Method of grinding graphite seal material for aircraft hydraulic piston pumps

Abstract

The present application relates to the technical field of precision machining of aircraft parts, and particularly relates to a grinding method for graphite sealing material of an aircraft hydraulic plunger pump, which comprises the following steps: constructing a grinding environment, selecting a bench grinder as a basic platform, and installing a resin copper synthetic grinding disc with an optical plane on the rotating workbench of the bench grinder; positioning and loading, placing a disc-shaped fixing tool in the grinding baffle ring of the grinder, and placing the graphite sealing ring to be machined into the mounting hole of the disc-shaped fixing tool so that the surface of the resin copper synthetic grinding disc directly contacts the grinding surface of the graphite sealing ring; applying counterweight and limiting, placing a stepped counterweight tool on the back of the graphite sealing ring, and applying vertical downward grinding pressure to the graphite sealing ring by using the stepped counterweight tool and performing radial limiting; and non-abrasive grinding, starting the grinder, setting the rotating speed and time, and rotating the resin copper synthetic grinding disc with the graphite sealing ring under the limiting of the grinding baffle ring to perform grinding.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for aircraft parts, and specifically to a grinding method for graphite sealing materials used in aircraft hydraulic plunger pumps. Background Technology

[0002] Aircraft hydraulic piston pumps are core power components of aircraft hydraulic systems, and the reliability of their internal sealing structures directly affects flight safety. The internal sealing structure of aircraft hydraulic piston pumps widely uses M298K graphite sealing material. Because this sealing structure operates under high temperature, high pressure, and high-speed rotation conditions, the design places extremely high demands on the flatness of the graphite ring sealing surface, typically requiring a flatness better than two helium bands, i.e., a flatness error of less than 0.6μm. To achieve this technical specification, precise grinding and polishing processes must be used to surface-treat the graphite sealing ring.

[0003] Currently, the processing of such precision graphite sealing rings mainly employs two traditional methods: The first is manual grinding using a precision mirror grinding platform. This method demands extremely high skill levels from the grinding workers, requiring them to possess superb fitter skills and extensive experience in manual grinding. Furthermore, manual grinding typically processes only one ring at a time, is time-consuming, and results in extremely low processing efficiency, making it difficult to meet the demands of mass production.

[0004] The second method involves adding extremely fine-grained polishing paste, a common practice in the industry. While this significantly improves grinding efficiency, it has a fatal flaw for specific graphite materials like M298K. Because this graphite sealing material has a porosity of less than 2%, extremely fine-grained polishing paste easily embeds itself into the micropores of the graphite surface during grinding. These embedded impurities are extremely difficult to clean, leading to a high failure rate after the parts have been assembled and used for a period of time due to impurity shedding or wear, severely impacting the reliability of the hydraulic pump.

[0005] In summary, how to reduce reliance on highly skilled manual labor and achieve efficient mass production while ensuring that the graphite sealing ring surface is free of sand embedding and meets flatness standards is a pressing technical challenge that needs to be addressed in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a grinding method for graphite sealing materials used in aircraft hydraulic plunger pumps, aiming to solve the technical problems of low efficiency and high dependence on personnel skills in manual grinding in the prior art, as well as the fact that traditional grinding paste polishing processes can easily lead to abrasive embedding in graphite micropores and causing component failure.

[0007] To achieve the above objectives, this invention proposes a grinding method for graphite sealing materials used in aircraft hydraulic plunger pumps, for processing dense graphite sealing rings with a porosity of less than 2%, comprising the following steps:

[0008] To construct the grinding environment, a benchtop grinder was selected as the basic platform, and a resin-copper composite grinding disc with an optical plane was installed on its rotating worktable.

[0009] Positioning and loading: Place a disc-shaped fixing fixture inside the grinding retaining ring of the grinding machine, and put the graphite sealing ring to be processed into the mounting hole of the disc-shaped fixing fixture so that the grinding surface of the graphite sealing ring directly contacts the surface of the resin copper composite grinding disc.

[0010] Apply counterweight and limit position: Place a stepped counterweight fixture on the back of the graphite sealing ring, and use the stepped counterweight fixture to apply a vertically downward grinding pressure to the graphite sealing ring and perform radial limit position.

