Position Detecting Device Wiring Area Capacitance Shielding
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Solution Overview
Problem
Position detection accuracy is compromised when wiring is arranged adjacent to the detection area in existing capacitance-based position detecting devices due to changes in capacitance caused by human body proximity.
Innovation Solution
A position detecting device with a sensor substrate featuring detection electrodes and a conductor connected to a fixed potential, positioned opposed to the wiring area, prevents capacitance changes by using a flexible substrate and a conductor shape that reduces eddy currents, thereby maintaining detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wiring is arranged adjacent to the detection area, then the device structure is simplified and easier to manufacture, but position detection accuracy deteriorates due to capacitance changes when human body approaches the wiring
Solution Approach 1:
A ground conductor is introduced as an intermediary element between the detection area and the wiring area. This ground conductor acts as a shield that prevents capacitive coupling between the human body and the wiring, thereby eliminating the harmful capacitance changes while allowing the wiring to remain in the adjacent area for manufacturing simplicity
Solution Approach 2:
The harmful capacitive effect is extracted and isolated by separating the wiring area from the detection area using a ground conductor barrier. The wiring is taken out from the immediate detection zone and placed in a dedicated wiring area where it cannot interfere with the detection capacitance
2Length of moving object
If the sensor substrate is placed on the surface of the case, then the device thickness is reduced, but capacitance stability deteriorates when human body approaches the wiring area
Solution Approach 1:
The ground conductor serves as a mediator between the sensor substrate and the external environment. When the sensor substrate is placed on the case surface, the ground conductor prevents direct capacitive interaction between the human body and the sensitive wiring areas, maintaining capacitance stability despite the thin profile
3Stability of the object's composition
If a conductor is provided at the position opposed to the wiring area, then capacitance stability is improved, but device complexity increases
Solution Approach 1:
The ground conductor is designed with a homogeneous continuous structure that covers the entire wiring area. This uniform grounding provides consistent capacitance shielding across all wiring regions without requiring complex segmented designs or multiple discrete conductors
Solution Approach 2:
The ground conductor is merged with the case structure or the sensor substrate backing layer, combining the shielding function with the existing structural elements. This integration eliminates the need for separate complex shielding mechanisms while achieving capacitance stability
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 effectively prevents lowering of position detection accuracy by stabilizing capacitance and reducing eddy currents, allowing for precise position detection using both capacitance and electromagnetic induction systems.
Implementation Method 1
the capacitance of the wiring included in the wiring area does not change even when a human body part is brought close to the wiring
Implementation Method 2
the above-described conductor has a shape that reduces the occurrence of an eddy current on the surface
Implementation Method 3
The magnetic flux detection substrate has at least one loop coil for detecting magnetic flux generated by a coil provided in a position indicator
Data Source
AI summary
A position detecting device is disclosed, which detects a position indicated by a human body. The position detecting device includes: a sensor substrate including a detection area, in which a plurality of detection electrodes are formed, and a wiring area, in which wiring led out from the detection electrodes is formed, and a case configured to house the sensor substrate. The sensor substrate further includes a conductor, which is connected to a fixed potential, provided at a position opposed to (facing) the wiring area.