Wave Generator Thermal Expansion Locking for High-Speed Efficiency
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Solution Overview
Problem
High-speed rotation in wave gear devices leads to significant agitation resistance from lubricating agents, resulting in reduced torque transmission efficiency due to the rolling movement of balls in the wave bearing.
Innovation Solution
A wave generator with a rigid cam plate featuring a minor axis-side portion made from a material with a high coefficient of linear expansion, which thermally expands to lock the rolling elements, preventing relative rotation and reducing agitation resistance by forming a locked state with the wave bearing during high-speed operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a plurality of balls roll at high speed in the wave bearing, then smooth rotation between the rigid cam plate and flexible externally toothed gear is achieved, but considerable agitation resistance acts on each ball due to the lubricating agent, reducing torque transmission efficiency
Solution Approach 1:
The invention changes the physical state of the wave bearing from a rolling state to a locked (integral rotation) state through thermal expansion. By heating the wave bearing, the clearance between balls and raceways changes, causing the balls to lock in position. This transforms the high-speed rolling motion that generates agitation resistance into a locked state where the wave bearing rotates integrally with the rigid cam plate, eliminating the harmful agitation resistance while maintaining smooth operation
Solution Approach 2:
The invention utilizes a phase transition in the operational state of the wave bearing. Through thermal heating, the wave bearing transitions from a state where balls freely roll (with lubricating agent agitation) to a locked state where balls are positioned such that the wave bearing rotates integrally with the cam plate. This phase transition in operational mode eliminates the agitation resistance problem during high-speed rotation
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 locked state of the wave bearing ensures smooth integral rotation with the rigid cam plate, maintaining adequate meshing between gears and preventing torque transmission efficiency reduction caused by agitation resistance, while allowing sufficient lubrication for high-speed operation.
Implementation Method 1
the minor axis-side portion is formed from a material having a large coefficient of linear expansion in comparison with a remaining portion of the rigid cam plate
Data Source
AI summary
A wave generator (4) of a wave gear device (1) is formed from a material in which only the minor axis-side portions (51, 52), which include the two end portions (51a, 52a) of an elliptical minor axis Lmin, has a larger coefficient of linear expansion than the other portions. When the temperature of a rigid cam plate (5) increases during high-speed rotational input, the minor axis-side portions (51, 52) thermally expand considerably more than the other portions do, and balls (10) other than several balls (10b) on a minor axis Lmin of a wave bearing (7) enter a tight state and form a locked state in which the wave bearing (7) rotates integrally with the rigid cam plate (5). Since the generation of agitation resistance of the lubricating agent due to the high-speed rolling movement of the balls (10) during high-speed rotational input can be avoided or reduced, a reduction of the torque transmission efficiency caused by the agitation resistance can be prevented or inhibited.