A method for improving the reliability of a gear box oil seal

Abstract

The application discloses a method for improving the sealing reliability of a gear box lubricating oil, and belongs to the technical field of aero-engine maintenance, and comprises the following steps: step 1, analyzing the sealing failure causes; step 2, checking the repaired engine gear box to determine the fault type; and step 3, formulating the method for improving the sealing reliability according to different fault types. The application draws a fault tree, combines the check on the engine gear box, determines the specific factors influencing the sealing of the lubricating oil sealing cavity, then processes the engine gear box according to the factors, and eliminates the fault factors before the engine gear box is reassembled, instead of finding the problems through tests after the assembly, so that the sealing reliability of the lubricating oil sealing cavity is improved, and the maintenance period is saved.

Description

Technical Field

[0001] This invention belongs to the field of aircraft engine maintenance technology, specifically relating to a method for improving the reliability of lubricating oil seals in engine gearboxes. Background Technology

[0002] Oil leakage frequently occurs at the mounting base of the main drive shaft of the gearbox in a certain type of repair engine. Troubleshooting this type of fault is costly and time-consuming, which seriously affects the production and delivery schedule of the repaired engine and reduces its reliability.

[0003] The gearbox main drive shaft mounting bracket is located directly below the engine. The design structure and seal assembly relationships of this area are as follows: Figure 1 As shown. The flange faces of the five end face seals—gearbox housing 1, drive gear shaft bearing seat 2, driven gear shaft bearing seat 3, inner oil seal seat 4, and seal seat support ring 5—are installed in a stacked manner. During assembly, sealant is applied to the mating end faces, and then the circumference is tightened to the gearbox housing with 12 bolts 7. The two radial seals, inner oil seal seat 4 and outer oil seal seat 6, are sealed with O-ring radial sealing rubber rings 8.

[0004] For controlling the sealing reliability of such end-face seals, the conventional process requires checking their fit using a dye penetrant test. This involves applying dye to one end face of each seal, installing and tightening the bolts one by one, then removing the seal and visually inspecting the dye transfer on the corresponding end face of the other seal. However, in the case of seal failure at the gearbox main drive shaft mounting location, while the fit of each seal passed the conventional process test, oil leakage recurred after reassembling and testing the lubricating oil seals. To address this issue, further analysis of the seal characteristics at the faulty location is needed to investigate effective methods to improve sealing reliability. Summary of the Invention

[0005] This invention provides a method to improve the reliability of gearbox lubricating oil sealing, thereby improving the sealing reliability of the lubricating oil sealing cavity at the main drive shaft mounting seat of the engine gearbox, reducing the lubricating oil leakage failure rate, and lowering engine repair and maintenance costs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for improving the reliability of gearbox lubricating oil seals includes the following steps:

[0008] S1. Starting from the structural characteristics of the gearbox main drive shaft mounting seat seal, list all the factors that cause gearbox lubricating oil seal failure;

[0009] S2. Inspect the engine gearbox to determine the specific factors contributing to the gearbox oil seal failure.

[0010] S3. Repair and maintain the gearbox oil seal according to the specific factors that caused the gearbox oil seal failure.

[0011] Furthermore, in step S1, the factors contributing to the failure of the gearbox lubricating seal include: torque decay of the end face seal fastening bolts; poor surface quality of the end face seal flange; poor quality of the end face sealant coating; improper installation of the rubber ring at the radial seal; and out-of-tolerance diameter of the rubber ring mounting groove on the radial seal.

