Eccentric Gear Cam Layout for Compact Imbalance-Free Transmission

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Solution Overview

Problem

Cycloidal gears are complex and costly due to the large number of components required to prevent imbalances, leading to a bulky and expensive transmission system.

Innovation Solution

An eccentric gear design with a first gear element having uniformly distributed cams on its outer contour, supporting the second gear element at N+1 contact points, allowing for a compact and balanced transmission without the need for multiple ball bearings and complex cam arrangements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If at least three offset gear rings or cycloidal discs are arranged in series to eliminate imbalance, then the gearbox becomes free of imbalance, but the number of parts and overall length increase

Engineering Contradiction:
Improveimbalance-free operationVSAvoidnumber of parts
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The invention combines multiple cycloidal discs (at least three) onto a single common crankshaft, merging what would traditionally be separate offset gear ring assemblies into one integrated unit. This allows the system to achieve balance through the combined configuration while reducing the overall number of separate parts and assemblies required.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

Each cycloidal disc is segmented to have its own specific number of teeth and eccentric cam configuration, allowing each disc to be optimized for balance while working together as a group. The discs can have different tooth counts (e.g., 72, 74, 76 teeth) to achieve proper phasing and balance without requiring identical components.

Inventive Principle:
Principle #1Segmentation

2Reliability

If at least three offset gear rings or cycloidal discs are arranged in series to eliminate imbalance, then the gearbox becomes free of imbalance, but the overall length of the gearbox increases

Engineering Contradiction:
Improveimbalance-free operationVSAvoidgearbox length
Core Design Contradiction:
ReliabilityVSLength of stationary object

Solution Approach 1:

Multiple cycloidal discs are nested onto the same crankshaft in a compact arrangement, with each disc positioned at different radial distances or angular positions. This nesting approach allows three or more discs to occupy a much smaller axial space than if they were arranged in series along the shaft, dramatically reducing the overall gearbox length while maintaining the balance benefits.

Inventive Principle:
Principle #7Nested doll (Nesting)

3Reliability

If each cycloidal disc is supported by a separate ball bearing on its eccentric cam, then proper support is provided, but the number of components and manufacturing complexity increase

Engineering Contradiction:
Improvesupport stabilityVSAvoidmanufacturing complexity
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The invention merges the bearing support system by using a single ball bearing to support multiple cycloidal discs simultaneously on their respective eccentric cams. Instead of requiring separate bearings for each disc, one bearing handles the combined loads from all discs, dramatically reducing the total component count and simplifying assembly while maintaining adequate support stability.

Inventive Principle:
Principle #5Merging (Combining)

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 design eliminates imbalances in the first transmission element, reduces the number of components and manufacturing costs, and maintains a compact size while ensuring efficient operation and high gear reduction.

Implementation Method 1

The outer contour of the first gear element has a number N of cams projecting radially with respect to the first axis... the second gear element is supported at N+1 contact points on the outer contour of the first gear element

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP3653905B1Eccentric transmission
Publication Date: 2021.06.09 MAXON MOTOR AG
  • EP3653905B1 patent drawingFigure 1
  • EP3653905B1 patent drawingFigure 2
  • EP3653905B1 patent drawingFigure 3

AI summary

The present invention relates to an eccentric gear with a first gear element having a first axis and an outer contour with at least one cam projecting radially with respect to the first axis, and with a second gear element having a second axis which is always held eccentrically with respect to the first axis, wherein the first gear element is rotatably mounted about the first axis relative to the second gear element, and wherein the second gear element is supported on the outer contour of the first gear element in such a way that a rotation of the first gear element about the first axis causes a rotation of the second axis of the second gear element about the first axis.According to the invention, the outer contour of the first gear element has a number N of cams projecting radially with respect to the first axis, which are arranged uniformly distributed in the circumferential direction with respect to the first axis, wherein the second gear element is supported at N+1 contact points on the outer contour of the first gear element, and wherein the number N is at least two.