Strain Wave Gear Fastening Structure for Radial Load Alignment

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Solution Overview

Problem

Existing strain wave gearings face issues with radial-direction deformation and displacement at fastening locations due to external loads, which can impair reliability by causing decentering between support bearings and the wave generator, especially when high loads are applied.

Innovation Solution

A component-fastening structure with tapered fastening surfaces inclined relative to the central axis is used, where fastening bolts secure components in the axial direction, preventing sliding and radial-direction displacement by mechanical engagement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional fastening structures with flat surfaces are used, then the structure is simple and easy to manufacture, but radial-direction deformation and displacement occur under external loads

Engineering Contradiction:
Improvefastening reliabilityVSAvoidfastening structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies curvature by replacing flat fastening surfaces with tapered surfaces that have a specific inclination angle. This curved/tapered geometry enables the fastening structure to resist radial-direction deformation under external loads, thereby improving fastening reliability without requiring complex additional components.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent changes the geometric parameters of the fastening surfaces by introducing a specific inclination angle for the tapered surfaces. This parameter modification allows the structure to effectively counteract radial forces while maintaining manufacturing feasibility, thus improving reliability without excessive complexity.

Inventive Principle:
Principle #35Parameter changes

2Strength

If fastening locations are designed based only on torsional moment, then the design is simple, but radial force resistance is insufficient causing decentering

Engineering Contradiction:
Improveradial force resistanceVSAvoidfastening design complexity
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The patent modifies the design parameters by incorporating the inclination angle of tapered fastening surfaces, which directly enhances radial force resistance. This parameter change allows the structure to handle both torsional moments and radial forces effectively, improving strength while keeping the design relatively simple.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent applies different geometric properties to different regions of the fastening structure. The tapered surfaces with specific inclination angles are applied locally at the fastening locations to provide enhanced radial force resistance, while other parts of the structure maintain their conventional simple design, thus balancing strength and ease of manufacture.

Inventive Principle:
Principle #3Local quality

3Stability of the object's composition

If support bearings are attached to end plates, then the structure is compact, but decentering occurs between bearings and wave generator under load

Engineering Contradiction:
Improvegear alignment stabilityVSAvoidfastening structure complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent uses tapered fastening surfaces with inclination angles to prevent radial-direction deformation of end plates. This curved geometry maintains the compact structure while preventing decentering between support bearings and the wave generator, thereby improving alignment stability without adding significant complexity.

Inventive Principle:
Principle #14Spheroidality (Curvature)

4Power

If high loads are applied to the output-side end plate, then the power transmission capability is high, but radial force causes displacement at fastening locations

Engineering Contradiction:
Improvepower transmission capabilityVSAvoidfastening reliability
Core Design Contradiction:
PowerVSReliability

Solution Approach 1:

The tapered fastening surfaces with specific inclination angles enable the structure to handle high loads effectively. The curved geometry distributes and resists radial forces generated during high power transmission, preventing displacement at fastening locations and maintaining reliability even under high power conditions.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

By changing the geometric parameters of the fastening surfaces to include specific inclination angles, the structure gains the capability to withstand high radial forces associated with high power transmission. This parameter modification allows high power transmission while maintaining fastening reliability.

Inventive Principle:
Principle #35Parameter changes

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 solution effectively suppresses radial-direction deformation and displacement, preventing decentering between the wave generator and support bearings, ensuring a firm fastening state and maintaining gear alignment under radial loads.

Implementation Method 1

The first and second tapered fastening surfaces are engaged with each other through a fastening bolt, thereby sliding of the first and second fastening surfaces in the radial direction is prevented.

Methodology Applied
Scientific EffectMechanical engagement: Friction

Data Source

PatentEP4711642A1Component-tightening structure and strain wave gearing
Publication Date: 2026.03.18 HARMONIC DRIVE SYST IND CO LTD
  • EP4711642A1 patent drawingFigure 1(A)~1(C)
  • EP4711642A1 patent drawingFigure 2
  • EP4711642A1 patent drawingFigure 3

AI summary

Provided is strain wave gearing (1), in which on a fastening surface between a boss (33) on an externally toothed gear (3) and a first end plate (8), formed are tapered fastening surfaces (331, 81), inclined with respect to an orthogonal plane that is orthogonal to a central axis (1a). Additionally, on a fastening surface between an internally toothed gear (2) and a second end plate (10), tapered fastening surfaces (21, 101) are formed. Due to engagement of the tapered fastening surfaces (331, 81) and engagement of the tapered fastening surfaces (21, 101), a firm fastening state can be formed, and radial-direction displacement of the first and second end plates (8, 10) that arises due to radial-direction load can be reduced. Decentering between a wave generator (4) and support bearings (7, 9) originating in the radial-direction displacement can be prevented or controlled, and the acting of unnecessary radial force on the wave generator (4) can be averted.