Hall Effect Mode Detection for Seat Belt Retractor
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Solution Overview
Problem
Current dual-mode seat belt retractors lack reliable mechanisms to transmit the selected mode information (ALR or ELR) to the electronic control unit (ECU) for effective operation of additional restraint devices, such as airbags, due to the limitations of simple switches like microswitches and inductive sensors.
Innovation Solution
A dual-mode retractor assembly utilizing a permanent magnet and a Hall Effect device (HED) with an interrupter plate, allowing the HED to detect the magnetic field in one mode and shield it in the other, enabling accurate mode detection and communication with the ECU.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple switches or inductive sensors are used for mode detection, then the device complexity is reduced, but the reliability of mode information transmission to ECU deteriorates
Solution Approach 1:
The patent replaces simple mechanical switches or inductive sensors with a Hall Effect device that uses magnetic field detection. This substitution provides more reliable mode information transmission while maintaining acceptable device complexity, as the Hall Effect sensor offers superior signal stability and immunity to electrical noise compared to traditional switches.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the detection mechanism and the ECU. The Hall Effect device detects changes in magnetic field strength caused by relative movement between magnetic elements, converting physical position changes into reliable electrical signals for mode identification without direct mechanical contact.
2Device complexity
If inductive sensors are used, then the device complexity is reduced, but the measurement precision of position detection deteriorates
Solution Approach 1:
The patent replaces inductive sensors with a Hall Effect device that directly measures magnetic field strength. This provides superior position detection precision because the Hall Effect sensor can detect subtle changes in magnetic field intensity corresponding to precise positional changes, unlike inductive sensors that rely on electromagnetic induction which is less sensitive to small displacements.
3Use of energy by moving object
If passive magnetic detection is used, then the use of energy is reduced, but the measurement precision and reliability deteriorate
Solution Approach 1:
The Hall Effect device is an active sensor that generates its own detection signal through its internal power supply, rather than relying on external electromagnetic fields. This self-service capability allows the sensor to actively measure magnetic field strength with high precision while consuming minimal power, overcoming the limitations of passive magnetic detection systems.
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
Provides reliable mode detection with a small, integrated package using active sensors like HEDs, which can detect position changes and ensure proper information transmission to the ECU, enhancing the control of restraint systems.
Implementation Method 1
A permanent magnet mounted on the first part cooperates with a Hall Effect device (HED) positioned to detect the magnetic field
Implementation Method 2
An interrupter plate is mounted on the second part in a position relative to the magnet, in which the interrupter plate allows the magnetic field to be detected by the Hall Effect sensor in the first mode and forms a shield between the magnet and the Hall Effect sensor in the second mode
Data Source
AI summary
A dual-mode retractor for an automotive seat belt webbing is configured to switch between a first mode and a second mode, the first mode being one of an ELR mode and an ALR mode, and the second mode being the other one of the ELR mode and the ALR mode. The retractor switches between the first mode and the second mode via a relative movement between a first part and a second part of the retractor. The magnetic field of a permanent magnet mounted on the first part is picked up by a Hall effect sensor. An interrupter plate is mounted on the second part in a position relative to the magnet, in which the interrupter plate, in which the interrupter plate exposes the HED to the original magnetic field in the first mode and to a modified magnetic field in the second mode.