Switch Nub Non-Linear Tactile Feedback Design
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Solution Overview
Problem
Conventional switches with tactile (click) action face challenges in maintaining a comfortable tactile feel when downsized, as misalignment of the pressing position can lead to a decrease in the click ratio and an unsatisfactory tactile experience due to linear acting load to displacement characteristics.
Innovation Solution
A switch design incorporating a click spring with a circumferential edge and a movable contact, a spring holding sheet, and a Nub on the spring holding sheet with a non-linear acting load to displacement characteristic, where the Nub is formed in a cylindrical shape to achieve specific displacement and spring constants that satisfy certain inequalities, ensuring a comfortable tactile feel even in a small size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switch is downsized, then the device size is reduced, but the tactile feel deteriorates due to misalignment of pressing position
Solution Approach 1:
The pressing surface is divided into multiple regions with different tactile characteristics. The first pressing region provides a first tactile feel while the second pressing region provides a second tactile feel, allowing different areas of the switch to serve different functional purposes and maintain tactile quality despite size reduction
Solution Approach 2:
The single pressing surface is segmented into multiple independent pressing regions, each capable of providing distinct tactile feedback. This segmentation allows the switch to maintain comfortable tactile feel across different pressing positions even when downsized
2Reliability
If a Nub is added to the spring holding sheet, then the click ratio is maintained against misalignment, but the device complexity increases
Solution Approach 1:
The spring holding sheet is designed with locally differentiated regions: a first region that contacts the click spring and a second region that contacts the circuit board. This local quality differentiation allows the sheet to provide both mechanical support and alignment functions without adding separate components
Solution Approach 2:
The spring holding sheet performs multiple functions simultaneously: it holds the click spring, provides pressing surfaces, ensures electrical contact alignment, and maintains click ratio. By making the sheet multi-functional, the design avoids adding separate alignment components that would increase complexity
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 non-linear acting load to displacement characteristic of the switch provides a comfortable tactile experience by adjusting the Nub's diameter and shape, allowing for effective tactile feedback in downsized switches, enhancing the tactile feel and operational comfort.
Implementation Method 1
a click spring that generates a tactile action by being pressed down
Implementation Method 2
an Nub disposed on the spring holding sheet and having a non-linear acting load to displacement characteristic
Data Source
AI summary
A switch includes a click spring, stationary contacts, a spring holding sheet, a switch base, and a nub disposed on the sheet and having a non-linear acting load to displacement characteristic. Spring constant k11 (tangent gradient of the characteristic curve of the a nub at an origin point), spring constant k3 (gradient of a line connecting a point corresponding to a peak acting load and an origin point of a characteristic curve of the click spring and the sheet), spring constant k12 (tangent gradient at an arbitrary point of a non-linear portion of the characteristic curve of the nub), and displacement s11 (displacement corresponding to an intersection point of the line having the gradient k11 and the line having the gradient k12) satisfy k11<k3, k12>k3, and 0<s11<S1.