Multicopter Planetary Transmission With Fluid Mist Cooling

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Solution Overview

Problem

Current transmission devices for aircraft, particularly multicopters, lack an effective cooling concept and are not compact enough to efficiently cool and lubricate their components, which can lead to performance issues and increased energy expenditure.

Innovation Solution

A compact transmission device with a planetary gear set, a drive shaft, and an electric machine, featuring a fluid mist cooling system that utilizes a first fluid circuit for lubrication and cooling, and a second fluid circuit for power electronics, where the fluid mist is generated by a filter element to evenly cool the electric machine components, and a pump is used to convey a second fluid for additional cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a common passively operated oil circuit is used for lubrication and cooling, then the system is simple in structure, but the cooling effectiveness is insufficient and energy expenditure increases

Engineering Contradiction:
Improvecooling system structureVSAvoidenergy expenditure
Core Design Contradiction:
Device complexityVSLoss of energy

Solution Approach 1:

The system uses the rotating output shaft to drive a pump that actively circulates cooling fluid through the system. The kinetic energy from the shaft's rotation is converted into pumping action, creating a self-sustaining cooling circuit that lubricates and cools components without requiring external power sources, thus reducing overall energy expenditure while maintaining structural simplicity

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent implements an active hydraulic cooling circuit where fluid is pumped through channels in the housing and components. This hydraulic system provides controlled fluid flow for effective cooling and lubrication, replacing passive oil circulation with an active pumped system that delivers sufficient cooling performance

Inventive Principle:
Principle #29Pneumatics and hydraulics

2Device complexity

If traditional cooling systems are used, then the system is simple to implement, but the transmission device is not compact enough

Engineering Contradiction:
Improvecooling system implementationVSAvoidtransmission device size
Core Design Contradiction:
Device complexityVSVolume of moving object

Solution Approach 1:

The cooling circuit channels are integrated directly into the housing structure of the transmission device. The housing serves dual purposes as both structural enclosure and cooling fluid conduit, eliminating the need for separate cooling channels or additional cooling components. This merging of functions reduces the overall volume of the transmission device while maintaining effective cooling capability

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The housing is designed with multi-functionality, serving simultaneously as structural support, mounting platform for components, and fluid conduit for cooling. This universal design approach eliminates redundant components and reduces the overall device volume while keeping the cooling system simple to implement

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 solution provides a compact, lightweight, and efficient cooling system that effectively lubricates and cools both the planetary gear set and electric machine, reducing energy expenditure and ensuring reliable operation even during startup, while also cooling power electronics in a modular and integrated drive unit.

Implementation Method 1

a first fluid circuit is provided for lubricating and/or cooling the elements of the planetary gear set and/or for cooling components of the electric machine

Methodology Applied
Scientific EffectLubrication: Lubrication

Implementation Method 2

the fluid mist is generated by a filter element to evenly cool the electric machine components

Methodology Applied
Scientific EffectFluid mist cooling: Aerosol

Implementation Method 3

a pump is used to convey a second fluid for additional cooling

Methodology Applied
Scientific EffectPumping: Pump

Implementation Method 4

a second fluid circuit for cooling components of power electronics and/or for cooling the first fluid

Methodology Applied
Scientific EffectHeat exchange: Heat Exchanger

Data Source

PatentEP3670965B1Transmission device for a multicopter
Publication Date: 2021.04.21 ZF FRIEDRICHSHAFEN AG
  • EP3670965B1 patent drawingFigure 1
  • EP3670965B1 patent drawingFigure 2
  • EP3670965B1 patent drawingFigure 2a

AI summary

The invention relates to a transmission device for a multicopter comprising a drive shaft, an output shaft, a planetary gear set, and an electric motor, wherein the planetary gear set has several elements, namely at least a first element, a second element, and a third element, and wherein the rotor of the electric motor is connected to the drive shaft. In the transmission device, the drive shaft is non-rotatably connected to the first element, and the output shaft is non-rotatably connected to the second element. The third element is fixed to a non-rotatable component.