Hybrid Engine Start via Torque Converter Angular Momentum
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Solution Overview
Problem
Modern hybrid vehicles face challenges in starting the internal combustion engine efficiently, especially at higher speeds and low temperatures, due to limited power reserve in 48 V lithium-ion battery systems, leading to hesitation and slow acceleration when switching from electric to hybrid driving modes.
Innovation Solution
A method and system that utilize a transmission unit with a torque converter and lock-up clutch, where the second clutch is disengaged to a predetermined torque level, the lock-up clutch is engaged, and the first clutch is used to bring the internal combustion engine to a rotational speed, allowing for quick starting by injecting fuel and igniting it, while additional torque from the electric machine enhances the start procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an Integrated Starter Generator (ISG) is used to propel the vehicle at higher speeds, then the vehicle can operate in electric driving mode, but the power reserve of the electrical system becomes insufficient for starting the internal combustion engine
Solution Approach 1:
The torque converter accumulates angular momentum during electric driving mode before the engine start is initiated. This preliminary accumulation of rotational energy in the torque converter provides the necessary starting power without requiring additional battery capacity, resolving the contradiction between power reserve and starting power.
2Reliability
If the internal combustion engine is started using traditional 12 V starter system, then the engine can be started reliably, but the vehicle cannot take advantage of the 48 V electrical system and hybrid architecture
Solution Approach 1:
The torque converter is designed to serve dual functions: traditional fluid coupling for power transmission and energy storage device for engine starting. This multi-functionality allows the 48 V electrical system and hybrid architecture to be utilized for engine starting while maintaining starting reliability, resolving the contradiction between reliability and adaptability.
3Ease of operation
If the engine is started while the vehicle is moving, then the transition from electric to hybrid mode can be achieved, but hesitation and slow acceleration occur due to power limitations
Solution Approach 1:
The torque converter accumulates angular momentum during the period before engine start is initiated. When the engine start is commanded, this pre-stored angular momentum is immediately transferred to the engine through the lock-up clutch, enabling rapid engine acceleration and smooth mode transition without hesitation, resolving the contradiction between ease of operation and acceleration speed.
4Power
If a flywheel is used for starting the internal combustion engine, then the engine can be started using stored rotational energy, but the solution is not suitable for modern hybrid vehicles requiring compact engine and transmission design
Solution Approach 1:
The torque converter is utilized for dual purposes: traditional power transmission during vehicle operation and energy storage for engine starting. By making the torque converter multi-functional, the patent eliminates the need for a separate flywheel system, achieving the required starting power without increasing system volume, thus resolving the contradiction between power and volume.
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
Enables quick and hesitation-free starting of the internal combustion engine, even in low temperatures, by optimizing the use of angular momentum and torque distribution, improving driveability and compactness of the vehicle design.
Implementation Method 1
A method and system for starting an internal combustion engine of a hybrid vehicle when the hybrid vehicle is powered by an electric machine... utilizing a transmission unit with a torque converter... where the second clutch is disengaged to a predetermined torque level such that there is a slip in the second clutch... bringing the internal combustion engine to a first rotational speed by the angular momentum stored in the torque converter
Data Source
AI summary
Method and system for starting an internal combustion engine of a hybrid vehicle, adapted to rotate a drive shaft providing torque via a transmission unit comprising a first clutch connecting the engine to an input shaft of a gearbox connected to a torque converter connected to a second clutch connecting the torque converter to the at least one driving wheel, where the input shaft is connected to an electric machine; the method comprising: disengaging the second clutch to a predetermined torque level such that there is a slip in the second clutch; engaging the lock-up clutch; engaging the first clutch to bring the engine to a first rotational speed; disengaging the first clutch when the engine has reached the first rotational speed; starting the engine, and engaging the first clutch when the engine has started and rotates with a second rotational speed.