Shaft Hub Tooth Hardness Gradient for Stress Peak Reduction
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Solution Overview
Problem
The existing hub components in shaft-hub connections, such as extruder screws, experience stress peaks due to the mismatch in rigidity between the shaft and hub, leading to potential failure from plastic deformation, especially under high torque conditions, as the force is concentrated at the hub edge and internal teeth, causing damage.
Innovation Solution
The hub component's teeth are locally softened by reducing their hardness at the ends compared to the center, using a targeted heat treatment to create a hardness profile that reduces stress peaks by allowing elastic deformation, thereby matching the hardness of the external teeth and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the internal teeth are made hard to resist wear and high forces, then the durability is improved, but stress peaks occur at the hub edge leading to plastic deformation and potential failure
Solution Approach 1:
The patent applies different hardness levels to different regions of the same tooth structure. The root region (near the hub edge) is kept softer to allow elastic deformation and absorb stress peaks, while the tip region remains harder to resist wear and high forces during operation. This gradient hardness distribution resolves the contradiction by optimizing each region's properties for its specific functional requirements.
Solution Approach 2:
The patent changes the physical parameter of hardness within the tooth structure by applying selective heat treatment processes. Through controlled heating and cooling, the root region undergoes tempering to reduce hardness, while the tip region maintains or achieves higher hardness through differential heating rates or selective heating methods, thereby creating the desired hardness gradient.
2Reliability
If material is mechanically removed to create gaps between external and internal toothing, then stress peaks are reduced, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces the mechanical material removal process (machining, grinding) with a thermal field-based heat treatment process. Instead of physically removing material to create gaps, the patent uses controlled heating to modify the material's physical properties (hardness) in specific regions, achieving stress peak reduction through elastic deformation capability rather than geometric gaps, thereby significantly reducing manufacturing complexity and cost.
3Power
If the shaft and hub component have different rigidities causing shaft torsion, then torque transmission is achieved, but stress peaks occur at the hub edge
Solution Approach 1:
The patent creates a local quality difference within the tooth structure by applying heat treatment selectively to the root region. This produces a softer zone that can deform elastically under the stress peaks generated by shaft torsion during torque transmission, while the rest of the tooth structure maintains sufficient rigidity for effective power transmission.
Solution Approach 2:
The patent beforehand cushions against stress peaks by creating a softer root region that can absorb and dissipate the high stresses generated during torque transmission. This pre-engineered softer zone acts as a cushion that deforms elastically under load, protecting the harder tooth tip and overall structure from damage while allowing normal torque transmission.
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 solution effectively reduces stress peaks and prevents damage to both the hub and shaft by allowing the internal teeth to deform elastically, ensuring the hub component can handle high torque without failure, while maintaining the structural integrity of the shaft.
Implementation Method 1
The invention provides for a hub component of the type mentioned above that the hardness of each tooth at least at one end is lower than in the area of the longitudinal center of the tooth
Implementation Method 2
a certain elastic deformation of the teeth of the internal gearing in their softer area can reduce the stress peaks on the edge of the hub component
Data Source
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AI summary
Hub component for a shaft-hub connection, comprising an internal toothing formed in a bore, extending axially from one end of the bore to the other end, with several teeth and grooves provided between them, wherein the hardness of each tooth (28) is lower at at least one end at least on one tooth flank (29, 30) than in the region of the longitudinal center of the tooth (28).