Golf Ball Core Hardness Gradient for Spin Control
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Solution Overview
Problem
Conventional multi-piece solid golf balls fail to optimize core hardness profile and overall performance, particularly in reducing spin rate on full shots while maintaining control on approach shots.
Innovation Solution
A golf ball design with a core having a gradual inner hardness gradient and a steep outer hardness gradient, accompanied by a paint film layer, where the hardness difference between core zones is maximized, and a spin index defined by the dynamic coefficient of friction is used to balance spin rates on full and approach shots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the core hardness profile is optimized with a gradual inner gradient and steep outer gradient, then the spin rate on full shots is reduced, but the manufacturing precision requirement increases
Solution Approach 1:
The core is designed with non-uniform hardness distribution, featuring a gradual hardness gradient in the inner zone and a steep hardness gradient in the outer zone. This local quality variation allows the core to exhibit different mechanical properties at different locations, reducing spin rate on full shots while maintaining manufacturability through controlled composition gradients.
Solution Approach 2:
The invention changes the hardness parameter distribution within the core by controlling the composition gradient of rubber components and fillers. The core composition is designed to create a continuous hardness transition from center to surface, with specific hardness differences between inner and outer zones, thereby optimizing flight performance without excessive manufacturing complexity.
2Speed
If the hardness difference between core inner and outer zones is increased, then the spin rate reduction effect is enhanced, but the structural stability decreases
Solution Approach 1:
The core structure employs localized hardness variation where the inner zone has a gradual hardness gradient for spin reduction, while the outer zone has a steep hardness gradient for structural stability. This spatial differentiation of material properties allows the core to simultaneously achieve performance optimization and structural integrity.
Solution Approach 2:
The core is conceptually divided into two functional zones: an inner zone with gradual hardness gradient that reduces spin rate, and an outer zone with steep hardness gradient that provides structural stability. This segmentation allows each zone to perform its specific function while maintaining overall core stability through the intermediate transition region.
Data Source
AI summary
In a multi-piece solid golf ball having a core, a cover and an intermediate layer therebetween, letting Hc be the JIS-C hardness at the core center, H12 be the JIS-C hardness at a position 12 mm from the core center and Ho be the JIS-C hardness at the core surface, the core has a hardness profile which satisfies the conditions 0≦H12−Hc≦15, 15≦Ho−H12≦30, (Ho−H12)−(H12−Hc)≧10 and 20≦Ho−Hc≦40. Also, letting A be the value represented by (Ho−H12)−(H12−Hc), the spin index of the ball, defined as the dynamic coefficient of friction for the ball multiplied by A, is at least 3.0. This golf ball can satisfy at a high level the flight and control performance relied on by professional golfers and skilled amateurs.