Integrated Gear Shaft Hardness Profiling for Bearing and Tooth Strength
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Solution Overview
Problem
Existing shafts with integrated gears and bearings face issues where the hardness distribution between the gear and bearing portions is not adequately differentiated during surface treatment, leading to insufficient strength, potential cracking, and surface peeling in the bearing, and breakage of gear teeth.
Innovation Solution
A shaft design where surface treatment is performed at specific depths to satisfy the required hardness ranges for both the gear and bearing portions, with the depth for the bearing portion being greater than that for the gear portion, ensuring distinct hardness distributions and preventing cracking and breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same surface treatment (such as hardening) is performed on both the gear portion and the bearing portion, then the manufacturing process is simple, but the hardness distribution becomes uniform and cannot satisfy the different required hardness values for each portion
Solution Approach 1:
The patent applies different surface treatment depths to different portions of the shaft. The gear portion receives surface treatment to a first depth to achieve required hardness for gear teeth, while the bearing portion receives surface treatment to a second depth (greater than the first) to achieve required hardness for bearing contact surfaces. This local differentiation of treatment depth satisfies the different hardness requirements of each portion.
2Strength
If the surface treatment depth is increased to satisfy the bearing portion's hardness requirement, then the bearing portion achieves sufficient hardness, but the gear portion becomes overly hardened and susceptible to tooth breakage
Solution Approach 1:
The patent specifies that the surface treatment depth at the gear portion (first depth) is less than the surface treatment depth at the bearing portion (second depth). This localized control of treatment depth ensures that the gear portion achieves sufficient hardness without excessive hardening that would make teeth brittle, while the bearing portion receives deeper treatment to achieve the higher hardness required for bearing contact resistance.
3Strength
If the surface treatment depth is decreased to satisfy the gear portion's hardness requirement, then the gear portion achieves sufficient hardness, but the bearing portion becomes insufficiently hardened and susceptible to cracking and surface peeling
Solution Approach 1:
The patent establishes that the surface treatment depth at the bearing portion (second depth) is greater than the surface treatment depth at the gear portion (first depth). This ensures that the bearing portion receives sufficient deep hardening to prevent cracking and surface peeling under bearing loads, while the gear portion receives appropriate shallower hardening suitable for gear tooth requirements.
4Volume of moving object
If the inner race of the bearing is integrated with the shaft, then the device size is reduced, but the hardness requirements of the integrated bearing portion conflict with the gear portion's hardness requirements
Solution Approach 1:
The patent integrates the inner race of the bearing with the shaft to achieve downsizing, while simultaneously applying localized surface treatment at different depths to the gear portion and bearing portion. This allows the integrated structure to maintain differentiated hardness distributions, with the bearing portion receiving deeper treatment than the gear portion, thus satisfying both the size reduction goal and the differentiated hardness requirements.
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 approach ensures that both the gear and bearing portions meet their respective required hardness levels, effectively preventing cracking, surface peeling, and breakage, thereby enhancing the structural integrity of the shaft.
Implementation Method 1
When the same surface treatment (such as hardening) is performed in a configuration in which a gear portion at which a gear is formed and a bearing portion at which an inner race is formed are integrated with each other
Data Source
AI summary
At a position of a depth of the first predetermined value from the surface of the gear portion, a surface treatment that satisfies a range of a required hardness defined in advance of the gear portion is performed. A surface treatment is performed at a depth of a second predetermined value from a surface of a bearing portion, the surface treatment satisfying a required hardness in a range prescribed in advance for the bearing portion. Since the second predetermined value is deeper than the first predetermined value, the hardness distribution is made different between the gear portion and the bearing portion. The required hardness in the gear portion and the required hardness in the bearing portion are respectively satisfied.