuum environment or an oxygen-free inert gas protection environment can prevent the formation of an oxide layer in the liquid metal.

[0059] In one embodiment, the above step 1) is performed in a closed space, and before the lower end of the inner shaft 2 is inserted into the inner hole 1.1 of the outer sleeve 1, the closed space is evacuated, and after the lower end of the inner shaft 2 is inserted into the inner hole 1.1 of the outer sleeve 1, the closed space is filled with inert gas. After the closed space is evacuated, the inner shaft 2 is allowed to fall under the action of gravity to squeeze the liquid metal, and then the press applies pressure to press the inner shaft 2 into the inner cavity of the outer sleeve 1, so that the liquid metal will fill the gap between the inner shaft 2 and the outer sleeve 1.

[0060] Preferably, in step 1), the lower end of the inner shaft 2 is inserted into the inner hole 1.1 of the outer sleeve 1 by using a press machine 8, and the lower end of the inner shaft 2 stops when it reaches the designed position.

[0061] In one embodiment, the liquid metal is a gallium-indium-tin ternary alloy, and the preparation method of the liquid metal comprises the following steps:

[0062] S1. Referring to the designed gallium-indium-tin ternary eutectic alloy, when preparing the ingredients, the amount of Ga added should be greater than the designed gallium-indium-tin ternary eutectic alloy to form an alloy with excessive Ga;

[0063] S2. Melting the gallium-indium-tin ternary alloy with excess Ga in a vacuum container, heating it to 100 degrees above the melting temperature, mixing it evenly, cooling it in a vacuum container to 0.2 degrees above the eutectic point temperature, and removing the crystalline Ga particles floating on the metal liquid surface by filtering;

[0064] S3, continue cooling the gallium-indium-tin ternary alloy in the vacuum container until 90% of the volume of the Ga-In-Sn alloy solidifies, and pour out the remaining liquid;

[0065] S4, repeat step S2 and step S3 twice;

[0066] S5. Finally, the liquid metal in the vacuum container is heated to a temperature 10 degrees higher than the eutectic point, and the liquid metal melted at this temperature is used for bearing packaging. Preferably, the vacuum degree of the vacuum container is 0.01Pa~0.0001PaMPa

[0067] In step S2, the temperature was cooled to 0.5, 2, and 6 degrees higher than the eutectic point in a vacuum container, and liquid metals with less impurities were prepared. In step S3, the gallium-indium-tin ternary alloy was cooled to 94%, 96%, and 97% by volume in a vacuum container, and the Ga-In-Sn alloy was solidified, and liquid metals with less impurities were prepared.

[0068] The embodiments of the present invention are described above in conjunction with the accompanying drawings. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention is not limited to the above-mentioned specific implementations, which are merely illustrative and not restrictive. Under the enlightenment of the present invention, those skilled in the art can also make many forms without departing from the scope of protection of the present invention and the claims, all of which belong to the protection scope of the present invention.

Claims

1. A method for assembling a liquid metal bearing, the liquid metal bearing comprising an outer sleeve (1), an inner shaft (2), an end cover (3) and a gasket (4), wherein one end of the inner shaft (2) is located in the outer sleeve (1), the inner shaft (2) is provided with an annular boss (2.1), the gasket (4) is located on the periphery of the annular boss (2.1), and the gasket (4) is fixed between the outer sleeve (1) and the end cover (3); It is characterized in that The assembly method includes the following steps: 1) placing the inner hole (1.1) of the outer sleeve (1) upward, injecting liquid metal into the inner hole (1.1), and inserting the lower end of the inner shaft (2) into the inner hole (1.1) of the outer sleeve (1); 2) The end cover (3) and the gasket (4) are both sleeved on the inner shaft (2), and the end cover (3) and the gasket (4) are fixed together by using a fixing tool (5); 3) Turning the outer sleeve (1) and the inner shaft (2) upside down, so that the inner hole (1.1) of the outer sleeve (1) is placed downward, and the end cover (3) and the gasket (4) are located below the outer sleeve (1) and the annular boss (2.1); 4) injecting liquid metal into the cavity (6) enclosed by the gasket (4) and the inner shaft (2), pressing the outer shaft sleeve (1), the gasket (4) and the end cover (3) together, and inserting the annular boss (2.1) into the interior of the gasket (4); 5) Using fasteners to fix the outer sleeve (1), the washer (4) and the end cover (3) together.

2. The assembly method of a liquid metal bearing according to claim 1, characterized in that: All the above assembly steps are completed in a vacuum environment or an oxygen-free inert gas protection environment.

3. The assembly method of a liquid metal bearing according to claim 1, characterized in that: The above step 1) is performed in a closed space, and before the lower end of the inner shaft (2) is inserted into the inner hole (1.1) of the outer shaft sleeve (1), the closed space is evacuated.

4. The assembly method of a liquid metal bearing according to claim 1, characterized in that: The outer peripheral surface of the gasket (4) is provided with a groove; the fixing fixture (5) has two claws, one of which abuts against the outer end surface of the end cover (3), and the other claw abuts against the groove.

5. The assembly method of a liquid metal bearing according to claim 1, characterized in that: In the step 1), a press machine (8) is used to insert the lower end of the inner shaft (2) into the inner hole (1.1) of the outer shaft sleeve (1), and the lower end of the inner shaft (2) stops when it reaches the designed position.

6. The assembly method of a liquid metal bearing according to claim 1, characterized in that: The fastener is a bolt.

7. The assembly method of a liquid metal bearing according to claim 1, characterized in that: The liquid metal adopts a gallium-indium-tin ternary alloy, and the preparation method of the liquid metal includes the following steps: S1. Referring to the designed gallium-indium-tin ternary eutectic alloy, when preparing the ingredients, the amount of Ga added should be greater than the designed gallium-indium-tin ternary eutectic alloy to form an alloy with excessive Ga; S2. Melting the gallium-indium-tin ternary alloy with excess Ga in a vacuum container, heating it to 100 degrees above the melting temperature, mixing it evenly, cooling it in a vacuum container to 0.2-6 degrees above the eutectic point temperature, and removing the crystallized Ga particles floating on the metal liquid surface by filtering; S3, continue cooling the gallium-indium-tin ternary alloy in the vacuum container until 90%-97% of the volume of the Ga-In-Sn alloy solidifies, and pour out the remaining liquid; S4, repeat step S2 and step S3 at least once; S5. Finally, the liquid metal in the vacuum container is heated to a temperature 10-20 degrees higher than the eutectic point to obtain liquid metal that melts at this temperature.

8. The assembly method of a liquid metal bearing according to claim 7, characterized in that: In step S2, the material is cooled in a vacuum container to a temperature 0.5-2 degrees higher than the eutectic point.

9. The assembly method of a liquid metal bearing according to claim 7, characterized in that: In step S3, the gallium-indium-tin ternary alloy is cooled in a vacuum container until 94%-96% of the volume of the Ga-In-Sn alloy is solidified.

10. The assembly method of a liquid metal bearing according to claim 7, characterized in that: In step S4, step S2 and step S3 are repeated twice.

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