Sheathed-Element Glow Plug Temperature Control
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Solution Overview
Problem
Existing methods for controlling the temperature of sheathed-element glow plugs in internal combustion engines are inadequate due to inhomogeneous temperature distribution and surface cooling by the fuel-air mixture, leading to inaccurate control based on internal heater temperatures rather than surface temperatures.
Innovation Solution
Determining the temperature difference between the glow plug heater and its surface as a function of a time constant and operating parameters, using exponential functions or power series to account for thermal inertia and dynamic operating conditions, allowing precise temperature assessment without additional thermocouples and enabling improved control quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the temperature control is based on the resistance of the current-conducting wire inside the glow plug, then the control can be implemented, but the control quality is inadequate because the internal temperature differs from the surface temperature
Solution Approach 1:
The patent introduces a thermal model as an intermediary between the measurable electrical parameters (power, time) and the desired temperature output. This model computes the temperature distribution within the glow plug and at its surface, bridging the gap between internal heater temperature and surface temperature without requiring direct surface measurement. The model acts as a virtual sensor that translates electrical control inputs into accurate surface temperature estimates.
Solution Approach 2:
The patent replaces the need for physical surface temperature sensors (such as thermocouples) with a computational thermal model. Instead of mechanically inserting additional measurement devices into the glow plug structure, the solution uses mathematical modeling and computation to derive surface temperature from electrical parameters, thereby substituting a mechanical sensing approach with a computational one.
2Measurement precision
If additional thermocouples are used to measure the surface temperature, then the temperature measurement accuracy improves, but the device complexity and hardware requirements increase
Solution Approach 1:
The patent creates a virtual copy of the thermal behavior of the glow plug through a computational model. Instead of physically copying the measurement function with additional thermocouples, the model replicates the thermal dynamics and temperature distribution patterns, providing an accurate representation of surface temperature without physical duplication of sensing hardware.
Solution Approach 2:
The thermal model serves as an intermediary that translates easily measurable electrical parameters (power consumption, heating duration) into accurate surface temperature estimates. This intermediary computation eliminates the need for complex hardware installations while maintaining measurement precision.
3Ease of operation
If the glow plug temperature is controlled without considering the cooling effect of the fuel-air mixture, then the control is simpler, but the temperature control accuracy deteriorates under dynamic operating conditions
Solution Approach 1:
The patent performs preliminary computation of the thermal model before actual temperature control is executed. By pre-calculating the thermal characteristics and incorporating cooling effects into the model, the system prepares accurate temperature predictions in advance, allowing simple real-time control based on these pre-computed relationships without sacrificing accuracy.
Solution Approach 2:
The patent implements a dynamic thermal model that adapts to changing operating conditions, including variable cooling effects from the fuel-air mixture. The model continuously adjusts temperature predictions based on current engine operating parameters, maintaining accuracy throughout transient and dynamic operation rather than relying on static assumptions.
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 approach allows for precise temperature control of sheathed-element glow plugs during dynamic engine operation, accounting for variable conditions and surface cooling, enhancing control quality by considering the time offset for thermal flow, thus maintaining optimal glow plug parameters without additional hardware.
Implementation Method 1
a heater which preheats the cold sheathed-element glow plug to a temperature which is high enough for igniting the fuel-air mixture
Implementation Method 2
the surface of the sheathed-element glow plug is always cooled by the air stream which flows as a fuel-air mixture past the sheathed-element glow plug
Implementation Method 3
the resistance is higher the greater the temperature of the wire
Data Source
AI summary
In a method for ascertaining a temperature of a sheathed-element glow plug in an internal combustion engine, a temperature difference between the temperature of a glow plug heater inside the sheathed-element glow plug and a temperature at an arbitrary location on the sheathed-element glow plug is determined as a function of at least one operating parameter of the internal combustion engine and/or at least one operating parameter of the sheathed-element glow plug. The temperature of the sheathed-element glow plug is ascertained from a temperature value represented by a measured value, and from the determined temperature difference.