Fixing Apparatus Capacitive Protection for Reduced Creepage Distance
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Solution Overview
Problem
Existing fixing apparatuses in image forming devices are hindered by excessive voltage surges, leading to potential damage and difficulty in downsizing due to insufficient electrostatic capacitance and varying potential between the heater and pressing roller, necessitating increased creepage and clearance distances.
Innovation Solution
A capacitive element is connected between the conductor on the substrate and the metal frame, redistributing excessive voltage and stabilizing electrostatic capacitance, allowing for reduced creepage and clearance distances, thus enabling downsizing while maintaining protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor is connected between the core metal of the pressing roller and the metal frame to protect from excessive voltage, then protection from excessive voltage is improved, but the electrostatic capacitance between the heater and core metal becomes insufficient and varies, requiring larger creepage and clearance distances
Solution Approach 1:
The patent introduces a conductive layer as an intermediary component between the heater and the capacitor connection point. This conductive layer is connected to the metal frame through a capacitor while being in close proximity to the heater, serving as a mediator that provides both electrostatic protection and sufficient capacitance without requiring large creepage and clearance distances. The conductive layer acts as a bridge that resolves the contradiction between protection effectiveness and compact spacing.
Solution Approach 2:
The patent segments the protection system into multiple components: the heater, insulating layer, conductive layer, and capacitor connection to the metal frame. By dividing the system into these segments, the electrostatic capacitance is distributed across multiple interfaces (heater-conductive layer, conductive layer-capacitor, capacitor-metal frame), providing sufficient total capacitance for protection while maintaining compact dimensions and reducing the required creepage and clearance distances.
2Reliability
If the distance between the heater and core metal of the pressing roller is increased to provide protection, then protection from excessive voltage is improved, but the electrostatic capacitance becomes insufficient and the apparatus size increases
Solution Approach 1:
The patent transitions from a one-dimensional spacing approach (increasing distance between heater and core metal) to a multi-dimensional solution by introducing a conductive layer and capacitor connection through the insulating layer. This allows the electrostatic protection system to function in multiple spatial dimensions, providing sufficient capacitance and protection effectiveness without increasing the overall apparatus volume.
Solution Approach 2:
The patent utilizes the insulating layer as a thin film structure that separates the heater from the conductive layer while maintaining electrical insulation. This thin film approach provides the necessary insulation for protection while occupying minimal space, enabling compact apparatus design without sacrificing electrostatic protection effectiveness.
3Stability of the object's composition
If the electrostatic capacitance between heater and core metal is increased to stabilize potential, then potential stability is improved, but the creepage and clearance distances must be enlarged
Solution Approach 1:
The conductive layer serves as an intermediary that provides a stable reference potential close to the heater. By connecting this conductive layer to the metal frame through a capacitor, the system achieves potential stabilization without requiring large creepage and clearance distances. The intermediary conductive layer maintains stable potential while enabling compact spacing.
Solution Approach 2:
The patent segments the electrostatic protection system into multiple capacitive interfaces (heater-insulating layer-conductive layer, conductive layer-capacitor-metal frame). This segmentation distributes the capacitance function across multiple interfaces, achieving stable potential reference while maintaining compact dimensions and reducing the required creepage and clearance distances.
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
The solution effectively reduces potential variations and enables the fixing apparatus to be downsized without compromising protection from excessive voltages, improving the overall compactness and reliability of the image forming apparatus.
Implementation Method 1
a heating element configured to generate heat by being supplied with power from an alternating current power source
Implementation Method 2
a capacitive element whose one end is connected to the metal frame and whose other end is connected to the conductive layer of the fixing apparatus
Data Source
AI summary
A metal frame provides a ground potential. An image forming unit forms a toner image on a sheet. A fixing apparatus fixes the toner image on the sheet. The fixing apparatus comprises a heating element for generating heat by being supplied with power from an alternating current power source. An insulating layer covers the heating element. A conductive layer contacts the insulating layer and insulated from the metal frame. A tube-shaped member is heated by the heating element. A pressing member is arranged opposing the tube-shaped member and forms a nip portion in cooperation with the tube-shaped member. A capacitive element whose one end is connected to the metal frame and whose other end is connected to the conductive layer of the fixing apparatus.