WAE Control for Fixer Temperature Ripple Reduction
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Solution Overview
Problem
In image forming apparatuses, the use of less expensive temperature sensors with slower responsiveness leads to deviations in controlling the surface temperature of the fixing rotating body, resulting in overshoot and temperature ripples, as they cannot accurately track the actual surface temperature due to their poor heat capacity and resistance characteristics.
Innovation Solution
Implementing a weighted average control with estimated temperature (WAE) control function, which simulates a thermal RC circuit to estimate the surface temperature based on the power supplied to the heating member, heat capacity, and resistance, using a heating control circuit that adjusts the energization pulses to maintain the target temperature, and includes a correction mechanism for variations in heat capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor with excellent responsiveness (e.g., thermopile) is used, then temperature control precision is improved, but device cost increases
Solution Approach 1:
The patent replaces expensive high-performance temperature sensors (thermopile) with inexpensive, slower-response sensors (thermocouple or thermistor). This substitution is compensated by implementing WAE control that uses a thermal RC circuit model to estimate the actual surface temperature, thereby achieving accurate temperature control without requiring expensive sensor hardware
Solution Approach 2:
The patent introduces a thermal RC circuit model as an intermediary between the temperature sensor and the control system. This model estimates the actual surface temperature by combining sensor readings with thermal parameters (heat capacity C and resistance R), effectively mediating the information gap caused by using slower, cheaper sensors
2Ease of manufacture
If a less expensive temperature sensor (e.g., thermocouple or thermistor) is used, then device cost is reduced, but temperature control precision deteriorates due to slower responsiveness
Solution Approach 1:
The patent implements WAE control with feedback mechanism that continuously monitors the temperature sensor output and adjusts the heating power accordingly. The control system uses the thermal RC circuit model to predict the actual temperature trajectory and compensates for the sensor's slow response by comparing estimated temperature with target temperature, thereby maintaining control precision despite using cheaper sensors
Solution Approach 2:
The thermal RC circuit model serves as an intermediary that transforms the slow sensor readings into accurate temperature estimates. By modeling the thermal dynamics of the fixing device, the system can infer the actual surface temperature from delayed sensor measurements, effectively bridging the gap between cheap sensor hardware and precise temperature control requirements
3Device complexity
If a fixed heat capacity value is used in WAE control, then control simplicity is maintained, but temperature control precision deteriorates due to heat capacity variations in each apparatus
Solution Approach 1:
The patent performs preliminary measurement of the actual heat capacity C of the fixing device during installation or initial operation. This measured value is stored and used in the WAE control calculations, allowing the system to compensate for apparatus-specific variations in heat capacity before normal operation begins, thereby improving temperature estimation accuracy without adding complexity to the ongoing control process
Solution Approach 2:
The patent changes the heat capacity parameter from a fixed design-standard value to a variable value that is actually measured for each specific apparatus. This parameter change allows the WAE control system to adapt to the unique thermal characteristics of each fixing device, improving temperature control precision while maintaining the overall simplicity of the control algorithm
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 approach allows for more accurate control of the surface temperature, reducing overshoot and temperature ripples by effectively compensating for the limitations of less responsive temperature sensors, ensuring the target temperature is maintained despite variations in heat capacity.
Implementation Method 1
a heating member (e.g., lamp, IH heater, or the like), and a temperature sensor. The temperature sensor detects a temperature at a surface of the fixing rotating body. A controller that controls the fixer thus controls a surface temperature of the fixing rotating body to be a target value by increasing or decreasing an amount of power supplied to the heating member
Implementation Method 2
Movement of heat in the fixer can be expressed equivalently as a RC time constant of an electric circuit. That is, a heat capacity of the fixer is replaced with a capacitor C, and a resistance of heat transfer is replaced with a resistor R.
Data Source
AI summary
According to one embodiment, an image forming apparatus includes a fixer including a rotating body and a heating member to heat the rotating body. A temperature sensor is positioned to detect a temperature of the rotating body and output a temperature detection result. A heating control circuit is configured to estimate the temperature of the rotating body based on the temperature detection result, a power supply voltage value, an energization pulse setting for controlling the heating member, a heat capacity of the fixer, and a heat resistance of the fixer. The control circuit generates an energization pulse for controlling power supplied to the heating member based on the estimated temperature and the temperature detection result. A controller detects a variation in the heat capacity of the fixer device and supplies a correction amount for the heat capacity corresponding to the detected variation to the heating control circuit.