Dual-Output Planetary Transmission With Sum-Torque-Free Layout

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Solution Overview

Problem

Existing transmissions are mechanically complex and have a longer axial length, which limits their efficiency and increases costs, and they generate sum torque that can lead to increased stress on rotating components.

Innovation Solution

A transmission design that integrates two planetary gear sets with specific connections to prevent sum torque generation, allowing for both torque conversion and distribution between output shafts, using a non-rotatable structural element to support one of the gear sets, thereby reducing complexity and axial length.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If traditional separate transmission and differential assemblies are used, then torque distribution is achieved, but device complexity and axial length increase

Engineering Contradiction:

Improvetransmission structure complexityVSAvoidtorque distribution function

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent combines the transmission gearing and differential transmission into a single integrated assembly. The planetary gear sets serve dual functions: torque conversion through gear reduction and torque distribution to output shafts. This merging eliminates the need for separate differential assemblies, reducing device complexity while maintaining torque distribution capability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The planetary gear sets are designed to perform multiple functions simultaneously. The same gear elements that provide torque conversion also enable torque distribution to multiple output shafts. This multi-functionality reduces the number of components needed while ensuring reliable torque distribution, directly addressing the contradiction between complexity and reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If sum torque is generated at differential cage, then torque distribution is achieved, but stress on rotating components increases

Engineering Contradiction:

Improvetorque distributionVSAvoidstress on rotating components

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent extracts the torque distribution function from the rotating differential cage and relocates it to the housing support structure. By fixing one element of the second planetary gear set to the housing, the housing becomes the support that receives reaction forces, eliminating sum torque from rotating components and reducing their stress while maintaining torque distribution.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The housing acts as an intermediary structure that absorbs and distributes reaction forces. Instead of rotating components bearing the full sum torque, the housing mediates the force distribution, protecting rotating elements from excessive stress while enabling torque distribution to output shafts.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If two separate assemblies are used for torque conversion and distribution, then functions are achieved, but axial length increases

Engineering Contradiction:

Improvetorque conversion and distribution functionsVSAvoidaxial length

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent implements a nested arrangement where planetary gear sets are positioned concentrically along the axial direction. Elements of the first planetary gear set are connected to elements of the second planetary gear set, creating a compact nested structure. This nesting reduces axial length while maintaining both torque conversion and distribution functions through the integrated design.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 integrated design achieves torque conversion and distribution efficiently, reduces stress on components, and lowers costs by eliminating the need for separate differential assemblies, while maintaining high efficiency and compactness.

Implementation Method 1

a torque introduced via the input shaft is converted and divided between the two output shafts in a defined ratio

Methodology Applied

Scientific EffectGear mechanism: Gear

Implementation Method 2

the planetary gear sets each comprise multiple elements in the form of sun gear, planet carrier and ring gear

Methodology Applied

Scientific EffectPlanetary gear set: Epicyclic Gearing

Data Source

PatentUS11884146B2Transmission and vehicle with transmission

Publication Date: 2024.01.30 ZF FRIEDRICHSHAFEN AG

AI summary

The disclosure relates to a transmission comprising an input shaft, a first output shaft, a second output shaft, a first planetary gear set, and a second planetary gear set which is connected to the first planetary gear set. Each of the planetary gear sets comprises multiple elements. The input shaft, the two output shafts, the planetary gear sets, as well as the elements thereof are arranged and designed such that—a torque introduced via the input shaft is converted and is distributed to the two output shafts in a defined ratio, and the development of a sum torque is prevented. At least one element of the first planetary gear set is rotationally fixed to another element of the second planetary gear set. Another element of the second planetary gear set is secured to a rotationally fixed component.