Impact Tool Torque Sensor Using Strain Gauge
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Solution Overview
Problem
Pneumatic impact tools suffer from measurement signal errors due to temperature variations and mechanical stress, and their magnetic torque sensors have a short working life and are sensitive to oxidation, making them unreliable for precise torque measurement in dynamic and stressful conditions.
Innovation Solution
The impact tool employs a magnetic coupling between two coils for precise torque measurement, using a resonant magnetic coupling for signal transfer and a low-clock-frequency microprocessor to minimize errors and extend lifespan, while protecting components from oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic torque sensor is used to measure torsional moment on the output shaft, then torque measurement capability is achieved, but measurement precision deteriorates due to temperature sensitivity and mechanical stress
Solution Approach 1:
The patent replaces the magnetic torque sensor with a purely mechanical measurement system consisting of a strain gauge transducer bonded to the output shaft. This mechanical system measures torque through strain detection, eliminating the temperature sensitivity and mechanical stress issues that plague magnetic sensors in high-vibration environments.
Solution Approach 2:
The strain gauge transducer is described as a simple, inexpensive component that can be easily replaced if needed. This approach trades component longevity for measurement reliability, using a robust mechanical sensor that withstands harsh conditions better than magnetic alternatives.
2Reliability
If a magnetic torque sensor is used for torque measurement, then torque detection is enabled, but device working life shortens due to oxidation and mechanical stress
Solution Approach 1:
The patent replaces the magnetic torque sensor with a mechanical strain gauge transducer system. This mechanical system is inherently more resistant to oxidation and mechanical stress, leading to extended working life in harsh environmental conditions.
Solution Approach 2:
The strain gauge transducer is bonded to the output shaft using adhesive, creating a composite structure that combines the electrical sensing capabilities of the strain gauge with the mechanical strength of the shaft and adhesive bond, resulting in a more durable assembly.
3Measurement precision
If coils are supplied with electric energy for magnetic field generation and sensing, then torque measurement is enabled, but device complexity increases
Solution Approach 1:
The patent replaces the complex dual-coil magnetic field system with a simple strain gauge transducer and Wheatstone bridge circuit. This mechanical/electrical hybrid system eliminates the need for magnetic field generation and sensing coils, significantly reducing system complexity.
Solution Approach 2:
The strain gauge transducer measures torque directly through the deformation of the output shaft itself, using the shaft's own mechanical properties for measurement. This self-service approach eliminates the need for separate magnetic field generation and sensing mechanisms.
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
This solution provides accurate, reliable, and long-lasting torque measurement, resistant to dynamic stress and environmental factors, at a low cost, ensuring precise tightening and loosening operations.
Implementation Method 1
The torque sensor comprises a strain gauge transducer fixed to a portion of outer surface of the cylindrical end portion of the output shaft and arranged for measuring a deformation of the outer surface
Implementation Method 2
both a supply signal and a measuring signal of the torsional moment, or data associated therewith, are transferred by magnetic coupling, in particular resonant, between two coils
Implementation Method 3
transferred by magnetic coupling, in particular resonant, between two coils
Data Source
AI summary
An impact tool comprises:a casing;a rotating hammer arranged in the casing and rotatable by a motor;a rotating interface element arranged in the casing and rotatable by the hammer by a series of impacts;an output shaft rotating around a rotation axis, the output shaft having a proximal end fixed to the interface element and a distal end protruding from the casing, the distal end ending with a connecting element for removable connection to an outer mechanical adaptor;a unit of measurement arranged for obtaining torque of the output shaft by a torque sensor mounted to the output shaft, the unit of measurement comprising a fixed measuring assembly mounted integrally to the casing and a rotating measuring assembly mounted so as to rotate integrally with the rotating output shaft;the fixed measuring assembly being configured to generate a supply signal and transmit the supply signal to the rotating measuring assembly to supply electrically the rotating measuring assembly;the rotating measuring assembly being configured to detect a measuring signal indicating the torque and condition the measuring signal in order to be able to send the measuring signal to the fixed measuring assembly;in which the fixed measuring assembly and the rotating measuring assembly comprise electronic devices that execute a two-directional communication in contactless mode by magnetic coupling between the fixed measuring assembly and the rotating measuring assembly, the communication being configured to supply magnetically the torque sensor and permit transmission of the measuring signal conditioned by the rotating measuring assembly to the fixed measuring assembly.