Wave Bearing Gap Control in Strain Wave Gearing
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Solution Overview
Problem
In strain wave gearing, the wave bearing's flexible races are flexed into an ellipsoidal shape by a rigid plug, leading to varying load conditions for rolling elements, resulting in tight and loose states with gaps between them, which existing retainers fail to maintain effectively, causing increased rotational torque and potential damage.
Innovation Solution
A wave generator with a rigid plug having a non-circular surface and a flexed wave bearing, utilizing gap securing members like elastic claws or magnets to maintain gaps between rolling elements in a tight state without the need for a retainer, ensuring proper spacing and reducing torque and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a retainer is provided to maintain balls at fixed intervals, then the number of balls is limited and rotational torque increases due to sliding between balls and retainer walls, but without a retainer, gaps between rolling elements cannot be maintained in tight state
Solution Approach 1:
The patent removes the retainer component from the wave bearing assembly, extracting the source of sliding friction and torque loss. Instead of using a retainer to maintain ball spacing, the invention relies on the elastic deformation of the wave bearing races themselves to maintain proper ball intervals, thereby eliminating the harmful sliding interactions while still maintaining the necessary geometric constraints for full complement ball operation
Solution Approach 2:
The patent applies different local conditions to different regions of the wave bearing. The wave bearing races are designed with specific elastic properties that allow them to deform locally under load, creating tight-state regions where gaps are maintained between balls. This local elastic deformation provides the necessary gap maintenance function without requiring a global retainer structure
2Quantity of substance
If the number of balls is increased to full complement without a retainer, then ball spacing is improved, but gaps cannot be maintained in tight state leading to ball offset and sliding
Solution Approach 1:
The patent employs dynamic elastic deformation of the wave bearing races to maintain ball positioning stability. As the wave generator rotates, the elastic races dynamically adjust their shape, creating and maintaining tight-state regions where gaps are preserved between adjacent balls. This dynamic elastic response ensures reliable ball spacing throughout the rotation cycle without requiring static retainer structures
Solution Approach 2:
The patent changes the physical state of the wave bearing races from rigid to elastic, allowing them to deform under operational loads. This parameter change enables the races to adapt their geometry in response to varying ball positions and loads, maintaining optimal gaps between balls in tight-state regions while supporting full complement ball configurations
3Manufacturing precision
If a retainer is provided, then ball intervals are maintained, but sliding occurs between balls and retainer walls increasing torque
Solution Approach 1:
The patent removes the retainer component that causes sliding friction, extracting the source of torque loss. The elastic wave bearing races themselves assume the function of maintaining ball intervals through their deformable geometry, eliminating the need for rigid retainer walls that create sliding interfaces and associated friction losses
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 allows for secure gaps between rolling elements in a tight state, preventing increased rotational torque and damage, enabling full complement ball or roller type bearings without the need for retainers, thus enhancing the performance and reliability of strain wave gearing.
Implementation Method 1
the first rolling element being in the loose state and the second rolling element being in the tight state, the gap securing member is a member for applying a braking force to the first rolling element against an orbital motion thereof in a direction toward the second rolling element
Implementation Method 2
an elastic member can be employed, in which the elastic member is disposed in a state capable of being in contact with the first rolling element and applies an elastic force as the braking force
Implementation Method 3
a magnet can be employed as the gap securing member, in which the magnet is disposed in a state capable of facing the first rolling element and applies a magnetic attraction force as the braking force
Implementation Method 4
the wave bearing is flexed into an ellipsoidal shape by the rigid plug, and the flexible inner and outer races thereof are forced to flex outward in the radial direction
Data Source
AI summary
A wave generator of a strain wave gearing is provided with a rigid plug, a wave bearing mounted to the ellipsoidal outer peripheral surface of the rigid plug, and four elastic claws that rotate integrally with the rigid plug. The balls of the wave bearing include balls in a loose state and balls in a tight state. The loose-state balls adjacent to the tight-state balls are applied with braking force by the elastic claws immediately before they transition into a tight state, and the orbital motion thereof is temporarily prevented or suppressed, whereby the gaps between the loose-state balls and the adjacent tight-state balls are secured. It is possible to prevent increase in rotational torque, damage to the balls or other defects due to ball-to-ball contact by the tight-state balls.