Wave-Gear Linear Actuator with Lead Screw on Circular Spline
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Solution Overview
Problem
Conventional wave-gear-type linear-actuation mechanisms have limited holding force in the axial direction due to the use of flexible, thin-walled screws, which restricts the ability to maintain the circular nut in place against external forces.
Innovation Solution
A wave-gear-type linear-actuation mechanism is designed with a first and second circular spline, a radially flexible cylindrical flexspline, and a wave generator that flexes the flexspline into a noncircular shape to mesh with the splines, featuring a lead screw on the outer peripheral surface of the first circular spline and a circular nut threaded onto it, allowing for increased axial holding force through reduced rotational speed and enhanced thrust generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a flexible, thin-walled screw is used in a cup-type wave gear mechanism, then the mechanism can achieve rotational to linear movement conversion, but the holding force in the axial direction is limited by the buckling strength of the diaphragm part and shear strength of the lead screw
Solution Approach 1:
The invention divides the single circular spline into two separate circular splines (first and second circular splines). The first circular spline carries the lead screw for thrust generation, while the second circular spline provides additional structural support. This segmentation allows the holding force function to be distributed across multiple components rather than relying solely on the flexible screw's limited strength.
Solution Approach 2:
The invention transitions from a single-plane cup-type structure to a multi-dimensional arrangement by introducing two coaxially disposed circular splines. The first circular spline rotates with the flexspline to generate thrust, while the second circular spline remains stationary to provide reaction support. This dimensional expansion from one to two parallel planes enables simultaneous achievement of movement conversion and high holding force.
2Volume of moving object
If a cup-shaped flexible screw is used, then the mechanism structure is compact, but the thrust generation capability is limited compared to rigid lead screw systems
Solution Approach 1:
The invention separates the thrust generation function (first circular spline with lead screw) from the structural support function (second circular spline). This allows the rigid first circular spline to generate high thrust while the overall mechanism maintains compact dimensions through the coaxial arrangement of the two splines.
Solution Approach 2:
The mechanism combines flexible and rigid components in a composite structure. The flexible cylindrical flexspline provides the necessary deformation for wave gear operation, while the rigid first and second circular splines provide structural strength for thrust generation and support. This composite approach enables both compactness and high power output.
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 mechanism achieves a higher holding force in the axial direction and allows for a larger diameter hollow part, improving the mechanism's performance compared to cup-type flexible screw systems.
Implementation Method 1
a radially flexible cylindrical flexspline disposed inside the first and second circular splines; a wave generator fitted inside the flexspline for flexing the flexspline into a noncircular shape
Implementation Method 2
a lead screw formed on an outer peripheral surface of the first circular spline; and a circular nut having a screw groove threaded onto the lead screw
Data Source
AI summary
A wave-gear-type linear-actuation mechanism comprises a flat-type wave gear; a lead screw that is a structural component of the wave gear and is formed on an outer peripheral surface of a first circular spline; and a linear-actuation cylinder threaded onto the lead screw, a linear-actuation cylinder 4 having a screw groove that is formed in an inner peripheral surface thereof. It is possible to obtain a linear-actuation mechanism whose holding force during reverse input mode (speed increasing mode) is higher than cases where a cup-type flexible screw is used.