Glow Plug Coil Segmentation for Rapid Heating
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Solution Overview
Problem
Conventional glow plugs with heat-resistant metals like W or Mo face challenges in rapid temperature rising due to high resistance ratios, leading to unstable combustion and increased exhaust emissions when voltage is lowered to maintain temperature.
Innovation Solution
A glow plug design with a front end coil made from high-melting-point metals like W or Mo, and a rear end coil from FeCrAI or NiCr alloys, where the resistance ratio is lower, ensuring rapid temperature rise while minimizing heat transfer and temperature decrease when voltage is reduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat resistant metal with high resistance ratio (W or Mo) is used for the coil, then the heating temperature can be increased, but the current value abruptly decreases and the rapid temperature rising property is not realized
Solution Approach 1:
The coil is divided into two segments: a front end coil made from heat resistant metal (W or Mo) for high temperature generation, and a rear end coil made from FeCrAl or NiCr alloy for lower resistance. This segmentation allows each part to fulfill different functions - the front end provides high heating temperature while the rear end maintains higher current flow capability, resolving the contradiction between high temperature and rapid temperature rise.
Solution Approach 2:
Different materials with different resistance ratios are used in different locations of the coil. The front end coil uses heat resistant metal with high resistance ratio for high temperature generation, while the rear end coil uses FeCrAl or NiCr alloy with lower resistance ratio to maintain current flow. This local differentiation of material properties resolves the contradiction between high heating temperature and rapid temperature rising property.
2Temperature
If the applied voltage is lowered to saturate the temperature, then the temperature can be maintained, but heat transfers to the rear end coil and the temperature of the front end coil decreases temporarily
Solution Approach 1:
The coil is segmented into front end and rear end portions with different resistance characteristics. When voltage is lowered for temperature saturation, the rear end coil's lower resistance allows it to dissipate heat more effectively, preventing excessive heat transfer to the front end coil and maintaining temperature stability.
Solution Approach 2:
The rear end coil acts as an intermediary element that manages heat distribution. By having the rear end coil made from FeCrAl or NiCr alloy with lower resistance, it serves as a heat buffer that prevents sudden temperature drops in the front end coil when voltage is adjusted for saturation, thereby stabilizing the overall temperature.
3Temperature
If a heat resistant metal with high resistance ratio is used for the coil, then the heating temperature can be increased, but the current value decreases and the rapid temperature rising property is not realized
Solution Approach 1:
The coil is divided into front end and rear end segments with different materials. The rear end coil made from FeCrAl or NiCr alloy has lower resistance and allows higher current flow, while the front end coil made from heat resistant metal generates high temperature. This segmentation resolves the contradiction between high heating temperature and sufficient current value for rapid energy delivery.
Solution Approach 2:
Different materials are used locally within the coil structure - heat resistant metal at the front end for high temperature generation and FeCrAl or NiCr alloy at the rear end for lower resistance and higher current flow. This local quality differentiation allows the system to achieve both high heating temperature and adequate current value simultaneously.
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 design achieves increased heating temperature and rapid temperature rising properties while stabilizing engine combustion and reducing exhaust emissions by optimizing the resistance distribution and structure of the coils.
Implementation Method 1
the resistance of the coil abruptly increases and the current value abruptly decreases... Since the heat generation amount is proportional to the square of the current value
Data Source
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AI summary
[Objective] To provide a glow plug that can realize increase in heating temperature and ensure rapid temperature rising property, and that can suppress temperature decrease when an applied voltage is lowered in order to saturate the temperature. [Means for Solution] This glow plug includes: a front end coil connected to the front end of a tube and containing W or Mo as a principal component; and a rear end coil connected to the rear end of the front end coil. A resistance ratio which is the ratio of a resistance value at 1000°C of the front end coil relative to a resistance value at 20°C of the front end coil is greater than a resistance ratio which is the ratio of a resistance value at 1000°C of the rear end coil relative to a resistance value at 20°C of the rear end coil. Relative to the resistance value at 20°C between the front end of the tube and the rear end of the front end coil, the proportion of the resistance value at 20°C between a position of the front end coil at 4 mm from the front end of the tube toward the rear side in the axis direction and the front end of the tube is 55% to 80%.