Nested Stud Sense Element for Occupant Weight Sensor Overload Protection
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Solution Overview
Problem
Current occupant weight sensors (OWS) in vehicles face challenges in accurately sensing forces applied to seats, particularly under normal and abnormal workloads, which can lead to incorrect airbag deployment decisions.
Innovation Solution
The design incorporates strain gauges, such as mono-crystalline silicon gauges, formed using epitaxy and deep reactive-ion etching, connected in a full-bridge circuit within an occupant weight sensor system, including a stud and sense element configuration that provides overload protection and enhanced signal-to-noise ratio, allowing for precise force measurement and communication to airbag deployment systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stud is fitted within the sense element with a gap at the first end, then overload protection is provided and manufacturing is simplified, but measurement precision may be affected
Solution Approach 1:
The stud is nested within the sense element, with the stud's second end fitted into the sense element's opening. This nested configuration allows the stud to be partially contained within the sense element structure, providing mechanical support and overload protection while maintaining the integrity of the force transmission path through the strained beams.
Solution Approach 2:
The gap between the stud's first end and the sense element's first end acts as a predetermined cushioning feature. Under normal workloads, the gap remains open and does not affect measurement. Under abnormal overload conditions, the gap closes and the stud contacts the sense element, preventing excessive strain and potential damage to the gauge circuitry.
2Manufacturing precision
If strain gauges are formed using epitaxy and deep reactive-ion etching, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces traditional mechanical strain gauge attachment methods with a monolithic semiconductor fabrication approach. Strain gauges are formed directly on the sense element beams using epitaxial growth and deep reactive-ion etching, integrating the gauge circuitry into the structural component itself rather than attaching separate gauge elements.
Solution Approach 2:
The sense element is constructed as a composite structure combining semiconductor materials (for the beams and strain gauges) with metallic materials (for the stud and fastening elements). This composite approach allows optimization of each material for its specific function while achieving overall system performance.
3Measurement precision
If a full-bridge circuit configuration is used, then signal-to-noise ratio is enhanced, but device complexity increases
Solution Approach 1:
The patent merges the structural sense element with the measurement circuitry by forming strain gauges directly on the beams. The full-bridge circuit is implemented by strategically placing four strain gauges (two on each of two opposing beams) that naturally form the bridge configuration, eliminating the need for separate circuit board assemblies and reducing overall device complexity.
Solution Approach 2:
The sense element beams serve multiple functions: they provide the structural support for the stud, transmit the applied force, and simultaneously serve as the substrate for the strain gauge circuitry. This multi-functionality reduces the number of separate components needed in the system.
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 configuration enables accurate detection of forces, ensuring appropriate airbag deployment by differentiating between normal and abnormal workloads, thereby enhancing safety and reliability in vehicle occupant monitoring.
Implementation Method 1
The sense element may include two beams, 280a-b, and a bridge circuit, 360, including four resistive elements may be formed using, for example, mono-crystalline silicon gauges, 220
Implementation Method 2
four resistive elements may be formed using, for example, mono-crystalline silicon gauges, 220, fabricated using an epitaxy and deep reactive-ion etching process
Implementation Method 3
fabricated using an epitaxy and deep reactive-ion etching process
Data Source
AI summary
In an embodiment, an apparatus may include a sense element having a first end and a second end; and a stud fitted inside the sense element. The stud may have a first end and a second end. The first end of the stud may be free floating with respect to the sense element. The second end of the stud may be attached to the second end of the sense element. The sense element may include one or more gauges. The gauges may sense strain on the sense element. The apparatus may include a ridge that may be used to provide overload protection of the apparatus. The ridge may be placed on the stud, the sense element, or the stud and sense element.