Press-Fit Inner Ring Gear Correction for OBD Variation
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Solution Overview
Problem
The Over Ball Diameter (OBD) of gears varies due to manufacturing deviations, limiting the ability to reduce these variations with gear manufacturing alone.
Innovation Solution
A corrected gear design involving a gear with a formed tooth profile and an annular inner ring that is press-fitted into the gear's inner surface, with the gear being heated to expand its inner diameter for easier insertion and then cooled to secure the ring, allowing for radial correction of the gear's diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gear manufacturing processes (cutting and heat treatment) are used, then gears can be produced with tooth profiles, but OBD variation increases due to manufacturing deviations
Solution Approach 1:
The gear system is divided into two independent parts: a base gear component and a separate correction ring. The correction ring is designed with a different OBD than the base gear, and when assembled together, their OBD differences compensate for each other, achieving overall OBD correction. This segmentation allows independent optimization of each component while achieving the desired overall precision.
Solution Approach 2:
The invention changes the OBD parameter by introducing a correction ring with specifically designed dimensional parameters. The correction ring's OBD is calculated to offset the manufacturing deviations of the base gear, thereby adjusting the overall OBD to the target value. This parameter change approach enables precise control of the final gear's OBD without reworking the entire manufacturing process.
2Manufacturing precision
If an insert is press-fitted into the gear's inner surface to correct diameter, then OBD variation is reduced, but the gear structure becomes more complex
Solution Approach 1:
The correction ring is nested inside the base gear's inner surface through press-fitting, forming a compact integrated structure. The correction ring fits within the gear's internal cavity, utilizing the existing space rather than adding external complexity. This nesting approach achieves OBD correction while maintaining a relatively simple overall structure.
3Ease of manufacture
If the gear is heated to expand the inner diameter for insert insertion, then the insert can be easily fitted, but additional heating and cooling processes are required
Solution Approach 1:
The gear is heated to utilize thermal expansion, temporarily increasing the inner diameter of the base gear to allow easy insertion of the correction ring. After insertion, the gear is cooled, causing the material to contract and create a tight interference fit between the correction ring and the gear. This thermal expansion principle enables simple assembly without requiring complex insertion mechanisms.
Solution Approach 2:
The invention utilizes the phase transition concept through thermal cycling - heating the gear to an elevated temperature state for expansion and insertion, then cooling it to a lower temperature state for contraction and securing. This controlled thermal phase transition enables the assembly process to proceed easily while achieving a permanent, secure fit.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces OBD variations by determining the necessary press-fitting deformation based on a model, thereby minimizing gear damage and improving manufacturing efficiency.
Implementation Method 1
the gear is heated at a predetermined temperature to make the diameter of the inner circumferential surface larger than the outer diameter of the inner ring, and then, the inner ring is inserted into the inner circumferential surface and cooled
Implementation Method 2
an insert that corrects a diameter of the outer circumferential surface of the gear in a radial direction by being press fitted into the inner circumferential surface of the gear
Data Source
AI summary
With respect to a gear (10) having an outer circumferential surface (16) on which a tooth profile (14) is formed and an inner circumferential surface (12), a diameter of the outer circumferential surface (16) of the gear (10) in the radial direction is corrected by press fitting an inner ring (20) into the inner circumferential surface (12).