Wave Gear Device with Internal Rigid Gear

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional wave gear devices, such as cup-shaped, silk-hat-type, and flat-type, face limitations in reducing the outside diameter dimension due to the restrictive nature of rigid internally toothed gears, leading to inefficiencies in space utilization and lubrication distribution.

Innovation Solution

A wave gear device design featuring a flexible internally toothed gear that can flex radially, with a rigid externally toothed gear and wave generator positioned internally, allowing the internal-tooth-formation portion and pushed portion to be displaced along the center axis, enabling effective utilization of external space and reducing the outside diameter dimension.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If rigid internally toothed gears are used in conventional wave gear devices, then the structure is simple and easy to manufacture, but the outside diameter dimension cannot be reduced and space utilization is inefficient

Engineering Contradiction:

Improveoutside diameter dimensionVSAvoidstructure complexity

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent inverts the conventional configuration by placing the rigid gear on the inside and the flexible gear on the outside. This inversion allows the rigid externally toothed gear to be positioned within the flexible internally toothed gear, enabling compact arrangement and reduction of the overall outside diameter dimension while maintaining structural simplicity

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies nesting by placing the rigid externally toothed gear inside the flexible internally toothed gear. This nested arrangement allows both gears to occupy overlapping spatial regions, effectively utilizing the internal space and reducing the device's external dimensions without increasing structural complexity

Inventive Principle:

Principle #7Nested doll (Nesting)

2Area of stationary object

If rigid internally toothed gears are positioned on the outside of the flexible gear, then the structure is conventional and easy to manufacture, but the external space cannot be effectively utilized

Engineering Contradiction:

Improveexternal space utilizationVSAvoidmanufacturing ease

Core Design Contradiction:

Area of stationary objectVSEase of manufacture

Solution Approach 1:

The patent inverts the conventional positioning by placing the rigid gear inside rather than outside the flexible gear. This inversion frees up the external space around the flexible internally toothed gear for other components or functions, while the inverted configuration remains manufacturable using standard gear manufacturing processes

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If lubricated components are positioned on both inside and outside of the flexible gear, then the lubrication coverage is comprehensive, but the grease-coated range is large and lubrication efficiency is reduced

Engineering Contradiction:

Improvelubrication coverageVSAvoidlubrication efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent merges the positioning of lubricated components to the inside only, combining the lubrication function into a single location. This merging reduces the total grease-coated range while maintaining reliable lubrication coverage for all moving parts, thereby improving lubrication efficiency and reducing energy loss

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

This design allows for a smaller outside diameter dimension, efficient space utilization, and improved lubrication distribution by positioning lubricated components internally, reducing the grease-coated range and enhancing lubrication efficiency.

Implementation Method 1

a flexible internally toothed gear capable of flexing in a radial direction

Methodology Applied

Scientific EffectFlexing: Elasticity

Implementation Method 2

a wave generator disposed on the inside of the flexible internally toothed gear, push the flexible internally toothed gear radially outward from the inside

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Data Source

PatentUS8997607B2Wave gear device and flexible internally toothed gear

Publication Date: 2015.04.07 HARMONIC DRIVE SYST IND CO LTD

AI summary

In a wave gear device, an annular rigid externally toothed gear is disposed on the inner side of a cup-shaped flexible internally toothed gear. An internal-tooth-formation portion of the flexible internally toothed gear and a pushed portion pushed by a wave generator and flexed ellipsoidally are formed in different positions along the center axis line. The wave generator is disposed on the inner side of the flexible internally toothed gear, the pushed cylindrical portion is pushed from the inner side to the outside along the radial direction thereof by the wave generator, whereby the pushed cylindrical portion is flexed ellipsodially. As the outside diameter dimension of the wave gear device is determined by that of the flexible internally toothed gear, a wave gear device having a small outside diameter dimension can be obtained.