[0011] For abrasive-free grinding, start the grinding machine, set the speed and time, and allow the graphite sealing ring to rotate with the resin-copper composite grinding disc under the limit of the grinding retaining ring for grinding.

[0012] During the entire grinding process, no granular grinding paste, polishing liquid, or free abrasive is added to the surface of the resin-copper composite grinding disc. Utilizing the self-lubricating properties of graphite material and the cutting characteristics of the resin-copper composite grinding disc surface, the sealing surface of the graphite sealing ring is ground to a predetermined accuracy through two-body friction cutting under the stable pressure provided by the stepped counterweight fixture.

[0013] This grinding method for graphite sealing materials used in aircraft hydraulic plunger pumps changes the traditional three-body grinding mode of workpiece-abrasive-grinding disc, and adopts a precision machining principle based on two-body friction between the workpiece and the grinding disc:

[0014] A resin-copper composite grinding disc is selected as the cutting substrate. This disc not only possesses optical-grade flatness, but the copper component in its material forms micro-cutting edges with a certain degree of hardness at the microscopic level, while the resin substrate provides good toughness and chip-holding space. Utilizing the self-lubricating properties of graphite, the graphite ring is directly rubbed against the resin-copper composite grinding disc without adding any free abrasive. A constant vertical pressure is applied by a stepped counterweight fixture. During rotation, the microscopic protrusions on the grinding disc surface perform purely physical micro-cutting and smoothing on the relatively soft graphite surface. As grinding progresses, the high points on the graphite surface are gradually removed, and the geometric precision of the grinding disc is directly copied onto the workpiece surface, ultimately achieving sub-micron-level flatness for the graphite sealing ring without any media interference.

[0015] Preferably, the stepped counterweight fixture includes an upper counterweight body and a lower positioning boss. The outer diameter of the positioning boss is smaller than the inner diameter of the graphite sealing ring, allowing it to extend into the inner hole of the graphite sealing ring to prevent it from tipping over in the absence of liquid film friction. The bottom surface of the counterweight body presses against the non-abrasive surface of the graphite sealing ring, providing continuous and stable axial pressure.

[0016] Preferably, the resin-copper composite grinding disc is made by mixing and curing copper powder and resin. The hardness of the resin-copper composite grinding disc is higher than that of the graphite sealing ring and lower than that of the cast iron disc. During the grinding process, the micro-morphology of the surface of the resin-copper composite grinding disc is used to perform micro-cutting on the graphite surface, while the peeled-off fine graphite powder forms a self-lubricating film.

[0017] Preferably, the resin-copper composite grinding disc rotates in one direction. The disc-shaped fixed fixture, restricted by the grinding retaining ring, rotates by friction with the resin-copper composite grinding disc, which drives the graphite sealing ring in the mounting hole to perform a compound rotation on the surface of the resin-copper composite grinding disc to achieve uniform grinding.

[0018] Preferably, before positioning and loading, the surface of the resin copper composite grinding disc is cleaned and trimmed to ensure that the surface of the resin copper composite grinding disc is dry and free of oil stains and residual particles, and maintains an optically flat state to match the dry grinding requirements of the graphite sealing ring.

[0019] Preferably, after grinding, the graphite sealing ring is removed from the fixture and the graphite powder adsorbed on the surface of the graphite sealing ring is removed by purging with clean air or ultrasonic cleaning.

[0020] As a preferred option, the benchtop grinder is equipped with three grinding retaining rings, each of which contains a disc-shaped fixing fixture. Each disc-shaped fixing fixture has at least three mounting holes for simultaneously grinding at least nine graphite sealing rings.

[0021] Preferably, the optical plane of the resin copper composite polishing disc is formed by the following finishing process: using a diamond dressing tool or a correction mechanism with a diamond dressing ring, the surface of the resin copper composite polishing disc is cut and finished so that its surface presents a bright surface capable of mirror reflection. The flatness error of the optical plane is controlled within 0.003mm, serving as the reference surface for the precision grinding of the graphite sealing ring.

[0022] Preferably, the optical plane is composed of a resin matrix and copper powder particles uniformly distributed therein. On the optical plane, the resin matrix and copper powder particles are at the same horizontal level, forming a continuous smooth surface without any bumps. The hardness of the copper powder particles supports the workpiece, and the toughness of the resin matrix provides grinding damping.

