PWM Thermal Control for Vehicle Electric Heater Overheating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric heating devices in motor vehicles face challenges in managing overheating, which can lead to damage of surrounding components and safety issues, particularly in high-temperature conditions or mechanical failures, and current methods for detecting overheating are not sufficient to prevent these issues.
Innovation Solution
A thermal management method that involves a control unit to regulate the setpoint of resistive elements using pulse width modulation, gradually lowering or raising the power setpoint to prevent overheating, and includes a detection threshold value for the duty cycle of the control signal to determine when to activate or stop the regulation phases, ensuring the electric heating device operates within safe temperature limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric heating device operates at high power to provide effective heating, then the heating performance is improved, but the risk of overheating and damage to surrounding components increases
Solution Approach 1:
The control unit proactively monitors temperature and adjusts power output before critical overheating occurs. By detecting temperature trends and predicting potential overheating conditions, the system takes preliminary action to reduce power output, preventing damage to surrounding components while maintaining effective heating operation.
Solution Approach 2:
The system continuously monitors temperature feedback from sensors and dynamically adjusts the power output of the heating device. This closed-loop control ensures that the heating device operates at high power when safe, but automatically reduces power when temperature approaches dangerous levels, resolving the contradiction between heating performance and safety.
2Reliability
If the setpoint is adjusted gradually to prevent overheating, then the safety is improved, but the response time to reach desired temperature increases
Solution Approach 1:
The control unit dynamically adjusts the setpoint based on real-time temperature conditions. When temperatures are safe, the system allows faster, more aggressive heating. When temperatures approach dangerous levels, the system gradually reduces the setpoint. This dynamic adaptation resolves the contradiction by making the heating rate variable rather than fixed.
Solution Approach 2:
The system changes the setpoint parameter dynamically based on temperature feedback. Instead of using a fixed setpoint, the control unit adjusts the setpoint value according to current thermal conditions, allowing fast heating when safe and gradual reduction when necessary, thus balancing safety with response time.
3Measurement precision
If the duty cycle threshold for overheating detection is set low, then the detection sensitivity is improved, but the false alarms increase
Solution Approach 1:
The control unit applies different threshold values for different heating zones or conditions. Instead of a single global threshold, the system can have zone-specific thresholds that account for local thermal characteristics, allowing sensitive detection in critical areas while maintaining higher thresholds in less sensitive areas, reducing false alarms.
Solution Approach 2:
The system performs preliminary analysis of temperature trends and operating conditions before triggering an overheating alarm. By evaluating the context and rate of temperature change, the system can distinguish between normal transient heating and actual overheating conditions, improving detection sensitivity while reducing false alarms.
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
Effectively manages overheating by gradually adjusting the setpoint of the electric heating device, preventing damage to surrounding components and ensuring safe operation by maintaining the electric heating device within acceptable temperature limits, thereby enhancing the safety and reliability of the heating and ventilation systems in motor vehicles.
Implementation Method 1
The resistive elements may be powered by an on-board electrical voltage source, namely batteries. An electrical connector connected to the on-board voltage source on the vehicle may be provided to supply the electrical power required to power the electric heating device
Implementation Method 2
the heating modules include resistive elements, for example with a positive temperature coefficient (PTC), such as ceramics also called PTC stones. These are elements whose resistive value varies very strongly depending on the temperature. More precisely, the ohmic value of PTC resistive elements increases very quickly beyond a predetermined temperature threshold
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to a method for managing heat in the event of detecting overheating of an electrical heating device, in particular for a motor vehicle, comprising a plurality of resistive elements configured to be supplied with electric power using a control signal by pulse width modulation according to a setpoint. According to the invention, the method comprises the following steps: - activating a first phase (P1) of gradual adjustment of the setpoint in a first direction of progression, and repeating the first phase (P1) of adjustment until the recorded duty cycle of the control signal by pulse width modulation (PWM_(sub)system) exceeds a determined detection threshold value (PWM_(sub)system_lim_i), and if not, - activating a second phase (P2) of adjustment of the setpoint in a second direction of progression opposite the direction of progression in the first adjustment phase (P1). The invention also relates to a control unit for implementing such a method.