Slotted Magnet Speed Sensor Assembly Air Gap Signal
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Solution Overview
Problem
Current output speed sensors with solid, cylindrical or rectangular magnet designs fail to meet minimum and maximum air gap requirements, leading to insufficient signal amplitude and potential saturation of Hall chips, which limits their effectiveness in detecting gear or target wheel speeds.
Innovation Solution
A speed sensor assembly featuring a printed circuit board (PCB) with a magnet having a slot, coupled to a pole piece that reduces the magnetic field amplitude, allowing the sensor to operate effectively across both minimum and maximum air gaps by localizing the magnetic field and guiding the flux to ensure appropriate strength for Hall-effect sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If solid, cylindrical or rectangular magnet designs are used, then the structure is simple, but the signal amplitude is insufficient and air gap requirements cannot be met
Solution Approach 1:
The magnet is divided into multiple segments with different magnetic pole arrangements. The magnet includes a first magnetic pole region, a second magnetic pole region, and a third magnetic pole region, creating a segmented structure that enhances signal amplitude while maintaining manufacturability.
Solution Approach 2:
Different regions of the magnet are assigned different magnetic properties and functions. The first magnetic pole region has a different magnetic pole arrangement than the second and third regions, optimizing the magnetic field distribution locally to improve signal characteristics.
2Measurement precision
If magnet length or magnet grade is increased to improve signal amplitude, then the signal strength increases, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of increasing overall magnet length or using higher grade materials, the invention segments the magnet into functional regions with different pole arrangements, achieving signal amplitude improvement through geometric configuration rather than material or size escalation.
Solution Approach 2:
The invention transitions from a simple cylindrical or rectangular magnet design to a multi-region magnet with complex pole arrangements, utilizing spatial dimensionality and magnetic field geometry to enhance signal amplitude without increasing magnet length or material grade.
3Measurement precision
If the magnetic field amplitude is increased to improve signal detection, then the signal strength improves, but the Hall chip may become saturated
Solution Approach 1:
Different magnetic pole regions create varying magnetic field strengths in different zones. The first magnetic pole region and the second/third regions have different pole arrangements that produce complementary magnetic field patterns, ensuring the Hall chip receives optimal field strength without saturation.
Solution Approach 2:
The alternating magnetic pole regions create a periodic magnetic field pattern that passes through the Hall chip. This periodic variation in magnetic field strength allows the Hall chip to detect speed information through the changing field polarity while avoiding continuous saturation that would occur with a uniformly strong magnetic field.
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 enables the sensor assembly to generate accurate digital signals proportional to speed across varying air gaps, ensuring robust operation of Hall chips and meeting magnetic field and peak-to-peak value requirements, thereby enhancing the reliability of transmission control and diagnostic functions.
Implementation Method 1
a magnet having a cylindrical or rectangular shape, the magnet facing a back side of the hall element, which senses the rotating target gear
Data Source
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AI summary
A speed sensor assembly (114) includes a printed circuit board (PCB) (120) having a first main side and a second main side, a magnet (116) directly coupled to the first main side of the PCB (120), a sensor (118) electrically connected to the PCB (120), and a pole piece (125) directly coupled to the magnet (116) and to the sensor (118), wherein the magnet (116) includes a slot partially enclosed by the pole piece (125). The speed sensor assembly (114) including a slotted magnet (116) to reduce magnetic field amplitude for single sensing element hall effect sensor applications. The speed sensor assemblies (114) operate with both minimum and maximum air gaps.