Center Differential Gear Assembly Torque Distribution
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Solution Overview
Problem
Existing center differential gear assemblies for motor vehicles lack an efficient mechanism for torque distribution and recuperation, particularly in mild hybrid vehicles, where the electric machine does not require high power, and there is a need for a compact design that combines electric superposition and hybrid functions.
Innovation Solution
A compact center differential gear assembly incorporating a planetary gear train with a clutch device that connects an electric machine to both driven shafts, allowing for differential torque compensation and recuperation, where the electric machine can directly connect with the second driven shaft in a second shift position for additional torque or energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional center differential gear assembly is used for torque distribution, then the basic differential function is provided, but the system lacks efficient torque recuperation capability and requires high power electric machines for mild hybrid vehicles
Solution Approach 1:
The patent combines the center differential gear assembly with an electric machine and clutch device to integrate torque distribution and recuperation functions into a single compact unit. The electric machine can operate in both motor mode (providing additional torque) and generator mode (recuperating energy), eliminating the need for separate high-power electric machine systems in mild hybrid vehicles.
Solution Approach 2:
The electric machine serves multiple functions: it acts as a torque amplifier during acceleration, a recuperator during deceleration, and can provide torque vectoring capability. This multi-functionality allows the system to achieve efficient energy recovery without requiring dedicated high-power electric machines, thereby reducing overall system complexity while improving energy efficiency.
2Productivity
If an electric machine is integrated into the center differential gear assembly for torque distribution and recuperation, then efficient energy recovery is enabled, but the device complexity increases
Solution Approach 1:
The patent segments the torque distribution function into two pathways: a mechanical pathway through the planetary gear train for continuous differential action, and an electrical pathway through the clutch-connected electric machine for active torque modulation. This segmentation allows each subsystem to operate independently yet cooperatively, improving overall torque distribution efficiency while keeping the added complexity manageable through functional separation.
3Power
If the electric machine is directly connected to the second driven shaft, then additional driving torque and recuperation are achieved, but the construction becomes less compact
Solution Approach 1:
The electric machine is nested within the existing center differential gear assembly structure, utilizing the space around the planetary gear train. The clutch device is integrated into the same housing, with the electric machine's input shaft connected to the differential case and output shaft connected to the second driven shaft. This nesting approach provides additional driving torque capability while maintaining a compact overall 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 efficient torque distribution and recuperation, providing a compact construction for mild hybrid vehicles that combines active center differential and hybrid functions, allowing for enhanced acceleration and energy recovery without the need for high power generation from the electric machine.
Implementation Method 1
an electric machine (31) which can be operatively connected via a clutch device (33) in a first shift position (34) with a differential gear (5) and in a second shift position (35) directly with a second driven shaft (4)
Implementation Method 2
to carry out a recuperation, in which the electric machine is operated as generator. Thus, at least the second driven shaft is slowed down by the electric machine during recuperation and respective kinetic energy is converted into electric energy
Data Source
AI summary
A center differential gear assembly for a drive device of a motor vehicle includes a driveshaft, a first driven shaft for a front axle of the motor vehicle, a second driven shaft for a rear axle of the motor vehicle, and a differential gear designed as a planetary gear train. A clutch device operatively connects an electric machine in a first shift position via the differential gear with the second driven shaft and in a second shift position directly with the second driven shaft. A superposition gear includes a first planetary gear train and a second planetary gear, with a ring gear of the first planetary gear train and a ring gear of the second planetary gear train being operatively connected in fixed rotative engagement with one another.