Multi-piece Golf Ball Core Hardness Gradient for Spin and Durability
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Solution Overview
Problem
Multi-piece solid golf balls fail to achieve a low spin rate and adequate durability to cracking and scuff resistance, particularly when used by amateur golfers with moderate head speed.
Innovation Solution
A multi-piece solid golf ball design with a core, envelope layer, and cover, where the core hardness increases from center to surface, and the hardness relationship among the layers is optimized, with specific thickness and material compositions to reduce spin rate and enhance durability and scuff resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the hardness relationship between intermediate layer and cover layer is optimized, then flight performance is improved, but durability to cracking and scuff resistance deteriorate
Solution Approach 1:
The patent applies local quality by creating different hardness characteristics in different regions of the core. The core has a softer center region and a harder surface region, with specific hardness values assigned to different radial positions. This gradient hardness profile allows the core to provide both flight performance (through the softer inner region) and durability (through the harder outer region), resolving the contradiction between improved flight performance and maintained durability.
Solution Approach 2:
The patent uses composite materials by combining multiple layers with different hardness characteristics. The core, intermediate layer, and cover layer are constructed as composite structures where each layer has specifically assigned hardness values. The core has hardness values ranging from 30-70 at the center to 70-90 at the surface, while the intermediate and cover layers have progressively higher hardness values. This composite approach enables simultaneous optimization of flight performance and durability to cracking and scuff resistance.
2Speed
If core hardness is increased to reduce spin rate, then distance is improved, but scuff resistance deteriorates
Solution Approach 1:
The patent resolves this contradiction by applying local quality through a radial hardness gradient in the core. The core center has lower hardness (30-70) while the core surface has higher hardness (70-90). This gradient allows the core to generate low spin rates (through the softer inner region) while maintaining scuff resistance (through the harder outer region that contacts the club face and environment).
Solution Approach 2:
The patent applies parameter changes by systematically varying the hardness parameter through the core radius. Specific hardness values are assigned at different radial positions: 30-70 at the center and 70-90 at the surface. This controlled parameter change enables the core to simultaneously achieve low spin rates and high scuff resistance, as the hardness transitions from softer inner regions (reducing spin) to harder outer regions (preventing scuffs).
Data Source
AI summary
The present invention provides a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer, and a cover, in this order, and has formed on a surface thereof a plurality of dimples. The core has a hardness which gradually increases from a center to a surface thereof, the hardness difference in JIS-C hardness units between the core center and the core surface being at least 15 and, letting (I) be the average value for cross-sectional hardnesses at a position about 15 mm from the core center and at the core center and letting (II) be the cross-sectional hardness at a position about 7.5 mm from the core center, the hardness difference (I)−(II) in JIS-C units being not more than ±2. The envelope layer, intermediate layer and cover have hardnesses which satisfy the condition: cover hardness>intermediate layer hardness>envelope layer hardness.