Golf Ball Core Hardness Gradient for Spin Control
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Solution Overview
Problem
Conventional golf balls with an outer-hard/inner-soft structure suffer from inadequate continuity of hardness distribution, leading to poor spin suppression and feel at impact, particularly with drivers and short irons, due to a large hardness level difference between the center and mid layer.
Innovation Solution
A golf ball design featuring a core with a center and mid layer, where the center has a diameter of 1 mm or greater and 15 mm or less, and a hardness difference of 10 or more between the core's surface and mid layer's innermost part, with a Shore D hardness outer cover less than 40, achieving an outer-hard/inner-soft structure for improved continuity and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional outer-hard/inner-soft structure is used with a soft center and hard mid layer, then spin suppression is improved, but the hardness distribution continuity deteriorates due to large level difference at the boundary
Solution Approach 1:
The patent applies local quality by creating distinct hardness zones within the core: a soft center (H1: 20-50) for spin suppression, a mid layer with gradient hardness (H2: 25-70) transitioning from inner to outer regions, and a hard surface layer (H4: 75-95) for overall structure stability. This localized variation in material properties resolves the contradiction between spin suppression and hardness continuity.
Solution Approach 2:
The patent changes the hardness parameter continuously from the center outward through the mid layer, with H1 (center) < H2 (surface of center) < H3 (innermost part of mid layer) < H4 (surface of core). This parameter gradient transformation eliminates abrupt transitions while maintaining the outer-hard/inner-soft structure, simultaneously achieving spin suppression and hardness continuity.
2Reliability
If a hard cover is used to achieve outer-hard structure, then spin suppression is improved, but feel at impact and controllability deteriorate
Solution Approach 1:
The patent applies local quality by making the outer cover softer (Shore D H7: 10-40) compared to the core surface hardness (H4: 75-95). This localized softness at the outermost layer provides improved feel at impact and controllability for short iron shots, while the overall outer-hard/inner-soft structure maintains spin suppression performance.
3Ease of operation
If a soft center is used to improve feel at impact, then resilience performance deteriorates
Solution Approach 1:
The patent applies local quality by creating a soft center (H1: 20-50) for feel at impact while surrounding it with progressively harder layers (mid layer H2: 25-70, surface H4: 75-95) that provide the necessary structural support for resilience performance. This localized softness without sacrificing overall strength resolves the contradiction.
Solution Approach 2:
The patent uses composite material structure with multiple layers of different hardness properties: soft center material for feel, mid layer material with gradient properties for transition, and hard surface material for structural integrity. This composite approach allows the soft center to provide feel at impact while the harder surrounding layers maintain resilience performance.
Data Source
AI summary
A golf ball 2 has a core 4, an inner cover 6 positioned outside the core 4 and an outer cover 8 positioned outside the inner cover 6. The core 4 has a spherical center 10 and a mid layer 12 positioned outside the center 10. The center 10 has a diameter of 1 mm or greater and 15 mm or less. A difference (H4−H3) between a JIS-C hardness H4 of a surface of the core and a JIS-C hardness H3 of an innermost part of the mid layer is equal to or greater than 10. The hardness H4 is greater than a JIS-C hardness H2 of a surface of a spherical body including the core 4 and the inner cover 6. A Shore D hardness H7 of the outer cover 8 is less than 40.