Heater Temperature Sensing Inversion for Thermal Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In image forming apparatuses, temperature sensing elements on the heater's surface reduce heat transfer efficiency and accuracy when thick protective layers or wider substrates are used to ensure withstand voltage, leading to increased apparatus size.
Innovation Solution
A temperature sensing element is placed on the substrate opposite to the heating element, with a separate temperature sensing circuit electrically insulated from both the primary and secondary side circuits, allowing for precise temperature control without compromising thermal responsiveness or heat transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thermistor is formed on the surface of the heater on the side of the nip portion, then the temperature sensing is enabled, but it is necessary to form the thermistor such that the thermistor has a thick surface protective layer or increase the width of the substrate to secure adequate withstand voltage
Solution Approach 1:
The temperature sensing element is positioned on the back surface of the heater substrate opposite to the nip portion side, rather than on the conventional front surface. This inversion allows the sensing element to be electrically insulated from the high-voltage heating circuit without requiring additional protective layers or substrate width increases, thereby resolving the contradiction between temperature sensing capability and heater structure simplicity
Solution Approach 2:
The solution moves the temperature sensing element from the two-dimensional surface plane of the heater to the third dimension by placing it on the opposite surface of the substrate. This spatial reconfiguration enables electrical insulation through the substrate thickness rather than requiring lateral expansion or additional protective coatings, thus maintaining structural simplicity while achieving accurate temperature sensing
2Reliability
When the thickness of the surface protective layer of the thermistor is increased, then the withstand voltage is secured, but the heat transfer efficiency of the heater and accuracy in sensing the nip temperature are reduced
Solution Approach 1:
The temperature sensing element is extracted from the high-voltage heating circuit environment by placing it on the opposite surface of the substrate. This separation eliminates the need for thick protective layers that would impede heat transfer, while the substrate itself provides sufficient electrical insulation. The sensing element operates in a low-voltage isolated circuit, achieving both reliability and heat transfer efficiency
Solution Approach 2:
The heater substrate acts as an intermediary that provides electrical insulation between the high-voltage heating circuit and the temperature sensing element. By utilizing the substrate's inherent insulating properties, the solution avoids the need for additional protective layers that would compromise heat transfer efficiency, while still ensuring adequate withstand voltage capability
3Reliability
When the width of the substrate of the heater is increased, then the withstand voltage is secured, but the size of the apparatus is increased
Solution Approach 1:
Instead of increasing substrate width to achieve electrical insulation, the solution inverts the approach by placing the sensing element on the opposite surface where the substrate's thickness provides the insulation barrier. This eliminates the need for lateral expansion of the substrate, maintaining compact apparatus dimensions while ensuring adequate withstand voltage
Solution Approach 2:
The solution changes the spatial parameter of the sensing element's position from the front surface to the back surface of the substrate. This parameter change utilizes the substrate's thickness dimension for electrical insulation rather than requiring increased width, thereby maintaining small apparatus size while achieving the required withstand voltage level
4Measurement precision
If the temperature sensing element is disposed on the sliding surface of the heater, then temperature sensing is enabled, but the thermal responsiveness and heat transfer efficiency of the heater are reduced
Solution Approach 1:
The temperature sensing element is inverted to the back surface of the heater substrate, away from the sliding surface that contacts the film. This positioning prevents the sensing element from acting as a thermal barrier between the heating element and the film, thereby maintaining high thermal responsiveness and heat transfer efficiency while still enabling accurate temperature sensing through the substrate
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 configuration enables accurate temperature sensing on the sliding surface of the heater while preventing a reduction in thermal responsiveness and heat transfer efficiency, and avoids increasing the size of the heater.
Implementation Method 1
a heating element provided on the substrate
Implementation Method 2
a temperature sensing element provided on a surface of the substrate opposite to a surface on which the heating element is provided
Implementation Method 3
a surface of the heater on a side where the temperature sensing element is provided is in contact with an inner surface of the film
Data Source
Figure 1
Figure 2
Figure 3~3(B)
AI summary
Provided is an image forming apparatus including a temperature sensing circuit to which a temperature sensing element is electrically connected, wherein a surface of a heater on a side where the temperature sensing element is provided is in contact with the inner surface of a film, a heating element is provided in a primary side circuit which is electrically connected to a commercial power supply, and the temperature sensing circuit is electrically insulated from both of the primary side circuit and a secondary side circuit which is electrically insulated from the primary side circuit.