[0012] In the further step S2, the inspection of the engine gearbox includes:

[0013] 1) Check if the tightening torque of the end-face sealing bolts has decreased;

[0014] 2) Inspect the mounting surface of the gearbox housing for wear;

[0015] 3) Inspect the flatness and parallelism of the flange surfaces of the drive gear shaft bearing housing, driven gear shaft bearing housing, internal lubricating oil seal seat, and seal seat support ring;

[0016] 4) Check for any problems in the assembly process of the gearbox housing, drive gear shaft bearing housing, driven gear shaft bearing housing, internal oil seal seat, and seal seat support ring;

[0017] 5) Inspect the sealant coating quality of the gearbox housing, drive gear shaft bearing housing, driven gear shaft bearing housing, internal oil seal seat, and seal seat support ring;

[0018] 6) Inspect the appearance of the rubber ring for damage or twisting defects, and measure the amount of protrusion of the rubber ring;

[0019] 7) Measure the inner and outer diameters of the radial sealing ring, as well as the width and diameter of the groove bottom of the radial sealing ring mounting slot.

[0020] In a further step S2, when the abrasion area of ​​the gearbox housing mounting surface is greater than 50%, the quality of the gearbox housing mounting surface is poor; when the flatness of the mounting surfaces of the drive gear shaft bearing seat, driven gear shaft bearing seat, inner oil seal seat, and seal seat support ring is greater than 0.025 mm, and the parallelism of the upper and lower sides of the mounting surfaces is greater than 0.045 mm, the quality of the end faces of the drive gear shaft bearing seat, driven gear shaft bearing seat, inner oil seal seat, and seal seat support ring is poor.

[0021] In further step S3, when the fault factor is the decrease in torque of the end face seal tightening bolts, the repair method includes the following steps:

[0022] SA1. During installation, first tighten the end face seal fastening bolt to half of the specified torque value, then continue to tighten it to full torque. After a set interval, check the torque again. If there is a decrease, continue to tighten it to full torque once more until the torque of the end face seal fastening bolt no longer decreases.

[0023] SA2. After the set time, check again whether the torque of the end face seal has decreased:

[0024] If there is no decay, the process ends; otherwise, proceed to step SA1.

[0025] In the further step SA2, the time is set to 2-3 hours.

[0026] In a further step S3, when the fault factor is the poor quality of the mounting surface of the gearbox housing, a grinding repair process is applied to the mounting surface. The grinding repair process includes the following steps:

[0027] SB1. Pull out the pin installed on the gearbox housing and bore the pin hole;

[0028] SB2. Align the gearbox housing;

[0029] SB3. Mill the mounting surface of the gearbox housing until the runout value of the mounting surface of the gearbox housing meets the requirements;

[0030] SB4. Based on the actual condition of the elliptical and enlarged pin hole, bore and ream the pin hole to set the hole diameter;

[0031] SB5: Deburring, cleaning, localized oxidation, and localized paint touch-up;

[0032] SB6. Check whether the fit between the mounting surface of the gearbox housing and the mating surface of the drive gear shaft bearing seat meets the requirements, and proceed with assembly; otherwise, repeat step SB5 until the coloring requirements are met.

[0033] In the further step of SB4, when the pin hole is bored or reamed to the set diameter, it is ensured that the thickness of the pin hole wall and the inner hole wall of the gearbox housing is greater than the set width.

[0034] Further in SB6, the requirements are: the radial contact area of ​​the gearbox housing is ≥60%, and the circumferential direction of the gearbox housing is unbroken.

[0035] In a further step S3, when the fault factor is poor surface quality of the drive gear shaft bearing housing, driven gear shaft bearing housing, internal oil seal seat and / or seal seat support ring, replace the drive gear shaft bearing housing, driven gear shaft bearing housing, internal oil seal seat and / or seal seat support ring with qualified ones.

[0036] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0037] This invention, by drawing a fault tree and considering the structure, sealing characteristics, and assembly process features of the engine gearbox sealing components, identifies the key factors affecting the sealing reliability of the lubricating oil sealing cavity. Then, it develops detailed and reliable solutions to problems such as gearbox housing end-face corrosion, thin-walled sealing component deformation, and torque attenuation. Eliminating potential faults before gearbox assembly reduces the failure rate during engine disassembly and troubleshooting due to sealing failure in this area during the overall engine inspection and testing phase, thereby achieving cost reduction, efficiency improvement, and ensuring delivery schedules.

