Composite lubricated electrical contact friction pair suitable for use in vacuum environment

Abstract

The application relates to the technical field of conductive slip ring, in particular to a composite lubricated electric contact friction pair slip ring suitable for a vacuum environment, which comprises a rotor assembly and a stator assembly, the rotor assembly comprises a rotating shaft, an insulating sheet and a conductive ring, the surface of the conductive ring is coated with conductive lubricating grease, the outer surface of the insulating sheet is infiltrated with lubricating base oil, and the concentration of the lubricating base oil is higher than that of the base oil in the conductive lubricating grease on the conductive ring; the stator assembly comprises a fence type brush holder and a partition ring, the brush holder is provided with an isolation cover which cooperates with the insulating sheet to form a semi-closed isolation space, a bundle of brush wires is correspondingly arranged in the isolation space, and the partition ring is a rotating labyrinth isolation layer structure and divides the functional area composed of the insulating sheet and the conductive ring into a power area and a signal area. The application solves the contradiction between the long-term supply of conductive lubricating grease and insulation safety in the vacuum environment through the cooperation of the oil concentration gradient automatic oil supplement of the oil-immersed insulating sheet and the isolation cover from two dimensions of wear reduction at the source and path blocking, and realizes reliable electric transmission of the billion revolution level life.

Description

Technical Field

[0001] This invention relates to the field of conductive slip ring technology, specifically to a slip ring for composite lubrication electrical contact friction pairs suitable for vacuum environments. Background Technology

[0002] Conductive slip rings are crucial precision devices for transmitting electrical energy and signals between two relatively rotating mechanisms. In the aerospace field, the performance and lifespan of spaceborne slip rings directly determine the on-orbit service life of spacecraft. The electrical contact friction pair between the slip ring's brush filaments and the ring body is in a dynamic sliding state, and its coefficient of friction, wear rate, and contact resistance directly affect the frictional torque, service life, and the quality of power and signal transmission.

[0003] In a vacuum environment, the core challenge of existing slip ring technology lies in the contradiction between lubrication and insulation. Conventional greases suffer from severe volatilization and creep loss in a vacuum, leading to rapid wear at electrical contacts and reducing slip ring lifespan. To address this wear, current technology adds conductive fillers to the grease to make it conductive. However, while conductive grease reduces contact resistance, it also introduces a fatal flaw: if it and its wear debris mixture bridge adjacent rings, it will directly cause insulation failure or even a short circuit. Furthermore, grease consumption is inevitable during the slip ring's lifespan, and existing slip ring structures lack any form of automatic lubrication mechanism. Once the grease is depleted, the slip ring enters a dry friction state, further impacting its lifespan.

[0004] Current technologies either focus solely on the formulation of grease materials or only address the mechanical isolation structure of the brush holder. Neither has been able to simultaneously solve the problems of long-term automatic supply of conductive grease and isolation and insulation of conductive wear debris mixtures at the level of systematic synergy between materials and structure. This bottleneck severely restricts the improvement of the lifespan of spaceborne slip rings. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a composite lubricated electrical contact friction pair slip ring suitable for vacuum environments. By organically combining an automatic oil replenishment mechanism of conductive grease and anti-creep oil-impregnated insulating sheet with a physical isolation mechanism of the grid-type brush holder bending channel and the isolation ring, the conductive slip ring achieves ultra-long lifespan and reliable electrical transmission in vacuum environments with hundreds of millions of revolutions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments, comprising a rotor assembly and a stator assembly.

[0007] The rotor assembly includes a shaft, several insulating sheets sleeved on the shaft, and conductive rings disposed between adjacent insulating sheets. The outer diameter of the insulating sheets is larger than the outer diameter of the conductive rings. The conductive rings and insulating sheets are alternately stacked on the shaft to form conductive channels in the rotor assembly. The conductive rings are made of copper alloy and have a gold-plated surface to reduce contact resistance and improve corrosion resistance. The number of conductive rings is determined according to the actual channel requirements.

[0008] The insulating sheet is placed between adjacent conductive rings to provide electrical isolation. To achieve insulation performance, high temperature resistance, and vacuum adaptability, the insulating sheet is made of polyimide material.

[0009] The outer surface of the conductive ring is coated with a conductive grease for vacuum environments. This grease consists of a base oil suitable for vacuum environments and conductive fillers incorporated therein as a thickener, and possesses conductive properties. The conductive grease has the following parameters: total vacuum mass loss (TML) not greater than 0.2%, condensable volatile matter (CVCM) of 0, and water vapor reabsorption (WVR) not greater than 0.1%. This conductive grease ensures that the contact resistance of the electrical contact friction pair is less than 1 milliohm, guaranteeing excellent electrical transmission performance.

[0010] The insulating sheet must undergo anti-creep oil impregnation treatment during implementation. Specifically, the insulating sheet is placed in the base lubricating oil used in the conductive grease and impregnated under vacuum conditions to allow the base oil to fully penetrate into the micropores of the insulating sheet. After the oil impregnation treatment, the concentration of the base lubricating oil impregnated in the insulating sheet is greater than the concentration of the base oil in the conductive grease on the conductive ring.

