Magnetic Field Sensor Webbing Retract
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Solution Overview
Problem
Existing seat belt webbing retractors require a large installation space due to the gear mechanism and metering wheel design, which limits the ability to sense webbing extension efficiently.
Innovation Solution
A method and webbing retractor design that uses a magnet and magnetic field sensor connected to a control unit to detect full turns and position, allowing for absolute webbing extension measurement without the need for a large metering wheel, with the control unit storing data in non-volatile memory for precise extension calculation and low-power operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gear mechanism and metering wheel are used to reduce belt reel rotation, then webbing extension can be sensed, but the installation space required increases
Solution Approach 1:
The patent replaces the mechanical gear mechanism and metering wheel system with a magnetic field sensing system. A magnet is mounted on the belt reel and a magnetic field sensor detects its position, eliminating the need for mechanical reduction gears and large metering wheels while still enabling webbing extension measurement.
Solution Approach 2:
The invention extracts the essential measurement function from the complex mechanical transmission system. By directly sensing the magnet's position on the belt reel through a magnetic field sensor, the patent removes the intermediate gear mechanism and metering wheel components that consumed installation space.
2Measurement precision
If the control unit continuously monitors magnet position, then accurate webbing extension data is obtained, but energy consumption increases
Solution Approach 1:
The control unit operates in cycles, switching between active measurement mode and low-power standby mode. During normal operation, the magnet position is monitored continuously for accuracy. When the vehicle is deactivated or during standby periods, the control unit reduces monitoring frequency or enters sleep mode, significantly lowering energy consumption while maintaining measurement capability when needed.
Solution Approach 2:
The system uses feedback from the magnetic field sensor to determine when measurement is necessary. The control unit monitors changes in magnet position and only performs full measurements when actual webbing extension changes are detected, rather than continuously sampling at fixed intervals, thus reducing unnecessary energy consumption.
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 and space-efficient sensing of seat belt webbing extension, reducing the size of the webbing retractor and extending battery life through low-power operation, while maintaining reliable operation across various vehicle states.
Implementation Method 1
a magnetic field sensor arranged in the magnetic field generated by the magnet
Data Source
AI summary
A method for sensing the webbing extension of a seat belt (12) from a webbing retractor (10) of a vehicle includes sensing the position of the magnet (18) by means of the magnetic field sensor (20) by the control unit (22). The control unit (22) detects when the magnet (18) has completed a full turn. The control unit (22) deposits the number of the full turns in a memory (26). The control unit (22) determines the webbing extension by way of number of the full turns and the position of the magnet (18). A webbing retractor (10) for a seat belt (12) has a magnet (18).