Front Fork Lower Tube Weight Reduction via Rolling Thread
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Solution Overview
Problem
Conventional front forks face challenges in weight reduction due to insufficient strength caused by reduced thickness of the screw portion on the lower tube, limiting the extent of thickness reduction.
Innovation Solution
The front fork design incorporates a diameter-reduced portion on the lower tube, where a screw thread is formed by plastic deformation through rolling, maintaining a consistent thickness with the upper portion and enhancing the screw thread's strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the screw portion at the lower end of the lower tube is reduced to achieve weight reduction, then the weight of the front fork decreases, but the strength of the screw thread becomes insufficient
Solution Approach 1:
The invention changes the manufacturing method parameter from cutting to rolling plastic deformation. This parameter change allows the screw thread to be formed by displacing material rather than removing it, thereby maintaining the base thickness while creating the thread structure. The rolling process creates a stronger thread root area because the material is compressed and densified rather than having material removed, resolving the contradiction between weight reduction and strength maintenance.
Solution Approach 2:
The invention applies preliminary plastic deformation to reduce the diameter of the lower end portion before forming the screw thread. This preliminary action creates a smaller diameter base that allows the screw thread to be formed with adequate thickness while maintaining overall weight reduction goals. By pre-shrinking the diameter area, the subsequent rolling process can create strong threads without requiring excessive material thickness.
2Weight of moving object
If the thickness of the lower tube is reduced to meet weight reduction demands, then the weight decreases, but the screw thread strength becomes insufficient
Solution Approach 1:
The invention fundamentally changes the screw thread formation parameter from material removal (cutting) to material displacement (rolling). This allows the lower tube to maintain adequate thickness for strength while still achieving weight reduction through optimized geometry. The rolling process creates threads with stronger roots because the material is compressed into the thread form rather than having material removed, enabling thinner walls to maintain sufficient strength.
Solution Approach 2:
The invention applies local quality by concentrating material and strength exactly where needed - at the screw thread location. The rolling process creates locally densified and strengthened material at the thread root, while other portions of the lower tube can be thinner. This localized strengthening allows weight reduction in non-critical areas while maintaining strength in the critical screw thread region.
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
This approach allows for weight reduction of the lower tube while ensuring the strength of the screw thread portion, facilitating further thickness reduction and weight loss without compromising structural integrity.
Implementation Method 1
a screw thread formed on an outer periphery of a diameter-reduced portion that is reduced in diameter by plastic deformation by rolling at the lower end portion of the lower tube
Data Source
AI summary
A front fork includes: an upper tube; a lower tube that is relatively movable in an axial direction with respect to the upper tube; and an axle bracket screwed to an outer periphery of a lower end portion of the lower tube, in which the lower tube has a screw thread formed on an outer periphery of a diameter-reduced portion that is reduced in diameter by plastic deformation by rolling at the lower end portion of the lower tube and the axle bracket is screwed to the screw thread.