[0011] Insulating sheets treated with anti-creep oil impregnation possess both anti-creep and automatic oil replenishment functions. This manifests as follows: the base oil impregnated in the insulating sheet forms an oil film on its surface, blocking the path of conductive grease from the conductive ring to creep onto the insulating sheet. In a vacuum environment, grease creep is one of the main causes of its loss from the working surface. By forming an oil film barrier on the insulating sheet surface, the channel for conductive grease migration along the insulating sheet surface is effectively cut off. When the conductive grease on the conductive ring surface is depleted during long-term friction and wear, the base oil stored in the micropores of the insulating sheet is slowly released and replenishes the conductive ring surface through capillary action. The driving force for this automatic oil replenishment process is the concentration gradient—the base oil concentration in the insulating sheet is higher than that in the conductive grease on the conductive ring—creating a chemical potential difference that drives the base oil to diffuse from the high-concentration area to the low-concentration area, ensuring the long-term lubrication state of the conductive ring surface.

[0012] Preferably, the outer circumferential surface of the conductive ring, which forms an electrical contact friction pair with the brush bristles, is formed with a plurality of slow-release grooves by a rolling process. The slow-release grooves are formed along the axial direction of the conductive ring, and their length is consistent with the width of the conductive ring, meaning the slow-release grooves extend axially through the entire width of the conductive ring. These slow-release grooves serve as storage microcavities and slow-release channels for conductive grease, working in conjunction with the oil-immersion supply mechanism of the insulating sheet to achieve long-term self-lubrication of the conductive ring surface.

[0013] Preferably, the cross-section of the slow-release groove is U-shaped or arc-shaped. The depth of the slow-release groove is 0.3 to 0.8 times the diameter of a single metal wire of the brush filament, and the width is 1.2 to 2 times the diameter of a single metal wire of the brush filament.

[0014] The stator assembly includes a support frame, a left flange, a right flange, a brush holder, an isolation ring, brush filaments, and an outer cover. The left and right flanges are respectively movably fitted onto the left and right ends of the rotating shaft via bearings. The support frame is coaxially fixed between the left and right flanges and fitted onto the outside of the rotating shaft. The outer cover is located between the left and right flanges and fitted onto the outside of the support frame to provide protection.

[0015] The support frame is a frame structure consisting of two annular fixed discs and two connecting rods. The two connecting rods connect the two fixed discs and are symmetrically distributed around the axis of the fixed discs, forming an installation gap between them. The rotating shaft is coaxially located inside the support frame.

[0016] The brush holder is a one-piece grid-type brush holder made of insulating material, including an arc-shaped cover plate and several partitions. The cover plate is arc-shaped, and the partitions are spaced apart along the length of the cover plate, with the length of the partitions perpendicular to the length of the cover plate, forming multiple spaced isolation covers; the free ends of the partitions are arc-shaped to accommodate the curvature of the insulating sheet.

[0017] After assembly, the brush holder is mounted between two connecting rods. The length direction of the cover plate is the same as that of the connecting rods. The partition plate extends to the outside of the conductive channel through the installation gap between the connecting rods. The isolation cover and the conductive channel form a semi-enclosed structure, and the brush filaments are arranged within this semi-enclosed structure. The partition plate does not contact the insulating sheet, thus spatially isolating each conductive ring channel. The free end of the partition plate can also extend between two adjacent insulating sheets, so that the channel between the partition plate and the insulating sheet is not a through channel parallel to the axis of rotation, but has a bend along the axis of rotation. This bend channel has a right-angle toothed cross-section in the axial direction, blocking the conductive grease and wear debris mixture that may be generated by the conductive grease in the stator assembly from conducting in the stator assembly, ensuring the safe insulation performance of the stator assembly.

[0018] Preferably, the cover plate covers the outside of the contact point between the brush filaments and the conductive ring. During the operation of the slip ring, the abrasive debris mixture generated by the electrical contact friction pair is attracted and migrates to the lower surface of the brush holder under electrostatic action, and will not remain on the electrical contact transmission surface. The partition plate blocks the conductive path of the abrasive debris mixture that has migrated to the brush holder plane due to electrostatic attraction from overlapping with adjacent ring channels, forming an insulating isolation.

[0019] To accommodate both power and signal transmission, the functional area composed of the insulating sheet and conductive ring is divided into a power region and a signal region. The power region and the signal region are physically isolated by a partition ring, which also serves to create a bent isolation channel between the power region and the signal region.

[0020] The partition ring is a rotating labyrinth isolation layer structure, including a connecting plate, an outer isolation ring, and an inner isolation ring arranged coaxially. The inner isolation ring is fixedly located inside the outer isolation ring, and two connecting plates are symmetrically arranged on the outer periphery of the outer isolation ring. Each of the left and right ends of the outer isolation ring has an annular outer groove, and the left end of the inner isolation ring has an annular inner groove.

