Glow Plug Temperature Control Using Calculated Current-Voltage Variable
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Solution Overview
Problem
Existing methods for controlling the surface temperature of glow plugs, particularly ceramic ones, suffer from poor precision due to large variations in cold resistance caused by manufacturing processes, leading to inconsistent performance.
Innovation Solution
A method that uses a calculated variable from current and voltage, rather than electrical resistance, for closed-loop control, with two specific calculation rules: one for the entire series of glow plugs and another adaptable to each individual plug, using a fit function with adaptable parameters to minimize temperature deviations, and adjusting the duty cycle of pulse-width modulation for precise temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If electrical resistance is used as control variable, then control method is simple, but temperature control precision deteriorates due to manufacturing tolerances
Solution Approach 1:
The patent changes the control parameter from electrical resistance to a newly defined variable calculated from current and voltage measurements. This new parameter better reflects the actual heating effect and is less sensitive to manufacturing tolerances, thereby improving temperature control precision while maintaining reasonable system complexity
Solution Approach 2:
The patent implements closed-loop feedback control where the calculated variable is continuously monitored and used to adjust the heating current. The control unit compares the actual value with the target value and modifies the duty cycle accordingly, ensuring precise temperature control despite variations in glow plug characteristics
2Measurement precision
If individual adaptation for each glow plug is implemented, then temperature control precision is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary characterization of each glow plug during manufacturing or initial operation to determine its specific calculation rule. This preliminary action captures individual characteristics and stores them for later use, enabling precise control without requiring complex real-time adaptation mechanisms
Solution Approach 2:
The patent introduces adaptable parameters in the calculation rule that can be individually adjusted for each glow plug based on its characteristics. These parameters allow the control system to dynamically adapt to individual plug variations while maintaining a unified control structure, balancing precision and complexity
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 control of glow plug surface temperature, reducing deviations and extending the service life by avoiding overheating, while being applicable across various manufacturing tolerances and engine conditions.
Implementation Method 1
the electrical resistance of the glow plug is used as a control variable. Here, the electrical resistance is calculated from continuously measured values of the heating current and of the electrical voltage
Data Source
AI summary
A method for controlling 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, a temperature-dependent control variable is calculated from measured values of the heating current and the voltage using a first calculation rule, a target value of the control variable is calculated from a target temperature using a second calculation rule, the control variable is compared with the target value and, to minimize any deviation, the duty cycle of the pulse-width modulation is changed in accordance with this deviation. A value other than electrical resistance dependent on current and voltage is used as the control variable. The calculation rule in accordance with which this variable is calculated from measured values of current and voltage is provided to carry out the method and is established in each case for a series of glow plugs.