Glow Plug Temperature Control via Segmented Resistance Measurement
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Solution Overview
Problem
Existing methods for closed-loop control of glow plug surface temperature are inefficient, particularly for ceramic glow plugs, due to the difficulty in determining the temperature of the heating resistor from the total resistance, which is influenced by the resistance of connected conductors and their temperature-dependent fluctuations.
Innovation Solution
A method that incorporates a correction term to account for the non-stationary temperature distribution within the glow plug, adapting the relationship between heating current, voltage, and surface temperature, and incorporating a factor to adjust the control algorithm based on changing heat dissipation, especially in the axial direction, to improve temperature control precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the total resistance of the glow plug is used as a control variable to determine surface temperature, then the temperature control can be implemented, but the measurement precision is poor because the total resistance is influenced by the resistance of connected conductors and their temperature-dependent fluctuations
Solution Approach 1:
The patent segments the total resistance into two components: the resistance of the heating resistor (R_H) and the resistance of the connected conductors (R_C). By measuring both the total resistance and the conductor resistance separately, the system can calculate the heating resistor temperature using only R_H, thereby eliminating the interference from conductor resistance fluctuations and achieving precise temperature measurement.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using the voltage drop across the heating resistor (U_H) and the heating current (I_H) to calculate the heating resistor resistance (R_H = U_H/I_H). This intermediary calculation allows the system to derive the temperature of the heating resistor without being affected by the conductor resistance, thus improving measurement precision.
2Measurement precision
If a correction term is added to account for non-stationary temperature distribution, then the temperature control precision is improved, but the device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the heating current (I_H) and voltage (U_H) across the heating resistor, calculating the instantaneous resistance (R_H), and comparing it with the target resistance corresponding to the desired surface temperature. The control system adjusts the heating current based on this feedback to maintain the target temperature, thereby achieving precise temperature control through dynamic adjustment.
Solution Approach 2:
The patent changes the control parameter from total resistance to heating resistor resistance only. By focusing on the resistance of the heating resistor (R_H) rather than the total resistance, the system can accurately reflect the temperature of the heating resistor without being influenced by the varying resistance of connected conductors, thus improving temperature control precision.
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 enables more precise temperature control by accurately linking actual electrical resistance with surface temperature, improving the quality of temperature regulation and adapting to non-stationary conditions, thereby enhancing the overall control process.
Implementation Method 1
the electrical resistance of the glow plug is normally used as a control variable. The electrical resistance is calculated from continuously measured values of the heating current and of the electrical voltage.
Implementation Method 2
heat flows from the heating resistor to adjacent parts of the glow plug, which are initially still cold but are heated with increasing operating time
Data Source
AI summary
A method for closed-loop control of the surface temperature of a glow plug. A heating current flowing through the glow plug and a voltage applied to the glow plug are measured, and a calculation rule is used, which assigns a value of the surface temperature to a value pair formed of a value of the heating current and a value of the voltage. The calculation rule takes into account the influence of a changing temperature of a feed line of the heating resistor on the relationship between the heating current measured at a given voltage and the surface temperature of the glow plug. Also disclosed is a method for controlling the surface temperature of a glow plug, in which a factor of the control algorithm is calculated by using a correction term, which takes into account the heat dissipation from a glow tip to cooler parts of the glow plug.