Rotational Position Sensor with Dual Wave Profile Disc
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Solution Overview
Problem
Existing rotational speed and position sensors for electric motor shafts in hybrid vehicles face challenges such as high cost, accuracy limitations, and contamination issues, particularly in applications where axial space is restricted.
Innovation Solution
A rotational position sensor arrangement featuring first and second sensors positioned adjacent to wave profiles on a metallic target disc, providing out-of-phase signals to a controller for precise position and speed determination, with optional additional wave profiles for enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a magnetic ring target is used, then manufacturing cost is reduced, but iron particles are attracted and conglomerate causing bearing contamination
Solution Approach 1:
The patent removes the magnetic ring target from the system entirely, replacing it with a non-magnetic target disc that has wave profiles. This extraction eliminates the source of magnetic attraction that causes iron particle congregation and bearing contamination, while maintaining the sensor functionality through alternative wave profile geometries.
Solution Approach 2:
The patent employs a simple metallic target disc with wave profiles instead of a magnetic ring, using inexpensive materials like aluminum or steel. This disposable-like approach prioritizes cost-effectiveness and simplicity over the durability of magnetic components, accepting that the target disc can be easily replaced if needed.
2Length of stationary object
If a single target disc with wave profile is used, then axial space is reduced, but measurement accuracy is limited
Solution Approach 1:
The patent divides the single target disc into multiple functional zones by adding multiple wave profiles (first, second, and optionally third wave profiles) at different axial positions. Each wave profile is detected by corresponding sensors, creating segmented measurement zones that collectively provide high-accuracy rotational position information within limited axial space.
Solution Approach 2:
The patent transitions from a single-plane wave profile to multiple wave profiles stacked axially on the target disc. By utilizing the axial dimension to arrange multiple measurement zones, the system achieves high measurement precision without increasing the radial or circumferential dimensions, effectively solving the space-accuracy trade-off.
3Reliability
If resolver type sensors are used, then robustness is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive resolver sensors with inexpensive inductive or Hall effect sensors that read wave profiles on a simple metallic target disc. This substitution dramatically reduces manufacturing cost while maintaining sufficient robustness for automotive applications, using off-the-shelf sensor components rather than specialized resolver assemblies.
Solution Approach 2:
The patent creates a simplified copy of the resolver functionality using inductive or Hall effect sensors that detect magnetic field changes caused by the metallic target disc's wave profiles. This copying approach replicates the essential measurement capability of resolvers without requiring the complex resolver construction, achieving cost reduction while preserving functional reliability.
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 offers improved accuracy and reduced manufacturing costs while minimizing axial space requirements, providing robust and cost-effective rotational position and speed sensing for electric motor applications.
Implementation Method 1
The first wave profile and the second wave profile alter a magnetic field of the first inductive or Hall effect sensor and the second inductive or Hall effect sensor, respectively, to provide out-of-phase signals to the controller
Implementation Method 2
The first sensor is an inductive sensor or a Hall effect sensor, or a TMR (Tunnel Magneto Resistance) sensor
Implementation Method 3
A rotational position sensor arrangement having first and second sensors and a target disc having a rotation axis and being formed of a metallic material
Data Source
AI summary
A rotational position sensor arrangement having first and second sensors positioned adjacent to first and second axial faces or a first axial face and a radial face of a target disc. The target disc has first and second wave profiles on the first axial face and the second axial or radial face, having respectively, first and second pluralities of segments, with each segment being formed with axially offset peaks and valleys which extend along radial lines/planes. The valleys separate the segments, and the number of the first plurality of segments is different than that of the second plurality of segments. The first and second sensors signal a controller with data on a field variance due to a difference in at least one of a size or location of the first and second wave profiles as they pass the first and second sensors to determine a rotational speed and/or position.