Dual Code Disk Angle Sensor for Precise Multi-Turn Shaft Position
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotational angle sensors for motor vehicle steering shafts face challenges in achieving high precision, resolution, and resistance to wear and tear, with measurement errors due to manufacturing and installation tolerances, as well as hysteresis and linearity issues, particularly in sensors using gear wheels and springs.
Innovation Solution
The use of two sensors, where one measures the displacement of the shaft directly and the other measures the displacement of an object coupled with the shaft via spring groups, with a first code disk providing a fine signal and a second code disk generating a coarse signal, allowing for precise determination of the rotational position by combining these signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gear wheels are used to transmit rotational motion, then mechanical coupling is achieved, but measurement errors occur due to manufacturing tolerances, installation tolerances, wear and tear, and clearance
Solution Approach 1:
The patent replaces the mechanical gear wheel transmission system with a magnetic coupling system. A magnetized code disk is coupled to the shaft, and magnetic sensors detect the rotational position without mechanical contact. This eliminates gear tooth clearance, manufacturing tolerances, and wear issues associated with mechanical gear engagement, thereby resolving the measurement errors caused by mechanical imperfections.
2Measurement precision
If a single sensor measures shaft displacement directly, then the structure is simple, but the resolution and precision are insufficient
Solution Approach 1:
The patent divides the measurement task into two segments: a first code disk provides a fine signal for high-resolution measurement within a rotation period, and a second code disk provides a coarse signal for determining the absolute rotational position across multiple rotations. This segmentation allows the system to achieve high precision and resolution without requiring a single complex sensor, instead using two simpler sensors that work together.
3Measurement precision
If spring-loaded tension is applied to measuring gear wheels, then clearance is reduced, but hysteresis errors and linearity errors increase
Solution Approach 1:
The patent eliminates the spring-loaded mechanical tensioning system by using magnetic coupling between the magnetized code disk and the magnetic sensors. This non-contact magnetic field interaction removes the need for mechanical tension, thereby eliminating hysteresis errors and linearity errors that arise from spring-loaded gear wheel engagement while maintaining accurate measurement.
4Adaptability or versatility
If the magnetic ring is coupled with the shaft by springs, then the magnetic ring can rotate independently, but kinetic energy release generates electrical impulses that complicate the measurement
Solution Approach 1:
The patent replaces the spring-coupled magnetic ring system with a directly magnetized code disk that rotates with the shaft. Magnetic sensors detect the rotational position through the magnetic field without mechanical coupling or springs. This eliminates the kinetic energy release and electrical impulse generation problems while maintaining rotational measurement capability, simplifying the overall 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
This approach delivers a highly precise output signal with good resolution and resistance to wear and tear, addressing the limitations of existing technologies by minimizing hysteresis and linearity errors, while being cost-effective and suitable for long service life in motor vehicle applications.
Implementation Method 1
a first sensor (4, 4') scans a first code disk (3, 3'), which rotates exactly with the shaft (2)
Implementation Method 2
a second sensor (6, 6') scans a second code disk (5, 5'), which is magnetized and rotates with the shaft (2)
Data Source
AI summary
The rotational angle sensor for measuring the rotational angle of a shaft has two code disks, the first code disk of which is rotationally fixed to the shaft while the second code disk is held between the shaft and the housing by two spring groups. Each code disk is assigned to a sensor. The sensor of the first code disk generates a periodic rotational angle signal while the sensor which is assigned to the second code disk generates a coarse signal (U2) which is different from the first signal and which can be used to ascertain which rotation of n possible rotations the shaft is in, wherein n>1.