Wave Generator Solid Displacement Elements Radial Rigidity

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Solution Overview

Problem

Conventional wave generators using solid displacement elements are insufficient in rigidity and deformation, making it difficult to achieve a large load torque capacity in strain wave gearing applications.

Innovation Solution

The use of monomorphic or bimorphic rectangular plate-shaped solid displacement elements that can be deformed from an arc shape into a semicircular shape, providing increased radial rigidity and deformation, allowing for reliable meshing with internally toothed gears and enabling the generation of a large load torque capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional solid displacement elements are used in wave generator, then the structure is simple, but the rigidity in radial direction is insufficient and deformation amount is small

Engineering Contradiction:
Improveradial rigidityVSAvoidstructure complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The solid displacement element is designed with an arc-shaped cross-section that can deform into a semicircular shape. This curvature design allows the element to achieve large radial displacement and high radial rigidity when transformed from the arc shape to semicircular shape, directly resolving the contradiction between maintaining structural simplicity and achieving sufficient radial rigidity and deformation capability for large load torque capacity.

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Manufacturing precision

If conventional solid displacement elements are used, then the device complexity is low, but the deformation amount required to flex externally toothed gear is insufficient

Engineering Contradiction:
Improvedeformation precisionVSAvoidelement structure complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The arc-shaped cross-section design enables the displacement element to transform into a semicircular shape with precisely controlled geometry. This curvature-based design provides the exact deformation amount needed to flex the externally toothed gear into proper meshing position with the internally toothed gear, achieving manufacturing precision without increasing device complexity.

Inventive Principle:
Principle #14Spheroidality (Curvature)

3Strength

If the solid displacement element is deformed into semicircular shape, then the radial rigidity becomes extremely high, but the element requires more energy for deformation

Engineering Contradiction:
Improveradial rigidityVSAvoidenergy consumption
Core Design Contradiction:
StrengthVSUse of energy by moving object

Solution Approach 1:

The wave generator operates by dynamically transforming the solid displacement elements between arc shape and semicircular shape in a cyclic manner. During the transformation to semicircular shape, energy is input to achieve the deformation; during the return to arc shape, energy is recovered. This dynamic operation allows the system to achieve extremely high radial rigidity at meshing positions while managing energy consumption through the cyclic nature of the wave generator operation.

Inventive Principle:
Principle #15Dynamics

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 increased radial rigidity and deformation capability of the semicircular shape enable the wave generator to effectively handle large load torques by utilizing the enhanced displacement and rigidity of the solid displacement elements, ensuring reliable meshing and relative rotation between the externally and internally toothed gears.

Implementation Method 1

a wave generator using piezoelectric elements which are solid displacement elements stretchable and contactable by energization

Methodology Applied
Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

the solid displacement elements are a monomorphic type or bimorphic type rectangular plate-shape element that is curved into an arc shape, and can be deformed from the arc shape into a semicircular shape by energization

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP3258590B1Strain wave gearing and wave generator
Publication Date: 2020.07.29 HARMONIC DRIVE SYST IND CO LTD
  • EP3258590B1 patent drawingFigure 1(a)~1(b)
  • EP3258590B1 patent drawingFigure 2(a)~2(c)
  • EP3258590B1 patent drawingFigure 3

AI summary

A wave generator (4) of a strain wave gearing (1) uses a plurality of solid displacement elements (12) to flex a flexible externally toothed gear (3) into a non-circular shape and partially mesh the externally toothed with a rigid internally toothed gear (2). The solid displacement elements (12) are obtained by curving a monomorphic or bimorphic type rectangular plate-shaped element into an arc shape and can be deformed from an arc shape (12A) to a semispherical shape (12B) by energization, the semicircular shape having a smaller radius than the arc radius of the arc shape. A wave generator can be realized, which can bear a large load torque by utilizing changes in rigidity, deformation amount, and deformation force associated with the deformation of the solid displacement elements (12).