CN101178095A - A solid-liquid compound lubricated shaft system for a space flywheel - Google Patents

Abstract

The invention belongs to the technical field of space tribology, and relates to a solid-liquid composite lubricating shaft system for a space flywheel, which uses a solid-liquid composite lubrication method and simultaneously adopts the lubricating oil supply of bearing self-lubricating cage-oil reservoir-labyrinth seal And the holding device, so that the shafting has good lubricating and frictional characteristics in the wide speed range from low speed to high speed, which effectively improves the initial running-in and prevents the start-up seizure, thereby improving the service life and reliability of the shafting, and improving the Control accuracy of shafting at low speeds.

Description

A solid-liquid compound lubricated shaft system for a space flywheel

Technical field:

The invention belongs to the technical field of space tribology, and relates to a solid-liquid composite lubrication wide speed range shaft system for a space flywheel.

Background technique:

The development of satellites requires the attitude control system to have high precision and long life and provide precise control torque, so more and more flywheel three-axis attitude stabilization systems are used. The space attitude control flywheel is generally composed of a rotor, a shaft system, a brushless DC motor and a sealed casing. Shafting is a key component in the flywheel, and its design directly determines the control accuracy, reliability and life of the flywheel.

Flywheels for attitude control include offset momentum wheels and reaction flywheels. The average speed of the offset momentum wheels is generally 2000 to 3000 rpm, and the flywheel rotates in one direction; the average speed of the reaction flywheel is 0, and it can rotate in both positive and negative directions. . Compared with the offset momentum wheel, the reaction flywheel has the characteristics of high angular momentum output range and good controllability under the same inertia condition, and has become an important development direction of the attitude control flywheel. At present, the development trend of foreign satellite attitude control schemes is to make the reaction flywheel work in a biased state to form zero momentum for the whole satellite, that is, the reaction flywheel is no more than zero. The domestic reaction flywheel is still in the development stage, and its lifespan and reliability are not high. The rotational speed of the reaction flywheel is less than zero, the output range of its angular momentum is reduced by half, and the function density of the reaction flywheel is reduced. At present, the main problem of the reaction flywheel is the friction and wear at low speed and the resulting low control accuracy at low speed (including zero time), which is essentially due to the severe wear of the current flywheel shafting at low speed, friction nonlinearity and Caused by problems such as poor lubrication. At the same time, increasing the flywheel speed can obtain a large angular momentum output under the same mass, thereby realizing the lightweight of the flywheel system.

At present, the supporting bearings of the flywheel shaft system for attitude control use steel angular contact ball bearings, and the lubrication method is liquid oil lubrication. It is difficult for oil lubrication to form a good elastohydrodynamic lubricating film at low speed, so the friction torque at low speed is large and the bearing wear is severe, which leads to low control accuracy of the shafting at low speed and causes attitude disturbance to the satellite. Therefore, the attitude The control flywheel can only work at higher operating speeds.

There are three ways of lubrication for attitude control flywheel shafting: grease lubrication, oil lubrication and solid lubrication. Among them, oil lubrication has the advantages of low friction torque, stable operation and low power consumption at higher speeds, but its lubrication condition at low speeds is not good, and an additional oil supply system is required, which increases the volume, weight and Complexity; grease lubrication is not easy to volatilize, the lubrication structure is simpler than oil lubrication, the lubrication condition at low speed is better than oil lubrication, but the power consumption is larger than oil lubrication at higher speed; solid lubrication has simple structure, friction performance does not change with temperature Changes and good low-speed characteristics, etc., but at higher speeds, the wear is severe and the life is limited.

Invention content:

Aiming at the problems existing in the prior art that the friction torque at low speed is large and the bearing wear is severe, resulting in low control precision of the shafting at low speeds, the present invention provides a solid-liquid composite lubrication shafting system for a space flywheel, which utilizes solid and liquid composite lubrication At the same time, the lubricating oil supply and holding device of bearing self-lubricating cage-oil reservoir-labyrinth seal is adopted, so that the shafting has good lubricating characteristics and friction characteristics in a wide speed range from low speed to high speed, effectively improving Initial break-in and prevention of start-up seizure, thereby improving the service life and reliability of the shafting.

