Developing Unit Rectangular AC Voltage for Image Unevenness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The small-sized tandem-type image forming apparatus experiences significant fluctuations in the developing gap, leading to image unevenness due to changes in the developing electric field, which affects both solid and halftone dot images, and existing technologies fail to effectively control image density and prevent toner scattering or adverse effects on fixing performance.
Innovation Solution
A developing unit with a developing roller and voltage-applying means that applies a developing bias voltage with a rectangular waveform AC voltage, having a duty ratio of 50% or more for developing the electrostatic latent image, and multiple cycles to ensure toner attachment, along with a voltage for pulling toner back to the roller, to stabilize image formation across varying gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the apparatus is downsized to reduce overall size, then the compactness is improved, but the fluctuation in developing gap becomes larger
Solution Approach 1:
The patent applies a rectangular waveform AC voltage with 50% or more duty ratio to the developing roller, changing the electrical parameter characteristics to compensate for mechanical instability. This voltage waveform ensures sufficient toner attachment time while pulling back excess toner, maintaining consistent image density despite developing gap fluctuations caused by downsizing.
Solution Approach 2:
The patent introduces dynamic voltage control with multiple cycles of rectangular waveform AC voltage that adapts to the developing gap conditions. The voltage alternates between attracting and pulling back toner in a controlled dynamic manner, compensating for the increased mechanical fluctuations inherent in compact apparatus designs.
2Adaptability or versatility
If the developing gap fluctuates, then the adaptability to compact design is improved, but the image density uniformity deteriorates
Solution Approach 1:
The patent changes the voltage application parameters by using rectangular waveform AC voltage with 50% or more duty ratio and multiple cycles, ensuring that toner attachment and pull-back processes are sufficiently completed despite varying gap conditions, thereby maintaining uniform image density in compact designs.
Solution Approach 2:
The patent implements an electrical feedback mechanism where the rectangular waveform voltage with pull-back phase compensates for gap variations. The multiple cycles allow the system to self-regulate toner distribution, providing feedback control that maintains image quality adaptability across different developing gap conditions.
3Manufacturing precision
If the AC voltage duty ratio is increased to 50% or more, then the toner attachment consistency is improved, but the energy consumption increases
Solution Approach 1:
The patent employs periodic rectangular waveform AC voltage with 50% or more duty ratio applied in multiple cycles. This periodic action alternates between toner attraction and pull-back phases, ensuring consistent attachment while managing energy consumption through the structured temporal pattern of voltage application.
Solution Approach 2:
The patent maintains continuous useful action by applying the rectangular waveform voltage across multiple cycles without interruption. The 50% or more duty ratio ensures that the useful toner attachment action continues sufficiently throughout each cycle, maintaining consistency while the periodic nature manages overall energy usage.
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 effectively suppresses image unevenness by ensuring consistent toner attachment and distribution, reducing density fluctuations in halftone dot images and preventing fog phenomena, even when the developing gap widens or narrows, thereby maintaining high image quality.
Implementation Method 1
voltage-applying means adapted to apply a developing bias voltage to the developing roller, in such a manner as to cause the toner transported by the developing roller to fly onto a surface of the image support member
Data Source
AI summary
A developing unit has a voltage-applicator (80) to apply a developing bias voltage to a developing roller (72). The voltage-applicator (80) applies the developing bias voltage for a first duration to apply an AC voltage having a rectangular waveform, and a second duration to stop applying the AC voltage. The AC voltage has a duty ratio of 50% or more in a direction for causing toner to develop an electrostatic latent image. The number of cycles of the AC voltage in the first duration is two or more, and the AC voltage has a voltage in a direction for pulling the toner back to the developing roller, just before transition to the second duration. The developing unit suppresses occurrence of image unevenness due to a fluctuation in developing gap. Thus, an image forming apparatus equipped with the developing unit forms a high-quality image while suppressing image unevenness.