Axial Flow Rotor Coupling With Hirth Teeth and Clean Air Gaps

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Solution Overview

Problem

Existing axial flow machines for motor vehicles face challenges in achieving a compact and secure connection of rotors, particularly in high-speed applications, while maintaining efficient lubrication and preventing lubricant ingress into critical air gaps.

Innovation Solution

The rotors are connected in a form-fit and rotationally fixed manner using Hirth toothings, bypassing the stator, and secured with a hollow screw element, while utilizing sealing elements and radial bearings to ensure lubrication and maintain air gap cleanliness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If rotors are connected using conventional fastening methods, then connection strength is achieved, but construction space and weight increase

Engineering Contradiction:

Improveconnection strengthVSAvoidconstruction space

Core Design Contradiction:

StrengthVSVolume of moving object

Solution Approach 1:

The Hirth toothing connection method allows one rotor to be nested within or adjacent to another rotor with interlocking toothings, creating a compact arrangement where rotors are directly connected without requiring separate mounting structures or additional fastening components, thereby reducing construction space while maintaining connection strength

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent replaces conventional mechanical fastening systems (screws, bolts, brackets) with a Hirth toothing mechanism that uses interlocking gear-like toothings on the rotor surfaces. This substitution eliminates the need for separate fastening components and reduces construction space while providing secure, torque-capable connections suitable for high rotation speeds

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If rotors are connected securely, then reliability at high rotation speeds is improved, but device complexity increases

Engineering Contradiction:

Improvereliability at high rotation speedsVSAvoidconnection structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The connection structure is segmented into modular Hirth toothing elements distributed around the rotor periphery. Each toothing segment independently contributes to the overall connection strength and torque transfer, allowing the system to handle high rotation speeds through distributed load bearing while maintaining a relatively simple overall structure that can be manufactured using standard gear-cutting processes

Inventive Principle:

Principle #1Segmentation

3Volume of moving object

If compact connection is achieved, then construction space is minimized, but manufacturing precision requirements increase

Engineering Contradiction:

Improveconstruction spaceVSAvoidtoothing engagement precision

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The Hirth toothing employs curved, arc-shaped tooth profiles that follow the rotational path of the rotors. This curvature allows for gradual engagement and disengagement of the toothing elements, providing self-aligning characteristics that reduce sensitivity to manufacturing tolerances while maintaining compact rotor connections suitable for high-speed operation

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS12609596B2Axial flow machine for a motor vehicle

Publication Date: 2026.04.21 MERCEDES BENZ GROUP AG

AI summary

An axial flow machine for a motor vehicle includes a stator having two rotors that can be rotated in relation to the stator. The stator is arranged between the rotors in the axial direction of the axial flow machine. The rotors are connected to each other in a rotationally fixed manner by means of respective toothings of the rotors, said toothings being arranged on sides of the rotors facing towards each other in the axial direction.