Constant-Velocity Joint Assembly for Accurate Power Tool Torque Sensing
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Solution Overview
Problem
Existing power tools, such as nutrunners, face challenges in accurate torque measurement due to external influences and bending forces that contaminate the readings, particularly when the torque sensor is integrated into the angle head, leading to extended length and reduced accuracy.
Innovation Solution
A joint assembly with a coupling structure and torque transducer decoupled from the output shaft, allowing angling at constant rotational speed, which reduces the transmission of bending forces and improves torque measurement accuracy, and a compact design that minimizes the footprint of the power tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the torque sensor is integrated into the angle head, then the torque measurement function is achieved, but the axial length of the power tool is extended and measurement accuracy is reduced due to bending forces
Solution Approach 1:
The power tool is divided into functionally independent modules: the torque sensor is separated from the output shaft assembly and integrated into the angle head, while the joint assembly acts as an independent decoupling module. This segmentation allows the torque sensor to be positioned where it can measure torque without being subjected to bending forces from output shaft angling, thereby maintaining measurement accuracy while managing the overall tool length efficiently.
Solution Approach 2:
The joint assembly serves as an intermediary element between the output shaft and the angle head containing the torque sensor. It enables angular adjustment of the output shaft relative to the angle head while decoupling the torque transmission path from the bending force path. This intermediary structure allows the torque sensor to remain isolated from bending forces while still measuring the torque transmitted through the joint assembly.
2Adaptability or versatility
If the torque sensor is integrated into the angle head, then torque measurement capability is provided, but bending forces from output shaft angling contaminate the torque measurements
Solution Approach 1:
The system is segmented into a torque measurement subsystem (angle head with torque sensor) and a mechanical transmission subsystem (output shaft with joint assembly). The torque sensor measures torque in the angle head while the joint assembly handles angling mechanically. This segmentation ensures that the measurement subsystem remains isolated from the mechanical stresses of angling, preserving measurement accuracy while maintaining adaptability.
Solution Approach 2:
The joint assembly acts as a mechanical intermediary that absorbs and accommodates angular misalignment between the output shaft and the angle head. It transmits torque while allowing relative angular movement, thereby protecting the torque sensor in the angle head from bending forces generated during angling operations.
3Adaptability or versatility
If the output shaft is allowed to angle relative to the coupling structure, then adaptability is improved, but bending forces are transmitted to the torque transducer
Solution Approach 1:
The joint assembly serves as a specialized intermediary mechanism positioned between the output shaft and the coupling structure. It consists of a joint body with a bearing that receives the output shaft, allowing relative angular movement. This intermediary structure enables the output shaft to angle while the coupling structure remains aligned with the torque transducer, preventing bending forces from being transmitted to the sensitive measurement device.
Solution Approach 2:
The angling function is extracted from the torque transmission path. The joint assembly provides the angling capability in a separate location, while the coupling structure and torque transducer maintain a rigid, aligned torque transmission path. This extraction ensures that bending forces associated with angling are isolated from the torque measurement system.
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 provides more accurate torque measurements and reduces the axial length of the power tool, enhancing its operational efficiency and accuracy while maintaining constant rotational speed.
Implementation Method 1
the torque transducer comprises strain gauge elements
Data Source
AI summary
A constant-velocity joint assembly for a power tool includes an output shaft and a coupling structure configured to drive the output shaft. The output shaft and the coupling structure form a joint configured to enable angling of the output shaft relative to the coupling structure at constant rotational speed, and the coupling structure is provided with a torque transducer configured to detect a torque acting on the coupling structure provided by the output shaft.