[0023] Preferably, after grinding, the optical plane of the resin copper composite grinding disc is inspected; when the specular reflection ability of the optical plane is found to be reduced or visible scratches are found, the resin copper composite grinding disc is repaired to remove the surface fatigue layer and expose a new copper powder-resin cross section, and the optical plane is reconstructed.

[0024] The grinding method for graphite sealing materials in aircraft hydraulic plunger pumps provided by this invention has the following outstanding substantive features and significant progress compared with the prior art:

[0025] This grinding method for graphite sealing materials in aircraft hydraulic plunger pumps utilizes a resin-copper composite grinding disc with a stepped counterweight fixture to achieve abrasive-free grinding of dense graphite materials. It fundamentally solves the fatal flaw of traditional grinding processes where extremely fine abrasive particles easily embed into the micropores of the graphite surface. Since no free abrasives such as grinding paste or polishing fluid are introduced during the entire grinding process, it effectively eliminates the risk of hydraulic pump wear and failure caused by impurities falling out of the micropores after the parts are assembled and used, significantly improving the operational reliability and flight safety of core aircraft hydraulic components.

[0026] Based on this, the present invention has successfully eliminated the heavy reliance on the manual experience of highly skilled fitters through a standardized mechanical grinding process. By using a combination of disc-shaped fixed fixtures and stepped counterweight fixtures, it has achieved precise control over grinding pressure, limit, and rotation speed. This not only ensures the high stability and consistency of processing quality, but also transforms the traditional inefficient manual mode into a highly efficient batch production mode that processes multiple parts simultaneously, significantly shortening the production cycle.

[0027] Furthermore, by eliminating expensive grinding aids and ensuring the workpiece surface is free of oil and abrasive residue, the difficulty and production cost of subsequent cleaning processes are significantly reduced. Ultimately, this method achieves low-cost, high-efficiency manufacturing while consistently ensuring the flatness error of the graphite sealing ring is less than 0.6μm, fully meeting the stringent design requirements of M298K graphite sealing material under extreme conditions of high temperature, high pressure, and high-speed rotation. Attached Figure Description

[0028] Figure 1 This is a flowchart of a grinding method for graphite sealing materials used in aircraft hydraulic plunger pumps, as described in an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the assembly structure of the graphite sealing ring and the resin-copper composite grinding disc in an embodiment of the present invention.

[0030] Reference numerals in the attached drawings: 1. Graphite sealing ring; 2. Resin-copper composite grinding disc; 3. Grinding retaining ring; 4. Disc-shaped fixing fixture; 5. Stepped counterweight fixture. Detailed Implementation

[0031] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0032] For aircraft hydraulic plunger pumps, the internal sealing structure must not only maintain long-term stability under extreme conditions of high speed and high pressure, but also prevent systemic failures caused by any minute impurities. The processing object targeted in this invention is M298K graphite sealing material. Although its porosity is controlled below 2%, it still contains a large number of micropores at the microscale. In traditional processing concepts, to achieve the ultimate flatness (flatness error less than 0.6μm), extremely fine-grained grinding pastes or polishing fluids are often used. This causes abrasive particles to easily wed into the micropores on the graphite surface under fluid pressure, creating a problem that is difficult to clean. Once these particles detach during hydraulic pump operation, they will cause fatal wear to the plunger. This invention constructs a novel abrasive-free dry two-body grinding system, completely abandoning traditional free abrasive media. By utilizing the matching characteristics of materials science and precise mechanical control, it achieves both high cleanliness and high precision.

[0033] like Figure 1 As shown in the embodiment of the present invention, a grinding method for graphite sealing materials used in aircraft hydraulic plunger pumps is proposed for processing dense graphite sealing rings with a porosity of less than 2%, comprising the following steps:

[0034] To construct the grinding environment, a benchtop grinder was selected as the basic platform, and a resin-copper composite grinding disc with an optical plane was installed on its rotating worktable.

[0035] Positioning and loading: Place a disc-shaped fixing fixture inside the grinding retaining ring of the grinding machine, and put the graphite sealing ring to be processed into the mounting hole of the disc-shaped fixing fixture, so that the grinding surface of the graphite sealing ring directly contacts the surface of the resin copper composite grinding disc.