[0038] This invention significantly improves the sealing reliability of the lubricating oil sealing cavity at the main drive shaft mounting seat of the engine gearbox. Faulty engines repaired using the above technical solution were all successfully delivered, and subsequent engines returned for repair showed a significant decrease in failure rate after implementing the same solution. This technical solution has broad applicability in improving the sealing effect of sealing cavities in multi-flange stacked installations. Attached Figure Description

[0039] Figure 1 A structural diagram of the sealing cavity of the gearbox main drive shaft mounting seat;

[0040] Figure 2 This is a diagram of a fault tree;

[0041] Figure 3 The condition of the gearbox housing mounting surface is shown.

[0042] Figure 4 This is a schematic diagram showing the positional relationship between the pin hole wall and the inner hole of the gearbox housing.

[0043] In the attached diagram: 1. Gearbox housing; 2. Driven gear shaft bearing housing; 3. Driven gear shaft bearing housing; 4. Inner oil seal seat; 5. Seal seat support ring; 6. Outer oil seal seat; 7. Bolt; 8. Radial sealing rubber ring; 9. Pin hole. Detailed Implementation

[0044] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0045] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] Reference Figure 2 A method for improving the reliability of gearbox lubricating oil seals includes the following steps:

[0047] Step 1: Analyze the causes of seal failure

[0048] Based on the structural characteristics of the gearbox main drive shaft mounting seat seal, the following is drawn: Figure 2 The fault tree shown includes the following fault factors: ① torque decay of the end-face seal fastening bolts; ② poor surface quality of the end-face seal flange face; ③ poor quality of the end-face sealant coating; ④ improper installation of the rubber ring at the radial seal; ⑤ out-of-tolerance diameter of the rubber ring mounting groove. The end-face seal includes the gearbox housing 1, the drive gear shaft bearing housing 2, the driven gear shaft bearing housing 3, the internal lubricating oil seal seat 4, and the seal seat support ring 5.

[0049] The analysis of the breakdown and inspection of multiple typical fault cases shows that fault number ③ is a common assembly process in engine assembly, the implementation process is controllable and can be eliminated. Faults number ④ and number ⑤ can be eliminated through measurement and inspection after disassembling the faulty machine.

[0050] ① Analysis of the cause of failure: When multiple sealing flanges are stacked and installed, sealant is applied to the mating surface. The torque reduction is related to the fact that this non-rigid sealant reduces the torque of the screws after the assembly is completed and left for a period of time.

[0051] Serial No. ② Fault Cause Analysis: After disassembly, most engines were found to have obvious wear marks on the end face of the gearbox housing (e.g. Figure 3 As shown in the diagram, this illustrates the fretting friction between the sealing components during engine operation. As the engine's service life increases, this leads to erosion and deformation of the sealing surfaces. Since the gearbox housing is made of magnesium alloy, the erosion is significant. The other four thin-walled end-face seals (drive gear shaft bearing seat 2, driven gear shaft bearing seat 3, internal lubricating oil seal seat 4, and seal seat support ring 5) are all steel. Although no obvious erosion marks are visible to the naked eye, the inevitable minute movements will still damage the surface quality of the sealing flanges, affecting the fit after assembly and thus reducing the reliability of the end-face seal.

[0052] Step 2: Inspect the engine gearbox to determine the cause of the malfunction.