[0021] The partition ring is sleeved on the outside of the rotating shaft and fixed between the two brush holders, with the connecting plate and the cover plate fixedly connected. The inner partition ring extends to the inner side between two adjacent insulating sheets, thus dividing the gap between the two insulating sheets into a bent isolation channel.

[0022] Preferably, in order to prevent external molecules or impurities from entering the slip ring or to prevent molecules from overflowing from inside the slip ring, structural improvements have been made at the connection between the rotating shaft and the left and right flanges, constructing a continuous bending channel with a labyrinthine right-angle tooth structure between the rotating shaft and the left or right flange.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. By using the anti-creep oil impregnation treatment of the insulating sheet and the concentration gradient between it and the conductive grease, the automatic and continuous replenishment of base oil to the contact surface is achieved, solving the problem of long-term supply of sliding ring grease in a vacuum environment and ensuring reliable lubrication within a 100 million revolutions life cycle. 2. The isolation cover and insulating sheet on the grid-type brush holder form a semi-enclosed isolation space, which effectively blocks the migration path of the conductive wear debris mixture, ensures the safety of inter-ring insulation when using conductive grease, and prevents the insulation safety performance between each conductive ring channel from decreasing due to wear debris migration; 3. The synergy between automatic oil replenishment lubrication and physical isolation of the bending channel completely solves the contradiction between the conductivity and insulation safety of conductive grease from the two dimensions of reducing friction at the source and blocking the path, producing technical effects that cannot be achieved by a single technical means. Attached Figure Description

[0024] Figure 1This is an axial sectional view of the slip ring of the present invention; Figure 2 This is a schematic diagram of the slip ring structure after removing the outer cover of the present invention; Figure 3 For the present invention Figure 1 Enlarged view of point A in the middle; Figure 4 For the present invention Figure 2 A schematic diagram of the radial section of the slip ring; Figure 5 This is a schematic diagram of the brush holder structure of the present invention; Figure 6 This is a left view of the brush holder of the present invention; Figure 7 This is an axial sectional view of the isolation ring of the present invention; Figure 8 For the present invention Figure 1 Enlarged view of point B in the middle; Figure 9 Vacuum curve of the electric slip ring prototype life test; Figure 10 The speed curve for the life test of the electric slip ring prototype; Figure 11 The friction torque curve for the life test of the electric slip ring prototype; Figure 12 The power loop voltage drop curve for the life test of the electric slip ring prototype; Figure 13 The voltage drop curve of the signal loop during the life test of the slip ring prototype; Figure 14 The instantaneous interruption test curve for the life test of the electric slip ring prototype; Figure 15 The packet loss rate curve is shown in the life test curve of the electric slip ring prototype.

[0025] In the figure: 1 rotor assembly, 11 shaft, 12 insulating sheet, 13 conductive ring, 111 first isolation groove; 2. Stator assembly, 21. Support frame, 22. Left flange, 23. Right flange, 24. Brush holder, 25. Spacing ring, 26. Brush filaments, 211. Fixing plate, 212. Connecting rod, 231. Second isolation groove, 241. Cover plate, 242. Partition plate, 251. Connecting plate, 252. Outer isolation ring, 253. Inner isolation ring, 2521. Outer groove, 2531. Inner groove; 3. Stator leads, 4. Rotor leads. Detailed Implementation

[0026] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, so that those skilled in the art can more clearly understand how to practice the present invention. Although the present invention has been described in conjunction with its preferred embodiments, these embodiments are merely illustrative and not intended to limit the scope of the invention.

[0027] See Figures 1-8 In one embodiment of the present invention, a slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environment includes: a rotor assembly 1, a stator assembly 2, a stator lead wire 3 and a rotor lead wire 4, and a matching bearing (not shown in the figure).

[0028] The rotor assembly 1 includes a rotating shaft 11, a plurality of insulating sheets 12 sleeved on the rotating shaft 11, and conductive rings 13 disposed between adjacent insulating sheets 12. The outer diameter of the insulating sheet 12 is larger than the outer diameter of the conductive ring 13. The conductive rings 13 and the insulating sheets 12 are alternately stacked on the rotating shaft 11 to form a conductive channel of the rotor assembly 1. The rotor leads 4 are introduced into the rotating shaft 11 from the right end and connected to the conductive rings 13 one by one.

[0029] The conductive ring 13 is made of copper alloy and its surface can be gold-plated to reduce contact resistance and improve corrosion resistance. The number of conductive rings 13 is determined according to the actual channel requirements; that is, the number of conductive ring channels can be determined based on the actual multi-channel signal and power transmission requirements.

[0030] The insulating sheet 12 is disposed between adjacent conductive rings 13, serving as an electrical isolation element. To achieve insulation performance, high-temperature resistance, and vacuum adaptability, it is made of polyimide material.

[0031] In this embodiment, the outer surface of the conductive ring 13 is coated with a conductive grease for a vacuum environment. The conductive grease is composed of a hydrocarbon-based lubricating base oil and a conductive filler compounded therein in the form of a thickener, and is in the form of a paste.

