Method for grinding engine gear shaft and grinding tooling

Abstract

The application discloses a kind of engine gear shaft's grinding method and grinding frock, the engine gear shaft's grinding method of the present application is first to the structural dimension of core rod is optimized design, ensure that gear shaft can be flexibly adjusted the runout of small end after being installed to core rod, then using auxiliary positioning frock and detachable centre top the big end of core rod, to facilitate the runout of gear shaft big end on grinding machine flexibly adjusted, when the intermediate shaft neck part of gear shaft is ground and is processed, it is convenient to find the runout of the small end outer circle and big end outer circle of gear shaft, so that the runout of both is not greater than 0.004, improves grinding processing quality and machining precision, to improve the repair qualification rate.

Description

Technical Field

[0001] This invention relates to the field of gear shaft grinding technology, and in particular, to a method for grinding engine gear shafts. It also relates to a grinding fixture for engine gear shafts. Background Technology

[0002] As a core component of the turboprop engine transmission system, the gear shaft's intermediate journal is the inner ring raceway surface of the gear bearing rollers. During engine operation, the bearing rollers roll on this intermediate journal, inevitably resulting in micro-wear. During a major overhaul of a certain type of engine, frequent wear was found on the intermediate journal of the gear shaft. Machining of this journal was necessary to restore the part's geometric dimensions and surface quality, ensuring acceptable roller clearance. However, when re-grinding the intermediate journal, it is crucial to align the runout between the small and large ends of the gear shaft's outer diameter to guarantee machining quality and accuracy. Figure 1 As shown, ΦB is the location to be machined on the outer diameter of the gear shaft, i.e., the intermediate journal. ΦC is the small end outer diameter of the gear shaft, and ΦA is the large end outer diameter of the gear shaft. During the grinding process at ΦB, the runout at ΦA and ΦC needs to be flexibly adjusted to be no greater than 0.004, so as to ensure that the mutual runout of the outer diameters at ΦA, ΦC and ΦB is no greater than 0.008, in order to guarantee the grinding quality and repair qualification rate of the gear shaft.

[0003] The existing method for regrinding gear shafts involves first mounting the gear shaft onto a micro-conical mandrel, then attaching grinding centers to both ends of the mandrel. These centers are positioned to firmly press against both ends of the mandrel, ensuring stability on the grinding machine during the grinding process. Specifically... Figure 2 As shown, the runout of ΦA and ΦC is then aligned to be no greater than 0.004. After checking the machining allowance at ΦB, the ΦB dimension is machined according to the process data requirements. However, during the grinding process of the gear shaft, because the mandrel and the large end of the gear shaft are interference fit, the clearance after assembly is too small. At the same time, the grinding machine center used is a dead center. After the part is fixed in the installation position, only the runout can be checked, but the runout values ​​at ΦA and ΦC cannot be adjusted. This results in a very low repair pass rate for the gear shaft, leading to a large number of scrapped parts. Summary of the Invention

[0004] This invention provides a grinding method and grinding fixture for engine gear shafts, which can flexibly adjust the runout of the small end and the large end of the gear shaft, thereby facilitating the alignment of the runout of the small end outer circle and the large end outer circle of the gear shaft, improving the grinding quality and machining accuracy, and thus increasing the repair qualification rate.

[0005] According to one aspect of the present invention, a method for grinding an engine gear shaft is provided, comprising the following:

[0006] The structural dimensions of the mandrel are optimized so that the runout of the small end of the gear shaft can be flexibly adjusted after the gear shaft is installed on the mandrel;

[0007] The gear shaft is installed on the mandrel machined according to the optimized design. The small end of the mandrel is held in place by the grinding center, and the large end of the mandrel is held in place by the auxiliary positioning fixture and the detachable center, so that the runout of the large end of the gear shaft can be flexibly adjusted on the grinding machine.

[0008] To correct the runout of the small and large outer diameters of the gear shaft, the intermediate journal of the gear shaft is ground.

[0009] Furthermore, the process of optimizing the structural dimensions of the mandrel includes the following:

[0010] Obtain the distance between the small end and the large end of the gear shaft, as well as the historical maximum runout values ​​of the outer diameters of the small end and the large end of the gear shaft relative to the intermediate journal position.

[0011] An optimization strategy was adopted, which involves an interference fit between the large end of the gear shaft and the mandrel, and a single-sided clearance between the small end of the gear shaft and the mandrel that is greater than or equal to the historical maximum runout value. The target taper of the mandrel was then calculated.

