Dual-Motor Differential Gear Unit for EV Torque Vectoring
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Solution Overview
Problem
Existing electric drive units for motor vehicles struggle to achieve a needs-based, particularly advantageous torque distribution, which is essential for efficient driving dynamics, especially during cornering.
Innovation Solution
The electric drive unit incorporates a differential with a sun gear connected to the sum shaft in a rotationally fixed manner, along with a superimposed planetary gear set, and includes switching units to couple the second rotor to the ring gear or sum shaft, allowing for torque vectoring and efficient single-engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a differential with superimposed planetary gear set is used, then torque distribution capability is improved, but device complexity increases
Solution Approach 1:
The patent combines a differential with a superimposed planetary gear set into a single integrated gear unit. The differential and planetary gear set share common components (sun gear, planetary gears, ring gear), merging two functions into one compact structure that enables both torque distribution and gear ratio variation without requiring separate mechanisms.
Solution Approach 2:
The gear unit serves multiple functions simultaneously: it acts as a differential for torque distribution between left and right wheels, a planetary gear set for torque amplification and gear ratio variation, and a torque vectoring mechanism for enhancing yaw moments. This multi-functionality resolves the contradiction by achieving versatile torque control without proportionally increasing device complexity.
2Adaptability or versatility
If two electric engines are used for torque vectoring, then torque distribution is improved, but use of energy increases
Solution Approach 1:
The patent implements dynamic switching between single-engine and dual-engine operation modes. The control unit activates the second electric engine only when torque vectoring is required (e.g., during cornering or emergency maneuvers), while relying on the first electric engine for normal driving conditions. This dynamic operation reduces overall energy consumption while maintaining torque vectoring capability when needed.
Solution Approach 2:
The system changes operational parameters by varying the torque contribution of each electric engine based on driving conditions. The control unit continuously adjusts the torque distribution between the two engines, optimizing energy efficiency while achieving the desired torque vectoring effect. This parameter-based control allows the system to achieve versatile torque distribution without continuously consuming maximum energy.
3Adaptability or versatility
If switching units are added to couple second rotor to ring gear or sum shaft, then adaptability is improved, but device complexity increases
Solution Approach 1:
The switching units are nested within the existing gear unit structure, utilizing the same spatial envelope and component interfaces. The switching mechanisms are integrated into the planetary gear set architecture, sharing mounting locations and structural support with existing gears and shafts. This nesting approach adds operational flexibility while minimizing the increase in overall device complexity.
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
This configuration enables higher torques in torque vectoring without losing drive power, allowing for enhanced yaw moments and efficient single-engine operation, thereby improving driving dynamics and acceleration.
Implementation Method 1
a first electric engine (18), in particular an axial flux machine, which has a first rotor (22), by means of which first drive torques can be supplied
Implementation Method 2
a second electric engine (24), in particular an axial flux machine, which has a second rotor (28), by means of which second drive torques can be supplied
Implementation Method 3
a superimposed planetary gear set (34), having a sun gear (42), a planetary carrier (44) and a ring gear (46), wherein the sun gear (42) is connected to the sum shaft (36) in a rotationally fixed manner
Data Source
AI summary
An electric drive unit has a first electric engine with a first rotor, a second electric engine which with a second rotor, and a gear unit having a differential, which has exactly three first shafts arranged coaxially to each other. The three first shafts are a sum shaft to which the first rotor is connected in such a way that torques supplied by the first rotor can be introduced into the gear unit via the sum shaft, a first differential shaft coupled to a first vehicle wheel in such a way that torques can be discharged from the gear unit via the first differential shaft and transmitted onto the first vehicle wheel, and a second differential shaft coupled to a second vehicle wheel in such a way that torques can be discharged from the gear unit via the second differential shaft and transmitted onto the second vehicle wheel.