[0053] The inspection items include:

[0054] 1) Check whether the tightening torque of the end-face sealing bolt 7 has decreased;

[0055] 2) Inspect the wear condition of the mounting surface of gearbox housing 1;

[0056] 3) Inspect the flatness and parallelism of the flange surfaces of the drive gear shaft bearing housing 2, driven gear shaft bearing housing 3, inner lubricating oil seal seat 4, and seal seat support ring 5;

[0057] 4) Manually inspect the assembly process records of gearbox housing 1, drive gear shaft bearing seat 2, driven gear shaft bearing seat 3, internal lubricating oil seal seat 4 and seal seat support ring 5 to determine if there are any problems with the assembly process;

[0058] 5) Inspect the sealant coating quality of the gearbox housing 1, the drive gear shaft bearing seat 2, the driven gear shaft bearing seat 3, the inner oil sealing seat 4, and the sealing seat support ring 5;

[0059] 6) Inspect the appearance of the rubber ring for damage, twisting or other defects, measure the amount of protrusion of the rubber ring, and determine the reliability of the rubber ring installation;

[0060] 7) Measure the inner and outer diameters of the radial sealing ring 8, as well as the width and diameter of the groove bottom of the radial sealing ring 8 mounting groove, and determine whether the diameter of the radial sealing ring mounting groove is out of tolerance.

[0061] Step 3: Develop methods to improve the reliability of the seal for different types of failures.

[0062] The improvement plan for fault number ① is as follows: The tightening process of the multi-sealing end-face fastening bolts is changed. The tightening process of the multi-sealing end-face fastening bolts in this invention is as follows:

[0063] SA1. During installation, first tighten the end face seal fastening bolt to half of the specified torque value, then continue to tighten it to full torque. After a half-hour interval, check the torque again. If there is a decrease, continue to tighten it to full torque once more until the torque of the end face seal fastening bolt no longer decreases.

[0064] SA2. After 2-3 hours, check again whether the torque of the end face seal fastening bolts has decreased:

[0065] If there is no attenuation, the process ends; otherwise, proceed to step SA1.

[0066] Improvement plan for fault number ②: Regarding the wear on the mounting surface of gearbox housing 1, based on the experience of troubleshooting multiple engines, an acceptance standard is established, namely, no radial penetrating wear is allowed, no wear with obvious bench-like resistance is allowed, and the wear area is not allowed to exceed 50%. For those that do not meet the acceptance standard, additional grinding is used to remove the wear marks.

[0067] For the remaining four thin-walled end face seals (drive gear shaft bearing housing 2, driven gear shaft bearing housing 3, internal lubricating oil seal 4, and seal support ring 5), a method is proposed to inspect the assembly fit by measuring the flatness and parallelism of the seal flange surfaces. Based on the test data of multiple repaired engines, an acceptance standard for the fit of the seal mounting surfaces is established, namely, the flatness of the mounting surface ≤ 0.025 mm, and the parallelism of the upper and lower sides of the mounting surface ≤ 0.045 mm.

[0068] Example 1

[0069] During bench testing of a faulty engine, an oil leak was discovered at the gearbox main drive shaft mounting area. The faulty engine was disassembled, and the cause of the leak was investigated according to fault tree ① to ⑤. Inspection revealed a significant decrease in torque when tightening bolt 7 of the end-face sealing component. The other four items were found to be normal. The faulty engine parts were reassembled using the aforementioned multi-sealing end-face sealing bolt tightening process: tightening to the specified torque, allowing it to rest for 2 hours, and then checking again until the torque no longer decreased. After reassembly, bench testing confirmed that the fault was resolved.

[0070] Example 2

[0071] An oil leak was discovered at the gearbox main drive shaft mounting area of ​​a faulty engine during field use. The engine was disassembled and the cause of the leak was investigated according to fault tree ①~⑤. Inspection revealed obvious abnormal wear marks on gearbox housing 1, and a grinding repair process was performed on this end face. The specific repair procedure is as follows:

[0072] (1) Drilling: Drill holes of φ4+0.150 mm and depth 9+0.150 on the four pins.

[0073] (2) Tapping: Tap an M5mm thread inside the pin hole.

[0074] (3) Pulling out the pins: Use a pin puller to pull out the four pins. After the pins are pulled out, the pin holes may be damaged and need to be bored.

[0075] (4) Alignment: Pull the end face of the seawater hole of the gearbox housing 1 until it is within 0.01mm, and the concentricity deviation between the center of the alignment hole and the positioning reference center of the housing is within 0.01mm.

