Fixing Device Heater Protection via Biasing Member Projection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In film heating-type fixing devices, the heater holder can soften and crack due to uneven load when power control is lost, leading to potential damage before protection elements can activate, and existing designs may not provide sufficient time to prevent heater cracking.
Innovation Solution
A fixing device with an elongated heater held by a thermoplastic resin holder, reinforced by a metal stay, and a thermosensitive member biased by a spring with a projection portion that regulates the thermosensitive member's position, extending the time before heater cracking by managing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection element such as a thermo switch is provided in the space between the heater holder and the reinforcing member, then the heater can be protected from excessive temperature, but it takes a certain amount of time until the protection element is activated due to heat capacity, so the heater may crack before the protection element is activated
Solution Approach 1:
A heat conductive member is introduced as an intermediary between the heater and the protection element. This mediator has higher thermal conductivity than the heater holder material, creating a thermal bridge that accelerates heat transfer to the protection element, enabling faster activation while maintaining reliable heater protection
Solution Approach 2:
The thermal conductivity parameter of the path between heater and protection element is changed by introducing the heat conductive member. This parameter change reduces the thermal resistance in the heat transfer path, allowing the protection element to detect temperature rise more quickly and activate before heater cracking occurs
2Ease of manufacture
If the heater holder is made from thermoplastic resin, then the heater can be held in position, but the holder becomes softened due to heat when power-feeding control is lost, causing uneven load and heater deflection and cracks
Solution Approach 1:
The system uses a composite structure combining thermoplastic resin holder with metal reinforcing member and heat conductive member. This composite approach leverages the manufacturing ease of resin while compensating for its heat resistance weakness through metal components that maintain structural integrity at high temperatures
Solution Approach 2:
The holder structure is segmented into multiple functional components: the thermoplastic resin holder for basic support, metal reinforcing members for structural strength, and heat conductive members for thermal management. This segmentation allows each component to specialize in its optimal function while working together to solve the overall problem
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 prolongs the time before heater cracking by accurately positioning the thermosensitive member and reducing deformation, ensuring the heater holder remains intact until the thermal fuse activates, thus preventing damage.
Implementation Method 1
a thermosensitive member which is provided in a space between the holder and the reinforcing member and which receives heat of the heater through a through-hole provided in the holder
Implementation Method 2
a biasing member which biases the thermosensitive member toward the heater
Data Source
AI summary
In a fixing device according to an exemplary embodiment of the present invention, a projection portion projected in a direction opposite to a direction biased by the biasing member, from a body part of the biasing member, is provided in a biasing member configured to push a thermosensitive member which receives heat from a heater, toward the heater, so that a crack in the heater at the time of an abnormal temperature rise is prevented.