Pressure-Responsive Seat Occupancy Sensor with Foam Intermediary
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Solution Overview
Problem
Existing pressure-sensitive seat occupancy sensors are often designed to be specific to each seat design, leading to high development costs and limited compatibility across different car seats and platforms, as they require uniform foam thickness and pressure transfer characteristics.
Innovation Solution
A pressure-responsive seat occupancy sensor unit featuring a support plate, a pressure-responsive membrane switch, spacers, and compressible foam, where the foam activates the switch only when a certain threshold force is applied, allowing for consistent detection across varying seat designs without constant foam contact, thus relaxing production requirements and maintaining occupant comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pressure-sensitive seat occupancy sensors are arranged between the foam body of the seat cushion and the seat cover, then the sensor can detect occupancy, but every seat design requires specific development effort leading to high development costs and limited compatibility
Solution Approach 1:
A foam block is introduced as an intermediary element between the pressure sensor and the seat cushion. The foam block acts as a mediator that transfers pressure from the seat cushion to the sensor while absorbing variations in foam thickness and material properties. This allows the same sensor design to be used across different seat configurations without requiring customization for each seat type.
Solution Approach 2:
The pressure sensor is designed with a universal mounting structure that can be adapted to different seat types through the use of the foam block intermediary. The sensor unit itself remains unchanged while the foam block accommodates variations in seat cushion properties, enabling one sensor design to serve multiple seat designs across different vehicle platforms.
2Measurement precision
If pressure sensor units are arranged on the B-surface of the seat cushion, then the seat cushion transfers pressure to the sensor, but uniform foam thickness and pressure transfer characteristics require significant investments in production control
Solution Approach 1:
The foam block serves as a pressure-transfer intermediary that decouples the sensor from direct contact with the seat cushion foam. This allows the sensor to receive pressure signals without requiring the foam above it to have uniform thickness or consistent elastic properties. The foam block's material properties are optimized to provide reliable pressure transfer while being tolerant of manufacturing variations.
Solution Approach 2:
The system changes the physical parameters of the pressure transfer path by introducing a dedicated foam block with controlled density and elasticity. This foam block is designed to compress in a predictable manner under load, providing a standardized pressure transfer characteristic that compensates for variations in the seat cushion foam above it. The pressure sensor can thus operate with consistent performance despite variations in overall seat cushion construction.
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 a sensor unit that is compatible with production tolerances of vehicle seats, reducing development costs and enhancing compatibility across different car seats and platforms while maintaining seating comfort and not influencing the H-point, with the ability to distinguish between occupants and objects based on applied force.
Implementation Method 1
The compressible foam is arranged in such a way that it penetrates into the support area in between the one or more spacers and activates the pressure-responsive membrane switch in response to a force applied on the top surface that exceeds a certain threshold force
Implementation Method 2
The pressure-responsive membrane switch comprises at least two electrodes arranged in facing relationship with each other in the cell on the first and the second carrier film, respectively, in such a way that they are brought closer together, possibly into contact with each other, when sufficient pressure is applied on the pressure-responsive membrane switch
Data Source
AI summary
A pressure-responsive seat occupancy sensor unit (10) for detecting an occupancy state of a seat comprises a support plate (12) with a support area (14), a pressure-responsive membrane switch (15), one or more spacers (16) arranged around the support area and a compressible foam. The membrane switch comprises a first carrier film and a second carrier film spaced from each other by a spacer film. The spacer film has therein an opening defining a cell. The membrane switch comprises at least two electrodes arranged in facing relationship with each other in the cell on the first and the second carrier film, respectively, in such a way that they are brought closer together, possibly into contact with each other, when sufficient pressure is applied on the membrane switch. The one or more spacers (16) protrude from the support, and define an upper surface (20) raised with respect to the support area. The compressible foam (18) rests with its bottom surface (22) on the upper surface of the one or more spacers. The compressible foam penetrates into the support area in between the one or more spacers and activates the pressure-responsive membrane switch in response to a force applied on the top surface that exceeds a certain threshold force.