Speed change mechanism process planning method based on assembly error transmission analysis

Abstract

The invention relates to a speed change mechanism process planning method based on assembly error transmission analysis, and the method carries out the assembly positioning constraint analysis based on an assembly directed graph in the assembly process of a speed change mechanism, and visually expresses the assembly positioning relation. According to the method, the key error source of error transmission in the assembly process can be effectively identified and controlled, and a speed change mechanism error transmission process planning method is established, so that the assembly error is reduced or eliminated, and the assembly precision and consistency of products are improved.

Description

Technical Field

[0001] The invention relates to a speed change mechanism process planning method based on assembly error transfer analysis, and belongs to the field of mechanical industry. Background Art

[0002] The transmission mechanism is the core of the assault vehicle's transmission system. It is responsible for speed change and gear shifting operations. It is a key component in the transmission system that transmits power and motion, ensuring that the assault vehicle can start and stop quickly, operate flexibly, travel at high speed, and overcome various terrain obstacles. With the increase in lightweight requirements, the size and weight of the transmission mechanism have been greatly reduced. At the same time, the number of internal parts is large, which makes the assembly process of the transmission mechanism extremely complicated and difficult to ensure high-precision assembly requirements.

[0003] Mechanical parts assembly is an extremely critical and indispensable part of the mechanical product manufacturing process. Its quality directly determines the overall quality and performance of the final product. In this link, the precise execution of each assembly step is crucial, because any slight deviation or error may accumulate and amplify, and ultimately have a significant impact on the product's working condition, durability and user experience.

[0004] In order to improve the stability and reliability of mechanical products, it is particularly important to deeply study and analyze the error transmission process during product assembly. This includes an in-depth understanding of the error transmission mechanism, that is, exploring how errors are transmitted and accumulated between different assembly stages, and ultimately affect the overall accuracy and performance of the product. Traditional assembly process modeling mainly relies on ideal models, which construct assembly constraints by setting ideal positioning benchmarks to form the assembly model of the product. However, this idealized assembly process often deviates from the actual assembly situation.

[0005] On the one hand, errors are inevitable in the process of machining and manufacturing of mechanical parts, which results in the geometric features of these parts often not being accurately aligned with the nominal position when they are positioned or connected through assembly features, resulting in deviations. On the other hand, considering the assembly order and direction of mechanical parts, the contact or fit of each pair of assembly features is not completed at the same time, but in a certain order. This means that there are differences in positioning priorities between assembly constraints, and the order of assembly positioning of parts will affect the constraint direction of each pair of assembly features, and thus affect the fit or fit state of assembly features. This influence may cause parts to fail to meet the expected assembly function requirements. The combined effect of these two factors will cause changes in the fit clearance between the assembly features of parts, and sometimes even cause the parts to be unable to be assembled normally, thereby reducing the success rate of part assembly.

[0006] Therefore, by conducting assembly positioning constraint analysis, assembly process priority analysis and error transmission mechanism analysis on the assembly process of the speed change mechanism, the key error sources in the assembly process can be effectively identified and controlled, thereby reducing or eliminating assembly errors and improving the assembly accuracy and consistency of the product. Summary of the invention

[0007] The purpose of the present invention is to propose a process planning scheme for transmission mechanism assembly error transfer that is widely applicable and easy to operate, in view of the problems of large assembly errors, insufficient precision, and lack of guidance for key assembly links encountered by current transmission systems when assembling complex parts. This method aims to reduce errors in the assembly process and improve assembly precision, thereby ensuring that the transmission mechanism can meet production standards with a high pass rate.

[0008] The technical implementation scheme adopted by the present invention is: a speed change mechanism process planning method based on assembly error transfer analysis, including: a speed change mechanism assembly positioning constraint relationship analysis method based on an assembly directed graph; for the multi-constraint coupling process of the speed change mechanism assembly, combining the small displacement screw method and the assembly constraint type, analyzing the error transfer properties of different assembly joint surfaces; conducting error transfer mechanism analysis of series-parallel joint surface groups, analyzing the error transfer process of series-parallel joint surfaces, and establishing a speed change mechanism error transfer process planning method.

[0009] The method for analyzing the assembly positioning constraint relationship of the transmission mechanism based on the assembly directed graph is to analyze the assembly positioning constraint relationship of the transmission mechanism by means of the assembly directed graph. The core problem in the process of part assembly positioning constraint is how to effectively express the constraint relationship of the part assembly features containing non-ideal surfaces. Traditionally, part assembly relies on the ideal CAD model, and the degree of freedom of the part is restricted by accurately aligning the registration elements between multiple ideal assembly features, such as points, lines, and surfaces. Successful assembly requires the ability to accurately identify the registration elements of these ideal assembly features and achieve accurate positioning matching with the corresponding actual elements. However, when the assembly feature decomposition is performed on actual parts containing assembly errors, the situation is much more complicated. The registration elements (points, lines, and surfaces) on these parts are not completely in the ideal position, but have slight translation and rotation errors. Therefore, the assembly positioning constraints of actual parts are far more complex than those in the ideal CAD model, which makes it difficult for the assembly matching conditions of parts to match the assembly positioning constraint relationship in the ideal CAD model.

