Fixing Device Temperature Estimation for Abnormality Source Detection
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Solution Overview
Problem
Existing image forming apparatuses face challenges in accurately detecting abnormalities in temperature sensors and heater circuits, which can lead to inefficient temperature control and potential device failures.
Innovation Solution
A temperature control device that utilizes a temperature estimation circuit to estimate the temperature of a temperature control target based on a CR circuit, compares the detected temperature with threshold values to determine abnormalities, and includes a temperature abnormality detection circuit to identify issues in the temperature sensor or circuit side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is used to detect the surface temperature of the heat roller, then temperature control can be achieved, but abnormality detection accuracy deteriorates because it is difficult to determine whether the detected temperature deviation is caused by sensor failure or circuit abnormalities
Solution Approach 1:
The patent introduces an intermediary estimation mechanism (temperature estimation circuit) that indirectly assesses the actual temperature by monitoring heater power consumption and temporal patterns, rather than relying solely on the temperature sensor. This intermediary approach allows the system to detect abnormalities without being misled by sensor failures or circuit issues, resolving the contradiction between measurement capability and reliability.
2Reliability
If existing abnormality detection methods are used (checking maximum output duration or preset range exceedance), then some abnormalities can be detected, but detection precision deteriorates because these methods cannot distinguish between temperature sensor failures and heater circuit abnormalities
Solution Approach 1:
The patent segments the abnormality detection process into distinct analytical components: power consumption monitoring, temporal pattern analysis, and estimation-based verification. By dividing the detection mechanism into these separate functional segments, the system can identify whether abnormalities originate from the temperature sensor, heater circuit, or control system, thereby improving both reliability and measurement precision simultaneously.
3Stability of the object's composition
If the system continuously monitors temperature to ensure precise control, then temperature stability is improved, but energy consumption increases due to continuous heater adjustments
Solution Approach 1:
The patent implements periodic action by using pulse-width modulation (PWM) to control heater energization rather than continuous operation. The heater is energized in periodic pulses with varying duty cycles based on temperature requirements, which maintains temperature stability while significantly reducing overall energy consumption compared to continuous heating.
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
Enhances the ability to detect and address temperature abnormalities, ensuring precise temperature control and preventing device failures in image forming apparatuses.
Implementation Method 1
a temperature estimation circuit to estimate an estimated temperature value of the fixing device by weighted average control with estimated temperature (WAE) based on a CR circuit in which a heat capacity of a film unit corresponding to a temperature control target is replaced by a capacitor C and a heat transfer resistance is replaced by a resistor R
Implementation Method 2
supply power to a heater of a fixing device, thereby controlling a temperature of the fixing device to which heat is propagated from the heater
Data Source
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AI summary
According to one embodiment, there is provided a temperature abnormality detection circuit provided in a temperature control device includes a target temperature determination circuit, a difference arithmetic circuit, a temperature abnormality determination circuit, and a storage circuit. The temperature abnormality detection circuit is configured to determine the presence or absence of temperature abnormality by a response situation of a detected temperature by a temperature sensor, calculate a current temperature difference from the detected temperature acquired by the temperature sensor if it is determined that there is a temperature abnormality and an estimated WAE temperature value, and determine whether the temperature sensor is abnormal or the control circuit side is abnormal based on the result of comparison between the temperature difference and a preset threshold value.