Bi-metal Spring for Temperature-Compensated Occupant Detection
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Solution Overview
Problem
The weight threshold for occupant detection in vehicle seat assemblies varies with ambient temperature, leading to inconsistent classification of occupants as the stiffness of seat materials changes with temperature, causing incorrect detection of occupancy states.
Innovation Solution
A spring is integrated into the occupant detection device, configured to provide a return force that varies with temperature, using bi-metal layers with distinct coefficients of thermal expansion to maintain a consistent threshold across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional spring is used in the occupant detection device, then the device structure is simple, but the detection threshold varies with temperature causing inconsistent occupancy classification
Solution Approach 1:
The spring is constructed as a composite structure with a first layer of material having a first coefficient of thermal expansion and a second layer of material having a second coefficient of thermal expansion. This bi-metallic composite design allows the spring to compensate for temperature-induced threshold variations while maintaining structural integrity and functionality.
2Reliability
If the spring return force is made temperature-independent, then consistent detection threshold is achieved, but the device requires complex temperature compensation mechanisms
Solution Approach 1:
The spring utilizes the differential thermal expansion properties of two materials with different coefficients of thermal expansion. As temperature changes, the two layers expand or contract at different rates, creating internal stresses that automatically adjust the spring's return force to compensate for temperature effects on the detection threshold.
Solution Approach 2:
The invention changes the physical parameters of the spring by selecting materials with specific coefficients of thermal expansion. By carefully choosing the material properties and layer thicknesses, the spring's mechanical characteristics are optimized to provide temperature-compensated performance without requiring active control 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
The temperature-compensated spring ensures consistent detection of occupants and objects across varying temperatures, preventing false positives or negatives in occupancy classification.
Implementation Method 1
The spring is configured to provide a return force that varies with a temperature of the spring... bi-metal layers with distinct coefficients of thermal expansion
Data Source
Figure 1~2
Figure 3~4
AI summary
An occupant detection device (12) for a vehicle seat is provided. The device (12) includes a sensor (40) and a spring (34). The sensor (40) is configured to indicate a first state when a seat is not occupied and a second state when the seat is occupied. The spring (34) is configured to urge the sensor (40) toward the first state. The spring (34) is also configured to provide a return force (54) that varies with a temperature (56) of the spring (34)