[0010] Furthermore, the assembly error transfer link of the model is constructed using the assembly directed graph to express information such as assembly specifications, part dependencies of assembly feature pairs, and assembly positioning link attributes.

[0011] Furthermore, letter symbols are used to express the characteristic surface of the model, and a single arrow solid line expresses the geometric relationship between two external parts.

[0012] Furthermore, the block diagram matching guide lines express the assembly positioning priority, assembly positioning connection type and matching type between two parts.

[0013] Furthermore, the multi-constraint coupling process in the parts assembly process is considered to obtain the topological structure properties of the transmission mechanism.

[0014] Furthermore, the typical geometric element types of the transmission mechanism are obtained to obtain the basic interface types.

[0015] Furthermore, according to the assembly relationship in the error transmission direction, the assembly joint surface is divided into a serial assembly joint surface and a parallel assembly joint surface.

[0016] Furthermore, the small displacement screw method A=[u,v,w,α,β,γ] is used to describe the displacement changes caused by constraints during the parts assembly process.

[0017] Furthermore, constraints are divided into hard constraints and soft constraints in combination with the positioning connection method and the matching method.

[0018] Furthermore, the actual error transmission properties of the series-parallel transmission mechanism are obtained by using the assembly positioning priority and constraint type division method.

[0019] Furthermore, the mating surfaces that mainly affect the error transmission of the speed change mechanism are obtained, and the key assembly processes are effectively monitored and planned.

[0020] The advantages of the present invention compared with the prior art are: analyzing the constraint relationship of the speed change mechanism by assembling directed graphs, intuitively expressing the assembly constraint form, introducing the small displacement screw method and series-parallel assembly error transmission properties to analyze the actual transmission process of the speed change mechanism, and providing a set of selection methods for the speed change mechanism assembly process to obtain the main influencing mating surfaces in the error transmission process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the overall flow chart of the present invention;

[0022] Figure 2 The present invention provides a flow chart for calculating the actual error transfer properties of the series-parallel assembly interface. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the present invention provides a speed change mechanism process planning method based on assembly error transmission analysis, and its process mainly consists of 6 steps:

[0025] 1. Assembly positioning constraint analysis: Assembly constraint analysis is performed based on the assembly directed graph method to obtain information such as assembly drawing specifications, assembly part dependencies, and assembly positioning requirements.

[0026] 2. Assembly constraint multi-coupling process analysis: Combined with the assembly interface type and connection type, the small displacement screw method is used to perform assembly constraint multi-coupling process analysis.

[0027] 3. Analysis of the impact of assembly joint surface constraints: Combine assembly constraint analysis and assembly constraint coupling process analysis to determine the impact of soft and hard constraints on different joint surfaces.

[0028] 4. Assembly positioning priority and constraint type classification: Prioritize according to actual assembly requirements and analyze the constraint types of different joint surfaces.

[0029] 5. Actual error transfer properties of series-parallel connection surfaces: The constraint set influence method and error transfer law analysis are used to obtain the actual error transfer properties.

[0030] 6. Obtain the main joint surfaces for error transmission during the assembly process: Use the actual error transmission properties to analyze the error transmission process of the speed change mechanism joint surface group and obtain the main error sources of the assembly process.

[0031] Figure 2 To calculate the actual error transfer properties of series-parallel assembly joint surfaces, it is first necessary to determine the type of part assembly joint surfaces, which are specifically divided into series assembly joint surfaces, same-body parallel assembly joint surfaces and different-body parallel assembly joint surfaces. The different-body parallel assembly joint surfaces indicate that the joint surfaces have both parallel and series conditions. They can be simplified according to the joint surface properties and equivalently treated as same-body parallel assembly joint surfaces.

[0032] Furthermore, by combining the assembly interface, constraint type, coordinate axis direction and small displacement screw method, the error transfer properties of the assembly interface can be divided into a hard constraint set S HC , soft constraint set S SC , unconstrained set S NC , its actual error transmission properties will be determined by the hard constraint set and the soft constraint set. Assume that the total constraint set of the part assembly interface is S A , then S A =(u,v,w,α,β,γ), each constraint set has the following expression relationship:

[0033]

[0034] If the part assembly interface is constrained on the error transmission path, it means that the fit change of the part assembly characteristics will be transmitted in the direction of the corresponding error component. This transmission process enables the fit change in the direction of the error component to be transmitted to the assembly interface of the next level part, thereby realizing the error transmission mechanism of the current assembly interface.

[0035] In the assembly process of building a complete product, as the assembly topology structure gradually takes shape, the assembly joint surface group is a complex network composed of multiple interconnected series or parallel assembly joint surfaces. The error transfer characteristics of these joint surfaces are jointly shaped by the comprehensive error transfer properties of the internally interconnected series or parallel assembly joint surface groups. Next, the error transfer property calculation methods of the series assembly joint surface group and the parallel assembly joint surface group in practical applications are elaborated in detail, and a set of composite error transfer property calculation processes for the series-parallel mixed assembly joint surface group are provided.