The present invention comprises a first ceramic bearing 1, a second ceramic bearing 2, a disc spring 3, an oil reservoir 4, an inner support sleeve 5, an outer support sleeve 6, a first labyrinth seal 7, a second labyrinth seal 8; an inner support sleeve 5 is connected to the flywheel stator, and the outer support sleeve 6 is connected to the flywheel rotor; the first ceramic bearing 1 and the second ceramic bearing 2 are coaxially arranged and installed between the inner support sleeve 5 and the outer support sleeve 6 to provide support for the shafting; the first ceramic bearing The inner ring 12 and the outer ring 9 of the bearing 1 and the second ceramic bearing 2 have a wear-resistant layer on the surface of the groove in contact with the rolling elements, and the wear-resistant layer is used to improve its anti-wear performance; a solid lubricating coating is attached to the wear-resistant layer Layer, the solid lubricating coating has a large load-carrying capacity, and avoids direct contact between the rolling elements and the inner ring 12 and outer ring 9 of the bearing at the initial stage of bearing startup and low-speed operation. At the same time, its own lubricating characteristics provide thin film lubrication for the bearing, reducing The starting friction torque is reduced, so that it has good low-speed characteristics; the bearing cage 11 is made of a polymer composite porous material with self-lubricating properties, so that the bearing cage 11 has good mechanical properties and self-lubricating properties; the disc spring 3 is installed Between the first ceramic bearing 1 and the second ceramic bearing 2, a preload is provided to the shafting to ensure the required stiffness and damping of the shafting; the oil reservoir 4 is installed between the disc spring 3 and the outer support sleeve 6 In the gap, the lubricating oil supply is provided for the long-term operation of the shaft system; the first labyrinth seal 7 and the second labyrinth seal 8 are respectively fixedly installed between the outer surface of the inner support sleeve 5 and the outer support sleeve 6 to reduce the amount of lubricating oil. Loss, limiting lubricant loss to molecular flow loss.

Beneficial effects: the present invention utilizes the solid and liquid compound lubrication method, and at the same time adopts the lubricating oil supply and retention device of the bearing self-lubricating cage-oil reservoir-labyrinth seal, so that the shafting can operate in a wide speed range from low speed to relatively high speed It has good lubricating and frictional properties, which effectively improves the initial run-in and prevents seizure at start-up, thereby improving the service life and reliability of the shafting system and improving the control accuracy of the shafting system at low speeds.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the present invention, which is also a summary drawing. Among the figure 1 is the first ceramic bearing, 2 the second ceramic bearing, 3 disc spring, 4 oil reservoir, 5 inner support sleeve, 6 outer support sleeve, 7 first labyrinth seal, 8 second labyrinth seal.

Fig. 2 is a structural schematic diagram of the first ceramic bearing and the second ceramic bearing of the present invention, in which 9 is the outer ring, 10 is the ceramic ball, 11 is the bearing cage, 12 is the inner ring, 13 is the groove of the inner ring, and 14 is the groove of the outer ring.

Detailed ways

As shown in Figure 2, for the key supporting parts of the shaft system - the first ceramic bearing 1 and the second ceramic bearing 2, high-precision ceramic ball bearings are used, and the surface of the ceramic ball 10 is modified, that is, a special process is adopted, Such as coating perfluoroalkyl siloxane to increase the lipophilicity of the surface to reduce the surface energy of the ceramic ball 10, so that the lubricating oil can freely and quickly cover the surface of the ceramic ball 10, improving the quality of the elastohydrodynamic lubricating oil film, In turn, the friction performance and speed control accuracy of the shafting system are improved. The inner ring 12 and outer ring 9 of the ceramic ball bearing 10 are made of bearing steel, and the surface of the inner ring groove 13 and the outer ring groove 14 where the bearing steel inner ring 12 and outer ring 9 of the ceramic ball bearing are in contact with the ceramic ball 10 are made of material Surface modification treatment, that is, ion sputtering wear-resistant layer, the material of the wear-resistant layer is TiC, so as to enhance the wear resistance of the surfaces where the inner ring channel 13 and the outer ring channel 14 are in contact with the ceramic ball 10 . The solid lubricating coating attached on the ion-sputtered TiC surface provides solid lubrication for the bearing, the solid lubricating coating is a _MoS2 film or a soft metal mixture or a mixture of _MoS2 film and soft metal, the soft metal is gold or silver. Bearing cage 11 is made of polymer composite porous material with self-lubricating properties. The polymer composite porous material is composed of PTFE (polytetrafluoroethylene) and solid lubricant. The volume of PTFE (polytetrafluoroethylene) and solid lubricant The ratio is 100:1; the solid lubricant is a mixture of _MoS2 film or soft metal or _MoS2 film and soft metal, wherein the soft metal is gold or silver, and _MoS2 and soft metal are mixed in a volume ratio of 10:1.

