Developing Device Duty Ratio Control for Transformer Magnetization
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Solution Overview
Problem
In image forming apparatuses using touch down developing methods, changing the duty ratio of the switching element can lead to asymmetric magnetization in transformers, resulting in overcurrent and potential breakdown of switching elements, and voltage fluctuations between capacitors cause large currents to flow at specific times.
Innovation Solution
The developing device step-wise changes the duty ratio of the control clock signal applied to the developing roller, utilizing a transformer and capacitor circuit to manage voltage and prevent large currents by adjusting the duty ratio in predetermined time slots, ensuring safe and quick transitions without magnetic saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the duty ratio of the switching element is changed to prevent leakage or uneven toner image, then image quality is improved, but asymmetric magnetization occurs in the transformer causing overcurrent and potential breakdown of the switching element
Solution Approach 1:
The control unit waits for the voltage between capacitor electrodes to return to a predetermined level before changing the duty ratio. This preliminary waiting action prevents asymmetric magnetization and overcurrent by ensuring the transformer is in a stable state before duty ratio adjustment, thus protecting the switching element while still allowing image quality optimization
Solution Approach 2:
The control unit monitors the voltage between capacitor electrodes and uses this feedback to determine when it is safe to change the duty ratio. By continuously checking the voltage level and waiting for it to return to the predetermined level, the system implements feedback control that prevents harmful current surges while enabling duty ratio adjustments for image quality optimization
2Speed
If the duty ratio is changed during voltage fluctuation period of the capacitor, then rapid response is achieved, but large current flows in the switching element at specific timing
Solution Approach 1:
The control unit performs a preliminary check of the voltage level before allowing duty ratio changes. By waiting for the voltage to return to the predetermined level, the system avoids changing duty ratio during harmful voltage fluctuation periods, preventing large current flow while still enabling rapid response when safe
3Reliability
If step-wise duty ratio change is implemented to prevent asymmetric magnetization, then switching element breakdown is prevented, but the time required for duty ratio adjustment increases
Solution Approach 1:
The control unit waits for the voltage to return to a predetermined level before changing the duty ratio. This preliminary action prevents asymmetric magnetization and protects the switching element, while the waiting period is minimized by monitoring the voltage recovery process efficiently
Solution Approach 2:
The control unit uses feedback from voltage monitoring to determine the optimal timing for duty ratio changes. By waiting only until the voltage returns to the predetermined level, the system achieves the minimum necessary wait time to prevent harmful effects, balancing reliability with adjustment speed
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 approach prevents large current flow in switching elements and allows for rapid duty ratio adjustments, enhancing image quality and preventing leakage issues while maintaining the integrity of the switching components.
Implementation Method 1
a transformer (82) connected to the capacitor (81) in the primary and outputting alternating voltage to be applied to the developing roller (11) from the secondary
Implementation Method 2
voltage between electrodes of the capacitor is periodically fluctuated due to energy oscillation between the primary of the transformer and the capacitor
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A developing device includes a developing roller, a magnetic roller, a capacitor, a transformer, and a switching portion. The magnetic roller supplies toner to the developing roller or takes off the toner from the same. The capacitor is connected to a primary of the transformer, and the developing roller is connected to a secondary of the same. During a period while the voltage between electrodes of the capacitor is changing, the switching portion changes the duty ratio in a predetermined second time slot in which current flowing in the switching portion is smaller than that flowing in a first time slot.