Hybrid Vehicle ISG Thermal Management and Engine Start Control
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Solution Overview
Problem
In hybrid vehicles, the integrated starter-generator's (ISG) increasing temperature reduces its torque generation capability, potentially preventing the internal combustion engine from starting and depleting batteries, as the ISG's magnetic strength decreases with temperature, necessitating a control system to manage engine operation and load shedding.
Innovation Solution
A controller is configured to start the engine and disable automatic shut-off when the ISG temperature exceeds a de-rated threshold, and further disable low-voltage loads when the temperature reaches a higher disable threshold, thereby maintaining engine operation and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the ISG operates at high temperature, then the vehicle can maintain operation, but the magnetic strength decreases and torque generation capability is reduced
Solution Approach 1:
The system changes operational parameters based on temperature thresholds. When ISG temperature exceeds the de-rated threshold, the controller modifies engine operation parameters (disabling automatic shut-off) and when temperature exceeds the disable threshold, the controller sheds low-voltage loads. This dynamic parameter adjustment compensates for the decreasing magnetic strength at high temperatures.
2Duration of action of stationary object
If the ISG temperature increases, then the vehicle continues operating, but the torque generation capability decreases potentially preventing engine start
Solution Approach 1:
The controller takes preliminary actions before the ISG fails completely. When the temperature exceeds the de-rated threshold, the controller proactively disables automatic engine shut-off and commands the engine to start. When temperature exceeds the disable threshold, the controller preemptively sheds low-voltage loads. These preliminary actions prevent the loss of torque generation capability rather than responding after failure occurs.
Solution Approach 2:
The system dynamically adjusts its operation based on real-time temperature monitoring. The controller continuously monitors ISG temperature and dynamically changes the engine control strategy and load management according to the temperature thresholds, allowing the system to adapt its power delivery and operational characteristics to maintain functionality despite decreasing torque capability.
3Reliability
If the controller disables automatic engine shut-off at high temperature, then the engine can be maintained running, but energy consumption increases
Solution Approach 1:
The controller changes operational parameters based on temperature conditions. At elevated temperatures exceeding the de-rated threshold, the system disables automatic engine shut-off to ensure reliability. When temperature exceeds the disable threshold, the system sheds non-critical low-voltage loads to reduce energy consumption. This conditional parameter adjustment balances reliability requirements with energy management.
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 solution ensures the internal combustion engine can be started and maintained when the ISG temperature is high, preventing battery depletion and optimizing energy usage by managing load reduction effectively.
Implementation Method 1
the ISG's magnetic strength decreases with temperature
Implementation Method 2
the percentage is associated with a permanent magnetic field strength (PMFS) having a value that is 1⁄2 of the PMFS at 0 degrees Celsius
Data Source
AI summary
A vehicle includes an engine and a controller. The controller may be configured to, responsive to indication of a temperature of a starter-generator exceeding a de-rated threshold, command the engine to start and disable engine automatic shut-off. And the controller may be configured to, responsive to indication of the temperature exceeding a disabled threshold, or the temperature exceeding the de-rated threshold and a traction battery discharge power being less than a threshold, command the engine to start and shed a load.