[0012] Obtain the large end diameter and the overall length of the mandrel, and calculate the small end diameter of the mandrel based on the target taper of the mandrel.

[0013] Furthermore, the target taper of the mandrel is calculated based on the following formula:

[0014] C = 2d / L0

[0015] Where C represents the target taper of the mandrel, d represents the historical maximum runout value, and L0 represents the distance between the small end and the large end of the gear shaft.

[0016] Furthermore, the small-end diameter of the mandrel is calculated based on the following formula:

[0017] D1 = D2 - C × L1

[0018] Where D1 represents the small end diameter of the mandrel, D2 represents the large end diameter of the mandrel, and L1 represents the total length of the mandrel.

[0019] Furthermore, the auxiliary positioning fixture includes a three-jaw chuck and a faceplate. The faceplate is fixedly mounted on the grinding machine. There is a gap after the three-jaw chuck and faceplate are combined. The detachable center is then clamped on the three-jaw chuck. The runout of the outer circle of the large end of the gear shaft can be adjusted by tapping the three-jaw chuck.

[0020] In addition, the present invention also provides a grinding fixture for an engine gear shaft, including a mandrel, an auxiliary positioning fixture, and a detachable tip. The mandrel has an optimized structural dimension for mounting the gear shaft, and the runout of the small end of the gear shaft can be flexibly adjusted after it is mounted on the mandrel. The auxiliary positioning fixture is mounted on a grinding machine, and the detachable tip is mounted on the auxiliary positioning fixture to tighten the large end of the mandrel. The small end of the mandrel is tightened by the grinding machine tip. The runout of the outer circle of the large end of the gear shaft can be adjusted by tapping the auxiliary positioning fixture.

[0021] Furthermore, the structural dimension optimization design process of the mandrel is as follows:

[0022] First, obtain the distance between the small end and the large end of the gear shaft, as well as the historical maximum runout values ​​of the outer circles of the small end and the large end of the gear shaft relative to the intermediate journal. Then, adopt an optimization strategy of interference fit between the large end of the gear shaft and the mandrel, and a single-sided clearance between the small end of the gear shaft and the mandrel greater than or equal to the historical maximum runout value, to calculate the target taper of the mandrel. Finally, obtain the large end diameter and the overall length of the mandrel, and calculate the small end diameter of the mandrel in combination with the target taper of the mandrel.

[0023] Furthermore, the target taper of the mandrel is calculated based on the following formula:

[0024] C = 2d / L0

[0025] Where C represents the target taper of the mandrel, d represents the historical maximum runout value, and L0 represents the distance between the small end and the large end of the gear shaft.

[0026] Furthermore, the small-end diameter of the mandrel is calculated based on the following formula:

[0027] D1 = D2 - C × L1

[0028] Where D1 represents the small end diameter of the mandrel, D2 represents the large end diameter of the mandrel, and L1 represents the total length of the mandrel.

[0029] Furthermore, the auxiliary positioning fixture includes a three-jaw chuck and a faceplate. The faceplate is fixedly mounted on the grinding machine. There is a gap after the three-jaw chuck and faceplate are combined. The detachable center is then clamped on the three-jaw chuck. The runout of the outer circle of the large end of the gear shaft can be adjusted by tapping the three-jaw chuck.

[0030] The present invention has the following beneficial effects:

[0031] The grinding method for engine gear shafts of the present invention first optimizes the structural dimensions of the mandrel to ensure that the runout of the small end of the gear shaft can be flexibly adjusted after the gear shaft is installed on the mandrel. Then, the large end of the mandrel is held in place by an auxiliary positioning fixture and a detachable center to facilitate flexible adjustment of the runout of the large end of the gear shaft on the grinding machine. When grinding the intermediate journal of the gear shaft, it is easy to align the runout of the outer circles of the small and large ends of the gear shaft, so that the runout of both is no greater than 0.004, which improves the grinding quality and machining accuracy, thereby increasing the repair qualification rate.

[0032] In addition, the grinding fixture for the engine gear shaft of the present invention also has the above-mentioned advantages.

[0033] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0035] Figure 1 This is a structural schematic diagram of the engine gear shaft;

[0036] Figure 2 This is a schematic diagram of the existing gear shaft grinding method, which involves fixing the gear shaft onto a grinding machine.

