Stepped Pin Gearbox Assembly to Prevent Bearing Raceway Scratches
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Solution Overview
Problem
Conventional gearbox assemblies with multi-bearing integrated shaft structures face surface scratches during assembly due to insufficient offset room between positioning pins and pin holes, affecting bearing performance and lifespan.
Innovation Solution
The use of stepped pins with a larger radial gap between the guide section and positioning pin hole prevents surface scratches by ensuring a sufficient radial space between the inner ring and rollers of the bearing, allowing the engagement section to enter the pin hole only after more than half of the axial length of the rollers enter the raceway, thus preventing compression during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If positioning pins with single diameter are used, then the assembly structure is simple, but surface scratches are formed on bearing components due to insufficient offset room
Solution Approach 1:
The positioning pin is divided into two distinct sections: a guide section with smaller diameter and an engagement section with larger diameter. This segmentation allows the guide section to provide sufficient radial clearance during assembly, preventing surface scratches on bearing components, while the engagement section ensures secure final positioning. The pin transitions from a single-diameter simple structure to a multi-section structured component that resolves the contradiction between simplicity and harm prevention.
Solution Approach 2:
The guide section of the positioning pin performs a preliminary action by providing radial clearance during the initial assembly phase, allowing bearing components to be positioned without compression or scratching. Only after this preliminary protective phase does the engagement section engage to provide final secure positioning. This sequential action prevents harm before the main positioning function is executed.
2Ease of manufacture
If positioning pins with single diameter are used, then the manufacturing process is simple, but compression between rollers and inner ring occurs during assembly
Solution Approach 1:
The positioning pin is segmented into a guide section with smaller diameter and an engagement section with larger diameter. This segmentation enables the guide section to provide sufficient radial clearance during assembly, preventing compression between rollers and the inner ring, while maintaining relatively simple manufacturing processes. The two-section design resolves the contradiction by allowing precise control of radial gaps without significantly complicating manufacturing.
Solution Approach 2:
The positioning pin utilizes parameter changes by varying the diameter along its length - the guide section has a smaller diameter to provide radial clearance, while the engagement section has a larger diameter for secure positioning. This parameter variation enables precise control over the radial gap during assembly, preventing compression of bearing components while maintaining manufacturing feasibility.
3Object-affected harmful factors
If larger radial gap is provided between positioning pin and pin hole, then surface scratches are prevented, but positioning accuracy may be reduced
Solution Approach 1:
The positioning pin is segmented into a guide section with smaller diameter that provides radial clearance to prevent surface scratches, and an engagement section with larger diameter that ensures accurate final positioning. This segmentation resolves the contradiction by separating the protective function (radial clearance) from the positioning function (accurate alignment), allowing both large radial gap for protection and high positioning accuracy to coexist.
Solution Approach 2:
The guide section performs a preliminary action by providing radial clearance during the initial assembly phase to prevent surface scratches. After this protective phase, the engagement section engages to provide precise final positioning. This sequential action resolves the contradiction between providing large radial gap for protection and maintaining positioning accuracy by performing these functions at different stages of assembly.
Data Source
Figure 1(a)
Figure 1(b)
Figure 1(c)
AI summary
An electrically driven power transmission system box assembly positioned by stepped pins (5) and the installation method thereof are disclosed. The box assembly comprises: a housing and shaft string assembly (4), several stepped pins (5), a first housing (3), and a first bearing. The housing and shaft string assembly (4) comprises a housing and a shaft string (9) supported on the housing. The stepped pin (5) comprises an engagement section and a guide section, a diameter of the engagement section is greater than a diameter of the guide section, and an end part of the engagement section is fixed in a fixing pin hole of the housing. The first housing (3) is installed and fixed to the housing and shaft string assembly (4) under the guidance of the guide section. The rear end of the shaft string (9) is supported on the first housing (3) via the first bearing. This technical solution utilizes the larger radial gap between the guide section of the stepped pin (5) and the positioning pin hole to prevent surface scratches on the raceway of the first bearing caused by the compression between the inner ring and rollers of the first bearing (7) during the assembly process of the shaft string (9) and the first housing (3), thereby improving the service life of the bearing and the entire system.