Thermopile Sensor Stray Light Suppression in Fusing Devices
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Solution Overview
Problem
Conventional temperature measuring devices for fusing devices using thermopile sensors suffer from false detection due to stray light radiation and airflow issues, leading to temperature measurement errors.
Innovation Solution
A temperature measuring device with a thermopile sensor held by a sensor holding member featuring a cylindrical member and an aperture, which blocks stray light radiation while maintaining the original light receiving range, and optionally includes a thermally conductive cylindrical member and a metal cap with low emissivity to reduce temperature differences and ventilation ports to manage airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a thermopile sensor is disposed inside the fusing device to measure temperature, then the temperature measurement responsiveness is improved, but the sensor cannot withstand the high temperature environment (upper temperature limit of 100°C or less)
Solution Approach 1:
An airflow path is introduced as an intermediary medium to transmit thermal information from the fusing device to the thermopile sensor. The airflow carries heat from the high-temperature fusing region to the sensor, enabling temperature measurement without direct thermal contact between the sensor and the fusing device.
Solution Approach 2:
The patent replaces direct thermal contact measurement with a fluid-mediated measurement system. Instead of placing the sensor in direct thermal contact with the fusing device, it uses airflow to transfer thermal energy, substituting a mechanical/thermal direct-contact system with a fluid-based indirect measurement system.
2Measurement precision
If the light-receiving angle of the thermopile sensor is made narrow to improve measurement precision, then the temperature measurement accuracy is improved, but the sensor cannot receive sufficient infrared light for accurate detection
Solution Approach 1:
The patent extends the measurement approach from a single-point narrow-angle detection to a distributed multi-point measurement system. Multiple thermopile sensors are arranged at different positions, each with a moderate field of view, collectively covering the entire fusing device surface. This transforms a one-dimensional narrow-angle measurement into a two-dimensional comprehensive measurement.
Solution Approach 2:
The fusing device surface is divided into multiple measurement zones, with each zone monitored by a separate thermopile sensor. This segmentation allows each sensor to operate within its optimal detection range while collectively providing complete surface temperature coverage, avoiding the need for any single sensor to have an excessively narrow or wide field of view.
3Quantity of substance
If water vapor is allowed to flow freely to the thermopile sensor to maintain humidity control, then the humidity regulation function is improved, but condensation occurs on the sensor lens causing measurement errors
Solution Approach 1:
The harmful condensation effect is extracted and separated from the useful humidity control function. A heating element is specifically introduced into the airflow path to prevent condensation on the sensor lens, while the overall airflow path continues to enable humidity regulation in the fusing device. This separates the condensation prevention function from the humidity control function.
Solution Approach 2:
The temperature parameter of the airflow path is changed by introducing a heating element, raising the local temperature above the dew point to prevent condensation. This parameter change (temperature increase in the airflow path) allows water vapor to pass through without condensing on the sensor lens, while still maintaining the humidity control function in the fusing device.
4Stability of the object's composition
If the airflow path is extended to improve temperature uniformity around the sensor, then the temperature distribution is improved, but the apparatus size increases due to the outer shell case
Solution Approach 1:
The airflow path structure serves multiple functions simultaneously: it provides temperature uniformity around the sensor, enables heat transfer from the fusing device, maintains humidity control, and prevents condensation. By making the airflow path multi-functional, the patent avoids adding separate structures for each function, thereby preventing excessive increase in apparatus volume.
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
The solution effectively prevents false detection by thermopile sensors by suppressing stray light radiation and managing airflow, resulting in accurate temperature measurements.
Implementation Method 1
a non-contact type temperature sensor (thermopile sensor) that is disposed opposite the heated object and measures infrared rays emitted from the heated object
Implementation Method 2
The sensor holding member is provided with a cylindrical member extending in front of the thermopile sensor and an aperture disposed at an end of the cylindrical member... By preventing the radiant heat from the outside by the cylindrical member and receiving the stray light radiation from the inner wall of the cylindrical member close to the sensor temperature
Implementation Method 3
the thermopile sensor and the cylindrical member are thermally conductive
Implementation Method 4
a metal cap with low emissivity to reduce temperature differences
Data Source
AI summary
A thermopile sensor that is a temperature measuring device of a fusing device is held on a substrate. The substrate is provided with a cylindrical member extending in front of the thermopile sensor and an aperture disposed at an end of the cylindrical member.