As shown in Figure 1, the material of the oil reservoir 4 is made of porous material-polyimide, and the adsorption performance of the porous polyimide material to lubricating oil is used as the oil reservoir 4, and the centrifugal force and siphon are used when the shafting is working. The principle is to supply oil to the bearing to ensure a good lubrication condition of the shafting during the entire working period.

In the present invention, the deposition technology is used to sputter TiC surfaces on the inner and outer rings of the first ceramic bearing and the second ceramic bearing, and a solid lubricating coating of _MoS2 or soft metal mixture or a mixture of _MoS2 film and soft metal is attached on the TiC surface , the solid lubricating coating has a large bearing capacity, and avoids direct contact between the ceramic ball and the inner and outer rings of the bearing at the initial stage of bearing startup and low-speed operation. At the same time, its own lubricating characteristics provide thin film lubrication for the bearing, reducing the starting friction torque So that it has good low-speed characteristics. When the rotor reaches a certain speed, the liquid lubricating oil forms an elastohydrodynamic film with the rotation of the bearing. At this time, the lubrication is the elastohydrodynamic lubrication of the liquid lubricating oil, thus ensuring the good performance of the bearing at medium and high speeds.

The invention adopts the solid-liquid compound lubrication method, which can effectively reduce the friction and wear of the shaft system, effectively improve the initial running-in, prevent the start-up bite, improve the low-speed performance of the shaft system, improve the control accuracy of the shaft system at low speed, and increase the service life of the shaft system .

Claims (9)

1. A solid-liquid composite lubricated shaft system for a space flywheel, characterized in that it includes a first ceramic bearing (1), a second ceramic bearing (2), a disc spring (3), an oil reservoir (4), and an inner support sleeve (5), outer support sleeve (6), first labyrinth seal (7), second labyrinth seal (8); inner support sleeve (5) is connected to the flywheel stator, and outer support sleeve (6) is connected to the flywheel rotor; the first The ceramic bearing (1) and the second ceramic bearing (2) are coaxially arranged and installed between the inner support sleeve (5) and the outer support sleeve (6); the first ceramic bearing (1) and the second ceramic bearing (2) There is a wear-resistant layer on the groove surface of the inner ring (12) and the outer ring (9) in contact with the rolling elements; a solid lubricating coating is attached to the wear-resistant layer; the bearing cage (11) is made of a polymer with self-lubricating properties composite porous material; the disc spring (3) is installed between the first ceramic bearing (1) and the second ceramic bearing (2); the oil reservoir (4) is installed between the disc spring (3) and the outer support sleeve (6 ) in the gap between; the first labyrinth seal (7) and the second labyrinth seal (8) are respectively fixedly installed between the outer surface of the two ends of the inner support sleeve (5) and the outer support sleeve (6). 2. The space flywheel according to claim 1 is characterized in that the inner ring (12) and the outer ring (9) of the first ceramic bearing (1) and the second ceramic bearing (2) are in contact with The material of the wear-resistant layer on the surface of the channel contacted by the rolling elements is TiC, and the solid lubricating coating is MoS2 film or soft metal mixture or a mixture of MoS2 film and soft metal. 3. The solid-liquid composite lubricated shaft system for a space flywheel according to claim 2, characterized in that the soft metal used in the solid lubricating coating is gold or silver. 4. The solid-liquid composite lubricated shaft system for a space flywheel according to claim 1, characterized in that the polymer composite porous material used in the bearing cage (11) is composed of PTFE and solid lubricant. 5. The solid-liquid composite lubricated shaft system for space flywheel according to claim 4, characterized in that the volume ratio of PTFE to solid lubricant is 100:1. 6. The solid-liquid composite lubricated shaft system for a space flywheel according to claim 5, wherein the solid lubricant is a MoS ₂ film or a soft metal or a mixture of a MoS ₂ film and a soft metal, wherein the soft metal is silver. 7. The solid-liquid composite lubricated shaft system for space flywheel according to claim 6, characterized in that the volume ratio of MoS2 to soft metal is 10:1. 8. The solid-liquid composite lubricated shaft system for a space flywheel according to claim 1, characterized in that the oil reservoir (4) is made of polyimide. 9. The space flywheel according to any one of claims 1, 2, 3, 4, 5 or 6 is characterized in that the first ceramic bearing (1) and the second ceramic bearing ( 2) High-precision ceramic ball bearings are used, and the surface of the ceramic ball (10) is coated with perfluoroalkyl siloxane.

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