[0032] In implementation, the hydrocarbon-based lubricating base oil can be selected from one or more of polyalphaolefins, synthetic hydrocarbon oils, and deeply hydrogenated mineral oils. The conductive filler can be selected from one or more of conductive carbon black, graphite, and metal powders. The hydrocarbon-based lubricating base oil and conductive filler are mixed, ground, and homogenized to ensure the conductive filler is uniformly dispersed in the hydrocarbon-based lubricating base oil and acts as a thickener, forming a paste-like conductive grease. Simultaneously, as a grease for aerospace-grade vacuum environments, this conductive grease must meet the following indicators: total vacuum mass loss (TML) not exceeding 0.2%, condensable volatile matter (CVCM) zero, and water vapor reabsorption (WVR) not exceeding 0.1%. Among these, TML is the core indicator for measuring the total volatile matter of the lubricant in a vacuum environment, and CVCM is a key parameter for measuring condensable contaminants, representing the core indicator of lubricant cleanliness. Aerospace-grade grease requires extremely low TML and zero CVCM to prevent volatile matter contamination of precision optical equipment and electronic components in spacecraft.

[0033] Hydrocarbon-based conductive greases that meet the above specifications can be achieved by selecting highly refined, low-volatility hydrocarbon base oils and combining them with appropriate fillers. Tests show that this conductive grease reduces the contact resistance of the electrical contact friction pair to less than 1 milliohm, ensuring excellent electrical transmission performance. It is understood that any hydrocarbon-based conductive grease that meets the above TML, CVCM, and WVR specifications can be used in the slip rings of this invention, without being limited to specific base oil grades or filler types.

[0034] Furthermore, after rough grinding, the surface of the insulating sheet 12 requires anti-creep oil impregnation treatment. Specifically, the insulating sheet 12 is placed in the base lubricating oil used in the conductive grease and impregnated under vacuum conditions to allow the base oil to fully penetrate the micropores on the surface of the insulating sheet. After the oil impregnation treatment, the concentration of the base lubricating oil in the insulating sheet 12 is greater than the concentration of the base oil in the conductive grease on the conductive ring 13.

[0035] After the above operations, the base oil impregnated in the insulating sheet 12 forms an oil film on the surface of the insulating sheet 12, blocking the path of the conductive grease in the conductive ring 13 to crawl onto the insulating sheet; in addition, when the conductive grease on the surface of the conductive ring 13 is worn away during long-term friction and wear, the base oil stored in the micropores of the insulating sheet 12 is slowly released and replenished to the surface of the conductive ring 13 through capillary action under the drive of concentration gradient, so that the surface of the conductive ring 13 always maintains a good conductive lubrication state.

[0036] In one embodiment, for slip rings with high structural strength requirements or small dimensions, the surface finish of the outer circumference of the conductive ring 13 needs to be treated to 0.4 during processing. During assembly, the brush bristles without conductive grease are first run-in with the conductive ring 13. During this run-in process, the brush bristles contact the surface of the conductive ring 13, forming micro-wear marks on its surface. After the run-in is complete, conductive grease is then applied to the surface of the conductive ring 13. The conductive grease adheres to the outer circumference of the conductive ring 13 due to its own surface tension and penetrates and fills the micro-wear marks formed during the run-in. These micro-wear marks act as oil reservoirs and slow-release agents, allowing the conductive grease to form a stable conductive lubricating film on the surface of the conductive ring 13.

[0037] In one embodiment, unlike the embodiments described above, the outer circumference surface of the conductive ring 13, i.e., the electrical contact surface that forms an electrical contact friction pair with the brush bristles, is further provided with a plurality of slow-release grooves 131. The slow-release grooves 131 are evenly distributed along the outer circumference of the conductive ring. The slow-release grooves 131 are formed along the axial direction of the conductive ring 13, and the length of the slow-release groove 131 is consistent with the width of the conductive ring 13, i.e., the slow-release groove extends axially through the entire width direction of the conductive ring. The cross-section of the slow-release groove 131 is preferably U-shaped or arc-shaped.

[0038] The dimensions of the slow-release groove 131 are determined based on the diameter of the individual metal wires constituting the brush bundle. Specifically, the depth of the slow-release groove 131 is 0.3 to 0.8 times the diameter of the individual wire, and the width is 1.2 to 2 times the diameter of the individual wire. In actual operation, the diameter of the individual brush wires is determined according to design requirements, for example, it can be φ0.25mm, φ0.20mm, φ0.15mm, φ0.10mm, etc. Taking a single wire diameter of φ0.10mm as an example, the depth of the slow-release groove 131 is 0.05 to 0.08mm, and the width is 0.12 to 0.20mm. The above size range has been verified by experiments: when the depth is less than 0.3 times the diameter of the individual wire, the oil storage capacity is insufficient and cannot meet the long-term lubrication requirements; when the depth is greater than 0.8 times the diameter of the individual wire, the individual brush wire may sink into the groove when sliding through the groove opening, generating additional impact and bending stress, and may affect the structural strength of the conductive ring. When the width is less than 1.2 times the diameter of a single filament, the filling and release of conductive grease are not smooth; when the width is greater than 2 times the diameter of a single filament, a single brush bristle is also at risk of getting stuck.

