On-Axis Electric Drive Axle With Nested Reduction and Disconnect Clutch
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Solution Overview
Problem
Existing electric axles with on-axis electric machines face challenges in accommodating additional components due to compactness, leading to reduced power and performance, and reliability issues, while existing solutions struggle to optimize space without increasing overall dimensions.
Innovation Solution
An electric axle design with a compact configuration featuring a tubular drive shaft, epicyclic reduction unit, and a nested differential, allowing for torque reduction and disconnection of the electric machine from the axle, using a tubular shaft interposed between the drive shaft and half-shaft, with a clutch mechanism to manage torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the electric machine is kept connected to the axle during driving, then continuous torque transmission is maintained, but energy losses due to eddy currents and stator winding excitation increase
Solution Approach 1:
The patent extracts the electric machine from the continuous torque transmission path by introducing a disconnection mechanism. The further tubular shaft can be disconnected from the drive shaft, effectively removing the electric machine from the torque transmission chain when it is not needed for propulsion, thereby eliminating eddy current losses and stator winding excitation losses during pure combustion engine operation.
Solution Approach 2:
The patent implements a dynamic torque transmission system where the connection between the electric machine and the torque transmission path can be changed based on operating conditions. The clutch mechanism or equivalent joint allows the system to switch between connected and disconnected states, enabling the electric machine to be dynamically integrated or extracted from the torque transmission path.
2Adaptability or versatility
If additional components such as suspensions and braking systems are accommodated in the axle, then vehicle functionality is improved, but the available space for the electric machine and transmission is reduced
Solution Approach 1:
The patent employs nested configuration where the first half-shaft is nested within the drive shaft, and the differential is nested within the reduction unit. This multi-level nesting arrangement allows multiple components to occupy the same spatial envelope, effectively increasing component accommodation capability without increasing the overall axle volume.
Solution Approach 2:
The patent utilizes axial positioning to arrange components along the longitudinal axis of the axle. The reduction unit is positioned axially adjacent to the electric machine, with its input port near the first end of the drive shaft. This axial arrangement optimizes the use of available space by distributing components along the length of the axle rather than competing for radial space.
3Volume of stationary object
If the overall dimensions of the axle are reduced for compactness, then space occupancy is improved, but the power and performance of the electric machine are decreased
Solution Approach 1:
The nested configuration of half-shafts and differentials within the compact axle structure allows the electric machine to maintain its power output without increasing overall axle dimensions. The nesting of transmission components creates efficient use of internal space, preserving the volume available for the electric machine while keeping the external dimensions compact.
4Volume of stationary object
If the reduction unit is positioned axially adjacent to the electric machine, then compact arrangement is achieved, but the complexity of torque transmission path increases
Solution Approach 1:
The differential is nested within the reduction unit, with the reduction unit's train carrier connected to the differential box. This nested arrangement integrates multiple torque transmission functions within a compact structure, achieving space efficiency while managing transmission path complexity through hierarchical component integration.
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 design achieves torque reduction without increasing overall dimensions, improves reliability by limiting eddy current losses, and optimizes space for additional components, enhancing performance and reducing stress on the parking wheel system.
Implementation Method 1
reduction unit preferably of the epicyclic type, more preferably of the 'stepped' type also named 'compound' having an input port, preferably defined by a sun gear, connectable for torque transmission to the drive shaft
Implementation Method 2
second end, opposite to the first, operatively connectable to said drive shaft, e.g. by means of a clutch mechanism or equivalent joint
Data Source
Figure 1
AI summary
Electric axle for an on-axis vehicle, comprising a casing, in which an electric machine is housed, comprising a tubular drive shaft having a first end and a second end opposite to the first, emerging with respect to a rotor of the electric machine, a reduction unit comprising an input port connectable in torque transmission to the drive shaft, arranged in an axial position with respect to the electric machine, in a position proximal to the first end, a differential at least partially nested in the reduction unit, a first and a second half-shaft coaxial with each other and operationally connected to said differential, wherein said first half-shaft is nested in the drive shaft, a further tubular shaft, operationally interposed between said drive shaft and said first half-shaft, wherein the further tubular shaft has a first end stably fixed to said first port of the reduction unit, and a second end, opposite to the first, operationally connectable with said drive shaft.