Magnet Recess for Hall Sensor Alignment

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Solution Overview

Problem

Existing non-contact angle measurement devices require large magnets to achieve sufficient magnetic field strength and homogeneity, leading to increased size and sensitivity to external fields and mechanical tolerances, which affects resolution and linearity, especially in applications with limited angular ranges like accelerator pedal modules.

Innovation Solution

The magnetic field-sensitive element is partially embedded in the magnet's blind hole-like recess, creating a homogeneous and concentrated magnetic field, allowing for a smaller magnet to be used while improving resolution and linearity, and the guide columns ensure accurate alignment and compensation for mechanical play.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If large magnets are used to achieve sufficient magnetic field strength and homogeneity, then measurement precision is improved, but device size increases and sensitivity to external fields worsens

Engineering Contradiction:
Improvemeasurement precisionVSAvoiddevice size
Core Design Contradiction:
Measurement precisionVSVolume of moving object

Solution Approach 1:

The magnetic field-sensitive element is nested within the blind hole-like recess of the magnet, allowing the sensor to be positioned inside the magnet's volume rather than outside. This nesting arrangement enables the use of smaller magnets while maintaining sufficient magnetic field strength and homogeneity at the sensor location, thereby reducing device size while preserving measurement precision.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

By positioning the magnetic field-sensitive element within the blind hole-like recess, the magnetic field is concentrated and optimized locally at the sensor position. This local quality enhancement ensures sufficient field strength and homogeneity exactly where needed, allowing reduction of overall magnet size while maintaining measurement precision.

Inventive Principle:
Principle #3Local quality

2Measurement precision

If large magnets are used to achieve sufficient magnetic field strength, then measurement precision is improved, but sensitivity to external fields increases

Engineering Contradiction:
Improvemeasurement precisionVSAvoidsensitivity to external fields
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The nested configuration of the magnetic field-sensitive element within the magnet's blind hole creates a concentrated magnetic field environment that shields the sensor from external field interference. The magnet effectively surrounds the sensor, providing magnetic shielding while maintaining measurement precision.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The blind hole-like recess concentrates the magnetic field locally around the sensor, creating a strong, homogeneous field that dominates over external field influences. This local field concentration improves measurement precision while reducing sensitivity to external fields.

Inventive Principle:
Principle #3Local quality

3Measurement precision

If large magnets are used to provide sufficient magnetic field homogeneity, then linearity is improved, but device complexity increases

Engineering Contradiction:
ImprovelinearityVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The nested arrangement simplifies the overall device structure by integrating the sensor within the magnet's volume rather than requiring separate mounting structures. The blind hole-like recess provides natural mechanical alignment and positioning, reducing the need for additional alignment mechanisms and reducing device complexity while maintaining linearity.

Inventive Principle:
Principle #7Nested doll (Nesting)

4Reliability

If the magnetic field-sensitive element is positioned far from the magnet, then mechanical play compensation is easier, but magnetic field strength decreases

Engineering Contradiction:
Improvemechanical play compensationVSAvoidmagnetic field strength
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The nested configuration places the magnetic field-sensitive element deep within the blind hole-like recess of the magnet, minimizing the air gap and maximizing magnetic field strength. This close proximity ensures sufficient field strength for high-resolution measurements while the guide columns provide mechanical play compensation.

Inventive Principle:
Principle #7Nested doll (Nesting)

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 configuration enhances measurement accuracy and reduces the influence of external fields, achieving high resolution and linearity with a smaller magnet, suitable for applications requiring precise angle detection.

Implementation Method 1

The Hall effect is one of the galvanomagnetic effects and is primarily evaluated using thin semiconductor plates. If such a current-carrying semiconductor wafer is perpendicularly penetrated by a magnetic field, a voltage proportional to the magnetic field can be tapped transversely to the direction of the current.

Methodology Applied
Scientific EffectHall effect: Hall Effect

Implementation Method 2

a magnetic field concentrator changes the course of the field lines of the magnetic field generated by the magnet in its vicinity and causes the field lines, which in the absence of the magnetic field concentrator to run parallel to the surface of the Hall elements would run, the Hall elements penetrate approximately perpendicular to its surface.

Methodology Applied
Scientific EffectMagnetic field concentration: Magnetic Field

Data Source

PatentEP1975569B1Measuring device for contactless recording of the rotation angle with a magnet sensitive element fitted into a recess of the magnet
Publication Date: 2015.02.18 ROBERT BOSCH GMBH
  • EP1975569B1 patent drawingFigure 1
  • EP1975569B1 patent drawingFigure 2~4

AI summary

The invention relates to a measuring device (1) for the non-contact detection of a rotation angle, comprising a first body (2) on which at least one magnet (8) is arranged and at least one magnetic field-sensitive element (10) carried by a second body (14) for generating a measurement signal, wherein the first body (2) and the second body (14) are rotatable relative to each other about a rotation axis (4) and the magnet (8) has a blind-hole-like recess (24). The invention provides that the at least one magnetic field-sensitive element (10) projects at least partially into the recess (24).