[0036] Apply counterweight and limit position: Place a stepped counterweight fixture on the back of the graphite sealing ring, and use the stepped counterweight fixture to apply a vertically downward grinding pressure to the graphite sealing ring and perform radial limit position.

[0037] For abrasive-free grinding, start the grinding machine, set the speed and time, and allow the graphite sealing ring to rotate with the resin-copper composite grinding disc under the limit of the grinding retaining ring for grinding.

[0038] During the entire grinding process, no granular grinding paste, polishing liquid, or free abrasive is added to the surface of the resin-copper composite grinding disc. Utilizing the self-lubricating properties of graphite material and the cutting characteristics of the resin-copper composite grinding disc surface, the sealing surface of the graphite sealing ring is ground to a predetermined accuracy through two-body friction cutting under the stable pressure provided by the stepped counterweight fixture.

[0039] Specifically, the core equipment uses a high-precision benchtop grinder as the base platform. This equipment must possess extremely stable rotational precision, with runout error controlled at the micrometer level. For example... Figure 2 As shown, a resin-copper composite grinding disc 2 is installed on the rotating worktable of the grinding machine. The resin-copper composite grinding disc 2 is a composite material made by mixing and curing copper powder particles with a special resin matrix. In this material system, the copper powder particles are uniformly distributed in the resin matrix. The copper powder particles act as hard support points and micro-cutting edges at the microscopic level, while the resin matrix provides the necessary toughness, damping, and microscopic chip-receiving pits.

[0040] Before mass production, the resin-copper composite grinding disc 2 requires rigorous surface dressing and cleaning to ensure grinding quality. The dressing process aims to eliminate microscopic deformations and oxide layers that may have occurred on the surface of the grinding disc due to previous processing or prolonged static conditions. Precision cutting is performed on the surface of the resin-copper composite grinding disc 2 using diamond dressing tools or a dedicated dressing mechanism with a diamond dressing ring.

[0041] The cutting process described above differs from ordinary turning; it is a micro-scraping process designed to remove the surface fatigue layer while exposing the fresh copper powder-resin cross-section. The finished grinding disc surface exhibits a bright finish capable of clear specular reflection, and its optical flatness error must be strictly controlled within 0.003 mm.

[0042] A flatness benchmark of 0.003 mm is the physical basis for the subsequent graphite sealing ring 1 to achieve an accuracy of 0.6 μm. After the optical plane is formed, the disk surface needs to be thoroughly cleaned to ensure that the surface is absolutely dry and free of any oil stains or residual particles. Because this invention uses a dry grinding process, the presence of any oil stains will form an uneven oil film between the workpiece and the disk surface, causing the graphite ring to float or slip during the grinding process, thus compromising the stability of the two-body friction; while residual particles will directly scratch the graphite surface, leading to processing failure.

[0043] like Figure 2 As shown, after preparing the bright resin-copper composite grinding disc 2, the process proceeds to the positioning and loading stage. This embodiment of the invention abandons the inefficient single-piece manual grinding method and adopts a multi-piece coordinated batch loading scheme. The working area of ​​the benchtop grinder is divided into three independent processing stations, each defined by a grinding retaining ring 3. The grinding retaining ring 3 is typically an auxiliary ring that can rotate freely or passively, with its inner diameter slightly larger than the outer diameter of the disc-shaped fixed fixture 4.

[0044] The operator places the disc-shaped fixture 4 inside the grinding retaining ring 3. The disc-shaped fixture 4 is usually made of engineering plastic or aluminum alloy, and its thickness is slightly less than that of the graphite sealing ring 1 to ensure that the graphite ring can protrude from the bottom surface of the fixture and contact the grinding disc.

[0045] Each disc-shaped fixture 4 has at least three evenly distributed mounting holes. Depending on the size of the graphite ring, even more holes can be provided. In this embodiment, each fixture simultaneously loads three graphite sealing rings 1, and a total of nine parts can be processed simultaneously across the three workstations. Compared to traditional manual single-part grinding, this improves efficiency by nearly an order of magnitude. After the graphite sealing ring 1 to be processed is placed into these mounting holes, the surface of the graphite sealing ring 1 to be ground directly contacts the optical plane of the resin-copper composite grinding disc 2 below. At this time, the graphite ring adheres to the disc surface by its own gravity.

