Charging Roller Frequency Control for Stable Discharge Current
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Solution Overview
Problem
Conventional discharge current control in image forming apparatuses is unsuitable for low-temperature environments, leading to unstable discharge current characteristics and potential damage to the photosensitive drum and charging roller, due to temperature-dependent resistance changes in ion-conductive agents used for resistance adjustment.
Innovation Solution
An image forming apparatus with a controller that sets a predetermined peak-to-peak voltage based on a specific frequency maintaining linearity between frequencies and alternating currents, determined through a test mode where various test AC voltages are applied to the charging roller, ensuring proper charging and image formation across different temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional discharge current control is used in low temperature environment, then target discharge current is achieved by setting high peak-to-peak voltage, but photosensitive drum and charging roller are deteriorated more than necessary
Solution Approach 1:
The patent changes the frequency parameter of the AC voltage applied to the charging roller. By setting the frequency to 2 kHz or higher, the patent achieves stable discharge current characteristics in low temperature environments without requiring excessively high peak-to-peak voltage, thereby reducing deterioration of the photosensitive drum and charging roller while maintaining reliable discharge current.
2Reliability
If high frequency AC voltage is applied to charging roller, then discharge current stability is improved, but electroconductivity generation time of ions cannot catch up with speed change of electric field
Solution Approach 1:
The patent optimizes the frequency parameter to 2 kHz or higher, which balances the electric field change speed with the ion response time. This frequency range is high enough to stabilize discharge current characteristics but not so high that ions cannot follow the field changes, thereby resolving the contradiction between discharge current stability and electroconductivity generation time.
3Ease of manufacture
If ion-conductive agent is used as resistance-adjusting agent, then resistance value adjustment is relatively easy, but environment dependency of resistance value is high
Solution Approach 1:
The patent compensates for the environment dependency of ion-conductive agents by changing the operating frequency to 2 kHz or higher. This frequency adjustment stabilizes the discharge current characteristics despite temperature variations affecting the resistance value, thereby maintaining reliability while preserving the ease of manufacture benefit from using ion-conductive agents.
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 allows for stable image formation by setting optimal peak-to-peak voltages, reducing the risk of image defects and extending the lifespan of the photosensitive drum and charging roller, even when the temperature sensor and actual charging roller temperatures differ.
Implementation Method 1
a change of a speed of an electric field in the charging roller is influenced by mobility of a molecular chain in a material of the charging roller and therefore a time required that ions exhibit electroconductivity is long
Implementation Method 2
the speed of the change of the electric field in the charging roller is high, and therefore, even in the normal temperature environment, an electroconductivity generation time of the ions cannot sufficiently catch up with the speed change of the electric field
Implementation Method 3
detecting member configured to detect an alternating current flowing between the voltage source and the charging roller
Implementation Method 4
charging roller configured to electrically charge the image bearing member in contact with the image bearing member
Data Source
AI summary
An image forming apparatus includes an image bearing member, a charging roller, a toner image forming portion, a voltage source, a detecting member, a controller, and a test executing portion configured to execute an operation in a test mode in which in a period in advance of the image forming period, a plurality of test AC voltages having a test peak-to-peak voltage with different frequencies are successively applied to the charging roller and alternating currents are detected by the detecting member. The test executing portion sets a predetermined peak-to-peak voltage on the basis of a specific frequency which is a maximum frequency at which a relationship between the frequencies and the alternating currents acquired in the operation in the test mode maintains linearity.