Hybrid Engine Start Using Torque Converter Energy Storage
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Solution Overview
Problem
Modern hybrid vehicles face challenges in starting internal combustion engines at low temperatures due to limited power from 48 V lithium-ion batteries and excessive friction torque, which can lead to hesitation and difficulty in compact engine and transmission designs.
Innovation Solution
A method and system that utilize a torque converter with a lock-up clutch and offset auxiliary drive source to accelerate the input shaft and torque converter to a predetermined rotational speed, engaging the clutch to start the engine with stored energy, preventing hesitation and enabling cold starts down to -30 °C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a 48 V lithium-ion battery and starter motor system is used in modern hybrid vehicles, then the electrical system voltage is increased to 48 V, but the starter motor cannot provide sufficient torque to overcome friction at very low temperatures below -15 °C
Solution Approach 1:
The system performs preliminary action by accelerating the input shaft and torque converter to a predetermined rotational speed before engine start. This stores kinetic energy in the rotating mass of the input shaft and torque converter, which is then released to provide the additional torque needed to overcome high friction at low temperatures during engine cranking.
Solution Approach 2:
The torque converter acts as an intermediary element between the auxiliary drive source and the internal combustion engine. It transmits and amplifies the torque from the auxiliary drive source to the engine, enabling the system to overcome the friction torque barrier at low temperatures without requiring a larger starter motor.
2Reliability
If additional starter motors or flywheels are added to enable cold starts, then the starting capability at low temperatures is improved, but the engine and transmission design becomes less compact
Solution Approach 1:
The auxiliary drive source is designed with multi-functionality, serving both as the primary propulsion motor for the hybrid vehicle and as the drive source for accelerating the input shaft and torque converter during engine start. This eliminates the need for a separate dedicated starter motor, maintaining compact packaging while enabling reliable cold starts down to -30 °C.
Solution Approach 2:
The system merges the starting function with the existing torque converter and input shaft components of the transmission system. By utilizing the rotational inertia and kinetic energy already present in these components, the invention combines multiple functions into existing structures, avoiding additional space-consuming components like traditional flywheel-starter assemblies.
3Device complexity
If the auxiliary drive source is directly coupled to the engine for starting, then the starting process is simplified, but hesitation occurs when switching from electrical driving mode to hybrid driving mode
Solution Approach 1:
The system performs preliminary acceleration of the input shaft and torque converter to a predetermined rotational speed before engaging the engine. This preliminary action ensures that when the engine starts and transitions to hybrid mode, the rotational speeds are already matched, preventing hesitation and ensuring smooth transition between electrical and hybrid driving modes.
Solution Approach 2:
The system dynamically controls the coupling and decoupling of the auxiliary drive source with the transmission system through clutch mechanisms. This dynamic control allows the auxiliary drive source to accelerate the input shaft independently when needed, then smoothly transfer to engine-driven operation without causing hesitation, adapting the system behavior to different operating conditions.
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 reliable and hesitation-free starting of internal combustion engines in hybrid vehicles at low temperatures, achieving a compact engine and transmission design without the need for additional starter motors or flywheels.
Implementation Method 1
accelerating the input shaft and the torque converter with the auxiliary drive source to a predetermined rotational speed
Implementation Method 2
a torque converter with a lock-up clutch and offset auxiliary drive source to accelerate the input shaft and torque converter
Implementation Method 3
engaging the clutch to start the engine with stored energy
Data Source
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AI summary
Method and system for starting an internal combustion engine of a hybrid vehicle, where the internal combustion engine is adapted to rotate a drive shaft providing torque to at least one driving wheel of the hybrid vehicle via a transmission unit; where the transmission unit comprises a first clutch connecting the internal combustion engine to an input shaft of a gearbox connected to a torque converter, where the torque converter is connected to a second clutch connecting the torque converter to the at least one driving wheel through a transmission, where the input shaft is connected to an auxiliary drive source in an offset arrangement with a predetermined torque ratio between the input shaft and the auxiliary drive source; the method comprising the steps of disengaging the first clutch, disengaging the second clutch to a predetermined torque level, accelerating the input shaft and the torque converter with the auxiliary drive source to a predetermined rotational speed; and engaging the first clutch to start the internal combustion engine with the energy stored in the input shaft, in the torque converter and in the auxiliary drive source.