A repair method for an aviation transmission gearbox

Abstract

The present invention belongs to the technical field of transmission gearboxes, and discloses a repair method for an aviation transmission gearbox. The method includes: obtaining a gearbox to be repaired and removing all bearing bushings on the gearbox housing; measuring and evaluating the diameter of the bottom holes of the gearbox housing and machining them; using the mounting surface and two external interfaces as references for machining; after repairing the bottom holes of the gearbox housing, installing new bearing bushings according to the actual sizes of the bottom holes and machining the inner holes of the installed bearing bushings; assembling the upper housing and the lower housing of the gearbox, and using the two external interfaces as references to successively machine the bearing bushings at the distal ends and the proximal ends of the corresponding shaft systems; machining the assembly holes for the positioning pins; separating the upper housing and the lower housing of the gearbox and respectively machining the remaining two bearing bushings; assembling the upper housing and the lower housing of the gearbox to obtain the repaired gearbox. Functionally, the purpose of repairing a split-type gearbox housing is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of transmission gearboxes, and particularly relates to a repair method for an aviation transmission gearbox. Background Art

[0002] Currently, the housings of aviation accessory transmission gearboxes are all thin-walled magnesium and aluminum alloy castings. The housings are split-type, usually composed of 2 to 3 housings, and are assembled into one body by stud bolts and nuts. The two housings are positioned by a plurality of positioning pins. Bearing mounting holes are designed on the housing. There is an interference fit between the bearing bushing and the bottom hole of the housing. As shown in, for example, Figure 2 , Figure 3 The gearbox is composed of an upper housing 1 and a lower housing 2, and has O1, O2, O3, and O4 shaft systems. Bearing bushings 4 are installed on the upper housing 1 and the lower housing 2. Positioning pins 3 are installed on the rear housing 2, and external mounting holes φA2 and φC2 are designed. To ensure the fitting accuracy between the housing and the bearing and the position accuracy of the bearing mounting holes at the same gear shaft position after the housing is assembled, the general tolerance of the bore diameter of the bearing bushing 4 is within 0.02 mm, and the position tolerance is generally specified within 0.05 mm. The position accuracy of the positioning pin 3 is 0.05 mm. Since the thin-walled gearbox housing of this structure is deformed after use, the accuracy of the reference surface, reference plane, and positioning pin deviates, and the bearing bushing 4 will also show a certain degree of wear. When repairing, the bearing bushing 4 needs to be replaced and the positioning pin 3 needs to be repaired again. However, due to the deformation of the casing and the wear of the positioning pin holes, when the flatness of the mating reference surface is greater than 0.08 mm, it is very difficult to repair the position accuracy of the casing bushing relative to the positioning pin, external mounting holes, and bearing bushing according to the design requirements at the same time. Summary of the Invention

[0003] The technical problem solved by the present invention: provides a repair method for an aviation transmission gearbox, which realizes the purpose of repairing a split-type gearbox housing functionally.

[0004] The technical solution of the present invention:

[0005] A repair method for an aviation transmission gearbox, the gearbox being a split-type gearbox, composed of an upper housing and a lower housing, having four shaft systems, with bearing bushings installed on the upper housing and the lower housing, and positioning pins and two external mounting holes designed on the lower housing; the method includes:

[0006] Step 1, obtain the gearbox to be repaired, and remove all bearing bushings on the gearbox housing;

[0007] Step 2, measure and evaluate the diameter of the bottom hole of the gearbox housing and machine it;

[0008] Step 3, use the mounting surface and the two external interfaces as references for machining;

[0009] Step 4: After repairing the bottom holes of the gearbox housing, install a new bearing bushing according to the actual size of the bottom holes, and machine the inner holes for installing the bearing bushings.

[0010] Step 5: Assemble the upper housing and the lower housing of the gearbox. Taking the two external interfaces as the reference, machine the bearing bushings at the distal end and the proximal end of the corresponding shafting in sequence.

[0011] Step 6: Machine the assembly holes for the locating pins.

[0012] Step 7: Separate the upper housing and the lower housing of the gearbox, and machine the remaining two bearing bushings respectively.

[0013] Step 8: Assemble the upper housing and the lower housing of the gearbox to obtain the repaired gearbox.

