Capacitive Sensor Assembly Nested Conductors Occupancy Detection
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Solution Overview
Problem
Existing capacitive sensor assemblies for motor vehicles face challenges in maintaining reliable occupancy detection and distinguishing between vehicle occupants and child seats due to variations in capacitance measurements influenced by humidity, wetness, and inconsistent distances between sensor elements.
Innovation Solution
A capacitive sensor assembly featuring a triaxial cable structure with a first electrical conductor as an outer conductor, a reference conductor as an inner conductor, and a second conductor element forming a shield, where the reference conductor can also serve as a heating element, and a dielectric that can deform under pressure to provide consistent capacitance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a capacitive sensor element and reference conductor are arranged in a vehicle seat to detect occupancy, then occupancy detection capability is improved, but measurement reliability deteriorates due to varying distances between sensor elements and occupants
Solution Approach 1:
The patent implements a nested conductor structure where an inner conductor is surrounded by an outer conductor, forming a coaxial arrangement. This nesting creates a defined geometric relationship between conductors, establishing a consistent measurement baseline that compensates for variable occupancy positions.
Solution Approach 2:
The patent utilizes the dielectric properties of materials between conductors and the capacitive coupling characteristics to create a measurement system that responds to occupancy while maintaining stability against positional variations. The capacitive sensor assembly leverages electrical parameter changes rather than direct mechanical contact.
2Adaptability or versatility
If heating conductors are integrated into the sensor mat to provide seat heating, then comfort function is improved, but measurement reliability deteriorates due to interference between heating conductors and capacitive sensor elements
Solution Approach 1:
The patent segments the electrical conductors into functionally distinct elements: capacitive sensor conductors for occupancy detection and heating conductors for thermal comfort. This segmentation allows independent optimization of each function and reduces interference by separating measurement and actuation pathways.
Solution Approach 2:
The coaxial conductor arrangement creates equipotential regions that reduce electromagnetic interference between heating and sensing functions. The symmetric geometric arrangement minimizes coupling between the AC heating signals and the capacitive measurement signals.
3Measurement precision
If the distance between capacitive sensor element and reference potential carrier is reduced to improve sensitivity, then measurement sensitivity is improved, but reliability deteriorates due to inconsistent spacing affecting measurement accuracy
Solution Approach 1:
The nested coaxial conductor structure fixes the relative positioning of sensor and reference elements through their geometric interrelationship. The inner conductor is centrally positioned within the outer conductor, creating a stable, reproducible measurement geometry that maintains consistent sensitivity across varying occupancy conditions.
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 enhances measurement sensitivity and reliability by maintaining a constant distance between sensor elements, allowing for accurate detection of vehicle occupants and child seats, while the deformable dielectric provides pressure-sensitive information for airbag inflation decisions.
Implementation Method 1
the capacitive coupling of the capacitive sensor element to the environment recorded and evaluated, as well as at least one (potential-carrying) electrical reference conductor element, which forms or defines an electrical reference potential (zero potential) when determining that measured variable or, more generally, when capacitively coupling the capacitive sensor element to the environment
Implementation Method 2
A further, second conductor element runs between the first conductor element as the outer conductor and the reference conductor element as the inner conductor, the first and second conductor elements and the reference conductor element forming a triaxial cable structure
Data Source
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AI summary
The invention relates to a capacitive sensor assembly for a motor vehicle, having a capacitive sensor element which comprises at least one first electrical conductor element, and having a reference conductor element defining an electrical reference potential and being interspaced from the first electrical conductor element. The invention is characterized in that the first electrical conductor element (1) is designed as an outer conductor surrounding the reference conductor element (3) which represents the inner conductor.