Electric Tool Torque Detection Using Gear Force Measurement
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Solution Overview
Problem
Existing power tools face challenges in detecting and mitigating reaction torque acting on the tool body when the tool bit is unintentionally locked, leading to potential swinging of the tool body due to increased torque, and existing solutions using planetary gear mechanisms result in increased tool size.
Innovation Solution
A hand-held power tool design that measures axial or radial forces between driving-side and driven-side gears using strain gauges or load cells to detect torque, with a torque transmission interrupting mechanism, such as an electromagnetic clutch, to control drive mechanism operation and prevent excessive reaction torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a planetary gear mechanism is used as a safety clutch to detect torque, then torque detection capability is improved, but the device size increases
Solution Approach 1:
The patent extracts the torque detection function from the complex planetary gear mechanism and implements it using a simple strain gauge mounted on the drive shaft. This separates the detection function from the power transmission function, allowing torque detection without requiring a bulky planetary gear mechanism.
Solution Approach 2:
The patent replaces the mechanical planetary gear mechanism with an electrical sensing system using strain gauges. Instead of using mechanical components to detect torque, the invention uses electrical resistance changes in the strain gauge to measure torque, significantly reducing the device size.
2Reliability
If a planetary gear mechanism with contact element is used to release outer ring member, then reaction torque control is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the reaction torque control function from the complex planetary gear mechanism with contact elements and implements it using a simple electromagnetic clutch. This separates the control function from the complex mechanical structure, achieving reliable torque control with minimal components.
Solution Approach 2:
The patent replaces the mechanical contact element and brake shoe system with an electromagnetic clutch that uses electromagnetic fields to control torque transmission. This substitution eliminates complex mechanical contact components while maintaining reliable reaction torque control through electrical actuation.
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
Enables effective detection and prevention of excessive reaction torque with a simple structure, improving safety and reducing tool size by using bevel gears and antifriction bearings for accurate torque measurement and controlled torque transmission.
Implementation Method 1
an axial force or a radial force caused by engagement between the driving-side gear and the driven-side gear is measured with use of a strain gauge or a load cell
Implementation Method 2
a torque transmission interrupting mechanism, such as an electromagnetic clutch, to control drive mechanism operation
Data Source
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AI summary
An electric tool causes a drive mechanism to drive a tip tool (119, 219) to thereby cause the tip tool (119, 219) to perform predetermined work, and the drive mechanism is provided with a driving gear (138, 221) and a driven gear (139, 231) which meshes with the driving gear (138, 221). The electric tool is configured in such a manner that an axial force or a radial force generated by the meshing between the driving gear (138, 221) and the driven gear (139, 231) is measured to detect the state of torque acting on the tip tool (119, 219), and drive control of the drive mechanism is performed according to the detected state of torque.