[0037] Figure 3 This is a schematic flowchart of a preferred embodiment of the grinding method for an engine gear shaft in this application;

[0038] Figure 4 yes Figure 3 A schematic diagram of the sub-process of step S1;

[0039] Figure 5 This is a schematic diagram illustrating the principle of structural dimension optimization design of the mandrel in a preferred embodiment of this application;

[0040] Figure 6 This is a schematic diagram of the gear shaft and mandrel mounted on a grinding machine in a preferred embodiment of this application. Detailed Implementation

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] Reference Figure 3As shown, a preferred embodiment of this application provides a method for grinding an engine gear shaft, used to grind the intermediate journal portion of the gear shaft, including the following:

[0043] Step S1: Optimize the structural dimensions of the mandrel so that the runout of the small end of the gear shaft can be flexibly adjusted after the gear shaft is installed on the mandrel;

[0044] Step S2: Install the gear shaft onto the mandrel machined according to the optimized design, use the grinding center to hold the small end of the mandrel, and use the auxiliary positioning fixture and the detachable center to hold the large end of the mandrel, so that the runout of the large end of the gear shaft can be flexibly adjusted on the grinding machine.

[0045] Step S3: Correct the runout of the small end outer circle and the large end outer circle of the gear shaft, and perform grinding on the intermediate journal of the gear shaft.

[0046] It is understood that the grinding method for the engine gear shaft in this embodiment first optimizes the structural dimensions of the mandrel to ensure that the runout of the small end of the gear shaft can be flexibly adjusted after the gear shaft is installed on the mandrel. Then, the large end of the mandrel is held in place by auxiliary positioning fixtures and detachable centers to facilitate flexible adjustment of the runout of the large end of the gear shaft on the grinding machine. When grinding the intermediate journal of the gear shaft, it is easy to align the runout of the outer diameter of the small end and the outer diameter of the large end of the gear shaft, so that the runout of the two is no greater than 0.004, which improves the grinding quality and machining accuracy, thereby improving the repair qualification rate.

[0047] It is understandable that when the gear shaft is fitted with the existing mandrel, the large end of the gear shaft has an interference fit with the mandrel, while the small end of the gear shaft has a clearance fit. However, after the gear shaft is installed on the mandrel, the clearance between the small end of the gear shaft and the mandrel may be too small, making it difficult to adjust the runout of the outer diameter of the small end of the gear shaft. For example, the inner diameter of the gear shaft is Φ34(+0.027, 0) mm, while the diameter of the small end of the existing mandrel, D1, is 34.014 mm, and the diameter of the large end of the mandrel, D2, is 34.034 mm. The small end of the gear shaft has a clearance fit with the mandrel, while the large end of the gear shaft has an interference fit. When the inner diameter of the gear shaft is positively larger due to machining accuracy (i.e., >Φ34 mm), the clearance between the small end of the gear shaft and the mandrel will be too small. Furthermore, the existing grinding method uses a dead center on the grinding machine to hold the two ends of the mandrel in place. The dead center cannot be adjusted, making it impossible to adjust the runout values ​​of the outer diameters of the small and large ends of the gear shaft. Therefore, in step S1, in order to flexibly adjust the runout of the outer circle of the small end of the gear shaft, the present invention has optimized the structural dimensions of the mandrel and increased the gap between the mandrel and the small end of the gear shaft, thereby facilitating the adjustment of the runout of the outer circle of the small end of the gear shaft.

[0048] Among them, such as Figure 4As shown, the process of optimizing the structural dimensions of the mandrel includes the following:

[0049] Step S11: Obtain the distance between the small end and the large end of the gear shaft, as well as the historical maximum runout values ​​of the outer circles of the small end and the large end of the gear shaft relative to the intermediate journal position.

[0050] Step S12: Adopt an optimization strategy of interference fit between the large end of the gear shaft and the mandrel, and unilateral clearance between the small end of the gear shaft and the mandrel being greater than or equal to the historical maximum runout value, and calculate the target taper of the mandrel;

[0051] Step S13: Obtain the large end diameter and the overall length of the mandrel, and calculate the small end diameter of the mandrel based on the target taper of the mandrel.

