Hybrid Engine Cranking Torque Control for Hydrolock Prevention
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Solution Overview
Problem
Hybrid electric vehicles face engine and transmission damage during restarts when the engine or transaxle is hydrolocked or seized, as traditional start/restart methods apply excessive torque, leading to potential damage.
Innovation Solution
A system and method that control engine cranking torque by applying a first limit if the engine rotates freely and a second, higher limit if it does not, allowing verification of rotation before full-torque start, with a diagnostic code to alert the driver of potential issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional starter motor or electric machine is used to rotate the engine at high torque for quick restart, then engine restart speed is improved, but engine or transmission damage may occur when engine is hydrolocked or seized
Solution Approach 1:
The system performs a preliminary low-torque cranking action before full engine start to verify engine freedom of rotation. The controller applies a first cranking torque limit during an initial cranking period to check if the engine rotates freely, and only if this verification succeeds does the system proceed to apply a second, higher cranking torque limit for complete engine startup. This preliminary verification prevents damage by detecting hydrolock or seizure conditions before full-power engagement.
Solution Approach 2:
The system dynamically changes the cranking torque parameter based on engine response verification. The controller adjusts the cranking torque limit between two distinct levels: a first limit for verification purposes and a second limit for full startup. This parameter adaptation allows the system to optimize between quick restart and damage prevention by selecting appropriate torque levels based on real-time engine behavior.
2Object-affected harmful factors
If lower torque is applied to verify engine rotation before full start, then engine damage prevention is improved, but restart time increases
Solution Approach 1:
The engine starting process is segmented into distinct phases with different torque characteristics. The first phase applies a limited cranking torque to verify rotation freedom over a predetermined period, and the second phase applies full cranking torque for complete startup. This temporal segmentation allows the system to efficiently verify engine status without significantly extending total restart time, as the verification phase is brief and conditional.
3Device complexity
If traditional engine start method is used without rotation verification, then device complexity is reduced, but reliability of engine operation decreases
Solution Approach 1:
The controller implements a feedback mechanism that monitors engine rotation response during the initial cranking period. Based on this feedback regarding whether the engine rotates freely or exhibits resistance (hydrolock/seizure), the controller automatically adjusts the cranking torque limit applied to the engine. This feedback control enhances reliability by preventing damage under abnormal conditions while maintaining operational simplicity through automated decision-making.
Data Source
AI summary
A system or method for controlling an engine in a hybrid vehicle include cranking the engine subject to a first torque limit in response to an engine start request, receiving an engine rotational position signal, and cranking the engine subject to a second torque limit in response to the engine rotational position signal indicating a number of engine revolutions being less than a threshold value.