Axial Rotation Torque Sensor with Segmented Beams
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Solution Overview
Problem
Conventional torque sensing structures with strain gauges suffer from inadequate accuracy and sensitivity, and they often result in a large radial volume due to inefficient design and placement of strain gauges in rotary drive mechanisms.
Innovation Solution
An axial rotation type torque sensor is designed with a torque sensing plate featuring parallel sheet-like beams that bear tangential forces, allowing strain gauges to be placed on these beams to accurately sense torque, thereby enhancing sensitivity and reducing the radial volume by arranging the beams parallel to the central axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are attached to radial webs of a torque-imparting gear, then torque sensing capability is provided, but the sensed strain includes both forward strain and shear strain resulting in poor accuracy and large radial volume
Solution Approach 1:
The torque sensing structure is segmented into multiple independent beam elements arranged circumferentially. Each beam independently senses torque-induced strain, allowing the system to achieve accurate torque measurement without requiring large radial dimensions. The segmentation enables distributed strain sensing that eliminates the need for large radial leverage arms.
Solution Approach 2:
The invention transitions from radial strain sensing to axial strain sensing by arranging beams parallel to the central axis. This dimensional change allows torque measurement through axial deformation of the beams rather than radial deformation, significantly reducing the required radial volume while maintaining or improving measurement accuracy.
2Strength
If a ring-shaped web is used to transmit torque, then the structure can support the torque, but the strain is dispersed over the entire area reducing the deformation amount and sensing accuracy
Solution Approach 1:
The continuous ring-shaped web is segmented into discrete beam elements. This segmentation concentrates the torque-induced strain onto individual beam elements rather than dispersing it across the entire ring area. Each beam experiences sufficient deformation to be accurately measured by strain gauges, solving the sensitivity problem while maintaining overall torque transmission capability through the combined action of multiple beams.
Solution Approach 2:
The beam elements are strategically positioned and dimensioned to create localized regions of high strain concentration where the strain gauges are attached. This local quality enhancement ensures that the critical measurement zones experience sufficient deformation for accurate sensing, while the overall structure maintains adequate strength for torque transmission.
3Measurement precision
If strain gauges are attached to a frame-shaped torque transferring element with radial ribs, then torque sensing is enabled, but the engaging location is subjected to bending moment reducing sensing authenticity and increasing radial volume
Solution Approach 1:
Instead of attaching strain gauges to radial ribs that experience complex bending moments, the invention inverts the approach by using axial beams that experience primarily axial tension and compression. This inversion simplifies the stress state at the gauge locations, providing more authentic torque measurement while reducing structural complexity.
Solution Approach 2:
The invention changes the orientation parameter of the sensing elements from radial to axial. This parameter change transforms the stress regime from complex bending to simpler axial loading, improving the authenticity of torque measurement and reducing the radial volume requirement while maintaining detection accuracy.
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 solution improves torque sensing sensitivity and reduces the radial volume of the torque sensor by effectively using strain gauges on beams that deform under tangential forces, providing accurate and sensitive torque measurements while minimizing the device's size.
Implementation Method 1
When the strain gauge deformed with the object where it attached to, it is possible to obtain the response of the strain of the mechanical components through the change of the resistance values of the strain gauge
Data Source
AI summary
The present invention provides an axial rotary type torque sensor comprising a planetary gear set disposed along a central axis between an input shaft and an output shaft. The input shaft drives the sun gear which meshes with planetary gears, and the planetary gears mesh with the ring gear of the planetary gear set to rotate along the circumference of the central axis. The ring gear is connected with a plurality of strip-like beams. At least one strain gauge is attached to the beams. One ending portion of the beam is fixed and the other ending portion is used for bearing a tangential force applied on the ring gear to generate a deformation at a rotation direction of a circumference. A strain gauge which senses the strain of the deformation used as a torque sensing value between the input shaft and the output shaft, thereby improving the poor sensing accuracy and sensitivity of the conventional torque sensors and solving the problem that the radial volume cannot be effectively reduced.