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 achieving reduced spin rates on full shots and improved spin control on approach shots, leading to suboptimal distance and control for professional and skilled golfers.
Innovation Solution
A golf ball design featuring a core with a rubber composition containing specific ingredients, including a base rubber, co-crosslinking agents, crosslinking initiators, and lower alcohols, with a hardness profile that includes a gradual inner zone and steep outer zone gradient, and a paint film layer, optimizing the dynamic coefficient of friction and spin index to balance spin rates on full and approach shots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the core hardness is increased to reduce spin rate on full shots, then distance performance improves, but spin control on approach shots deteriorates
Solution Approach 1:
The core is designed with non-uniform hardness distribution, featuring an inner zone with lower hardness (Hc) and an outer zone with higher hardness (Ho). This local quality variation allows the inner soft zone to reduce spin on full shots while the outer hard zone maintains spin control on approach shots, resolving the contradiction between distance and control.
Solution Approach 2:
The core is segmented into distinct zones with different hardness characteristics - an inner zone and an outer zone. This segmentation enables each zone to perform its specific function: the inner zone reduces spin on full shots for distance, while the outer zone provides spin control on approach shots.
2Speed
If the core hardness gradient is made steeper to reduce spin rate, then flight performance improves, but the balance between full shot and approach shot spin control deteriorates
Solution Approach 1:
The invention optimizes specific parameter ranges for the hardness difference between zones (Ho-Hc between 22-40 JIS-C hardness units) and defines the spin index parameter (product of hardness difference and dynamic coefficient of friction) to be greater than a given value. These parameter changes achieve improved flight performance while maintaining the balance between full shot and approach shot spin control.
3Ease of manufacture
If conventional core formulations are used to simplify manufacturing, then production ease improves, but performance optimization deteriorates
Solution Approach 1:
The core uses a composite rubber composition incorporating base rubber, co-crosslinking agents (α,β-unsaturated carboxylic acid and/or metal salt), crosslinking initiators, and lower alcohols (molecular weight below 200). This composite material system enables the complex hardness profile to be achieved through a single-core construction, maintaining manufacturing simplicity while ensuring performance consistency.
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 a significant reduction in spin rate on full shots while maintaining control on approach shots, enhancing flight and control performance beyond conventional golf balls, thereby meeting the demands of professional and skilled golfers.
Implementation Method 1
the core is formed of a rubber composition containing (b) a co-crosslinking agent which is an α,β-unsaturated carboxylic acid and/or a metal salt thereof, (c) a crosslinking initiator
Implementation Method 2
a base rubber, (b) a co-crosslinking agent which is an α,β-unsaturated carboxylic acid and/or a metal salt thereof, (c) a crosslinking initiator
Implementation Method 3
by providing an inner zone of the core with a relatively gradual hardness gradient and an outer zone of the core with a relatively steep hardness gradient, and by making the hardness difference between the inner and outer zones of the core large, an even larger reduction in the spin rate of the ball on full shots can be achieved
Implementation Method 4
having also a paint film layer formed on the cover surface... defining the numerical value obtained by multiplying the hardness difference between the inner and outer zones by the dynamic coefficient of friction for the overall ball as the spin index of the ball
Data Source
AI summary
In order to satisfy at a high level the golf ball flight and control performances relied on by professional golfers and skilled amateurs, this invention provides a multi-piece solid golf ball G having a core 1, a cover 3 and an intermediate layer 2 therebetween wherein the core is formed of a rubber composition that includes a lower alcohol having a molecular weight below 200. Also, letting Hc be the JIS-C hardness at the center of the core, H12 be the JIS-C hardness at a position 12 mm from the core center and Ho be the JIS-C hardness at the surface of the core, the core has a hardness profile in which these hardnesses satisfy fixed relationships defined by specific formulas.