Capacitive Key Input Structure Without Membrane Switch Interference
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Solution Overview
Problem
Existing input devices, such as those described in PTL 1, often fail to accurately output key information and positional information due to inappropriate changes in capacitance, primarily because the membrane switch sheet interferes between the user's finger and the electrode sheet, preventing proper capacitance detection.
Innovation Solution
The input device eliminates the need for a membrane switch sheet by directly sensing capacitance changes on an electrode sheet, allowing for accurate detection of capacitance changes at multiple positions, which enables appropriate output of key information and positional information without the membrane switch sheet's interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a membrane switch sheet is disposed between the electrode sheet and the user's finger, then the device structure is more complete with dedicated switch functionality, but the capacitance detection accuracy deteriorates due to interference from the membrane switch sheet
Solution Approach 1:
The patent removes the membrane switch sheet from between the electrode sheet and the user's finger. The electrode sheet is positioned to directly face the user's finger without the membrane switch sheet in between, eliminating the interference that prevented accurate capacitance detection while maintaining switch functionality through the keyboard structure itself
2Reliability
If a membrane switch sheet is disposed between the electrode sheet and the user's finger, then the device has dedicated switch components, but the device structure becomes more complex
Solution Approach 1:
The patent combines the switch functionality with the keyboard structure itself. The keyboard keys are configured to directly interact with the electrode sheet, eliminating the need for a separate membrane switch sheet. This merging of functions simplifies the overall device structure while maintaining reliable switch operation
3Measurement precision
If the electrode sheet directly senses capacitance changes without a membrane switch sheet, then the capacitance detection accuracy improves, but the protection of the electrode sheet from direct finger contact is reduced
Solution Approach 1:
The patent introduces the keyboard keys as an intermediary between the user's finger and the electrode sheet. The keys allow capacitance detection to occur through their structure while providing physical protection and a tactile interface for the user, mediating between the need for direct capacitance sensing and the need to protect the electrode sheet
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 solution allows for reliable output of key and positional information, simplifies the device structure, and provides an appropriate typing experience by ensuring accurate capacitance detection when a user's finger approaches a key or presses it, effectively addressing the limitations of previous configurations.
Implementation Method 1
The electrode sheet directly senses a change in capacitance at a position where an object approaches when the object approaches the electrode sheet
Data Source
AI summary
An input device of the present disclosure includes an electrode sheet, a plurality of keys, and a controller. The electrode sheet directly senses a change in capacitance at a position where an object approaches when the object approaches the electrode sheet. The plurality of keys are depressibly disposed on the electrode sheet. The controller detects capacitance change amounts at a plurality of positions on the electrode sheet, outputs positional information indicating the position, among the plurality of positions, at which a capacitance change amount detected satisfies a first given condition, and outputs key information indicating a key among the plurality of keys corresponding to the position, among the plurality of positions, at which a capacitance change amount detected satisfies a second given condition.