Glow Plug Control via Temperature Gradient Monitoring
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Solution Overview
Problem
Existing methods for controlling glow plug temperature in diesel engines during the preheating phase are challenging due to rapid temperature rises, which can lead to overheating and damage, and are hindered by production-related resistance scatter and the complexity of physical or mathematical modeling.
Innovation Solution
The method involves measuring the time derivative of a temperature-dependent electric variable, comparing it with threshold values, and adjusting the supply voltage to control the heating process, thereby managing the temperature gradient to prevent overloading and ensure safe, rapid heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the glow plug is heated rapidly to reach ignition temperature quickly, then the engine can be started without delay, but the glow plug risks being overloaded and damaged due to excessive temperature overshoot
Solution Approach 1:
The control device monitors the actual temperature of the glow plug during preheating and compares it with the desired temperature curve. Based on this feedback, the control device adjusts the supply voltage dynamically to keep the temperature within safe limits while achieving rapid heating, thus preventing damage due to excessive temperature overshoot.
Solution Approach 2:
The control device dynamically adjusts the supply voltage to the glow plug during the preheating phase based on real-time temperature measurements. This dynamic control allows the system to optimize the heating rate at each moment, ensuring rapid temperature rise while preventing thermal overload and extending glow plug service life.
2Measurement precision
If direct temperature measurement is implemented to control glow plug temperature, then precise temperature control is achieved, but the device complexity increases
Solution Approach 1:
The control device uses an intermediary approach by measuring temperature-dependent electrical properties (such as resistance) of the glow plug instead of directly measuring temperature with complex thermal sensors. This intermediary measurement method provides sufficient temperature information for control purposes while keeping the system relatively simple.
3Measurement precision
If the glow plug resistance scatter due to production variations is accounted for, then measurement accuracy improves, but the control system complexity increases
Solution Approach 1:
The control device compensates for production-related resistance scatter by dynamically adjusting measurement and control parameters based on actual glow plug characteristics. Instead of using fixed parameters, the system adapts its parameters in real-time to account for variations in glow plug resistance, thereby maintaining measurement accuracy without requiring complex calibration procedures.
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 control of the glow plug temperature without direct temperature measurement, reducing the risk of damage and optimizing the heating process by adjusting the voltage based on the gradient, ensuring the glow plug reaches the desired temperature quickly and safely.
Implementation Method 1
The voltage supply 7 supplies a steady voltage for the microprocessor 2 and the interface 5. When the diesel engine is started in cold condition, then the control unit 1 supplies the heater plugs 1 with a heating-up voltage of 11 Volts, for example, in time average so that the glow plugs will as quickly as possible exceed the ignition temperature—approximately 860° C.—and reach the steady-state temperature
Data Source
AI summary
A method for controlling a glow plug in a diesel engine, in particular in the preheating phase, is described. According to the invention, it is provided that the time gradient of an electrical variable which varies according to the temperature of the glow plug is measured and compared with a threshold value, and when said time gradient exceeds or drops below the threshold value, the electric supply voltage of the glow plug is changed.