Contactless Torque Sensor for Drive Shafts
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Solution Overview
Problem
Existing torque sensors for drive shafts in vehicles face challenges such as reduced robustness, increased maintenance needs, and complex manufacturing processes, particularly with magnetic sensors that require ferromagnetic shafts and can be prone to demagnetization, and differential transformers that are difficult to align accurately.
Innovation Solution
A contactless torque sensor design featuring a drive shaft with a first and second cylindrical portion and an intermediate torsion portion, along with toothed wheels and a coil arrangement that generates a magnetic field, allowing for accurate measurement of torque without electronic components on the shaft, ensuring robustness and ease of calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If deformation gauge sensors with rotating transformers or remote measurement systems are used, then torque measurement capability is achieved, but robustness is reduced and maintenance needs increase due to electronics mounted on the drive shaft
Solution Approach 1:
The patent extracts the electronic measurement components from the rotating drive shaft and places them only on the stationary housing. The measurement is achieved through magnetic field interaction between a magnet on the shaft and a sensor on the housing, eliminating the need for electronics on the rotating part while maintaining torque measurement capability.
Solution Approach 2:
The patent replaces the mechanical/electronic sensor system with a magnetic field-based measurement system. Instead of using deformation gauges or rotating transformers with electronics on the shaft, it uses a magnet mounted on the shaft interacting with a stationary differential transformer sensor, substituting mechanical contact and electronics with magnetic field interaction.
2Measurement precision
If torque meters with differential transformers are used, then contactless torque measurement is achieved, but manufacturing is complex and time-consuming due to precise alignment requirements between coils and apertures
Solution Approach 1:
The patent segments the measurement system into two independent parts: a magnet mounted on the shaft and a stationary differential transformer sensor mounted on the housing. This segmentation eliminates the need for precise alignment between rotating and stationary components, as the magnetic field interaction occurs regardless of angular position, greatly simplifying manufacturing.
Solution Approach 2:
The patent creates a universal measurement system where the stationary differential transformer sensor can measure torque across a wide range of shaft positions and orientations. The magnetic field-based approach allows the sensor to function effectively regardless of the shaft's angular position, making the system universally applicable without requiring precise alignment.
3Measurement precision
If differential transformer sensors with overlapping cylindrical elements are used, then torque measurement is achieved, but the mounting process is complex and inaccurate
Solution Approach 1:
The patent extracts the complex alignment requirements by separating the magnet from the sensor. The magnet is mounted on the shaft while the differential transformer sensor is mounted independently on the stationary housing. This extraction of the magnetic field source from the sensor eliminates the need for precise overlapping alignment between cylindrical elements, greatly simplifying the mounting process.
4Measurement precision
If shaft magnetization-based torque meters are used, then ferromagnetic shafts are required, but this compromises the solidity and reliability of the shaft
Solution Approach 1:
The patent introduces a magnet as an intermediary element mounted on the shaft to generate the magnetic field for measurement. This allows non-ferromagnetic shafts (which have better mechanical properties) to be used, as the magnetic field is generated by the external magnet rather than requiring the shaft material itself to be ferromagnetic. The magnet acts as a mediator between the shaft and the 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 sensor provides accurate, reliable, and robust torque measurement independent of shaft rotation speed, with a simple calibration process and reduced sensitivity to mechanical play, ensuring consistent results across varying torsion values.
Implementation Method 1
said sensor comprising means for generating a magnetic field and an arrangement formed by a first coil, a second coil, a third coil and a fourth coil arranged side-by-side between the first toothed wheel and the second toothed wheel, parallel to said first toothed wheel and to said second toothed wheel
Data Source
AI summary
Disclosed is an assembly formed by a drive shaft for a vehicle and a sensor for measuring the value of a torque applied to the shaft, the sensor including a unit for generating a magnetic field and an arrangement formed by a first coil, a second coil, a third coil and a fourth coil arranged side-by-side between a first toothed wheel of the shaft and a second toothed wheel of the shaft, parallel to the first toothed wheel and to the second toothed wheel, arranged to be immersed in the magnetic field, the overall length of the first coil, of the second coil, of the third coil and of the fourth coil being equal to the period of the first toothed wheel and of the second toothed wheel.