Axially Movable Traction Gear for Compact Transmission

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Solution Overview

Problem

Existing traction drives in motor vehicle transmissions experience high wear due to axial offset compensation, which limits their use in transmissions with limited installation space.

Innovation Solution

The traction mechanism allows the first traction wheel to be axially movable relative to the bearing journal, eliminating the need for axial offset compensation by the traction mechanism, thereby reducing wear and enabling a compact design suitable for transmissions with limited space.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the chain is used to compensate for axial offset between traction wheels, then the axial offset is compensated, but high wear occurs on the chain and the traction drive size increases

Engineering Contradiction:
Improveservice life of traction mechanismVSAvoidwear on chain
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The first traction wheel is made axially movable relative to the bearing journal through a bearing that permits axial movement. This dynamic design allows the first traction wheel to automatically adjust its axial position to match the second traction wheel, eliminating the need for chain-based compensation and thereby preventing wear on the chain while maintaining reliable torque transmission.

Inventive Principle:
Principle #15Dynamics

2Reliability

If the chain is made long enough to compensate for axial offset, then axial offset compensation is achieved, but the traction drive cannot be used in transmissions with little installation space

Engineering Contradiction:
Improveaxial offset compensationVSAvoidsize of traction drive
Core Design Contradiction:
ReliabilityVSVolume of moving object

Solution Approach 1:

The bearing journal is designed with a bearing that allows the first traction wheel to move axially within a certain range. This dynamic positioning capability enables the traction drive to accommodate axial misalignment without requiring a long chain, thus maintaining a compact design suitable for transmissions with limited installation space while ensuring reliable operation.

Inventive Principle:
Principle #15Dynamics

3Device complexity

If the first traction wheel is fixed relative to the bearing journal, then the structure is simple, but axial offset between traction wheels causes high wear and requires larger size

Engineering Contradiction:
Improvestructural simplicityVSAvoidservice life of traction mechanism
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The bearing journal incorporates a bearing that enables axial movement of the first traction wheel while maintaining rotational support. This dynamic feature adds minimal structural complexity but dramatically improves reliability by eliminating wear on the chain through automatic axial alignment, extending the service life of the entire traction mechanism.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP3453917B1Traction drive for a motor vehicle transmission
Publication Date: 2021.08.04 ZF FRIEDRICHSHAFEN AG
  • EP3453917B1 patent drawingFigure 1
  • EP3453917B1 patent drawingFigure 2
  • EP3453917B1 patent drawingFigure 3

AI summary

The invention relates to a traction drive for a motor vehicle transmission, comprising a first traction gear which can be connected to a first transmission component in a rotationally fixed manner, a second traction gear which is connected to the first traction gear by means of a traction element and which can be connected to a second transmission component in a rotationally fixed manner, and a bearing journal for supporting the first traction gear. The traction drive is characterized in that the first traction gear is arranged to be axially movable relative to the bearing journal.