Vehicular Seat Foam with Rate-Sensitive Overlay
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Solution Overview
Problem
Conventional vehicular seats, designed for the 50th percentile of male passengers, fail to provide comfort for a significant portion of passengers who do not fit this profile, particularly large, tall individuals, and women and children, due to the uniform specification profile of HR polyurethane foam across all operation temperatures.
Innovation Solution
A vehicular seat element featuring a rate-sensitive foam element on the occupant-contacting surface combined with a conventional HR polyurethane foam core, which reduces pressure on the under-thigh region by using a viscoelastic foam with a glass transition temperature above -20°C, providing improved comfort for a wider range of passenger sizes and weights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If HR polyurethane foam with uniform specification profile across all operation temperatures is used, then the seat maintains consistent mechanical properties, but it fails to provide comfort for a significant portion of passengers (5th to 95th percentile weight and size range)
Solution Approach 1:
The seat foam is divided into two distinct segments: a first foam material (HR polyurethane) providing structural support and a second foam material (rate-sensitive foam) providing temperature-dependent comfort. Each segment performs its specific function, allowing the overall seat to accommodate a wider range of passenger sizes while maintaining stable mechanical properties through the HR foam core.
Solution Approach 2:
Different regions of the seat foam have different properties. The HR polyurethane foam provides uniform structural support throughout, while the rate-sensitive foam layer (with glass transition temperature above -20°C) is positioned to provide localized comfort adaptation at the occupant contact surface, creating varying foam characteristics in different zones.
2Ease of operation
If a single foam material with uniform properties is used throughout the seat, then manufacturing is simplified, but pressure distribution across different body regions (particularly under-thigh area) is inadequate for diverse passenger populations
Solution Approach 1:
The foam structure is segmented into multiple layers with different materials: the HR polyurethane foam core and the rate-sensitive foam overlay. This segmentation enables differentiated pressure distribution characteristics in different zones, improving comfort for diverse passengers while keeping each individual foam type relatively simple to manufacture.
Solution Approach 2:
The seat employs a composite foam structure combining HR polyurethane foam and rate-sensitive foam materials. This composite approach leverages the strengths of each material type to achieve superior pressure distribution and comfort across the 5th to 95th percentile passenger range, outweighing the increased manufacturing complexity.
3Reliability
If HR polyurethane foam is selected for its support factor and flammability compliance, then structural integrity is maintained, but the seat cannot adapt to varying occupant weights and sizes across different temperature conditions
Solution Approach 1:
The seat foam system is segmented into functional zones: the HR polyurethane foam handles structural support and flammability requirements reliably, while the rate-sensitive foam overlay handles adaptability to different occupant profiles. This functional segmentation allows each material to excel at its primary role without compromise.
Solution Approach 2:
Different foam materials are assigned to different functional regions. The HR polyurethane foam provides consistent structural properties throughout for reliability, while the rate-sensitive foam at the occupant interface provides localized adaptation to varying weights and sizes, achieving both reliability and versatility simultaneously.
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 combination of rate-sensitive and HR polyurethane foams in the vehicular seat element significantly reduces overall and under-thigh pressure, enhancing comfort for passengers across the 5th to 95th percentile weight and size range, as demonstrated by static and dynamic testing.
Implementation Method 1
the rate sensitive foam element and the foam core element being different wherein the rate sensitive foam element has a glass transition temperature above about -20° C.
Implementation Method 2
High resiliency (HR) polyurethane foam has an impact resilience (i.e., ball rebound) greater than 50%
Data Source
AI summary
Disclosed is a vehicular seat element comprising a first major surface, a second major surface and a foam core element disposed therebetween. The first major surface is configured to be in contact with an occupant of the vehicle and the second major surface is configured to be in contact with a support surface of the vehicle. The first major surface comprises a rate sensitive foam element secured with respect to the foam core element. The foam core element and the rate sensitive foam element are different from one another.