Acceleration Sensor Lever Positioning via Limiting Portion
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Solution Overview
Problem
Conventional acceleration sensors for seat belt retractors face challenges in maintaining precise positioning of the sensor lever, leading to unstable operation due to potential deviations in the rotation axis, which complicates the design and size reduction of the locking mechanism.
Innovation Solution
The acceleration sensor features a sensor holder with a limiting portion that contacts the sensor lever to restrict its shifting in both directions, ensuring precise positioning and preventing contact between the base and supports, thus stabilizing the sensor lever's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sensor lever is supported with clearance for ease of mounting and rotation, then the ease of manufacture and operation is improved, but the positioning precision deteriorates causing shifting in the rotation axis direction
Solution Approach 1:
A positioning pin is introduced as an intermediary element between the sensor lever and the support structure. The positioning pin fits into a positioning hole to restrict shifting of the sensor lever in the rotation axis direction, while the sensor lever remains rotatable about its rotation axis. This mediator enables both ease of mounting and precise positioning by separating the functions of rotation support and position restriction.
2Ease of operation
If clearance is provided for movability of the sensor lever, then the ease of operation is improved, but the stability deteriorates due to play between components
Solution Approach 1:
The support structure is segmented into multiple functional elements: supports that provide rotation clearance, a positioning pin that restricts axial shifting, and a positioning hole that receives the pin. This segmentation allows the sensor lever to have both movability for operation and stability through restricted positioning, eliminating play between components while maintaining necessary freedom of rotation.
3Reliability
If the locking mechanism is designed to account for positional deviation of the sensor lever, then the reliability is improved, but the device complexity increases
Solution Approach 1:
Positioning features (positioning pin and positioning hole) are incorporated into the assembly design to pre-establish accurate positioning of the sensor lever before operation. This preliminary action prevents positional deviation from occurring in the first place, eliminating the need for complex compensation mechanisms in the locking system and reducing overall device complexity while maintaining reliability.
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 solution enables precise positioning of the sensor lever, enhancing the stability and reliability of the acceleration sensor, which is crucial for effective activation of the locking mechanism during vehicle acceleration events.
Implementation Method 1
an inertia mass that is displaced by an inertia force due to acceleration
Data Source
AI summary
There is provided an acceleration sensor enabling precise positioning of a sensor lever of the acceleration sensor, for ensuring a stable operation of the acceleration sensor, and a seat belt retractor including the acceleration sensor. Shafts of a sensor lever projects from a base. The sensor lever is supported between supports of a sensor holder so as to be rotatable and shiftable in a rotation axis direction. The sensor lever is rotated by displacement of an inertia mass. A limiting portion of the sensor holder is brought into contact with contact portions of the sensor lever. The limiting portion limits shifting of the sensor lever in the rotation axis direction, so as to avoid contact between the base and the supports.