Waveform Heating Resistor for Rapid Thermal Cycling in Furnaces
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Solution Overview
Problem
Conventional heat processing furnaces face issues with durability and cost due to thermal expansion and contraction of helical heating elements, leading to potential short-circuits and limited ability to quickly increase or decrease temperature, and existing solutions either compromise durability or are expensive.
Innovation Solution
A heat processing furnace design featuring a cylindrical heater with strip-shaped heating resistors bent into a waveform, pin members for radial movement, and a divided heat insulating member with groove sections and connecting plates to manage thermal expansion and facilitate quick temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a helical heating element is used to allow thermal expansion and contraction, then the heating element can accommodate temperature changes, but the repeated thermal expansion and contraction causes creep strain and deformation leading to short-circuits and disconnection
Solution Approach 1:
The heating element is designed with a waveform shape that allows dynamic movement and deformation without causing short-circuits. The waveform structure can expand and contract radially while maintaining electrical isolation, accommodating thermal cycles without compromising reliability
Solution Approach 2:
The heating element transitions from a simple helical shape to a waveform shape with radial dimension variations. This adds another dimension of movement capability, allowing the element to expand and contract in the radial direction while maintaining its functional integrity and preventing short-circuits
2Speed
If the heating element is quickly cooled by blowing air to decrease temperature, then temperature adjustment speed is improved, but the repeated rise and drop in temperature increases the likelihood of deformation and disconnection
Solution Approach 1:
The waveform heating element is designed to dynamically accommodate rapid temperature changes through its flexible structure. The waveform shape allows the element to flex and move during rapid cooling and heating cycles, absorbing thermal shocks and preventing deformation that would lead to disconnection
3Stability of the object's composition
If a fixing member is attached to the heating element by welding to prevent accumulation of elongation, then the heating element position is stabilized, but the joined portion is exposed to high temperature causing stress concentration and deterioration of durability
Solution Approach 1:
A pin member is introduced as an intermediary component between the heating element and the heat insulating member. This pin member acts as a mediator that provides fixing functionality while being thermally isolated from the high-temperature heating element, preventing stress concentration and durability deterioration at the joined portion
4Device complexity
If a bar-like fixing member is used to fix the heating element, then the fixing structure is simple, but the fixing member may easily drop out of the heat insulating member resulting in insufficient holding force
Solution Approach 1:
The pin member is designed with a curved or bent shape rather than a straight bar-like form. This curvature allows the pin to be inserted through the heat insulating member and bent back to create a locking mechanism, preventing the pin from dropping out while maintaining structural simplicity and providing sufficient holding force
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 design allows for improved durability and reduced costs by enabling rapid temperature adjustments while preventing deformation and disconnection of heating elements, using inexpensive materials and enhancing assembly efficiency.
Implementation Method 1
a heating resistor disposed on an inner circumferential surface of the heat insulating member via a supporting member... The heating element can heat an inside of the furnace to a high temperature such as about 800° C. to 1000° C.
Implementation Method 2
The heat insulating member can reduce a heat quantity lost as radiant heat and conductive heat, so as to enhance efficiency in heating.
Implementation Method 3
the heating element undergoes a creep strain, and slowly increases in length over time. In addition, the heating element is thermally expanded during a heating operation.
Implementation Method 4
there is an apparatus that quickly cools the heating element by blowing air thereto so as to decrease a temperature.
Data Source
AI summary
There is provided a heat processing furnace capable of quickly increasing and decreasing a temperature, while achieving improvement in durability. A heat processing furnace 2 comprises: a processing vessel 3 for accommodating an object to be processed w and performing thereto a heat process; and a cylindrical heater 5 disposed to surround an outer circumference of the processing vessel 3, for heating the object to be processed w. The heater 5 includes a cylindrical heat insulating member 16, and heating resistors 18 arranged along an inner circumferential surface of the heat insulating member 16. Each of the heating resistors 18 is formed of a strip-shaped member that is bent into a waveform having peak portions and trough portions. Pin members 20 are arranged in the heat insulating member 16 at suitable intervals therebetween, the pin members 20 holding the heating resistor 18 such that the heating resistor 18 is movable in a radial direction of the heater.