[0076] (5) Milling the plane: Milling the mounting surface of the gearbox housing (i.e. Figure 3 (As shown in the corrosion test), mill until the surface is smooth. Use a dial indicator on the machine to check that the runout of the mounting surface is no more than 0.01mm.

[0077] (6) Boring and reaming pin hole 9: During repair, according to the actual condition of the pin hole being elliptical or enlarged, the pin hole is bored or reamed to the following groups: the purpose is to determine what hole diameter is damaged.

[0078] Group Locating pin hole diameter ΦA (mm) Standard Group Φ6.3~Φ6.282 R Φ6.55~Φ6.532 S Φ6.8~Φ6.782 T Φ7.05~Φ7.032

[0079] After enlarging pin hole 9, the wall thickness of the pin hole and the inner wall thickness of the gearbox housing must not be less than 4.9mm to ensure that the strength meets the requirements. Figure 4 As shown.

[0080] (7) Deburring and cleaning: Remove the burrs from the parts, clean them with cleaning gasoline and blow them dry.

[0081] (8) The mounting surface of the gearbox housing milled in step (5) is subjected to oxidation treatment.

[0082] (9) Apply touch-up paint to the mounting surface of the gearbox housing that was milled in step (5).

[0083] (10) Coloring inspection: Check the fit between the mounting surface of the gearbox housing 1 and the mating surface of the drive gear shaft bearing seat 2. The radial fit area should be ≥60%, and there should be no interruption in the circumferential direction.

[0084] If the above requirements are not met, the gearbox housing mounting surface shall be re-milled.

[0085] (11) Select the locating pins of matching size group according to the pin hole group for assembly.

[0086] After the faulty engine underwent the aforementioned repair process, it was reassembled, and bench testing confirmed that the fault was resolved.

[0087] Example 3

[0088] An engine with a fault was found to be leaking oil at the gearbox main drive shaft mounting location during field use. The engine was disassembled and the cause of the leak was investigated according to fault tree ①~⑤. Inspection revealed that the parallelism of the end face of the internal oil seal 4 was out of tolerance (test data shown in the table below). A qualified internal oil seal 4 was replaced and reassembled, and bench testing confirmed that the fault was resolved.

[0089] Parameter name Drive gear shaft bearing housing 2 Driven gear shaft bearing housing 3 Lubricating oil seal seat 4 Sealing seat support ring 5 Flatness of mounting end face C (≤0.025 mm) 0.002 0.010 0.025 0.016 Flatness of the opposite side of C (≤0.025 mm) 0.002 0.007 0.025 0.024 Parallelism between the two surfaces (≤0.045 mm) 0.020 0.030 0.065 (out of tolerance) 0.030

[0090] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for improving the reliability of gearbox lubricating oil seals, characterized in that, Includes the following steps: S1. Starting from the structural characteristics of the gearbox main drive shaft mounting seat seal, list all the factors that cause gearbox lubricating oil seal failure; S2. Inspect the engine gearbox to determine the specific factors contributing to the gearbox oil seal failure. S3. Repair and treat the gearbox oil seal according to the specific factors that caused the gearbox oil seal failure; In step S1, the factors contributing to the failure of the gearbox lubricating oil seal include: torque decay of the end face seal fastening bolts; poor surface quality of the end face seal flange; poor quality of the end face sealant coating; improper installation of the rubber ring at the radial seal; and out-of-tolerance diameter of the rubber ring mounting groove of the radial seal. In step S2, the inspection of the engine gearbox includes: 1) Check whether the tightening torque of the end-face sealing fastener bolt (7) has decreased; 2) Inspect the wear condition of the mounting surface of the gearbox housing (1); 3) Check the flatness and parallelism of the flange surfaces of the drive gear shaft bearing housing (2), driven gear shaft bearing housing (3), internal lubricating oil seal seat (4) and seal seat support ring (5); 4) Check whether there are any problems with the assembly process of the gearbox housing (1), the drive gear shaft bearing seat (2), the driven gear shaft bearing seat (3), the internal lubricating oil seal seat (4) and the seal seat support ring (5); 5) Inspect the sealant coating quality of the gearbox housing (1), drive gear shaft bearing seat (2), driven gear shaft bearing seat (3), internal lubricating oil seal seat (4) and seal seat support ring (5); 6) Inspect the appearance of the rubber ring for damage or twisting defects, and measure the amount of protrusion of the rubber ring; 7) Measure the inner diameter and outer diameter of the radial sealing ring (8), as well as the bottom width and diameter of the mounting groove of the radial sealing ring (8); In step S3, when the fault factor is the decrease in torque of the end-face seal tightening bolt, the repair method includes the following steps: SA1. During installation, first tighten the end face seal fastening bolt to half of the specified torque value, then continue to tighten it to full torque. After a set interval, check the torque again. If there is a decrease, continue to tighten it to full torque once more until the torque of the end face seal fastening bolt no longer decreases. SA2. After the set time, check again whether the torque of the end face seal has decreased: If there is no decay, the process ends; otherwise, proceed to step SA1.

