Sensor Device Stray Field Suppression
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Solution Overview
Problem
Conventional sensor devices for determining rotation angles of shafts are ineffective in suppressing magnetic stray fields, particularly in environments with strong magnetic interference like motor vehicles, and lack precision in angle detection.
Innovation Solution
A sensor device with a semiconductor body and integrated pixel cells, each equipped with magnetic field sensors in orthogonal directions, combined with a rotatable magnet having diametric magnetization, allowing for differential evaluation of magnetic field signals to determine rotation angles while suppressing stray fields through a double design of magnetic field sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single magnetic field sensor design is used, then device complexity is low, but measurement precision deteriorates due to inability to suppress magnetic stray fields
Solution Approach 1:
The sensor device is segmented into multiple pixel cells (first pixel cell and second pixel cell), each containing orthogonal magnetic field sensors. This segmentation allows differential measurement between cells to suppress common-mode magnetic stray fields while maintaining individual cell simplicity.
Solution Approach 2:
Each pixel cell is equipped with magnetic field sensors oriented in specific orthogonal directions (x-direction and y-direction), creating local directional sensitivity. This local quality enhancement enables precise angle detection by measuring magnetic field components in multiple directions at each pixel cell location.
2Measurement precision
If magnetic field sensors are arranged in orthogonal directions within pixel cells, then measurement precision improves for angle detection, but device complexity increases due to integrated circuit requirements
Solution Approach 1:
Multiple magnetic field sensors detecting different directions are merged into integrated pixel cells on a single semiconductor body. The first and second magnetic field sensors in each pixel cell are combined with circuit arrangements to form unified sensing units, reducing overall device complexity while enabling precise angle detection through orthogonal component measurement.
3Reliability
If double design of magnetic field sensors in orthogonal directions is implemented, then reliability improves by suppressing stray field effects, but manufacturing precision requirements increase
Solution Approach 1:
The magnetic field sensors are arranged in orthogonal directions (x-direction and y-direction) within each pixel cell, creating an asymmetric sensing configuration. This asymmetric design provides complementary measurement capabilities that, when combined through differential evaluation, suppress the effects of magnetic stray fields and improve reliability.
4Measurement precision
If pixel cells are spaced apart along connecting line with magnet positioned between them, then measurement precision improves for rotation angle detection, but device complexity increases due to magnet integration
Solution Approach 1:
A magnet with diametric magnetization is introduced as an intermediary element positioned between the first and second pixel cells. This magnet creates a controlled magnetic field that enables differential measurement between the pixel cells, improving rotation angle detection precision while its fixed position and symmetric design help manage integration complexity.
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 accurate detection of rotation angles of both stationary and rotating shafts, effectively mitigating the impact of stray fields, and simplifies engine start-stop systems by enhancing the precision of crankshaft and camshaft position determination, especially in electric/hybrid vehicles.
Implementation Method 1
each pixel cell has a first magnetic field sensor and a second magnetic field sensor, and whereby the first magnetic field sensor detects a magnetic field in the x-direction and the second magnetic field sensor a magnetic field in the y-direction
Implementation Method 2
a magnet is provided, whereby the magnet has a planar main extension surface in the direction of the x-y plane and has a magnetization with two magnetic poles in the direction of the x-y plane
Implementation Method 3
A permanent magnet whose magnetic flux penetrates the sensor is arranged adjacent to the package
Implementation Method 4
Provided that the magnet or the IC package rotates, the signals have a sinusoidal or cosinusoidal shape
Data Source
AI summary
A sensor device is provided for suppressing a magnetic stray field, having a semiconductor body with a surface formed in an x-y plane, the x-direction and the y-direction are formed orthogonal to one another, and the sensor device has a first pixel cell and a second pixel cell integrated into the surface of the semiconductor body. A first magnetic field sensor detects a magnetic field in the x-direction and a second magnetic field sensor detects a magnetic field in the y-direction. The two pixel cells in a projection along an imaginary lengthening of the axis are arranged at an edge or next to an extension of the magnet in the x-y plane.