Fixing Device Conductive Member Transfer Current Control
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Solution Overview
Problem
Conventional fixing devices in image forming apparatuses face issues with transfer defects, such as defects in image transfer density, particularly when the recording medium has high moisture content, due to transfer currents flowing to the separating member, leading to increased costs and device size with the use of electric resistors.
Innovation Solution
A fixing device with an electrically grounded frame supporting the fixing and pressure members, and a conductive member with higher resistance than the frame inserted between the frame and the separating member, allowing the separating member to be electrically conductive only via this conductive member, preventing transfer currents from flowing directly to the frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separating member is directly connected to the grounded frame, then the separating operation is effective, but transfer currents flow to the separating member causing transfer defects
Solution Approach 1:
A conductive member with higher electric resistance than the frame is inserted between the separating member and the frame to serve as an electrical intermediary. This conductive member has lower electrical conductivity than the frame, thereby blocking transfer currents from flowing to the separating member while still allowing the separating member to be supported and grounded through it. The conductive member acts as a selective barrier that permits mechanical support and grounding function while preventing harmful electrical current flow.
2Reliability
If an electric resistor is provided to ground the separating member, then transfer defects are prevented, but the cost and device size increase
Solution Approach 1:
The conductive member serves multiple functions simultaneously: it provides mechanical support for the separating member, establishes electrical grounding connection, and acts as a resistance barrier to block transfer currents. By integrating these multiple functions into a single component, the invention eliminates the need for separate electric resistors and grounding components, thereby reducing device complexity, size, and cost while maintaining the separating operation effectiveness.
Solution Approach 2:
The conductive member inherently possesses the necessary electrical resistance property to block transfer currents without requiring additional active control mechanisms or external power sources. The material selection and structural design of the conductive member itself provide the current-blocking function, allowing the system to self-regulate the electrical properties without external intervention.
3Reliability
If the separating member is made highly conductive, then charge dissipation is effective, but transfer currents cause image transfer density defects
Solution Approach 1:
The electrical conductivity is localized differently in different parts of the system: the frame maintains high conductivity for effective charge dissipation, while the conductive member connecting to the separating member has higher resistance to block transfer currents. This spatial differentiation of conductivity properties allows the system to simultaneously achieve effective charge management at the frame level while preventing harmful current flow to the separating member that would cause image transfer density defects.
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 prevents transfer defects and reduces the need for additional components, maintaining the separating member's function without increasing the device's cost or size, while effectively managing electric charges on the separating plate.
Implementation Method 1
a conductive member inserted between a supporting portion of the frame and a supported portion of the separating member and having a higher electric resistance than the frame
Implementation Method 2
a fixing member configured to heat and melt a toner image to fix the toner image onto a recording medium
Implementation Method 3
a fixing member configured to heat and melt a toner image to fix the toner image onto a recording medium
Implementation Method 4
a pressure member abutting the fixing member to form a nip portion into which the recording medium is fed
Data Source
AI summary
A disclosed fixing device includes a fixing member configured to heat and melt a toner image to fix it onto a recording medium; a pressure member abutting the fixing member to form a nip into which the recording medium is fed; a separating member disposed on the downstream side in the moving direction of the fixing member in relation to the nip in a manner to oppose the fixing member, and configured to perform a separating operation to prevent the recording medium from winding around the fixing member; an electrically grounded frame supporting the fixing member, the pressure member and the separating member; and a conductive member inserted between a supporting portion of the frame and a supported portion of the separating member and having a higher electric resistance than the frame. The separating member and the frame are rendered electrically conductive to each other only via the conductive member.