Heat Roller Temperature Estimation for Overshoot-Free Heater Control
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Solution Overview
Problem
The existing temperature control systems in image forming apparatuses face challenges with overshoot and temperature ripple due to the high cost of responsive temperature sensors and the lag between temperature detection and actual surface temperature of the heat roller.
Innovation Solution
A temperature control device with a temperature estimation unit and a control signal generation unit that uses a capacitor-resistor circuit to estimate the temperature of the heat roller, generating a conduction pulse based on both temperature detection and estimation results, including a high-frequency component correction to accurately control the heater power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor with good responsiveness (e.g., thermopile) is used, then temperature control accuracy is improved, but cost increases
Solution Approach 1:
A thermal diffusion model is introduced as an intermediary computational layer between the temperature sensor and controller. The model estimates the heat roller surface temperature by calculating thermal diffusion from the heater through the roller structure, bridging the gap between slow sensor response and the need for accurate real-time temperature control
Solution Approach 2:
Instead of directly measuring the heat roller surface temperature with a responsive sensor, the system creates a computational copy of the temperature field by solving the thermal diffusion equation. This virtual temperature model allows accurate temperature estimation without requiring expensive high-response sensors
2Ease of manufacture
If a temperature sensor with slow responsiveness is used, then cost is reduced, but temperature control accuracy deteriorates due to overshoot and temperature ripple
Solution Approach 1:
The system performs preliminary temperature estimation by solving the thermal diffusion equation before actual temperature measurement is available. This predictive approach allows the controller to anticipate temperature changes and adjust heater power in advance, preventing overshoot and temperature ripple
Solution Approach 2:
A feedback mechanism is implemented where the thermal diffusion model continuously adjusts temperature estimates based on actual sensor readings and heater power history. This closed-loop feedback compensates for sensor lag, maintaining accurate temperature control despite using low-cost slow-response sensors
3Productivity
If heater power is increased to reach target temperature faster, then productivity is improved, but temperature overshoot occurs
Solution Approach 1:
The thermal diffusion model provides preliminary temperature predictions that allow the controller to apply pre-compensation to heater power. By anticipating the thermal inertia and heat distribution patterns, the system can apply higher initial power without causing overshoot, thus improving heating speed while maintaining temperature stability
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 reduces the need for expensive high-response temperature sensors, effectively preventing overshoot and temperature ripple while maintaining accurate temperature control of the heat roller, thereby improving the efficiency and cost-effectiveness of the image forming process.
Implementation Method 1
a temperature estimation unit that estimates a temperature of the heat roller based on conduction to the heater
Implementation Method 2
a heater configured to heat the heat roller
Data Source
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AI summary
A temperature control device controls a temperature of a temperature control target to which heat propagates from a heater by supplying power to the heater and includes a control circuit. The control circuit includes a temperature estimation unit and a control signal generation unit. The temperature estimation unit estimates the temperature of the temperature control target based on conduction to the heater. The control signal generation unit outputs a conduction pulse for controlling power to be supplied to the heater based on a temperature estimation result and a temperature detection result of the temperature control target by a temperature sensor.