Golf Ball Core Hardness Gradient for Driver Distance and Iron Control
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Solution Overview
Problem
Golf balls with an outer-hard/inner-soft core structure experience excessive energy loss when hit with a driver, leading to deteriorated resilience and flight distance, and low spin rates when hit with a short iron, affecting control performance.
Innovation Solution
A golf ball design featuring a core with a specific hardness distribution, a mid layer, and a cover made from thermoplastic polyurethane, where the core has a volume proportion of at least 76% and a JIS-C hardness gradient that minimizes energy loss and spin, while the mid layer and cover enhance resilience and control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a core with outer-hard/inner-soft structure and excessively large hardness distribution is used, then spin rate is reduced, but energy loss increases and resilience performance deteriorates
Solution Approach 1:
The core is designed with a specific hardness distribution where the hardness at the outer peripheral portion is lower than conventional designs, while the central portion maintains appropriate hardness. This local differentiation resolves the contradiction by reducing energy loss at impact (improving resilience) while maintaining sufficient spin rate through the overall hardness distribution pattern.
Solution Approach 2:
The invention changes the hardness parameter distribution within the core by specifying that the JIS-C hardness at the outer peripheral portion should be lower than conventional outer-hard/inner-soft designs. This parameter modification allows the core to achieve both lower energy loss and adequate spin rate by optimizing the hardness gradient from center to periphery.
2Loss of energy
If a core with outer-hard/inner-soft structure and excessively large hardness distribution is used, then energy loss is reduced, but spin rate becomes too low and control performance deteriorates
Solution Approach 1:
The core employs a differentiated hardness structure where the outer peripheral portion has lower hardness to reduce energy loss, while the central portion maintains higher hardness to generate sufficient spin rate. This local quality variation allows simultaneous achievement of low energy loss and good control performance.
Solution Approach 2:
The invention optimizes the hardness parameter distribution by controlling the JIS-C hardness at the outer peripheral portion to be within a specific range (40-70) and ensuring it is lower than the central hardness. This parameter optimization enables the core to minimize energy loss while maintaining adequate spin rate for control performance.
3Speed
If core volume proportion is increased to improve resilience, then flight distance increases, but spin rate decreases
Solution Approach 1:
The core with large volume proportion (70-85% of total ball volume) incorporates a hardness distribution where the outer peripheral portion has lower hardness. This local quality feature allows the large core to maintain high resilience for flight distance while the softer outer region generates sufficient spin rate despite the increased core size.
Data Source
AI summary
Golf ball wherein, at all points Pa included in zone "A" away from the central point of its core at a distance of >=1 mm and <5 mm, this mathematical expression is satisfied: Ha2-Ha1<5, wherein Ha1 and Ha2 each represents hardness at a point located respectively inside a point Pa and outside the point Pa. Also, at any point Pb included in zone "B" away from the central point of its core at a distance of >=5 mm and @10 mm, this mathematical expression is satisfied: Hb2-Hb1>=5, wherein Hb1 and Hb2 each represents hardness at a point located respectively inside a point Pb and outside the point Pb. This hardness distribution provides a golf ball with reduced energy loss when hit with a driver, and with excellent control performance when hit with a short iron.