Capacitive Stylus with Piezoelectric Tip for Pressure Sensing
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Solution Overview
Problem
Conventional capacitive and electromagnetic styluses fail to accurately depict lines with varying thicknesses and require additional costly components like electromagnetic sensor boards for pressure sensing, limiting their functionality and increasing costs.
Innovation Solution
A stylus with a conductive pen tip that generates capacitance changes on capacitive touch panels for position detection and emits electromagnetic signals for pressure sensing, featuring a magnetic core, induction coil, and a pen tip with a cylindrical and spherical surface design to increase contact area and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitive stylus with conductive rubber or foam is used, then touch input accuracy is improved compared to finger input, but the ability to depict lines with various thicknesses and realize pressure sensing is lost
Solution Approach 1:
The patent merges the capacitive touch function and electromagnetic pressure sensing function into a single stylus body. The conductive pen tip provides capacitive coupling for position detection, while the piezoelectric crystal embedded in the pen tip generates electromagnetic signals in response to applied pressure, combining both functionalities without requiring separate devices or additional sensor boards.
Solution Approach 2:
The stylus is designed to perform multiple functions: it acts as a capacitive touch input device for position detection and simultaneously as a pressure sensing device through the piezoelectric crystal. This multi-functional design allows the single stylus to replace both conventional capacitive stylus and electromagnetic stylus with pressure sensing, eliminating the need for costly electromagnetic sensor boards.
2Adaptability or versatility
If an electromagnetic sensor board is added behind the touchscreen to achieve pressure sensing, then pressure-sensitive input capability is improved, but device complexity and cost are significantly increased
Solution Approach 1:
The patent extracts the pressure sensing function from the touchscreen system and relocates it to the stylus itself. Instead of adding an electromagnetic sensor board to the touchscreen, the piezoelectric crystal is embedded directly in the pen tip, transferring the sensing capability to the input device and eliminating the need for additional sensor boards in the touchscreen assembly.
Solution Approach 2:
The piezoelectric crystal acts as an intermediary that converts mechanical pressure directly into electromagnetic signals within the stylus. This intermediary mechanism enables pressure sensing without requiring complex electromagnetic sensor boards behind the touchscreen, simplifying the overall system architecture.
3Measurement precision
If the pen tip contact area is increased to improve pressure sensing, then pressure sensitivity is improved, but writing accuracy for fine locations deteriorates due to larger pen tip size
Solution Approach 1:
The pen tip is designed with non-uniform geometry, featuring a broader contacting portion for pressure distribution and a narrower rod portion for precision. This local quality variation allows the broader end to enhance pressure sensing while the overall compact design maintains writing accuracy for fine locations.
Solution Approach 2:
The contacting portion of the pen tip features a spherical or curved surface that distributes pressure over a larger area, improving pressure sensing capability. The curved geometry also provides stable contact with the touchscreen surface while maintaining a compact overall pen tip size for accurate positioning.
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
Enables accurate position detection and pressure-sensitive input on capacitive touch panels without the need for additional sensor boards, enhancing writing accuracy and pressure sensitivity while maintaining a compact design.
Implementation Method 1
When a finger is closes to or contacts the touch panel, a coupling capacitor is formed between the finger and the transparent electrode patterns because the finger is a conductor and has static electricity. Meanwhile, electrical capacitance of the electrode positioned at a touch point on the touch panel will change
Implementation Method 2
the stylus can also emit the electromagnetic signal to have the function of the pressure sensing
Data Source
AI summary
A stylus provided in the present invention is utilized to input accompanying with a capacitive touch panel. The stylus includes a housing, a magnetic core and a pen tip. The magnetic core is disposed inside the housing. The magnetic core has an axial through hole which defines a bore diameter. The pen tip is disposed at an end of the housing, and the pen tip is made of conductor. The pen tip has a rod portion and a contacting portion. The rod portion is inserted into the axial through hole, and the contacting portion protrudes from the pen shell. The contacting portion has a cylindrical surface and a part spherical surface. The cylindrical surface defines a first diameter; the part spherical surface defines a second diameter. The first diameter is less than the second diameter, and the first diameter is greater than or equal to the bore diameter.