Piezoelectric Powder Sensor Phase Detection for Vibration Noise
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Solution Overview
Problem
Conventional powder sensors for photocopier toner detection are prone to misjudgment due to vibrations or shocks, especially in environments with increased mechanical activity, leading to false negatives where toner is present.
Innovation Solution
A powder sensor design incorporating a piezoelectric element, an oscillator circuit, and a phase judgment circuit that requires consecutive phase judgments to determine the absence of toner, reducing false positives by setting a threshold for phase lead or lag, thereby enhancing reliability in noisy environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional phase detection method is used to detect powder presence/absence, then the detection is simple and responsive, but misjudgment occurs when vibration or shock is applied
Solution Approach 1:
The system performs preliminary phase detection multiple times (n consecutive detections) before making a final powder presence/absence judgment. This preliminary repeated detection filters out temporary phase shifts caused by vibration or shock, ensuring that only consistent phase shift patterns trigger a powder absence judgment, thereby eliminating misjudgments while maintaining a straightforward detection architecture.
2Volume of moving object
If the sensor is made compact to reduce size, then the overall device size is reduced, but the piezoelectric element becomes more susceptible to vibration influence
Solution Approach 1:
The system incorporates feedback through multiple consecutive phase detections and comparison with threshold values. The phase detection circuit continuously monitors phase shifts, and when n consecutive detections indicate a phase shift beyond the threshold, the system confirms powder absence. This feedback mechanism compensates for the increased vibration susceptibility of compact piezoelectric elements by filtering out transient vibrations and relying on sustained phase shift patterns.
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 reduces misjudgments caused by vibrations or shocks, ensuring accurate toner detection by requiring multiple consecutive phase judgments, thus improving the sensor's reliability and accuracy in environments susceptible to mechanical noise.
Implementation Method 1
a powder sensor element (two-terminal piezoelectric element)
Implementation Method 2
an output signal having a frequency equal to or near a resonance frequency of the piezoelectric element
Data Source
AI summary
A powder sensor includes a piezoelectric element, an oscillator circuit, a phase determination circuit, and a powder presence/absence determination circuit. The oscillator circuit applies to the piezoelectric element an output signal having a frequency equal to or near a resonance frequency of the piezoelectric element. The phase determination circuit determines phase of a terminal voltage of the piezoelectric element relative to phase of the output signal from the oscillator circuit. The powder presence/absence determination circuit determines that powder is absent if the phase determination circuit determines, n consecutive times (where “n” is an arbitrary integer satisfying n≧2), that the phase of the terminal voltage of the piezoelectric element, relative to the phase of the output signal from the oscillator circuit, satisfies a predetermined condition.