Sprung Transaxle Mounting for EV Vibration Isolation

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Solution Overview

Problem

Existing powertrain configurations for electric vehicles face challenges in minimizing vibration of transaxle components, increasing unsprung mass, complicating electrical and fluid line routing due to suspension travel, and requiring complex design elements like hypoid or bevel gears.

Innovation Solution

The powertrain configuration includes a drive unit and a transaxle with a transmission and axle assembly, where the drive unit and transmission are mounted transverse to the chassis and offset from the rotational axis to isolate them from vibrational loads. This configuration contributes to a reduced unsprung mass and improved vibration isolation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the transmission is mounted on the rotational axis, then the powertrain structure is simplified, but the transmission is subjected to vibrational loads from the wheels

Engineering Contradiction:

Improvepowertrain structureVSAvoidvibrational loads on transmission

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

A subframe is introduced as an intermediary component between the transmission and the vehicle chassis. The subframe is flexibly mounted to the chassis and carries the transmission, actuating as a vibration isolator to prevent vibrational loads from the wheels from being transmitted to the transmission, while maintaining structural connectivity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Volume of moving object

If the drive unit and transmission are integrated closely, then space is optimized, but vibration isolation becomes more difficult

Engineering Contradiction:

Improvepowertrain spaceVSAvoidvibration transmission

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The powertrain is segmented into distinct functional modules: the drive unit (electric motor), the transmission, and the axle assembly. Each module is independently mounted - the drive unit and transmission on the subframe, and the axle assembly separately - allowing vibration isolation while maintaining compact overall packaging

Inventive Principle:

Principle #1Segmentation

3Stability of the object's composition

If conventional rigid mounting is used, then structural stability is maintained, but vibration isolation is poor

Engineering Contradiction:

Improvepowertrain structural stabilityVSAvoidvibrational loads

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The subframe mounting system transitions from rigid to dynamic compliance. The subframe is flexibly mounted to the chassis using compliant connections that allow controlled movement and vibration absorption, providing both structural stability for power transmission and vibration isolation for the transmission

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12220986B2Multispeed transaxle with sprung powertrain mounting and methods therefor

Publication Date: 2025.02.11 ALLISON TRANSMISSION INC

AI summary

Vehicles, powertrains for vehicles, and methods of mounting powertrains to chassis of vehicles are disclosed herein. A vehicle includes a chassis, a plurality of wheels, and a powertrain. The chassis extends along a longitudinal axis from a first end to a second end arranged opposite the first end. The plurality of wheels are coupled to the chassis between the first end and the second end and configured for rotation about a rotational axis. The powertrain is mounted to the chassis transverse to the longitudinal axis between the first end and the second end. The powertrain is configured to drive rotation of the plurality of wheels about the rotational axis in use of the vehicle.