[0046] In traditional wet grinding, the surface tension and viscous resistance of the grinding fluid help stabilize the workpiece. However, in the dry grinding of this invention, the lack of liquid adsorption makes the workpiece prone to jumping or tipping over during high-speed rotation. To address this, this invention specifically designs a stepped counterweight fixture 5.

[0047] like Figure 2 As shown, the stepped counterweight fixture 5 includes an upper counterweight body and a lower positioning boss. Firstly, the outer diameter of the lower positioning boss is precisely designed to be slightly smaller than the inner diameter of the graphite sealing ring 1. During loading, the positioning boss extends into the inner hole of the graphite sealing ring 1, utilizing the inner hole of the graphite ring as a positioning reference. When the graphite ring moves with the grinding disc, the positioning boss acts like a shaft, effectively limiting the radial sway of the graphite ring and preventing it from tipping over or tilting under dry friction conditions without a liquid film.

[0048] Secondly, the bottom surface of the upper counterweight body is flat, and its diameter is larger than the inner diameter of the graphite ring, directly pressing against the non-abrasive surface of the graphite sealing ring 1. The mass of the counterweight body is designed to provide a constant and suitable vertical downward abrasive pressure. Through the setting of the stepped counterweight fixture 5, flexible clamping and dynamic stability of the lightweight graphite ring are achieved without clamping.

[0049] After completing the above preparations, start the grinding machine and set the appropriate speed and time. The resin copper composite grinding disc 2 begins to rotate in one direction. At this time, the disc-shaped fixture 4 located inside the grinding retaining ring 3 is driven by the frictional force of the grinding disc surface. Since the grinding retaining ring 3 restricts the revolution range of the fixture 4, and the retaining ring itself usually rotates, the disc-shaped fixture 4 will rotate under the constraint of the grinding retaining ring 3.

[0050] This motion transmission mechanism enables each graphite sealing ring 1 within the mounting hole to undergo a complex composite rotational motion on the surface of the resin-copper composite grinding disc 2. It follows both the revolution trend of the grinding disc and the rotational motion of the fixed fixture, ensuring that every point on the surface of the graphite ring can make random and uniform contact with different areas on the surface of the grinding disc, thereby effectively eliminating directional textures and ensuring uniform wear.

[0051] During the grinding process, no granular grinding paste, polishing liquid or free abrasive is added. Traditional three-body grinding relies on the rolling cutting of abrasive particles free between the workpiece and the disc surface. However, the two-body friction in this embodiment of the invention uses the micro-morphology of the surface of the resin copper composite grinding disc 2 to directly trim the graphite surface.

[0052] Specifically, although the resin-copper composite grinding disc 2 has a smooth, mirror-like surface on a macroscopic scale, at the microscopic scale, the copper powder particles solidified in the resin slightly protrude or have a hardness advantage, forming countless tiny planing blades. When the softer graphite sealing ring 1, under the pressure of counterweight, scrapes across these microscopic copper particles, the microscopic protrusions on the graphite surface are first contacted and cut or sheared away.

[0053] Meanwhile, the unique crystal structure of graphite endows it with excellent self-lubricating properties. During friction cutting, a very small amount of graphite powder will peel off from the workpiece surface. In traditional thinking, this powder is waste that needs to be washed away, but in the dry grinding system of this invention, the fine graphite powder forms an extremely thin solid lubricating film at the contact interface, reducing the coefficient of friction and preventing excessive frictional heat generation that could lead to workpiece deformation. At the same time, it also fills the tiny gaps on the surface of the grinding disc, making the cutting process more gentle and delicate, gradually transitioning from initial micro-cutting to smoothing and polishing. The resin matrix has a certain elastic deformation capacity. When encountering large hard points on the graphite surface or experiencing instantaneous impact due to vibration, the resin matrix can slightly retract, protecting the graphite surface from scratches, while also providing the necessary frictional resistance to ensure a smooth grinding process.

[0054] As the grinding time progresses, the flatness error of the sealing surface of the graphite sealing ring 1 decreases rapidly under the dual effects of cutting by copper powder particles and its own self-lubricating polishing. Since there is no free abrasive involved, there is no possibility of particles embedding into the graphite micropores under pressure. All cutting occurs on the outermost layer, and the cutting product is only graphite powder. Even if the powder remains in the micropores, it is the same material as the matrix and is soft, preventing mechanical wear during subsequent use. This fundamentally solves the problem of impurities causing hydraulic pump failure.

