Development Bias Voltage Generating Circuit for Image Forming Apparatus
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Solution Overview
Problem
Conventional development bias voltage generating circuits for electrophotographic image forming apparatuses face challenges in efficiently applying pulse waveforms with blank periods and duty ratios other than 50%, leading to increased component count, size, and cost, as well as difficulties in generating desirable voltages due to magnetic flux saturation and capacitor smoothing effects.
Innovation Solution
A development bias voltage generating circuit utilizing a transformer, capacitor, and switching elements, with a control unit to independently control voltages and switching actions, allows for the application of pulse waveforms with blank periods and duty ratios other than 50%, using an H-bridge circuit configuration and voltage control to maintain balanced positive and negative voltages and adjust for load imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional development bias voltage generating circuits are used to apply pulse waveforms with blank periods and duty ratios other than 50%, then image development quality can be improved, but device complexity, size, and cost increase
Solution Approach 1:
The patent employs a universal H-bridge circuit configuration that can generate multiple types of pulse waveforms (50% duty ratio, non-50% duty ratio, and blank period waveforms) using the same basic circuit structure. This multi-functional approach eliminates the need for separate circuits for each waveform type, thereby reducing device complexity while maintaining image development quality
Solution Approach 2:
The patent implements dynamic control of the H-bridge circuit through a control unit that adjusts switching element operation based on required waveform characteristics. By dynamically controlling the timing and duration of voltage applications, the circuit can adapt to generate different duty ratios and blank periods without physical reconfiguration, reducing component count while achieving precise voltage control for quality image development
2Reliability
If conventional circuits are used to generate pulse waveforms with non-50% duty ratios, then developing ability is improved, but magnetic flux saturation and capacitor smoothing effects prevent desirable voltages
Solution Approach 1:
The patent incorporates feedback mechanisms where the control unit monitors the actual voltage output and adjusts the switching element operation accordingly. This feedback loop compensates for magnetic flux saturation and capacitor smoothing effects by dynamically adjusting the duty cycle and switching timing, ensuring accurate voltage generation for non-50% duty ratios while maintaining reliable developing ability
Solution Approach 2:
The patent changes operational parameters of the H-bridge circuit by adjusting switching element timing and duration based on the required voltage characteristics. For non-50% duty ratios, the control unit modifies the on-time and off-time parameters to achieve the desired voltage waveform, overcoming the limitations of magnetic flux saturation and capacitor smoothing while maintaining voltage accuracy and developing ability
3Productivity
If high voltage is applied to development gap, then development process is effective, but ring marks are generated on recording paper
Solution Approach 1:
The patent applies periodic pulse waveforms with controlled duty ratios and blank periods to the development bias voltage generating circuit. By using periodic action with specific timing characteristics, the circuit can maintain sufficient development effectiveness while creating blank periods that prevent continuous high voltage exposure, thereby reducing ring mark generation on recording paper
Solution Approach 2:
The patent dynamically adjusts the development bias voltage through controlled switching elements with variable duty ratios and blank periods. This dynamic control allows the system to optimize development effectiveness during active periods while introducing pauses that prevent ring marks, achieving a balance between productivity and quality without harmful artifacts
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 configuration enables the accurate and efficient application of development bias voltages with predetermined blank periods and duty ratios, improving image development quality by maintaining balanced voltages and correcting for load imbalances, thus stabilizing the developing process.
Implementation Method 1
a transformer (T1), a capacitor (C1) connected to one end of a primary winding of the transformer
Implementation Method 2
a capacitor (C1) connected to one end of a primary winding of the transformer
Data Source
AI summary
An image forming apparatus includes a charging device to electrically charge a photosensitive member, an exposure unit to expose the charged photosensitive member to light, a development device to develop, with a developer, a latent image formed on the photosensitive member by the exposure unit, and a development bias voltage generating circuit to apply a development bias voltage to the development device. The development bias voltage generating circuit includes a transformer, a capacitor connected to one end of the transformer, first-fourth switching elements, a power source to supply a voltage to the first and third switching elements, and a control unit to control an on and off action of the first to fourth switching elements and independently control the voltages applied by the power source to the first and third switching elements.