Vehicle Axle Drive Coupling for Front Axle Drag Loss Reduction
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Solution Overview
Problem
Existing all-wheel-drive electric vehicles experience drag losses due to deactivated front axle drives being dragged along during rear-wheel-only operation, which reduces efficiency and vehicle range.
Innovation Solution
A drive device with a positive-lock coupling mechanism between the electric motor and vehicle wheels, controlled by a coordinator, allows for seamless coupling and decoupling to prevent drag losses by using an actuator and synchronization processes to manage torque and speed alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor is deactivated during rear-wheel-only operation, then energy efficiency is improved, but drag losses increase due to the deactivated front axle drive being dragged along
Solution Approach 1:
The drive shaft is segmented into two separate shaft sections (wheel-side and electric motor-side) that can be independently controlled. The positive-lock coupling allows these segments to be connected when needed and separated when the electric motor is deactivated, preventing the drag losses that occur when the entire drive train remains connected.
Solution Approach 2:
The coupling state between the two shaft sections is made dynamic rather than fixed. The positive-lock coupling mechanism allows the system to transition between coupled and decoupled states based on driving conditions, enabling the front axle to be dynamically disconnected from the electric motor during rear-wheel-only operation to eliminate drag losses.
2Force
If the positive-lock coupling is used to connect shaft sections, then torque transmission is improved, but coupling complexity increases due to the need for synchronization and control mechanisms
Solution Approach 1:
Before the positive-lock coupling engages, the coordinator controls the electric motor to synchronize the rotational speeds of the two shaft sections. This preliminary synchronization action ensures that when the coupling engages, there is minimal speed differential, reducing mechanical shock and simplifying the coupling process despite the added complexity of the control system.
Solution Approach 2:
The actuator control unit receives feedback about the coupling state and shaft speeds to control the actuator and electric motor appropriately. This feedback mechanism allows the system to monitor and adjust the coupling process in real-time, managing the complexity through intelligent control rather than purely mechanical means.
3Ease of operation
If the sliding sleeve is made axially displaceable on the splined connection, then coupling ease is improved, but manufacturing precision requirements increase
Solution Approach 1:
The sliding sleeve acts as an intermediary element between the two shaft sections. It engages with the splined connection to transmit axial movement and control the coupling engagement. This intermediary component simplifies the coupling operation by providing a dedicated mechanism for engagement/disengagement while the splined connection handles the precision requirements through its self-aligning geometry.
Data Source
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AI summary
The invention relates to a drive apparatus for a vehicle axle (VA) of a two-tracked vehicle, having an electric machine (EM) which outputs to output shafts (7, 9) via an axle differential (3), each of which output shafts leads to a vehicle wheel, wherein one of the output shafts (9) is subdivided into a wheel-side shaft portion (17) and an electric-machine-side shaft portion (19) which can be drivingly coupled to each other by means of a form-fit coupling (21) in order to bring the electric machine (EM) into driving connection with the vehicle wheels (5) during driving operation, or which can be decoupled form each other in order to prevent drag losses during driving operation when the electric machine (EM) is deactivated.