[0052] Specifically, such as Figure 5 As shown, first, the distance L0 between the small end and the large end of the gear shaft is obtained, as well as the historical maximum runout value d of the outer diameter of the small end (i.e., at φC) and the outer diameter of the large end (i.e., at φA) of the gear shaft relative to the intermediate journal position during long-term use. Then, an optimization strategy is adopted to optimize the taper design of the mandrel by ensuring an interference fit between the large end of the gear shaft and the mandrel, and ensuring that the single-sided clearance between the small end of the gear shaft and the mandrel is greater than or equal to the historical maximum runout value. This aims to increase the adjustable clearance between the small end of the gear shaft and the mandrel. Specifically, the target taper of the mandrel is calculated based on the following formula:

[0053] C = 2d / L0

[0054] Where C represents the target taper of the mandrel, d represents the historical maximum runout value, and L0 represents the distance between the small end and the large end of the gear shaft.

[0055] Then, the large-end diameter D2 and the overall length L of the mandrel are obtained. Combined with the target taper of the mandrel, the small-end diameter D1 can be calculated. Finally, the large-end diameter D2 and the small-end diameter D1 are input into the mandrel machining program, and the mandrel can be machined according to the optimized design scheme. The small-end diameter of the mandrel is calculated based on the following formula:

[0056] D1 = D2 - C × L1

[0057] Where D1 represents the small end diameter of the mandrel, D2 represents the large end diameter of the mandrel, and L1 represents the total length of the mandrel.

[0058] For example, assuming the inner diameter of the gear shaft is D0, which is φ34.027mm, the distance L0 between the small end and the large end of the gear shaft is 100mm, the large end diameter D2 of the mandrel is 34.034mm, the total length of the mandrel is 220mm, and the taper formula of the mandrel is: C=(D2-D1) / L, we need to solve for the small end diameter D1 of the mandrel. First, based on the length of the section where the mandrel fits the small and large ends of the gear shaft, we can obtain: C = (D'2 - D'1) / L0, where D'2 represents the diameter of the interference fit between the mandrel and the large end of the gear shaft, D'2 = D0 = 34.027 mm, and D'1 represents the diameter of the mandrel at the small end of the gear shaft. Through statistical analysis of long-term usage data of the gear shaft, we find that the runout of the outer surface of φA and φC relative to φB is between 0.005 mm and 0.03 mm, i.e., the historical maximum runout value d = 0.03 mm. In order to ensure that the alignment requirements are met when machining φB, the minimum single-sided clearance between φC and the mandrel should be 0.03 mm, D'1 ≥ (D0 - 2d), so let D'1 = (D0 - 2d). Combining C = (D'2 - D'1) / L, we know that C = (D0 - (D0 - 2d)) / L0 = 2d / L0 = 2 × 0.03 mm / 100 mm = 0.0006. Furthermore, considering the overall taper of the mandrel, we know that C = (D2 - D1) / L, from which we derive D1 = D2 - C × L1. Therefore, we can calculate D1 = 34.034 mm - 0.0006 × 220 mm = 33.902 mm.

[0059] Of course, in other embodiments of the present invention, after calculating the small end diameter D1 of the mandrel, this dimension is a theoretical dimension, and a large number of experiments can be conducted to correct the theoretical dimension. For example, after calculating D1 = 33.902 mm, the present invention conducted a large number of experiments and found that when D1 = 33.900 mm, the outer circle runout at φC met the part machining requirements. Therefore, D1 was set to 33.900 mm.

[0060] It is understandable that after optimizing the processing of the mandrel, the gear shaft is installed onto the mandrel processed according to the optimized design. The small end of the mandrel is held in place by the dead center of the grinding machine, while the large end is held in place by auxiliary positioning fixtures and detachable centers. At this time, the small end of the gear shaft cannot be adjusted for clearance using the grinding machine center, while the large end of the gear shaft can have its runout adjusted using the auxiliary positioning fixtures and detachable centers. For example, Figure 6As shown, the auxiliary positioning fixture includes a three-jaw chuck and a faceplate. The faceplate is fixedly mounted on the grinding machine, and the three-jaw chuck is mounted on the faceplate. There is a gap after the three-jaw chuck and faceplate are combined. The detachable center is then clamped on the three-jaw chuck. When aligning the outer circle at φA, the center of the detachable center can be finely adjusted by tapping the three-jaw chuck, thereby adjusting the runout of the outer circle of the large end of the gear shaft. In addition, the three-jaw chuck also has the advantages of automatic centering, high positioning accuracy, and fast clamping.

[0061] It is understandable that after the gear shaft and mandrel are installed on the grinding machine, the runout of the small end outer circle and the large end outer circle of the gear shaft can be adjusted by the adjustable clearance between the small end of the gear shaft and the mandrel, and the clearance between the three-jaw chuck and the face plate, so that the runout at ΦA and ΦC is no greater than 0.004, thereby ensuring that the mutual runout of the outer circles at ΦA, ΦC and ΦB is no greater than 0.008, which can improve the quality of the grinding process at ΦB and the repair qualification rate.