[0055] The endpoint control of the grinding process is usually based on time settings set by experience or determined by online monitoring devices. The machine is stopped when the predetermined grinding time is reached. The graphite sealing ring 1 is removed from the disc-shaped fixture 4. Since no oil-based grinding paste is used, the workpiece surface is dry and clean, with only a small amount of floating graphite powder adhering to it. Therefore, there is no need to use expensive organic solvents or complex ultrasonic cleaning solutions; simply purging with clean compressed air or performing simple ultrasonic cleaning with pure water / alcohol is sufficient to thoroughly remove the adsorbed powder from the surface. This not only greatly reduces cleaning costs but also avoids the potential corrosive or penetrating effects of chemical cleaning agents on graphite materials.

[0056] To verify the grinding effect, optical flat interferometry is typically used for testing. The cleaned graphite sealing ring 1 is attached to a standard optical flat, and the interference fringes are observed under monochromatic light. The graphite ring processed by the method of this invention typically exhibits regular, straight interference fringes with fewer than two fringes, translating to a flatness error of less than 0.6 μm. Furthermore, the surface displays a uniform matte or semi-mirror finish, free from scratches, pits, or embedded sand, fully meeting the stringent standards of aerospace-grade seals.

[0057] Furthermore, to ensure the stability of mass production, this embodiment of the invention also proposes periodic maintenance of the resin-copper composite grinding disc 2. Although the resin-copper disc has good wear resistance, under prolonged dry friction, the copper powder particles on the surface will gradually wear down and flatten, or the surface of the resin matrix will be compacted and carbonized, resulting in a decrease in cutting ability, or visible scratches may appear on the surface due to unexpected factors.

[0058] Therefore, operators need to periodically check the mirror reflectivity and roughness of the grinding disc, for example, every 5-10 batches. If a blurred reflection, significantly reduced cutting efficiency, or microscopic scratches are found, the aforementioned finishing process must be performed immediately. This involves removing an extremely thin layer of surface material using diamond tools to remove the fatigue layer and re-expose the copper powder-resin cross-section, thereby restoring the grinding disc's optical flatness and cutting activity.

[0059] In practical production, the parameters of this method can be fine-tuned according to the specific size and material batch of the graphite ring. For example, for graphite rings with a larger diameter, the weight of the counterweight can be increased appropriately to ensure constant pressure per unit area; for batches of graphite with slightly harder material, the rotation speed of the grinding disc can be increased to increase cutting work.

[0060] This invention presents a grinding method for graphite sealing materials in aircraft hydraulic piston pumps. By employing a combination of a resin-copper composite grinding disc and stepped counterweight tooling, a non-abrasive dry grinding process was successfully implemented in the machining of the M298K graphite sealing ring for aircraft hydraulic piston pumps. This not only eliminates the risk of abrasive embedding from a physical perspective, ensuring the purity and safety of the hydraulic system, but also transforms a process that was originally highly dependent on the skill of highly skilled technicians into a standardized industrial process that can be mass-produced and has controllable parameters through standardized tooling and equipment parameter settings. This significantly improves production efficiency, reduces scrap rates and manufacturing costs, and provides a solid manufacturing process guarantee for the long-term stable operation of aircraft hydraulic systems, demonstrating extremely high industrial application value and promising prospects for widespread adoption.

