Strain Wave Gearing With Selective Friction for Retention Torque Relief
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Solution Overview
Problem
In pancake-shaped or flat strain wave gearings, it is challenging to lower increased-speed efficiency without reducing reduced-speed efficiency, which is necessary to minimize electric power consumption during different operating conditions.
Innovation Solution
The implementation of a friction member with a friction surface that the externally toothed gear contacts during increased-speed operation, allowing for a reduction in torque transmission efficiency only during increased-speed operation by inducing friction loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a friction member is added to reduce increased-speed efficiency, then input-side retention torque is reduced, but device complexity increases
Solution Approach 1:
The externally toothed gear is designed with flexibility to enable axial movement during speed changes. This flexible structure allows the gear to naturally contact the friction member during increased-speed operation without requiring complex retention mechanisms, thereby reducing input-side retention torque while maintaining relatively simple device architecture
Solution Approach 2:
The friction member acts as an intermediary element that selectively engages with the externally toothed gear during increased-speed operation. This intermediary component enables controlled friction loss to reduce retention torque requirements while maintaining reduced-speed efficiency, adding minimal complexity to achieve the desired force reduction
2Loss of energy
If friction loss is introduced during increased-speed operation, then torque transmission efficiency is reduced, but energy consumption is optimized
Solution Approach 1:
The system dynamically adjusts friction loss based on operating conditions. During increased-speed operation, the externally toothed gear moves axially to contact the friction member, introducing controlled friction loss to optimize energy consumption. During reduced-speed operation, no friction loss is introduced, maintaining high torque transmission efficiency when it is most needed
Solution Approach 2:
The friction coefficient between the externally toothed gear and friction member is specifically optimized to achieve the desired balance. By controlling the friction parameter to be sufficient for reducing retention torque during increased-speed operation but not excessive, the system optimizes energy consumption while preserving adequate torque transmission efficiency for load-bearing operations
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 solution effectively reduces the input-side retention torque even under high load torque conditions, while maintaining reduced-speed efficiency, thus optimizing energy consumption.
Implementation Method 1
a friction member provided with a friction surface with which the externally toothed gear, moving in a first direction, can come into contact
Data Source
AI summary
In a strain wave gearing, a thrust force applied on an externally toothed gear during an increased-speed operation causes the externally toothed gear to move along an axis in a first direction, and the output-side end surface thereof is pressed, by a prescribed force, against a friction surface of a friction plate integrated with a rotating shaft part of a strain wave generator. Torque transmission efficiency can be reduced only during increased-speed operation, by means of a friction loss occurring between the externally toothed gear and the friction plate. When large load torque is applied from an output shaft which is an output-side member during reduced-speed operation, retention torque of the strain wave generator which is an input-side member during speed-reduction operation can be reduced.