[0039] The edge of the slow-release groove 131 is provided with a rounded chamfer, and the chamfer radius is not less than half the diameter of the single filament, so as to avoid the sharp edge from causing a cutting effect on the brush filament.

[0040] The slow-release groove can be formed using a roll forming process. During implementation, a roll forming tool with shaped protrusions on its surface is required. The roll forming tool is used to roll the outer circumference of the conductive ring blank under a preset pressure, causing plastic deformation of the blank surface and forming a slow-release groove extending axially. The roll forming is a cold roll forming process using multiple progressive passes. After roll forming, a residual compressive stress layer is formed around the slow-release groove, improving the hardness and wear resistance of the conductive ring surface. After roll forming, the entire conductive ring is gold-plated, with the plating naturally covering and smoothing the microscopic edges of the slow-release groove.

[0041] The slow-release groove 131 serves as a storage microcavity and slow-release channel for conductive grease. During slip ring operation, the conductive grease in the slow-release groove is continuously carried out to the electrical contact surface under frictional heat and capillary action, providing supplemental lubrication to the friction pair. Simultaneously, the base oil stored in the insulating sheet diffuses to the surface of the conductive ring through a concentration gradient, and a portion of it enters the slow-release groove for storage, forming a complete oil supply chain: oil storage in the insulating sheet, oil supply through a concentration gradient, slow-release oil storage in the slow-release groove, and lubrication of the contact surface. The stator assembly 2 includes a stator frame, a brush holder 24, brush filaments 26, and an outer cover (not shown in the figure). See reference. Figure 1 , Figure 2 and Figure 4 The stator frame includes a support frame 21, a left flange 22, and a right flange 23. The left flange 22 and the right flange 23 are respectively movably sleeved on the left and right ends of the rotating shaft 11 via bearings. The support frame 21 is coaxially fixed between the left flange 22 and the right flange 23 and sleeved on the outside of the rotating shaft 11.

[0042] The support frame 21 is a frame structure consisting of two ring-shaped fixed disks 211 and two connecting rods 212; the two connecting rods 212 are connected between the two fixed disks 211, and the two connecting rods 212 are symmetrically distributed around the axis of the fixed disks 211, forming an installation gap between the two connecting rods 212; the rotating shaft 11 is coaxially located on the inner side of the support frame 21.

[0043] Preferably, the support frame 21 can be a one-piece molded structure. Using a one-piece molded structure eliminates assembly gaps and connection interfaces between separate parts, improves the overall rigidity and assembly accuracy of the support frame, reduces the risk of loosening due to micro-vibrations in a vacuum environment, simplifies the assembly process, and ensures batch consistency.

[0044] The outer cover is located between the left flange 22 and the right flange 23 and is fitted over the outside of the support frame 21 to provide protection.

[0045] See Figure 5 and Figure 6 The brush holder 24 is integrally formed from high-strength insulating material and consists of multiple isolation covers arranged sequentially along the axial direction and integrally connected. Each isolation cover includes a top wall and two side walls connected to both sides of the top wall. The top wall is an arc-shaped cover plate 241, and the two side walls are partitions 242 spaced apart along the length of the cover plate 241. Multiple isolation covers share the same cover plate 241 and are separated from each other by the partitions 242 between adjacent isolation covers, forming an integrally formed grid-type brush holder structure.

[0046] The brush filaments 26 are installed in groups, with each group of brush filaments housed within the internal space of a corresponding isolation cover. Specifically, each group of brush filaments is installed between two partitions 242 of an isolation cover, with its free end extending obliquely and elastically pressing against the outer circumferential surface of the corresponding conductive ring 13.

[0047] See Figure 3 and Figure 4 After assembly, the brush holder 24 is mounted between the two connecting rods 212 of the support frame 21. The free ends of each partition 242 pass through the installation gap between the connecting rods 212 and extend to the outer side of the insulating sheet 12 on the rotor assembly. The free end side of the partition 242 is arc-shaped and coaxial with the rotating shaft 11, and its curvature matches the outer circular surface of the insulating sheet 12. During the operation of the slip ring, the rotor assembly 1 rotates relative to the stator assembly 2, and a small and stable radial gap is always maintained between the arc-shaped side of the partition 242 and the outer circular surface of the insulating sheet 12, forming a non-contact dynamic isolation structure. This structure ensures physical isolation without introducing additional frictional resistance and can adapt to minor wear and thermal deformation during long-term operation.

[0048] See Figure 4 After assembly, each isolation cover is placed on the outside of a conductive ring 13 channel. The cover plate 241 and two partition plates 242 of the isolation cover, together with the insulating sheets 12 on both sides of the conductive ring 13, form a hollow fan-shaped space. The two ends of the fan-shaped space are open in the circumferential direction.

