Hybrid EV Engine Start Control With Motor Generator Power Suspension
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Solution Overview
Problem
Existing hybrid electric vehicle controllers face challenges in efficiently starting the engine using a motor generator, as they may fail to account for varying engine rotation speeds and prolonged power supply, potentially damaging the battery and failing to start the engine quietly.
Innovation Solution
A controller for a hybrid electric vehicle that employs a two-stage engine starting process, including a first starting process and a second starting process, where power supply to the motor generator is suspended and resumed based on engine rotation speed thresholds and time limits, allowing for successful engine start with the starter if the motor generator fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor generator is driven continuously to crank the engine, then the engine starting reliability is improved, but the battery may be damaged due to prolonged high voltage power supply
Solution Approach 1:
The control device implements periodic action by suspending power supply to the motor generator at specific intervals during the starting process. When the engine rotation speed remains below the threshold after a predetermined time, the power supply is suspended temporarily, then resumed if the engine has not yet started. This periodic suspension and resumption of power supply prevents continuous high voltage discharge that would damage the battery, while still maintaining sufficient starting attempts to ensure engine starting reliability.
2Reliability
If the starter is used to start the engine, then the engine can be started even when the motor generator fails, but loud noise is produced
Solution Approach 1:
The control device acts as an intermediary by intelligently selecting between the motor generator and the starter based on real-time engine rotation speed feedback. The system prefers to use the motor generator (quiet method) but automatically switches to the starter (reliable method) when the engine rotation speed indicates failure to start within the predetermined time. This intermediary control strategy maintains quiet operation whenever possible while ensuring starting capability when needed.
3Object-affected harmful factors
If the power supply to the motor generator is suspended, then the battery is protected from damage, but the engine may fail to start
Solution Approach 1:
The control device implements feedback control by continuously monitoring the engine rotation speed during the starting process. When power supply is suspended, the system checks whether the engine rotation speed has increased above the threshold. If the engine has not started (rotation speed remains below threshold), the power supply is automatically resumed. This feedback mechanism ensures that power supply suspension does not prevent successful engine starting, as the system adapts based on real-time engine response.
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
The two-stage starting process effectively reduces battery damage risk while increasing the likelihood of a quiet and successful engine start by adapting to varying engine conditions, ensuring efficient operation and reduced noise.
Implementation Method 1
driving the motor generator 12 by supplying the motor generator 12 with power from the high-voltage battery 26
Implementation Method 2
the starter is driven by power from a battery. This rotates the crankshaft and then starts the engine
Data Source
AI summary
A controller for a hybrid electric vehicle executes an engine starting process including a first starting process and a second starting process. The first starting process drives a motor generator. The second starting process is executed when a shifting condition is satisfied in the first starting process. The second starting process includes suspending the supply of power to the motor generator and then driving the motor generator. When an engine rotation speed becomes greater than or equal to an engine rotation speed threshold value and an elapsed time is within a second time threshold value during the second starting process, the controller determines that an engine is successfully started. The second time threshold value is greater than a first time threshold value that is compared with the elapsed time during the first starting process.