Fixing Device Sleep State Control for Kink Prevention
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Solution Overview
Problem
In image forming apparatuses, the generation of kink (plastic concaved crush) in fixing members due to thermal expansion differences during the transition to a sleep state leads to abnormal images and potential damage, especially when energy saving measures result in rapid power shutdowns and incomplete heat dissipation.
Innovation Solution
A fixing device with a temperature detecting unit and controller that prohibits the transition to a sleep state if the fixing member's temperature in the heat source region exceeds a predetermined level after a certain time period has elapsed since rotation stop, allowing for controlled heat dissipation and preventing kink generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the fixing member is made thin to reduce heat capacity for rapid heating and energy saving, then the warm-up time and energy consumption are reduced, but the fixing member becomes more susceptible to temperature fluctuations and kink generation
Solution Approach 1:
The patent changes the thermal parameters of the fixing member by incorporating a heat storage layer with specific thermal properties. This layer has sufficient heat capacity to buffer temperature fluctuations while the overall structure maintains rapid heating capability. The heat storage layer's thermal conductivity and specific heat are optimized to prevent kink generation during sleep state transitions while preserving energy efficiency during operation.
Solution Approach 2:
The fixing member is constructed as a composite structure with multiple layers including a heat storage layer. This composite design combines materials with different thermal properties - the heat storage layer provides thermal buffering to prevent temperature shocks, while other layers maintain the low heat capacity needed for rapid heating. The composite structure resolves the contradiction between thin design for energy saving and sufficient thermal mass for reliability.
2Use of energy by stationary object
If the power supply is rapidly shut down to enter sleep state for energy saving, then energy consumption is reduced, but excess heat in the fixing member causes thermal expansion differences and kink generation
Solution Approach 1:
The patent implements preliminary cooling action before the sleep state transition. The control unit monitors the fixing member's temperature and initiates a cooling process using the cooling unit before allowing the sleep state to be entered. This preliminary action ensures that thermal expansion differences are minimized before the rapid power shutdown, preventing kink generation while still achieving energy saving through quick sleep state transition.
Solution Approach 2:
The system employs temperature feedback control where temperature detection units continuously monitor the fixing member's temperature. Based on this feedback, the control unit determines the appropriate timing for sleep state transition and activates the cooling unit when necessary. This feedback mechanism ensures that the fixing member's temperature is within safe ranges before entering sleep state, preventing thermal expansion damage while maintaining energy efficiency.
3Power
If the heat source is positioned away from the fixing nip portion to enable localized heating, then heating efficiency is improved, but thermal expansion differences between heated and non-heated regions cause kink generation
Solution Approach 1:
The patent applies local quality by providing regional heating support through the heat storage layer. While the heat source is positioned away from the fixing nip for efficient localized heating, the heat storage layer distributes thermal energy more uniformly across the fixing member. This creates different thermal zones - the heated region for efficient energy use and the heat storage region that buffers thermal gradients - preventing kink generation while maintaining high heating efficiency.
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 effectively prevents kink formation and ensures energy savings by allowing the fixing device to shift to a sleep state only when safe, thereby maintaining image quality and extending the lifespan of the fixing member.
Implementation Method 1
a halogen heater for heating the fixing member by radiant heat
Implementation Method 2
a developer, in particular, toner included in an unfixed image is melted and softened and penetrated into a recording medium by heating the unfixed image carried by the recording medium
Implementation Method 3
during the image fixing operation, the temperature of the fixing member is not abnormally increased because a recording medium passing through a fixing nip portion takes heat from the fixing member
Implementation Method 4
the temperature of a surface of a fixing member may be increased by the excess heat of a reflector, a stay, and inside air whose temperature has been increased after the rotation of the fixing member is stopped
Data Source
AI summary
A fixing device capable of shifting to a sleep state includes a heat source; a rotatable fixing member that is partly heated by the heat source to heat an unfixed image carrying surface of a recording medium; a rotatable pressing member that is in pressure contact with the fixing member to form a nip portion between the pressing member and the fixing member; a rotation drive unit that directly or indirectly rotates the fixing member; a temperature detecting unit that detects a temperature of the fixing member; and a controller configured to prohibit the fixing device from shifting to the sleep state when the temperature of the fixing member in a region facing the heat source is equal to or more than a predetermined temperature T1 at a point when a predetermined time period t1 has elapsed from the stop of rotation drive of the rotation drive unit.