[0062] In addition, another embodiment of the present invention provides a grinding fixture for an engine gear shaft, preferably applicable to the grinding method of the engine gear shaft as described above, including a mandrel, an auxiliary positioning fixture, and a detachable tip. The mandrel has an optimized structural dimension for mounting the gear shaft, and the runout of the small end of the gear shaft can be flexibly adjusted after the gear shaft is mounted on the mandrel. The auxiliary positioning fixture is mounted on a grinding machine, and the detachable tip is mounted on the auxiliary positioning fixture for pressing the large end of the mandrel. The small end of the mandrel is pressed by the grinding machine tip, and the runout of the outer circle of the large end of the gear shaft can be adjusted by tapping the auxiliary positioning fixture.

[0063] It is understood that the grinding fixture for the engine gear shaft in this embodiment, through the optimized design of the mandrel, can adjust the runout of the small end of the gear shaft, and through the auxiliary positioning fixture and the detachable tip, can adjust the runout of the large end of the gear shaft. When grinding the intermediate journal of the gear shaft, it is easy to align the runout of the outer circles of the small end and the large end of the gear shaft, so that the runout of the two is no greater than 0.004, which improves the grinding quality and processing accuracy, thereby improving the repair qualification rate.

[0064] The structural dimension optimization design process of the mandrel is as follows:

[0065] First, obtain the distance between the small end and the large end of the gear shaft, as well as the historical maximum runout values ​​of the outer circles of the small end and the large end of the gear shaft relative to the intermediate journal. Then, adopt an optimization strategy of interference fit between the large end of the gear shaft and the mandrel, and a single-sided clearance between the small end of the gear shaft and the mandrel greater than or equal to the historical maximum runout value, to calculate the target taper of the mandrel. Finally, obtain the large end diameter and the overall length of the mandrel, and calculate the small end diameter of the mandrel in combination with the target taper of the mandrel.

[0066] Specifically, first, obtain the distance L0 between the small end and the large end of the gear shaft, and the historical maximum runout value d of the outer diameter of the small end (i.e., at φC) and the outer diameter of the large end (i.e., at φA) of the gear shaft relative to the intermediate journal during long-term use. Then, adopt an optimization strategy of interference fit between the large end of the gear shaft and the mandrel, and ensuring that the single-sided clearance between the small end of the gear shaft and the mandrel is greater than or equal to the historical maximum runout value, to optimize the taper design of the mandrel, thereby increasing the adjustable clearance between the small end of the gear shaft and the mandrel. Specifically, the target taper of the mandrel is calculated based on the following formula:

[0067] C = 2d / L0

[0068] Where C represents the target taper of the mandrel, d represents the historical maximum runout value, and L0 represents the distance between the small end and the large end of the gear shaft.

[0069] Then, the large-end diameter D2 and the overall length L of the mandrel are obtained. Combined with the target taper of the mandrel, the small-end diameter D1 can be calculated. Finally, the large-end diameter D2 and the small-end diameter D1 are input into the mandrel machining program, and the mandrel can be machined according to the optimized design scheme. The small-end diameter of the mandrel is calculated based on the following formula:

[0070] D1 = D2 - C × L1

[0071] Where D1 represents the small end diameter of the mandrel, D2 represents the large end diameter of the mandrel, and L1 represents the total length of the mandrel.

[0072] For example, assuming the inner diameter of the gear shaft is D0, which is φ34.027mm, the distance L0 between the small end and the large end of the gear shaft is 100mm, the large end diameter D2 of the mandrel is 34.034mm, the total length of the mandrel is 220mm, and the taper formula of the mandrel is: C=(D2-D1) / L, we need to solve for the small end diameter D1 of the mandrel. First, based on the length of the section where the mandrel fits the small and large ends of the gear shaft, we can obtain: C = (D'2 - D'1) / L0, where D'2 represents the diameter of the interference fit between the mandrel and the large end of the gear shaft, D'2 = D0 = 34.027 mm, and D'1 represents the diameter of the mandrel at the small end of the gear shaft. Through statistical analysis of long-term usage data of the gear shaft, we find that the runout of the outer surface of φA and φC relative to φB is between 0.005 mm and 0.03 mm, i.e., the historical maximum runout value d = 0.03 mm. In order to ensure that the alignment requirements are met when machining φB, the minimum single-sided clearance between φC and the mandrel should be 0.03 mm, D'1 ≥ (D0 - 2d), so let D'1 = (D0 - 2d). Combining C = (D'2 - D'1) / L, we know that C = (D0 - (D0 - 2d)) / L0 = 2d / L0 = 2 × 0.03 mm / 100 mm = 0.0006. Furthermore, considering the overall taper of the mandrel, we know that C = (D2 - D1) / L, from which we derive D1 = D2 - C × L1. Therefore, we can calculate D1 = 34.034 mm - 0.0006 × 220 mm = 33.902 mm.

