Fixing Device Belt Abnormality Detection via Heating Delay
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Solution Overview
Problem
In image forming apparatuses with fixing devices, partial slipping or deviation of the fixing belt can lead to abnormal heating of the heating roller, potentially causing ignition or damage to apparatus components due to inadequate temperature sensing at torn or lifted sections.
Innovation Solution
Incorporating a magnetic flux generating unit, temperature sensing portion, stopped time measuring portion, abnormality determination portion, and heating delay portion to prevent excessive heating by delaying the start of heating based on temperature change rates and stopped time measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensor is disposed at the fixing belt to measure temperature, then temperature control is improved, but when the fixing belt is torn or lifted upward, the temperature sensor does not detect the actual temperature increase, leading to abnormal heating of the heating roller
Solution Approach 1:
The control unit delays the start of heating operation for a predetermined time period after receiving a heating start instruction. This preliminary delay allows the system to prepare for potential abnormalities and prevents immediate heating that could cause damage if the fixing belt is already in an abnormal state (torn or lifted).
Solution Approach 2:
The control unit continuously monitors the temperature detected by the temperature sensor during heating operation. By comparing the temperature change rate against expected values, the system can detect abnormalities in the fixing belt state and stop heating operation to prevent excessive heating and potential damage to the heating roller and other components.
2Productivity
If heating operation is started immediately upon receiving heating start instruction, then productivity is improved, but the heating roller may be heated to abnormal levels if the fixing belt is in an abnormal state
Solution Approach 1:
The control unit implements a predetermined delay period before starting heating operation. This preliminary action allows the system to verify the fixing belt state before committing to heating, balancing quick response with safety. The delay is not excessive to maintain productivity while preventing harmful abnormal heating.
Solution Approach 2:
The control unit prepares to stop heating operation immediately if temperature increases exceed expected rates during heating. This preliminary protective measure counteracts the potential harmful effect of abnormal heating by having the stop command ready to be executed, preventing damage to the heating roller and surrounding components.
3Reliability
If the control unit continuously monitors temperature to detect belt abnormalities, then reliability is improved, but the system complexity increases
Solution Approach 1:
The control unit uses simple feedback logic by monitoring the temperature detected by the temperature sensor and comparing it against expected temperature change rates. This feedback mechanism provides reliable abnormality detection without requiring complex additional sensors or sophisticated algorithms, maintaining system simplicity while improving reliability.
Solution Approach 2:
The temperature sensor already present in the system serves dual purposes: normal temperature control and abnormality detection. The control unit utilizes the existing temperature data for both heating control and safety monitoring, eliminating the need for additional dedicated abnormality detection sensors and keeping the system complexity low.
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
Prevents excessive heating of the heating roller by accurately determining belt abnormalities and delaying heating initiation, thereby preventing potential damage from torn or lifted fixing belts.
Implementation Method 1
a magnetic flux generating unit (76), a first rotary body (71), and a second rotary body (72). The first rotary body is configured to generate heat through action of magnetic flux generated by the magnetic flux generating unit
Data Source
AI summary
A fixing device is provided with a magnetic flux generating unit, first and second rotary bodies, a fixing belt, a temperature sensing portion, a stopped time measuring portion, an abnormality determination portion, and a heating delay portion. The fixing belt extends between the first and second rotary bodies, and is heated by the first rotary body. The temperature sensing portion is disposed downstream of the first rotary body and senses the temperature of the fixing belt. The stopped time measuring portion measures a time period after heating has been stopped before an instruction to start heating is inputted. The abnormality determination portion determines any abnormality in the fixing belt based on a change in temperature after heating has started. When a stopped time is shorter than a pre-configured time period, the heating delay portion delays the start time via magnetic flux based on the instruction to start heating.