Powder Sensor Phase Judgment Circuit Vibration Noise Immunity
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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 incorrectly detected as absent.
Innovation Solution
A powder sensor design incorporating a piezoelectric element, an oscillator circuit, a first square wave signal generator, a second square wave signal generator, and a phase judgment circuit, which generates and processes square wave signals to reduce noise-induced misjudgments by only transitioning during specific detection terms, utilizing a phase judgment circuit to determine toner presence or absence based on phase comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional phase comparison method is used for powder detection, then simple detection structure is achieved, but misjudgment occurs due to vibration or shock causing phase shift
Solution Approach 1:
The patent applies preliminary action by generating a clear signal before the detection term to reset the second square wave signal to its initial level. This preparation step ensures that any phase shifts caused by vibrations or shocks occurring outside the detection term do not affect the detection result, thereby preventing misjudgment while maintaining a relatively simple detection structure.
Solution Approach 2:
The patent implements periodic action by dividing the detection process into distinct cycles with detection terms and non-detection terms. The oscillator circuit generates periodic output signals that drive the piezoelectric element in regular cycles. By confining phase comparisons to specific detection terms within each cycle and resetting between cycles using the clear signal, the system achieves reliable powder detection despite periodic vibrations or shocks from the photocopier motor.
2Speed
If phase comparison is performed continuously, then detection responsiveness is improved, but false detection occurs due to noise-induced phase shifts
Solution Approach 1:
The patent implements periodic action by dividing the detection process into distinct cycles with detection terms and non-detection terms. The oscillator circuit generates periodic output signals that drive the piezoelectric element in regular cycles. By confining phase comparisons to specific detection terms within each cycle and resetting between cycles using the clear signal, the system achieves reliable powder detection despite periodic vibrations or shocks from the photocopier motor.
Solution Approach 2:
The patent extracts only the necessary phase comparison operation from the continuous signal processing and confines it to specific detection terms. The second square wave signal generator is designed to transition only when the first square wave signal changes during the detection term, effectively extracting and isolating the useful detection signal from the noisy continuous waveform while ignoring phase shifts occurring outside the detection window.
3Reliability
If detection window is restricted to specific term, then noise immunity is improved, but detection coverage may be reduced
Solution Approach 1:
The patent implements periodic action by dividing the detection process into distinct cycles with detection terms and non-detection terms. The oscillator circuit generates periodic output signals that drive the piezoelectric element in regular cycles. By confining phase comparisons to specific detection terms within each cycle and resetting between cycles using the clear signal, the system achieves reliable powder detection despite periodic vibrations or shocks from the photocopier motor.
Solution Approach 2:
The patent maintains continuity of useful action by performing the detection operation repeatedly in each cycle during the detection term. Although the phase comparison is restricted to specific terms, the periodic repetition ensures continuous monitoring of powder presence. The oscillator continuously drives the piezoelectric element through multiple cycles, and each detection term provides another opportunity to detect powder, maintaining effective continuous detection coverage.
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 or eliminates misjudgments caused by vibrations or shocks, maintaining accurate toner detection even in noisy environments, and is suitable for integration into IC configurations for cost reduction.
Implementation Method 1
a powder sensor element (two-terminal piezoelectric element)
Implementation Method 2
an oscillator circuit, which applies to the piezoelectric element 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 first square wave signal generator, a second square wave signal generator, and a phase judgment 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 first square wave signal generator generates a first square wave signal by converting a terminal voltage of the piezoelectric element. The second square wave signal generator generates a second square wave signal that transits from an initial level to a detection level when the first square wave signal rises or falls in a detection period and that does not transit outside of the detection period. The detection period is a part of each cycle of the output signal of the oscillator circuit. The phase judgment circuit determines phase of the second square wave signal.