Capacitive Pressure Sensor Tip Geometry for Light-Load Response
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Solution Overview
Problem
Existing pressure detection elements in position indicators face challenges in detecting slight pressure, following pressure changes effectively, and maintaining hysteresis characteristics, leading to trade-offs between on-load and response characteristics.
Innovation Solution
A pressure detection element with a capacitive system, featuring a dielectric with opposing surfaces, a conductor layer on one surface, a conductive elastic member on the other surface, and a pressing member with a curved end surface and protrusion, allowing for improved contact and detection of pen pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conductive elastic member with a protrusion at the tip is used to allow detecting slight pressure, then on-load characteristics are improved, but response characteristics deteriorate because the restoring force acts only in the deformed range
Solution Approach 1:
The pressing member has a non-uniform end surface with a central protrusion that creates localized high-pressure contact at the apex for detecting slight pressure, while the surrounding curved surface provides broader contact area for improved response characteristics during pressure release
Solution Approach 2:
The end surface of the pressing member is designed with a curved surface and central protrusion, where the curvature allows the elastic member to be pushed up more effectively during pressure release, improving response characteristics while maintaining the protrusion's ability to detect slight pressure
2Speed
If the pressing end surface is made closer to a plane to increase contact area, then response characteristics improve, but on-load characteristics deteriorate because large force is necessary to deform the elastic member
Solution Approach 1:
The pressing member combines a curved surface with a central protrusion, where the protrusion concentrates force to a small area for detecting slight pressure, while the overall curved geometry provides sufficient contact area for response characteristics
3Measurement precision
If the end surface has a hemispherical shape with short radius of curvature to improve on-load characteristics, then slight pressure can be detected, but response characteristics deteriorate because restoring force is generated only in the deformed range
Solution Approach 1:
The end surface is designed with a curved surface and central protrusion where the curvature radius is optimized to balance two functions: the protrusion detects slight pressure while the curved surface geometry allows the elastic member to be pushed up more effectively during pressure release, improving response characteristics
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 solution enables reliable detection of pen pressure with enhanced on-load characteristics, response characteristics, and hysteresis characteristics, allowing for accurate detection of tapping operations and continuous input.
Implementation Method 1
A pressure detection element of a capacitive system... The capacitance generated between the first electrode and the second electrode can be detected... When a contact area of the second electrode and the other surface of the dielectric increases, the capacitance value between the first and second terminals increases.
Implementation Method 2
a conductive elastic member provided on the second surface of the dielectric... a pressing member configured to push the conductive elastic member toward the dielectric... the elastic body and the second electrode are pressed against the core and elastically deformed
Data Source
AI summary
A pressure detection element of a capacitive system includes a dielectric having two opposing surfaces including a first surface and a second surface, a conductor layer provided on the first surface of the dielectric, a conductive elastic member provided on the second surface of the dielectric, a spacer that positions the conductive elastic member at a predetermined distance from the second surface of the dielectric, and a pressing member configured to push the conductive elastic member toward the dielectric. An end surface of the pressing member that presses the conductive elastic member has a predetermined curvature, with an apex at a center of the end surface. A protrusion is provided at the apex at the center of the end surface of the pressing member.