2. The method for improving the reliability of gearbox lubricating oil sealing according to claim 1, characterized in that, In step S2, when the abrasion area of ​​the mounting surface of the gearbox housing (1) is greater than 50%, the quality of the mounting surface of the gearbox housing (1) is poor; when the flatness of the mounting surfaces of the drive gear shaft bearing seat (2), the driven gear shaft bearing seat (3), the inner lubricating oil seal seat (4) and the seal seat support ring (5) is greater than 0.025 mm, and the parallelism of the upper and lower sides of the mounting surfaces is greater than 0.045 mm, the end face quality of the drive gear shaft bearing seat (2), the driven gear shaft bearing seat (3), the inner lubricating oil seal seat (4) and the seal seat support ring (5) is poor.

3. The method for improving the reliability of gearbox lubricating oil sealing according to claim 1, characterized in that, In step SA2, the time is set to 2-3 hours.

4. The method for improving the reliability of gearbox lubricating oil sealing according to claim 1, characterized in that, In step S3, when the fault factor is the poor quality of the mounting surface of the gearbox housing (1), a grinding repair process is adopted on the mounting surface. The grinding repair process includes the following steps: SB1. Pull out the pin installed on the gearbox housing (1) and bore the pin hole; SB2. Align the gearbox housing (1); SB3. Mill the mounting surface of the gearbox housing (1) until the runout value of the mounting surface of the gearbox housing (1) meets the requirements; SB4. Based on the actual condition of the elliptical and enlarged pin hole, bore and ream the pin hole to set the hole diameter; SB5: Deburring, cleaning, localized oxidation, and localized paint touch-up; SB6. Check whether the fit between the mounting surface of the gearbox housing (1) and the mating surface of the drive gear shaft bearing seat (2) meets the requirements, and then assemble; otherwise, repeat step SB5 until the coloring requirements are met.

5. The method for improving the reliability of gearbox lubricating oil seals according to claim 4, characterized in that, In SB4, when the pin hole is bored or reamed to the set diameter, the thickness of the pin hole wall and the inner hole wall of the gearbox housing is greater than the set width.

6. The method for improving the reliability of gearbox lubricating oil sealing according to claim 4, characterized in that, In the SB6, the requirements are: the radial contact area of ​​the gearbox housing (1) is ≥60%, and the circumferential direction of the gearbox housing (1) is free of breaks.

7. The method for improving the reliability of gearbox lubricating oil sealing according to claim 1, characterized in that, In step S3, when the fault factor is poor surface quality of the drive gear shaft bearing housing (2), driven gear shaft bearing housing (3), inner oil seal seat (4) and / or seal seat support ring (5), replace the drive gear shaft bearing housing (2), driven gear shaft bearing housing (3), inner oil seal seat (4) and / or seal seat support ring (5) with qualified ones.

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