[0061] This invention is not limited to the specific technical solutions described in the above embodiments. Besides the above embodiments, this invention may have other implementation methods. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A grinding method for graphite sealing materials used in aircraft hydraulic plunger pumps, characterized in that, The process for machining dense graphite sealing rings with a porosity of less than 2% includes the following steps: To construct the grinding environment, a benchtop grinder was selected as the basic platform, and a resin-copper composite grinding disc with an optical plane was installed on its rotating worktable. Positioning and loading: Place a disc-shaped fixing fixture inside the grinding retaining ring of the grinding machine, and put the graphite sealing ring to be processed into the mounting hole of the disc-shaped fixing fixture so that the grinding surface of the graphite sealing ring directly contacts the surface of the resin copper composite grinding disc. Apply counterweight and limit position: Place a stepped counterweight fixture on the back of the graphite sealing ring, and use the stepped counterweight fixture to apply a vertically downward grinding pressure to the graphite sealing ring and perform radial limit position. For abrasive-free grinding, start the grinding machine, set the speed and time, and allow the graphite sealing ring to rotate with the resin-copper composite grinding disc under the limit of the grinding retaining ring for grinding. During the entire grinding process, no particulate grinding paste, polishing liquid, or free abrasive is added to the surface of the resin copper composite grinding disc. Utilizing the self-lubricating properties of graphite material and the cutting characteristics of the resin copper composite grinding disc surface, the sealing surface of the graphite sealing ring is ground to a predetermined accuracy through two-body friction cutting under the stable pressure provided by the stepped counterweight fixture. The resin-copper composite grinding disc is made by mixing and curing copper powder and resin. The hardness of the resin-copper composite grinding disc is higher than that of the graphite sealing ring and lower than that of the cast iron disc. During the grinding process, the microstructure of the resin-copper composite grinding disc is used to perform micro-cutting on the graphite surface, while the detached fine graphite powder forms a self-lubricating film.

2. The grinding method for graphite sealing material in aircraft hydraulic plunger pumps according to claim 1, characterized in that, The stepped counterweight fixture includes an upper counterweight body and a lower positioning boss. The outer diameter of the positioning boss is smaller than the inner diameter of the graphite sealing ring, and it can extend into the inner hole of the graphite sealing ring to prevent it from tipping over in the absence of liquid film friction. The bottom surface of the counterweight body presses on the non-abrasive surface of the graphite sealing ring to provide continuous and stable axial pressure.

3. The grinding method for graphite sealing material in aircraft hydraulic plunger pumps according to claim 1, characterized in that, The resin-copper composite grinding disc rotates in one direction. The disc-shaped fixed fixture, under the constraint of the grinding retaining ring, rotates by friction with the resin-copper composite grinding disc, which drives the graphite sealing ring in the mounting hole to perform a compound rotation on the surface of the resin-copper composite grinding disc to achieve uniform grinding.

4. The grinding method for graphite sealing material in aircraft hydraulic plunger pumps according to claim 1, characterized in that, Before positioning and loading, the surface of the resin copper composite grinding disc is cleaned and trimmed to ensure that the surface of the resin copper composite grinding disc is dry and free of oil stains and residual particles, and to maintain the optical plane state to match the dry grinding requirements of the graphite sealing ring.

5. The grinding method for graphite sealing material in aircraft hydraulic plunger pumps according to claim 1, characterized in that, After grinding, the graphite sealing ring is removed from the fixture and the graphite powder adsorbed on the surface of the graphite sealing ring is removed by purging with clean air or ultrasonic cleaning.

6. The grinding method for graphite sealing material in aircraft hydraulic plunger pumps according to claim 1, characterized in that, The benchtop grinder is equipped with three grinding retaining rings, and a disc-shaped fixing fixture is placed inside each grinding retaining ring. Each disc-shaped fixing fixture has at least 3 mounting holes for simultaneously grinding at least 9 graphite sealing rings.

7. The grinding method for graphite sealing material in aircraft hydraulic plunger pumps according to claim 1, characterized in that, The optical plane of the resin-copper composite polishing disc is formed through the following finishing process: Using a diamond dressing tool or a correction mechanism with a diamond dressing ring, the surface of the resin copper composite grinding disc is cut and dressed to make its surface present a bright surface capable of mirror reflection. The flatness error of the optical plane is controlled within 0.003mm, which serves as the reference surface for the precision grinding of the graphite sealing ring.

8. The grinding method for graphite sealing material in aircraft hydraulic plunger pumps according to claim 1, characterized in that, The optical plane is composed of a resin matrix and copper powder particles uniformly distributed therein. On the optical plane, the resin matrix and copper powder particles are at the same horizontal level, forming a continuous and smooth surface without any bumps. The hardness of the copper powder particles supports the workpiece, and the toughness of the resin matrix provides grinding damping.

9. The grinding method for graphite sealing material in aircraft hydraulic plunger pumps according to claim 1, characterized in that, After grinding, the optical plane of the resin-copper composite grinding disc is inspected; When the specular reflectivity of the optical plane is found to be reduced or visible scratches are found, the resin-copper composite polishing disc is repaired to remove the surface fatigue layer and expose a new copper powder-resin cross section, thereby reconstructing the optical plane.

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