Strain Wave Gear Unit Structure Using Sliding Bearings
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Solution Overview
Problem
Conventional strain wave gearings are bulky and heavy due to the use of rolling bearings, which limits their compactness and weight reduction potential.
Innovation Solution
Employing a sliding bearing instead of a rolling bearing to support the rigid internally toothed gear and flexible externally toothed gear, with a cylindrical housing and output member, and applying surface treatments for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rolling bearing is used to support the internally toothed gear and externally toothed gear, then the bearing capacity and load support are improved, but the device size and weight increase
Solution Approach 1:
The patent replaces the rolling bearing mechanical system with a sliding bearing system. The sliding bearing uses a cylindrical bush with a plain surface or lubricated coating instead of rolling elements, eliminating the complex structure of rollers or balls while maintaining load support capability through sliding friction and lubrication films.
Solution Approach 2:
The patent changes the bearing type parameter from rolling contact to sliding contact. This parameter change allows for a more compact design with reduced weight, as sliding bearings have simpler structure and fewer components compared to rolling bearings, while still providing adequate support for the strain wave gearing mechanism.
2Strength
If a rolling bearing is used to support the internally toothed gear and externally toothed gear, then the load support is improved, but the device complexity increases
Solution Approach 1:
The patent substitutes the complex rolling bearing system with a simpler sliding bearing system. The sliding bearing consists of a cylindrical bush with a plain bore, eliminating the need for rollers, cages, retainers, and other components associated with rolling bearings, thereby reducing device complexity while maintaining load support function.
Solution Approach 2:
The patent extracts and removes the unnecessary rolling elements and complex internal structure from the bearing system. By using a simple cylindrical bush with lubricated surfaces, the design eliminates extraneous components while retaining the essential function of supporting and guiding the gear rotation.
3Volume of moving object
If a sliding bearing is used instead of a rolling bearing, then the device compactness is improved, but the friction and wear may increase
Solution Approach 1:
The patent replaces the rolling bearing system with a sliding bearing system that uses lubrication films to reduce friction and wear. The cylindrical bush is designed with smooth surfaces and appropriate clearance to maintain hydrodynamic or boundary lubrication, preventing direct metal-to-metal contact and reducing harmful friction and wear effects.
Solution Approach 2:
The patent introduces a lubricant as an intermediary substance between the sliding surfaces of the bearing. The lubricant forms a protective film that separates the contacting surfaces, reducing friction and wear while allowing the compact sliding bearing design to function reliably over time.
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 enables a more compact and lightweight strain wave gearing while maintaining required surface characteristics, such as hardness and lubricity, through the use of materials like light alloys and plastics.
Implementation Method 1
a sliding bearing for supporting a stationary-side part and a driving-side part in a radial direction and in a thrust direction in a state in which the driving-side part is relatively rotatable with respect to the stationary-side part
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
A cup-type strain wave gearing (20) having a unit structure and having: a stationary-side part including a unit housing (22) and an internally toothed gear (23); a driving-side part including an output member (25) and an externally toothed gear (26); and a sliding bearing (28) supporting the stationary-side part and the driving-side part in the radial direction and the thrust direction in a state in which relative rotation is possible. The sliding bearing (28) has a cylindrical bushing (28a) accommodated in a radial gap, and annular bushings (28b, 28c) accommodated respectively in thrust gaps. Thus, it is possible to provide an advantageous strain wave gearing having a unit structure that is more lightweight and compact than when a rolling bearing is used.