Golf Ball Core Hardness Gradient for Spin Suppression
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Solution Overview
Problem
Existing golf balls fail to achieve optimal flight performance due to issues with spin rate and resilience, often resulting in inadequate flight distance and durability.
Innovation Solution
A golf ball design featuring a core with a specific hardness distribution, a mid layer with a higher specific gravity than the core, and a cover with a higher Shore D hardness than the mid layer, utilizing a rubber composition crosslinked with an organic sulfur compound and an ionomer resin, ensuring no hardness decrease from the central point to the surface and optimizing spin suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a core with a great difference between central hardness and surface hardness is used, then spin rate is reduced, but resilience performance deteriorates
Solution Approach 1:
The core is designed with a specific hardness distribution where the hardness at 5mm from the center is significantly harder than the center, creating local quality variations that suppress spin while maintaining overall resilience. This localized hardness enhancement at the periphery reduces spin rate without compromising the energy return of the entire core.
Solution Approach 2:
The patent specifies precise hardness parameter relationships: the hardness difference between 5mm from center and center must be ≥6.0, and the hardness difference between surface and 12.5mm from center must be ≥10.0. These parameter changes create an optimized hardness gradient that balances spin suppression with resilience maintenance.
2Speed
If a mid layer with higher specific gravity than core is added, then flight distance is improved, but resilience performance is deteriorated
Solution Approach 1:
The mid layer is positioned specifically between the core and cover, creating a localized density variation. The higher specific gravity of the mid layer (greater than core) is confined to this intermediate region, providing flight distance enhancement without allowing the hardness gradient to extend through the entire ball structure, thus preserving core resilience.
Solution Approach 2:
The golf ball employs a composite multi-layer structure with distinct material properties: a resilient core with specific hardness distribution, a mid layer with higher specific gravity, and a cover with appropriate hardness. This composite structure allows each layer to contribute its optimal property—resilience from the core, flight distance from the dense mid layer, and surface performance from the cover.
3Speed
If a complex core structure with multiple layers is used, then spin rate is suppressed, but energy loss increases and durability decreases
Solution Approach 1:
Instead of multiple discrete layers, the core uses a continuous hardness gradient achieved through controlled crosslinking of rubber composition. The hardness varies locally from center to periphery according to specific criteria, suppressing spin while maintaining energy efficiency and durability through a unified material structure rather than layered interfaces.
Solution Approach 2:
The core utilizes a composite rubber composition crosslinked with organic sulfur compounds, creating a material with spatially varying properties. This composite approach achieves the desired hardness distribution and spin suppression within a single integrated core material, avoiding the energy loss and durability issues associated with multiple bonded layers.
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
The design achieves low energy loss, excellent resilience, and a low spin rate, resulting in a larger flight distance and improved durability.
Implementation Method 1
a core, in which a hardness distribution is appropriate
Implementation Method 2
The base polymer of the resin composition includes an ionomer resin as a principal component
Implementation Method 3
A difference between: a JIS-C hardness H(5.0) at a point which is located at a distance of 5.0 mm from a central point of the core; and a JIS-C hardness Ho at the central point is equal to or greater than 6.0
Implementation Method 4
The mid layer is constituted with a resin composition. The base polymer of the resin composition includes an ionomer resin as a principal component
Data Source
AI summary
A golf ball 2 includes a spherical core 4, a mid layer 6, and a cover 8. The core 4 is obtained by crosslinking a rubber composition. The difference between: a hardness H(5.0) at a point which is located at a distance of 5 mm from the central point of the core 4; and a hardness Ho at the central point is 6.0 or greater. The difference between: a hardness H(12.5) at a point which is located at a distance of 12.5 mm from the central point; and the hardness H(5.0) is 4.0 or less. The difference between a hardness Hs at the surface of the core 4 and the hardness H(12.5) is 10.0 or greater. The difference between the hardness Hs and the hardness Ho is 22.0 or greater. There is no zone in which a hardness decreases from the central point to the surface. A Shore D hardness H3 of the cover is greater than a Shore D hardness H2 of the mid layer.