[0014] The features and further improvements of the technical solution of the present invention are as follows:

[0015] (1) In Step 1, the method for removing the bearing bushing is as follows: Machine the bearing bushing thinner, machine an internal thread in the bearing bushing, and use an extraction tool with an external thread to remove the bearing bushing, preventing the bottom holes of the bearing bushing from being damaged during the disassembly of the bearing bushing.

[0016] (2) In Step 2, for the case where the roundness of the bottom hole is greater than 0.03 mm, it is necessary to repair it by reaming until the roundness reaches 0.02 mm.

[0017] (3) In Step 3, measure and evaluate the flatness of the installation surface, perform local polishing on the protruding high points on the surface, and perform overall grinding treatment when there is no influence from the stud bolts;

[0018] Taking the two external interfaces as the reference holes for subsequent repair, first measure and evaluate the dimensional accuracy of the external interfaces, and within the allowable range of the dimensions of the external mating parts, repair the roundness of the external interfaces to within 0.02 mm.

[0019] (4) In Step 4, machining allowance should be left when machining the inner holes, and the machining allowance is within 0.5 mm.

[0020] (5) In Step 5, machine the dimensions of the bearing bushings at the distal end of the corresponding shafting through the two external interfaces respectively, ensuring that the coaxiality is within 0.03 mm; then, taking the machined bearing bushings as the reference, machine the dimensions of the remaining bearing bushings at the proximal end respectively, ensuring that the coaxiality is within 0.05 mm.

[0021] (6) In step six, the assembly hole of the positioning pin on the upper housing and the positioning pin are in clearance fit, and the assembly hole of the positioning pin on the lower housing and the positioning pin are in interference fit. After the positioning pin hole is machined, a steel ball is used to close the outer end face of the hole on the upper housing to prevent the positioning pin from falling out after assembly.

[0022] (7) In step seven, ensure that the hole diameters of the remaining two bearing bushes are within 0.05 mm with respect to the hole diameter of the bearing bush of the reference shaft and the positional tolerance of the mounting surface.

[0023] The method for combined machining and repairing the housing provided by the present invention can adapt to the influence brought by the change of the design reference caused by the deformation of the gearbox after long-term operation, get rid of the limitation of the initial design, and directly achieve the major repair of the product from the function. It can greatly improve the repair qualification rate of the product, reduce the replacement part cost, effectively extend the service life of the product, and has been applied to multiple products at present. Brief Description of the Drawings

[0024] Figure 1 is a schematic flow chart of the gearbox housing repair method provided by the present invention;

[0025] Figure 2 is a schematic design structure diagram of the upper housing of the gearbox provided by the present invention;

[0026] Figure 3 is a schematic design structure diagram of the lower housing of the gearbox provided by the present invention;

[0027] Figure 4 is a schematic diagram of combined machining of the housing;

[0028] Figure 5 is a schematic diagram of separate machining of the housing. Detailed Description of the Embodiment

[0029] The technical solution of the present invention will be described in detail below with reference to the drawings.

[0030] For the existing split-type gearbox housing, in order to ensure the combined accuracy after assembly during design, strict regulations are required for the accuracy of single parts. However, during the repair of the product during the overhaul period, due to the deformation of the thin-walled gearbox housing, the original machining reference deviates, making it impossible to accurately evaluate other dimensions that need to be repaired and unable to repair the accuracy according to the original design requirements, resulting in a large amount of scrapped housing parts and high repair costs.

[0031] The present invention provides a repair method for a split-type gearbox housing to improve the repair qualification rate of the gearbox housing.

[0032] The embodiment of the present invention provides a repair method for an aviation transmission gearbox, and its implementation process is as Figure 1As shown, the gearbox is a split-type gearbox, which consists of an upper housing and a lower housing. It has four shaft systems, and bearing bushes are installed on the upper housing and the lower housing. A positioning pin is installed on the lower housing, and two external mounting holes are designed; the method includes:

[0033] Step 1: Obtain the gearbox to be repaired and remove all the bearing bushes on the gearbox housing;

[0034] Step 2: Measure and evaluate the diameter of the bottom hole of the gearbox housing and machine it;

[0035] Step 3: Use the mounting surface and the two external interfaces as the reference for machining;