[0073] Of course, in other embodiments of the present invention, after calculating the small end diameter D1 of the mandrel, this dimension is a theoretical dimension, and a large number of experiments can be conducted to correct the theoretical dimension. For example, after calculating D1 = 33.902 mm, the present invention conducted a large number of experiments and found that when D1 = 33.900 mm, the outer circle runout at φC met the part machining requirements. Therefore, D1 was set to 33.900 mm.

[0074] In addition, the auxiliary positioning fixture includes a three-jaw chuck and a faceplate. The faceplate is fixedly mounted on the grinding machine, and the three-jaw chuck is mounted on the faceplate. There is a gap after the three-jaw chuck and faceplate are combined. The detachable center is then clamped on the three-jaw chuck. When aligning the outer circle at φA, the center of the detachable center can be finely adjusted by tapping the three-jaw chuck, thereby adjusting the runout of the outer circle of the large end of the gear shaft. Moreover, the three-jaw chuck also has the advantages of automatic centering, high positioning accuracy, and fast clamping.

[0075] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0076] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for grinding engine gear shafts, characterized in that, Includes the following: The structural dimensions of the mandrel are optimized so that the runout of the small end of the gear shaft can be flexibly adjusted after the gear shaft is installed on the mandrel; The gear shaft is installed on the mandrel machined according to the optimized design. The small end of the mandrel is held in place by the grinding center, and the large end of the mandrel is held in place by the auxiliary positioning fixture and the detachable center, so that the runout of the large end of the gear shaft can be flexibly adjusted on the grinding machine. To correct the runout of the small and large outer diameters of the gear shaft, the intermediate journal of the gear shaft is ground. The process of optimizing the structural dimensions of the mandrel includes the following: Obtain the distance between the small end and the large end of the gear shaft, as well as the historical maximum runout values ​​of the outer diameters of the small end and the large end of the gear shaft relative to the intermediate journal position. An optimization strategy was adopted, which involves an interference fit between the large end of the gear shaft and the mandrel, and a single-sided clearance between the small end of the gear shaft and the mandrel that is greater than or equal to the historical maximum runout value. The target taper of the mandrel was then calculated. Obtain the large end diameter and the overall length of the mandrel, and calculate the small end diameter of the mandrel based on the target taper of the mandrel; The target taper of the mandrel is calculated based on the following formula: C=2d / L 0; Where C represents the target taper of the mandrel, d represents the historical maximum runout value, and L0 represents the distance between the small end and the large end of the gear shaft; The small-end diameter of the mandrel is calculated based on the following formula: D1=D2-C×L 1; Where D1 represents the small end diameter of the mandrel, D2 represents the large end diameter of the mandrel, and L1 represents the total length of the mandrel.

2. The method for grinding engine gear shafts as described in claim 1, characterized in that, The auxiliary positioning fixture includes a three-jaw chuck and a faceplate. The faceplate is fixedly mounted on the grinding machine. There is a gap after the three-jaw chuck and faceplate are combined. The detachable center is then clamped on the three-jaw chuck. The runout of the outer diameter of the large end of the gear shaft can be adjusted by tapping the three-jaw chuck.

3. A grinding fixture for engine gear shafts, applicable to the grinding method described in claim 1 or 2, characterized in that, It includes a mandrel, an auxiliary positioning fixture, and a detachable center. The mandrel has an optimized structural dimension for mounting a gear shaft. After the gear shaft is mounted on the mandrel, the runout of the small end of the gear shaft can be flexibly adjusted. The auxiliary positioning fixture is mounted on a grinding machine, and the detachable center is mounted on the auxiliary positioning fixture to tighten the large end of the mandrel. The small end of the mandrel is tightened by the grinding machine center. The runout of the outer circle of the large end of the gear shaft can be adjusted by tapping the auxiliary positioning fixture.

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