Torque Sensing Unit With Single Reaction Arm
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Solution Overview
Problem
Existing torque sensing units in power wrenches are bulky and prone to tolerance-related variations due to multi-point connections, leading to uncertainties in signal generation from strain gauges.
Innovation Solution
A compact torque sensing unit with a torque transferring element featuring an annular body and a single radially extending reaction arm, rotationally locked to the ring gear via matching teeth, and equipped with strain gauges on weak portions to measure reaction torque accurately, independent of manufacturing tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a torque sensing unit with multiple arms is used to transfer reaction torque from the ring gear to the housing, then the torque transfer capability is improved, but the device complexity and manufacturing tolerance sensitivity increase
Solution Approach 1:
The patent extracts the essential torque transfer function from a complex multi-arm structure and implements it through a single reaction arm. The annular body provides the torque transfer path from the ring gear teeth to the single reaction arm, which then transfers the torque to the housing. This extraction of the core function reduces structural complexity while maintaining torque transfer capability.
Solution Approach 2:
Instead of using multiple arms to distribute torque transfer (conventional approach), the patent inverts the approach by using a single reaction arm combined with an annular body that engages the ring gear teeth. This inversion simplifies the structure by eliminating the need for multiple arms while achieving the same torque transfer function through a different architectural approach.
2Measurement precision
If multiple strain gauges are distributed on several arms to measure reaction torque, then the measurement coverage is improved, but the measurement precision is degraded due to tolerance variations
Solution Approach 1:
The patent merges the torque measurement function from multiple distributed strain gauges on several arms into a concentrated measurement system on a single reaction arm. By combining the measurement location into one critical point, the system eliminates the problem of tolerance variations affecting multiple measurement points differently, thereby improving signal consistency and measurement precision.
Solution Approach 2:
The patent applies local quality by concentrating the strain gauge measurement on a specific location of the single reaction arm where the torque stress is most representative. Instead of distributing multiple gauges throughout the structure, the design places measurement sensors at the optimal local position on the reaction arm, improving measurement precision by focusing measurement capability where it is most needed.
3Length of moving object
If a compact torque sensing unit is designed to reduce axial extension, then the power wrench dimensions are improved, but the manufacturing complexity increases
Solution Approach 1:
The torque sensing unit is segmented into distinct functional components: the annular body with teeth for ring gear engagement, the single reaction arm for torque transfer, and the strain gauge mounting location. This segmentation allows each component to be manufactured and assembled separately, reducing the overall axial length while managing manufacturing complexity through modular construction rather than a monolithic compact design.
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 accurate measurement of output torque while maintaining a compact design, reducing uncertainties and manufacturing complexities, and is cost-effective to produce.
Implementation Method 1
carrying a strain measuring sensors arranged to generate electric signals in response to the magnitude of the transferred reaction torque
Data Source
Figure 1~6
AI summary
A power wrench with a torque sensing unit (20) comprising a housing (10, 22), a motor, an output shaft (13), and a planetary reduction gearing (14) connecting the motor to the output shaft (13) and including a stationary ring gear (19) supported in the housing (10, 22), wherein the torque sensing unit (20) includes a torque transferring element (23) with a single radially extending reaction arm (25) arranged to transfer reaction torque from the ring gear (19) to the housing (10, 22) and carrying strain measuring sensors (36, 37) for generating signals in response to the transferred reaction torque. The torque transferring element (23) comprises an annular body (24) with two weak portions (34, 35) to be elastically deformed during torque transfer and having flat surfaces (32, 33) for carrying the strain measuring sensors (36, 37).