Wave Gear Modified Tooth Profiles Prevent Coning Interference
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Solution Overview
Problem
Coning-induced interference occurs in wave gear devices with cup-shaped or 'silk hat'-shaped flexsplines when the tooth profiles of the splines are designed with the same depth, limiting the use of typical gear cutting methods due to the inability to perform linear machining effectively.
Innovation Solution
A wave gear device with modified tooth profiles featuring tapered surfaces on both the external and internal teeth, allowing for constant tooth depth with parallel bottom and top lands, preventing interference by adjusting the angles and ranges of the tapered surfaces to avoid coning, enabling the use of typical machining mechanisms like linear machining for gear cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the tooth profiles of the splines are designed with the same depth (constant tooth depth), then the manufacturing process becomes simpler and typical gear cutting methods can be used, but coning-induced interference occurs at the open end of the flexspline where the tip surfaces of the teeth interfere with the bottom lands of the other spline
Solution Approach 1:
The patent applies local quality by making the tooth depth variable along the tooth trace direction. Specifically, the tooth depth is reduced in the region affected by coning (near the open end of the flexspline) while maintaining constant tooth depth in other regions. This localized modification eliminates the interference between tip surfaces and bottom lands caused by coning, while preserving the simplicity of manufacturing in unaffected areas.
2Object-affected harmful factors
If end relief machining is performed to make teeth gradually recede to prevent coning-induced interference, then tooth interference is eliminated, but linear machining cannot be used and limitations are imposed on gear cutting methods
Solution Approach 1:
The patent applies parameter changes by modifying the tooth depth parameter along the tooth trace direction. Instead of using complex end relief machining that changes the tooth profile shape, the invention simply reduces the tooth depth parameter in the affected region. This approach eliminates coning-induced interference while maintaining compatibility with typical linear gear cutting methods, as the modified tooth profile can still be generated using standard machining processes.
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 modified tooth profiles allow for interference-free meshing and enable the use of standard machining processes, such as wire cutting, to manufacture the gear components, overcoming the limitations of coning-induced interference in wave gear devices.
Implementation Method 1
a cup-shaped or 'silk hat'-shaped flexspline is bent into an elliptical shape to mesh with a circular spline
Implementation Method 2
the external teeth of the cup-shaped or 'silk hat'-shaped flexspline, bent in a state in which the amount of bending gradually increases in a radial direction toward the open end of the flexspline, to mesh with the internal teeth of the circular spline without interference
Data Source
AI summary
A bending state known as “coning,” in which the amount of bending of the flexspline gradually decreases in accordance with the distance from the open end of the spline, occurs in cup-type or “silk hat”-type wave gear devices. A tooth profile in which the tooth depth is kept constant and in which the bottom lands and top lands are parallel to each other along the tooth trace direction is used as the basic tooth profile for the circular spline and the flexspline of the wave gear device. A taper surface is formed on a part of the top land near the open end of the flexspline in the basic tooth profile, whereby a modified tooth profile is obtained. The modified tooth profile is employed as the tooth profile for both of the splines. Both of the splines can be caused to mesh together without generating coning-induced interference. Both of the splines can also be subjected to gear cutting by a simple process using a typical machining mechanism.