Ravigneaux Drive Unit for Seamless Gear Shifting and NVH Control

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Solution Overview

Problem

Existing drive units for motor vehicles lack efficient gear switching mechanisms that allow for uninterrupted power transmission and compact design, leading to suboptimal NVH behavior and limited power density.

Innovation Solution

A drive unit featuring a Ravigneaux gear set with a switching assembly and a translation assembly, coupled with an electric machine, a differential, and brake systems, enabling seamless gear shifting and compact dimensions, thereby improving power density and NVH performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a conventional transmission design is used, then the structure is simpler, but the power density and NVH behavior are suboptimal

Engineering Contradiction:

Improvepower densityVSAvoidtransmission structure

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent combines two sun gears (first and second sun gears) and two sets of planetary gears (first and second planetary gears) into a single integrated shift assembly known as a Ravigneaux gear set. This merging of components allows multiple gear ratios to be achieved within a compact structure, significantly increasing power density while maintaining manageable complexity through systematic design.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The transmission assembly employs a nested arrangement where the first and second planetary gears are concentrically positioned around the first and second sun gears respectively, with the second planetary carrier nested within the first planetary carrier structure. This nesting enables compact packaging of multiple gear trains, improving power density without proportionally increasing overall size.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Adaptability or versatility

If gear switching is implemented, then multiple gear ratios are achieved, but uninterrupted power transmission becomes difficult

Engineering Contradiction:

Improvegear ratio switchingVSAvoiduninterrupted power transmission

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The transmission design ensures continuous power transmission through overlapping engagement of brake elements during gear shifts. The first brake and second brake are coordinated such that as one brake disengages, the other is already engaged or in the process of engaging, eliminating any interruption in power flow from the electric motor through the transmission to the differential.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The first ring gear and second planet carrier act as intermediary elements that facilitate smooth transitions between different gear ratios. These components provide continuous mechanical connection paths, allowing power to be redirected between different planetary gear sets without complete disengagement, thereby maintaining uninterrupted transmission.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Volume of moving object

If compact dimensions are achieved, then installation space is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improvetransmission volumeVSAvoidmanufacturing complexity

Core Design Contradiction:

Volume of moving objectVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

Inventive Principle:

Principle #5Merging (Combining)

4Object-affected harmful factors

If a Ravigneaux gear set is used, then NVH behavior is enhanced, but device complexity increases

Engineering Contradiction:

ImproveNVH behaviorVSAvoidshift assembly structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The Ravigneaux gear set utilizes asymmetric tooth configurations and differential positioning of the first and second planetary gears at different radial distances from the center. This asymmetric design creates favorable NVH characteristics by distributing meshing forces more evenly and reducing vibration, while the systematic arrangement keeps manufacturing complexity manageable.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentEP3967535B1Drive unit

Publication Date: 2025.01.15 ROBERT BOSCH GMBH

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AI summary

The invention relates to a drive unit (10) comprising an electric machine (12) and a transmission (14), wherein the transmission (14) has a switching assembly (18) and a transmission assembly (32).