[0049] Each isolation enclosure contains two sets of brush filaments 26, which extend obliquely from the inside of the cover plate 241 toward the corresponding conductive ring 13 of the isolation enclosure, arranged in a figure-eight pattern within the fan-shaped space. The two sets of brush filaments 26 circumferentially span the interior region of the fan-shaped space, significantly obscuring the openings at both ends of the fan-shaped space. Thus, the arc-shaped cover plate 241, the two partitions 242, the insulating sheets 12 on both sides, and the two sets of brush filaments 26 arranged in a figure-eight pattern within each isolation enclosure together form a further sealed chamber.

[0050] Although the chambers within each isolation enclosure are not completely sealed, their circumferential openings are significantly blocked by the two sets of brush filaments 26, creating a more tortuous migration path. Under vacuum molecular flow conditions, the gas flow or field-induced migration carrying conductive wear particles must bypass the obstruction of the brush filaments 26 to enter and exit each chamber, further reducing conductivity and compressing the probability of wear particles migrating across the ring. Simultaneously, the creep of conductive grease is effectively suppressed due to the extended and tortuous migration path.

[0051] Furthermore, during implementation, the arc-shaped side of the free end of the partition 242 can be embedded into the annular area between the outer circular surface of the insulating sheet 12 and the rotating shaft 11, forming a tortuous path similar to a labyrinth seal. This makes its flow conduction much lower than that of a straight channel, greatly reducing the probability of wear debris conducting across the ring. At the same time, once wear debris is generated, it is confined within the isolation space, and its escape path is naturally blocked, further enhancing the reliability of the isolation.

[0052] By molding multiple isolation covers into a single brush holder, not only is the manufacturing and assembly process simplified, but the insulation safety performance between each conductive ring channel is also ensured to remain unaffected by the migration of wear debris.

[0053] Furthermore, the cover plate 241 spans and completely covers all contact areas between the brush filaments 26 and the conductive ring 13 in the circumferential direction. During slip ring operation, the electrical contact friction pair generates wear debris containing conductive filler due to friction. This mixture of conductive grease and wear debris, formed by mixing with conductive lubricating grease, is thrown radially outward under centrifugal force and captured by the cover plate 241, adhering to its inner surface without drifting to other conductive ring channels. Since the partition plates 242 are spaced apart along the length of the cover plate, and the brush filaments are separated from the partition plates by insulating sheets, the wear debris mixture adsorbed to the lower plane of the cover plate is further segmented and isolated by each partition plate 242 on the plane of the cover plate, preventing continuous overlap to form a cross-ring conductive film, thereby forming a reliable insulating barrier in the outer ring portion of the stator.

[0054] Furthermore, to improve the capture and adsorption capacity of the arc-shaped cover plate 241 for the conductive grease-grind mixture ejected by centrifugation, the inner surface of the arc-shaped cover plate 241 can be surface-treated. In one embodiment, the inner surface of the arc-shaped cover plate 241 is provided with multiple adsorption grooves, the cross-section of which can be rectangular, V-shaped, or arc-shaped, and the multiple adsorption grooves are arranged axially or circumferentially. The adsorption grooves serve as microcavities for receiving the grinding debris mixture, increasing the effective adsorption area of ​​the inner surface and preventing the captured grinding debris from falling off and flowing back to the electrical contact surface under gravity or vibration.

[0055] In another embodiment, the inner surface of the arc-shaped cover 241 is roughened, such as by sandblasting, chemical etching, or laser texturing, to form a microscopic uneven structure. The roughened inner surface has micron-level roughness and undulations, making it easier for the conductive grease and abrasive debris mixture to adhere under capillary action and van der Waals forces, significantly improving the capture efficiency. The above-mentioned adsorption tank opening and roughening treatment can be used alone or in combination.

[0056] Furthermore, the central angle corresponding to the cover plate 241 is 80~100 degrees. This angle has been verified by experiments to ensure sufficient coverage of the contact area and capture of wear debris while taking into account the requirements of miniaturization and weight reduction of the brush holder.

[0057] The stator lead 3 is introduced from the outer side of the left end to the outer side of the outer cover and support frame 21 and is connected one by one to the brush wires 26.

[0058] Furthermore, the brush holder 24 is provided in two sets, and the two sets of brush holders 24 are symmetrically distributed around the axis of rotation 11.

[0059] In one embodiment, depending on the actual channel configuration requirements of the slip rings, the stator assembly 2 further includes a partition ring 25 disposed between adjacent shields. The number of partition rings 25 is one or more, specifically determined by the number and layout of the power and signal regions. Figure 3 and Figure 7 As shown, each partition ring 25 is a rotating labyrinth isolation layer structure, including an outer isolation ring 252, an inner isolation ring 253, and two connecting plates 251 arranged coaxially. The inner isolation ring 253 is fixedly disposed on the inner side of the outer isolation ring 252, and the two connecting plates 251 are symmetrically disposed on the outer periphery of the outer isolation ring 252. Each of the axial ends of the outer isolation ring 252 has an annular outer groove 2521, and one axial end of the inner isolation ring 253 has an annular inner groove 2531.

