Transfer Case Torque Distribution for Hybrid 4WD
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Solution Overview
Problem
Hybrid four-wheel drive or all-wheel drive vehicles require extensive design changes and cost increases due to specialized powertrains that differ significantly from traditional powertrains, making it challenging to integrate both internal combustion engines and electric motors efficiently.
Innovation Solution
A transfer case design incorporating an input shaft, primary and secondary output shafts, an electric motor, and a planetary gear set, with a torque transfer mechanism that allows selective coupling between the shafts and gears, enabling indirect torque transfer between the electric motor and secondary output shaft, and controlled operation modes by a controller to optimize power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a specialized hybrid powertrain is used to enable both internal combustion engine and electric motor operation, then the vehicle can operate in multiple drive modes (engine-only, electric-only, hybrid), but the device complexity and manufacturing cost increase significantly
Solution Approach 1:
The transfer case is designed to perform multiple functions: it serves as the traditional torque distribution device for engine-only operation, while also functioning as a hybrid integration point that can couple the electric motor to either the input shaft or output shafts. The same transfer case housing and gear set accommodate both traditional 4WD operations and hybrid powertrain operations, eliminating the need for separate specialized components for each drive mode.
Solution Approach 2:
The transfer case acts as an intermediary component between the electric motor and the drivetrain. Rather than directly coupling the electric motor to the wheels or requiring complex dedicated hybrid components, the transfer case provides a flexible interface that can route electric motor torque through its existing gear set and shafts, simplifying the overall hybrid system architecture.
2Device complexity
If the electric motor is directly coupled to the secondary output shaft, then torque transfer is simplified, but the device complexity increases due to specialized coupling mechanisms
Solution Approach 1:
The transfer case's existing shafts and gear set are utilized to provide the torque transfer path for the electric motor. The input shaft, output shafts, and planetary gear set serve dual purposes: traditional 4WD torque distribution and electric motor torque transfer. This eliminates the need for dedicated coupling mechanisms specifically designed for electric motor integration.
3Adaptability or versatility
If extensive design changes are made to integrate the electric motor, then hybrid operation is enabled, but manufacturing cost increases
Solution Approach 1:
The transfer case is designed as a universal component that maintains compatibility with traditional 4WD systems while accommodating hybrid powertrain integration. The same housing, gear set, and shafts serve both traditional and hybrid operations, allowing manufacturers to leverage existing 4WD transfer case manufacturing capabilities and supply chains for hybrid vehicle production.
Solution Approach 2:
The system incorporates selectable coupling mechanisms that allow the electric motor to be dynamically connected or disconnected from the drivetrain based on operating conditions. This dynamic configuration capability enables the same hardware to support multiple drive modes without requiring permanent structural modifications that would increase manufacturing complexity and cost.
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 solution allows for efficient power distribution between the engine and electric motor in various modes, including engine-only, electric-only, hybrid, and regeneration, while maintaining compatibility with traditional powertrain components, reducing design and cost complexities.
Implementation Method 1
The planetary gear set has a ring gear rotatably fixed to the input shaft, a planet carrier rotatably fixed to the primary output shaft, and a sun gear rotatably fixed to an output of the electric motor
Data Source
AI summary
A transfer case capable of multiple drive ratios (i.e. high and low) in all operating modes of a hybrid all-wheel or four-wheel drive vehicle. The transfer case comprises an input shaft, a primary output shaft, a secondary output shaft, an electric motor, and a planetary gear set. The secondary output shaft is selectively rotatably coupled to the primary output shaft. The planetary gear set has a ring gear rotatably fixed to the input shaft, a planet carrier rotatably fixed to the primary output shaft, and a sun gear rotatably fixed to an output of the electric motor.