[0036] Step 4: After repairing the bottom hole of the gearbox housing, install new bearing bushes according to the actual size of the bottom hole, and machine the inner hole of the installed bearing bushes;

[0037] Step 5: Assemble the upper housing and the lower housing of the gearbox. Using the two external interfaces as the reference, machine the bearing bushes at the distal end and the proximal end of the corresponding shaft systems in sequence;

[0038] Step 6: Machine the assembly holes for the positioning pins;

[0039] Step 7: Separate the upper housing and the lower housing of the gearbox and machine the remaining two bearing bushes respectively;

[0040] Step 8: Assemble the upper housing and the lower housing of the gearbox to obtain the repaired gearbox.

[0041] The gearbox housing repair method provided by the present invention is applicable to products manufactured with magnesium and aluminum alloy thin-walled casting housings. Taking Figure 2 、 Figure 3 as an example, the gearbox consists of two upper and lower housings, and the parts included are the upper housing 1, the lower housing 2, the positioning pin 3, and the bearing bush 4. The relative position after assembly of the gearbox is determined by the cooperation of two positioning pins 3 and the pin holes, and it is connected by bolts and nuts. The structure includes four gear shaft systems O1, O2, O3, and O4, and external mounting ports φA2 and φC2 are designed at the positions of O1 and O3 shafts; there is an interference fit between the bearing bush 4 and the upper housing 1 (4 bearing bushes) and the lower housing 2 (4 bearing bushes); the positional tolerance of the bearing bush 4 relative to the mounting surface (reference surface A) and the positioning pin 3 (references C and D) is 0.05 mm, and the positional tolerance between the positioning pins (reference D relative to reference C) is 0.05 mm.

[0042] The gearbox housing repair method provided by the present invention includes:

[0043] Step 1: Disassemble the bearing bushing 4, thin the bearing bushing 4, and process the internal thread, and remove the bearing bushing 4 using an extraction tool with an external thread, so as to protect the bottom hole from being damaged when removing the bearing bushing;

[0044] Step 2. Since the bearing sleeve 4 is interference fit with the upper shell 1 and the lower shell 2, the bottom hole accuracy has a great influence on the stress uniformity after the sleeve is assembled. It is necessary to first measure and evaluate the diameter of the shell bottom hole (such as φA2 and φA3 for the O1 shaft). If the bottom hole roundness is greater than 0.03mm, it is necessary to repair it by expanding the hole until the roundness reaches 0.02mm; the reference plane A is the reference plane for all measurements, so its flatness has a direct impact on the accuracy of the measurement of other dimensions. It is necessary to first measure and evaluate the flatness of the installation surface, perform local polishing on the protruding high points on the surface, and perform overall grinding when there is no influence of screw piles; the external interfaces φA2 and φC2 are the reference holes for subsequent repairs. It is necessary to first measure and evaluate the dimensional accuracy of the external interfaces, and repair the roundness of the interfaces to within 0.02mm within the allowable range of the external matching dimensions.

[0045] Step 3: After the bottom hole of the shell is repaired, re-match and install the bearing bushing according to the actual size of the bottom hole, and leave a machining allowance for the inner hole. The machining allowance should be as small as possible, generally within 0.5, to avoid excessive machining allowance, which will lead to excessive cutting force and excessive material removal during subsequent processing, resulting in excessive deformation and affecting dimensional accuracy.

[0046] Step 4: Figure 4 As shown, the upper shell 1 and the lower shell 2 are assembled, and then the O1 and O3 shafts are processed. During the processing, the φA and φC1 dimensions of the corresponding bearing bushings 4 at the far ends of the O1 and O3 shaft systems are processed respectively based on the external interfaces φA2 and φC2 as the reference (S2 and K2 references) to ensure the coaxiality requirement of 0.03mm; then the φA1 and φC dimensions of the corresponding bearing bushings 4 are processed respectively based on the processed bearing bushings 4 as the reference (S and K1 references) to ensure the coaxiality of 0.05mm.

[0047] Step 5: Process the assembly holes φG and φG1 of the positioning pin 3. The φG on the upper shell 1 and the positioning pin are clearance fit, and the φG1 on the lower shell 2 and the positioning pin are interference fit to facilitate subsequent assembly. After the positioning pin hole is processed, use a steel ball to close the outer end surface of the φG hole on the upper shell 1 to prevent the positioning pin from falling out after assembly. And match the positioning pin 3 according to the actual size of φG and φG1.