[0060] After assembly, the connecting plate 251 is fixedly connected to the arc-shaped cover plate 241 of the adjacent shield, so that the entire partition ring 25 is stably positioned between the two adjacent shields. The inner isolation ring 253 extends into the gap between a set of adjacent insulating sheets 12 at the junction of the power area and the signal area, dividing the gap into radially extending bent isolation channels. After assembly, the outer groove 2521 and the inner groove 2531 form a multi-axially tortuous gap structure, which cooperates with the outer circular surface of the insulating sheet 12 and the outer peripheral surface of the rotating shaft 11 to form a non-contact rotary labyrinth seal.

[0061] In a vacuum molecular flow state, the gas flow or field-induced migration carrying conductive wear debris particles must pass through the aforementioned tortuous channels to reach adjacent functional regions from one functional region. The conductance of the tortuous channels is much lower than that of the straight channels, significantly reducing the probability of wear debris migration across functional regions. When the slip ring simultaneously transmits power current and signals, one or more isolation rings 25 effectively isolate the power region from the signal region, preventing electromagnetic interference from high-current loops and wear debris from affecting signal transmission quality.

[0062] In one embodiment, to prevent external molecular contaminants from entering the slip ring and to prevent the leakage of trace amounts of base oil vapor volatilized inside, a labyrinth seal structure is provided at the connection between the rotating shaft 11 and the left and right flanges. Taking the right end of the electric slip ring as an example, as follows... Figure 8 As shown, an annular first isolation groove 111 is machined on the right end of the rotating shaft 11, and a corresponding annular second isolation groove 231 is machined on the inner end face of the right flange 23. After assembly, the raised ridge of the first isolation groove 111 and the groove of the second isolation groove 231 interlock with each other, forming multiple narrow channels with right-angle bends, which greatly increases the flow resistance of gas and particles, thus constituting an effective non-contact dynamic seal. Performance verification: The SRH60127-28 conductive slip ring prototype manufactured according to the above embodiments was tested in an environment with a vacuum degree better than 6.65 × 10⁻³ Pa. Figure 9 An accelerated life test was conducted at 100,125,900 revolutions (over 100 million revolutions), indicating that: Figure 9 The four small peaks in the vacuum degree monitoring curve are due to the re-vacuuming during the recovery test after four opening inspections. The vacuum degree was monitored after the recovery test, and its value was approximately 6 × 10⁻⁶. -4 The pressure was slightly higher than the previous value, but as the experiment continued, the vacuum level gradually returned to the previous level. The test rotation speed was 180 rpm. Figure 10 The power loop carries a 10A current, and the signal loop (12 loops in series) carries a 0.5A current.

[0063] The test results show that ( Figure 11Throughout the entire test cycle, the frictional torque of the slip ring remained stable between 0.15 and 0.29 N·m, with a maximum fluctuation of only 7.6%. Furthermore, it showed a good trend of gradually decreasing and stabilizing as the rotational speed increased. Figure 12 During the test, the voltage drop fluctuation of the entire current loop A when a 10A current is applied is between 0.004 and 0.01V. According to Ohm's law, the dynamic contact resistance fluctuation of the current loop A when a 10A current is applied is between 0.4 and 1mΩ during the entire life test. Figure 13 In the test, the voltage drop fluctuation of the entire current loop B (signal loop) when a current of 0.5A is applied is between 0.002 and 0.010V. According to Ohm's law, the dynamic contact resistance fluctuation of the 12 current loops B (signal loops) in series with a current of 0.5A during the entire life test is between 4 and 20mΩ. Therefore, the dynamic contact resistance fluctuation of each current loop B (signal loop) is between 0.33 and 1.67mΩ. Figure 14 In this process, there is no transient interruption within a 100ns time accuracy, the maximum dynamic contact resistance is only 39.82mΩ, and the CAN signal transmission packet loss rate is zero. Figure 15 ).

[0064] After 100 million revolutions, an inspection was conducted upon opening the cover. No visible wear debris was found in any of the internal structural components of the slip ring, the contact of the ring brush was normal, the conductive grease was evenly distributed, and no abnormal conductive traces were observed in the isolation area. The test fully demonstrates the excellent reliability and performance stability of the automatic oil replenishment and bending channel isolation collaborative scheme of this invention under high vacuum and ultra-long life conditions, providing a solid component foundation for spacecraft to serve in orbit for more than 15 years.

