Touch Input Device Position Fixing Mechanism

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Solution Overview

Problem

Touch input devices that detect both touch position and pressing amount often inaccurately change the detected operation position when a pressing force is applied, leading to unintended changes in operation input contents, such as image enlargement or reduction.

Innovation Solution

A touch input device comprising a touch sensor, a pressing sensor, and a control unit that fixes the operation position before a pressing force is applied, using thresholds to determine when to stabilize the detected position and when to allow movement, and utilizing a piezoelectric film made of uniaxially stretched polylactic acid for sensitive press detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a pressure-sensitive sensor and touch panel are overlapped to detect both touch position and pressing amount, then the device can detect operation inputs with pressing force, but the detected operation position changes inaccurately when pressing force is applied

Engineering Contradiction:

Improvedetection capabilityVSAvoidoperation position detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The control unit stores the operation position detection result obtained before the press detection signal exceeds the threshold as a reference position. When the press detection signal exceeds the threshold, the control unit uses this previously stored position instead of the current detected position, thereby preventing the operation position from changing due to pressing force application.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control unit introduces a threshold-based intermediary mechanism that mediates between the touch sensor and pressing sensor. When the press detection signal exceeds the threshold, the control unit switches to using the stored reference position, effectively filtering out the inaccurate position changes caused by pressing force while still allowing position detection during light touch.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the operation position is allowed to change with pressing force, then the device can detect dynamic finger movements, but unintended changes in operation input contents occur

Engineering Contradiction:

Improvefinger movement detectionVSAvoidoperation input accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control unit preemptively counteracts the harmful effect of pressing force on position detection by switching to the stored reference position when the press detection signal exceeds the threshold, preventing unintended changes in operation input contents before they can occur.

Inventive Principle:

Principle #9Preliminary anti-action

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

Prevents erroneous detection of the operation position due to changes in pressing force, allowing accurate determination of intended operation inputs, including precise image enlargement or reduction based on the operator's intended pressing amount.

Implementation Method 1

utilizing a piezoelectric film made of uniaxially stretched polylactic acid for sensitive press detection

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10013093B2Touch input device and touch input detecting method

Publication Date: 2018.07.03 MURATA MFG CO LTD

AI summary

A touch input device that includes an operation input unit, a control unit, a memory unit and a display unit. The operation input unit includes a pressing sensor and a touch sensor. When obtaining a detected operation position (x, y) based on an operation detection signal from the touch sensor, the control unit compares a signal level DSp of a press detection signal from the pressing sensor and a first threshold THSp. When determining that the signal level DSp is larger than the first threshold THSp, the control unit reads the detected operation position (x, y) obtained immediately before the determination, and fixes the detected operation position (x, y). The control unit determines operation input contents by using the fixed detected operation position (x, y) and a pressing amount based on the signal level DSp obtained at each sampling timing.