[0048] Step 6: Separate the two shells. Figure 5As shown, the bearing bushes 4 of the remaining O2 axis and O4 axis are processed separately to ensure that the hole diameters of the bearing bushes 4 of the O2 axis and O4 axis are respectively 0.05 mm with respect to the hole diameters of the bearing bushes 4 of the O1 axis and O3 axis and the position degree of the installation plane (reference plane A).

[0049] The method for combined machining and repairing the housing provided by the present invention can adapt to the influence brought by the change of the design reference caused by the deformation of the gearbox after long-term operation, get rid of the limitation of the initial design, and directly achieve the major repair of the product functionally. It can greatly improve the repair qualification rate of the product, reduce the replacement part cost, effectively extend the service life of the product, and has been applied to multiple products at present.

Claims

1. A repair method for an aviation transmission gearbox, characterized in that, The gearbox is a split gearbox, which consists of an upper shell and a lower shell, and has four shaft systems. The upper shell and the lower shell are equipped with bearing bushings, and the lower shell is equipped with a positioning pin and is designed with two external mounting holes. The method includes: Step 1: Get the gearbox to be repaired and remove all bearing bushings on the gearbox housing; Step 2: Measure, evaluate and process the bottom hole diameter of the gearbox housing; Step 3: Use the mounting surface and two external mounting holes as reference for processing; Step 4: After the bottom hole of the gearbox housing is repaired, a new bearing bushing is installed according to the actual size of the bottom hole, and the inner hole for installing the bearing bushing is processed; Step 5: Assemble the upper housing and the lower housing of the gearbox, and use the two external mounting holes as references to sequentially process the bearing bushing at the far end and the bearing bushing at the near end of the corresponding shaft system; Step 6: Process the assembly hole of the positioning pin; Step 7: Separate the upper and lower housings of the gearbox and process the remaining two bearing bushings respectively; Step 8: Assemble the upper housing and the lower housing of the gear box to obtain a repaired gear box.

2. A method for repairing an aviation transmission gearbox according to claim 1, characterized in that: In step one, the method for removing the bearing bushing is: thinning the bearing bushing, processing internal threads in the bearing bushing, and removing the bearing bushing using an extraction tool with external threads to prevent the bottom hole of the bearing bushing from being damaged when removing the bearing bushing.

3. The method for repairing an aviation transmission gearbox according to claim 1, characterized in that: In step 2, if the bottom hole roundness is greater than 0.03 mm, it needs to be repaired by expanding the hole until the roundness reaches 0.02 mm.

4. The method for repairing an aviation transmission gearbox according to claim 1, characterized in that: In step 3, the flatness of the installation surface is measured and evaluated, and the protruding high points on the surface are partially polished and repaired, and the whole surface is polished if there is no influence of the screw pile; The two external mounting holes are used as reference holes for subsequent repairs. The dimensional accuracy of the external mounting holes is first measured and evaluated. Within the allowable size range of the external accessories, the roundness of the external mounting holes is repaired to within 0.02mm.

5. The method for repairing an aviation transmission gearbox according to claim 1, characterized in that: In step five, the sizes of the bearing bushings at the far ends of the corresponding shaft systems are processed through the two external mounting holes to ensure the coaxiality is 0.03 mm; then the sizes of the remaining proximal bearing bushings are processed based on the processed bearing bushings to ensure the coaxiality is 0.05 mm.

6. The method for repairing an aviation transmission gearbox according to claim 1, characterized in that: In step six, the assembly hole of the locating pin on the upper shell is a clearance fit with the locating pin, and the assembly hole of the locating pin on the lower shell is an interference fit with the locating pin. After the locating pin hole is processed, the outer end surface of the hole on the upper shell is closed with a steel ball to prevent the locating pin from falling out after assembly.

7. The method for repairing an aviation transmission gearbox according to claim 1, characterized in that: In Step 7, ensure that the position tolerances of the apertures of the remaining two bearing bushes with respect to the aperture of the bearing bush of the reference shaft and the mounting surface are 0.05 mm respectively.

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