Magnetic Field Sensor for Vehicle Seat Displacement Detection

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Solution Overview

Problem

Existing systems for detecting the absolute displacement position of a vehicle seat are prone to wear, noise, and failure due to mechanical and electromechanical limitations, and previous sensor arrangements using Hall sensors and magnetic strips can only determine two positions, failing to provide continuous and accurate measurement of the seat's displacement path.

Innovation Solution

A method and device utilizing a magnetic field-sensitive sensor device that monitors changes in magnetic field strength along a measuring section corresponding to the vehicle seat's displacement, allowing for the detection and conversion of absolute displacement positions, which is durable and wear-free, and can determine multiple positions accurately without initialization after installation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If mechanical and electromechanical detector systems are used to determine seat position, then the seat position can be detected, but the systems are susceptible to wear and produce noise

Engineering Contradiction:

Improveseat position detectionVSAvoidwear susceptibility

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces mechanical and electromechanical detector systems with a magnetic field-based detection system. A magnetic strip is attached to the movable rail, and a magnetic sensor (such as a Hall sensor) mounted on the stationary rail detects changes in magnetic field strength as the seat moves. This substitution eliminates mechanical contact and wear between detection components, thereby improving reliability while maintaining measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If Hall sensor and magnetic strip are placed close together to maximize signal, then the sensor signal is as large as possible, but the components grind relative to each other causing noise and damage

Engineering Contradiction:

ImproveHall sensor signal strengthVSAvoidgrinding contact

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a magnetic field as an intermediary between the magnetic strip and the Hall sensor. Instead of requiring direct physical proximity that would cause grinding contact, the magnetic field transmits information about seat position wirelessly across a small gap. The magnetic strip generates the magnetic field, and the Hall sensor detects changes in this field strength, allowing signal transmission without mechanical contact and thus eliminating grinding noise and damage.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If incremental detection using magnetic strip and Hall sensor is used, then relative position can be detected, but absolute displacement position cannot be established after power disconnection

Engineering Contradiction:

Improverelative position detectionVSAvoidzero point information

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent applies preliminary action by pre-programming absolute position values into the magnetic strip at known reference points (such as the rearmost position of the seat). When the seat is at these predetermined positions, the magnetic sensor detects specific magnetic field patterns that correspond to known absolute positions. This allows the system to reinitialize and establish absolute displacement position information after power disconnection, preventing loss of zero point information.

Inventive Principle:

Principle #10Preliminary action

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 provides continuous, accurate, and reliable detection of the vehicle seat's displacement position, enabling precise control of airbag inflation and maintaining functionality even after power disconnection and reconnection, with a resolution accuracy of less than 20 mm.

Implementation Method 1

monitoring as the vehicle seat is being displaced a change of one magnetic field component generating an output signal by the sensor device

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Implementation Method 2

at least one permanent magnet for generating a magnetic field, whose change along a displacement length of a vehicle seat is detected

Methodology Applied

Scientific EffectMagnetic field generation: Magnetism

Data Source

PatentUS10940819B2Method and device for detection of the displacement position of a motor vehicle seat

Publication Date: 2021.03.09 POLYCONTACT

AI summary

A method for detecting the displacement position of a vehicle seat is described. When the vehicle seat is being displaced, a magnetic field-sensitive sensor device monitors a change of one magnetic field component and depending on the output signal which has been generated by the sensor device, a conclusion is drawn about the adjustment position of the vehicle seat. The magnetic field-sensitive sensor device is displaced relative to a measuring section using the magnetic field-sensitive device. An absolute value of the magnetic field strength of a magnetic field whose magnetic field strength changes essentially continuously along a longitudinal extension of the measuring section is detected and converted into an absolute displacement position of the vehicle seat.