[0065] This technical solution achieves automatic and continuous replenishment of base oil to the contact surface through the anti-creep impregnation treatment of the insulating sheet and the concentration gradient between it and the conductive grease. This solves the problem of long-term supply of sliding ring grease in a vacuum environment and ensures reliable lubrication throughout the lifespan of hundreds of millions of revolutions. The isolation cover on the grid-type brush holder and the insulating sheet form a semi-enclosed isolation space, effectively blocking the migration path of the conductive wear debris mixture and ensuring the safety of inter-ring insulation when using conductive grease. The synergy between automatic oil replenishment lubrication and the physical isolation of the bending channel completely solves the contradiction between the conductivity and insulation safety of conductive grease from the two dimensions of reducing friction at the source and blocking the path, producing technical effects that cannot be achieved by a single technical means.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments, comprising a rotor assembly and a stator assembly; the rotor assembly comprising a shaft (11), a plurality of insulating sheets (12) alternately sleeved on the outer periphery of the shaft (11) along the axial direction, and a plurality of conductive rings (13), wherein the outer diameter of the insulating sheets (12) is larger than the outer diameter of the conductive rings (13); the stator assembly comprising a stator frame, a brush holder (24), and multiple bundles of brush filaments (26), wherein the shaft (11) is movably disposed inside the stator frame via bearings, characterized in that: The outer surface of the conductive ring (13) is coated with conductive grease, which contains a base oil and a conductive filler dispersed in the base oil; the insulating sheet (12) is impregnated with a base oil, and the concentration of the base oil impregnated in the insulating sheet (12) is greater than the concentration of the base oil in the conductive grease on the conductive ring (13). The brush holder (24) is integrally formed from multiple isolation covers. Each isolation cover includes an arc-shaped cover plate (241) and two partition plates (242) spaced apart along the axial direction of the rotating shaft (11) on the inner side of the cover plate (241). Each isolation cover is correspondingly placed on the outside of a conductive ring (13) channel, and together with the insulating sheets (12) on both sides of the conductive ring (13) to form a semi-closed isolation space. Each isolation cover is provided with two sets of brush filaments (26). The two sets of brush filaments (26) extend obliquely from the cover plate (241) to the corresponding conductive ring (13) and respectively block the openings at both ends of the circumferential direction of the isolation space.

2. The slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 1, characterized in that: The free end side of the partition (242) has an arc-shaped structure that matches the radial clearance of the outer edge of the insulating sheet (12).

3. The slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 1, characterized in that: The length of the cover plate (241) matches the axial length of the functional area composed of the insulating sheet and the conductive ring; the cover plate (241) spans and covers the contact area between the brush filaments (26) and the conductive ring (13) in the circumferential direction.

4. The slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 1, characterized in that: The stator frame includes a support frame, a left flange, and a right flange. The left flange and the right flange are coaxially and movably sleeved on both ends of the rotating shaft via bearings. The support frame is fixed between the left flange and the right flange. The support frame consists of two annular fixed discs and two symmetrically arranged connecting rods. An installation gap is formed between the two connecting rods. The cover plate (241) is fixed on the support frame. The free end of the partition plate (242) extends into the inside of the stator frame through the installation gap.

5. The slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 1, characterized in that: The stator assembly (2) further includes at least one partition ring (25) arranged along the axial direction; the partition ring (25) is disposed between two adjacent isolation covers, dividing the multiple conductive ring (13) channels into power areas and signal areas; the inner edge of the partition ring (25) extends into the gap between a corresponding set of adjacent insulating sheets (12), forming a radially bent isolation channel.

6. The slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 5, characterized in that: The partition ring (25) includes a connecting plate (251), an outer isolation ring (252), and an inner isolation ring (253). The connecting plate (251) is fixedly connected to the cover plate (241) of the adjacent isolation cover. The outer isolation ring (252) is fixedly connected to the connecting plate (251), and the inner isolation ring (253) is fixedly disposed on the inner side of the outer isolation ring (252). The inner isolation ring (253) is located between a group of adjacent insulating sheets (12). Both the outer isolation ring (252) and the inner isolation ring (253) have grooves with annular structures.

7. The slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 1, characterized in that: The outer circular electrical contact surface of the conductive ring (13) is provided with a plurality of uniformly distributed slow-release grooves. The length of the slow-release groove is equal to the width of the conductive ring, and the slow-release groove is coated with conductive lubricating grease. The cross-section of the slow-release groove is U-shaped or arc-shaped. The depth of the slow-release groove is 0.3 to 0.8 times the diameter of a single metal wire of the brush filament, and the width is 1.2 to 2 times the diameter of a single metal wire of the brush filament.

8. The slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 7, characterized in that: The edge of the slow-release groove is provided with a rounded chamfer, and the chamfer radius is not less than half the diameter of a single metal wire constituting the brush bristles (26).

9. A slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 1, characterized in that: A labyrinth sealing structure is provided at the mating point between the rotating shaft (11) and the stator frame; the labyrinth sealing structure includes a first isolation groove (111) opened on the rotating shaft (11) and a corresponding second isolation groove (231) opened on the stator frame, the first isolation groove and the second isolation groove are interlocked to form a multi-toothed continuous bending isolation channel.

10. A slip ring for a composite lubricated electrical contact friction pair suitable for vacuum environments according to claim 1, characterized in that: The inner surface of the cover plate (241) is provided with an adsorption groove.

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