[0036] When the assembly of parts completely relies on the serial assembly interface as the medium for error transmission, the transmission of error components will be limited to the HC and SC directions of the interface. For unconstrained directions, the corresponding error components will not be able to continue to be transmitted. Therefore, the serial assembly interface will screen each error component layer by layer and level by level according to the topological structure of the assembly, and the error components that are finally retained will constitute the error transmission characteristics of the serial assembly interface. Let the error transmission property of the serial assembly interface be A s Indicates that the corresponding hard constraint set and soft constraint set are S s,HC , S c,SC , then:

[0037]

[0038] Where: n represents the total number of assembly feature pairs; for the ith assembly feature pair of the serial assembly interface, S i,HC , S i,SC , S i,NC To represent its hard constraint set, soft constraint set and unconstrained set.

[0039] Since the various joint surfaces in the serial assembly joint surface group are in a sequentially connected relationship, their respective error transmission characteristics will not be disturbed by the positioning constraints of other joint surfaces. Therefore, during the gradual development of the assembly topology, the actual error transmission properties of the serial assembly joint surface group will remain stable and will not change. This means that the formula given above can still be used to calculate the actual error transmission properties of the serial assembly joint surface group.

[0040] However, the combination of parallel assembly surfaces opens up multiple potential paths for error transmission, allowing error components to be transmitted more widely through these combinations of surfaces. In the actual assembly process, given the complex interactions between parallel assembly surfaces, especially the connection type, matching characteristics, and assembly order of the surfaces, when different parallel assembly surfaces between adjacent parts have intersections in error transmission characteristics, that is, when they have overlapping constraints in certain error component directions, the surfaces that have completed assembly positioning first will impose restrictions on the positioning of subsequent surfaces in these error component directions, thereby causing changes in the error transmission characteristics of the parallel assembly surfaces. Therefore, based on the consideration of assembly priority, it is necessary to calculate the actual error transmission characteristics of the combination of parallel assembly surfaces.

[0041] Furthermore, the actual error transfer properties of the parallel assembly joint surface group show the following rules: (1) For the parallel assembly joint surface with a higher assembly positioning priority, its HC direction will remain unchanged; (2) If the SC direction of the parallel assembly joint surface with a higher assembly positioning priority is consistent with the HC direction of the corresponding joint surface with a lower assembly positioning priority, the SC direction constraint of this part will fail; (3) If the HC direction or SC direction of the parallel assembly joint surface with a lower assembly positioning priority is consistent with the HC direction of the corresponding joint surface with a higher assembly positioning priority, all relevant constraints of this part will fail.

[0042] Assume that in the parallel assembly, the HC corresponding to the joint surfaces J1 and J2 is S p,HC1 and S p,HC2 , SC is S p,SC1 and S p,SC2 In terms of assembly priority, J1>J2. When the two joint surfaces are successfully assembled, the actual constraint sets of J1 and J2 can be expressed as follows:

[0043]

[0044] Where: S′ p1 and S′ p2 They represent the actual constraint sets of the assembly joint surfaces J1 and J2 respectively.

[0045] Therefore, in order to determine the actual error transfer properties of the parallel assembly joint surface group, calculations can be performed one by one according to the order of assembly priority from high to low, so as to obtain the actual error transfer characteristics of the parallel assembly joint surface group.

[0046] Finally, the error transfer properties of the series-parallel joint surfaces are integrated to complete the calculation of the actual error transfer properties of the series-parallel assembly joint surfaces, and the main error sources affecting the error transfer are obtained.

[0047] The above implementation method is provided only for the convenience and purpose of describing the present invention, and is not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A speed change mechanism process planning method based on assembly error transfer analysis, the characteristics of which include: The analysis method of assembly positioning constraint relationship of transmission mechanism based on assembly directed graph; Analysis method of error transmission mechanism during assembly of series-parallel combined face groups of speed change mechanism.

2. The method for analyzing the assembly positioning constraint relationship of a transmission mechanism based on an assembly directed graph as described in claim 1 is mainly characterized in that: an assembly error transmission link of the model is constructed using an assembly directed graph to express information such as assembly specifications, part dependencies of assembly feature pairs, and assembly positioning link attributes; letter symbols are used to express the feature surface of the model; a single arrow solid line expresses the geometric relationship between two external parts; and a block diagram matching guide line expresses the assembly positioning priority, assembly positioning connection type, and matching type between the two parts.

3. The error transmission mechanism analysis method for the assembly process of the series-parallel combined surface group of the speed change mechanism as described in claim 1, its main characteristics are: for the multi-constraint coupling process in the part assembly process, the displacement changes caused by the constraints in the part assembly process are obtained, and the positioning connection method and the matching method are combined, and the assembly positioning priority and constraint type division method are used to obtain the actual error transmission properties of the series-parallel speed change mechanism.

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