Capacitive HMI Electrode Carrier Layout for Uniform Backlighting
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Solution Overview
Problem
Existing capacitive proximity sensor systems for operating devices, particularly in vehicles, require high installation effort and face challenges with uniform backlighting due to the integration of sensors, which complicates the design and assembly process.
Innovation Solution
The operating device incorporates electrode carrier elements made of rigid plastic, with electrodes arranged on the back of the front wall and connected to a carrier plate via conductive areas, allowing for compact and easy installation, and featuring a cavity for backlighting to prevent scattered light, while spring arms ensure reliable contact and tolerance compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive proximity sensors are integrated into the button body with electrodes arranged close to the front wall, then the detection reliability of approaching objects is improved, but the backlighting uniformity deteriorates and assembly complexity increases
Solution Approach 1:
The sensor system is divided into modular sensor modules, each comprising an electrode carrier element with integrated electrode and spring arm assembly. This segmentation allows independent optimization of each module's detection function while simplifying overall assembly through standardized modular units that can be independently manufactured and tested before final integration into the operating device.
Solution Approach 2:
An electrode carrier element is introduced as an intermediary component between the front wall and the evaluation unit. This carrier element holds the electrode at the optimal position for detection reliability while providing a structured interface for electrical connections and mechanical mounting, thereby reducing assembly complexity by organizing multiple functions (electrode support, electrical connection, positioning) into a single intermediate component.
2Measurement precision
If capacitive proximity sensors are integrated into the button body, then the detection function is improved, but the backlighting uniformity deteriorates
Solution Approach 1:
The electrode is extracted from direct integration into the button body and instead mounted on the electrode carrier element positioned behind the front wall. This extraction allows the electrode to maintain its optimal detection position while removing it from the light path, thereby preserving backlighting uniformity through the front wall while maintaining detection function.
Solution Approach 2:
The sensor system transitions from a two-dimensional planar integration (electrode on front wall surface) to a three-dimensional arrangement where the electrode is positioned on a carrier element behind the front wall. This dimensional change allows the electrode to be optimally positioned for detection while leaving the front wall surface clear for uniform backlighting transmission.
3Ease of manufacture
If electrical conductors are routed from the printed circuit board to the rear of the front wall to contact the sensor layer, then the electrical connection is established, but the contact reliability deteriorates over time due to external influences
Solution Approach 1:
The rigid electrical conductor connection is replaced with a dynamic spring arm mechanism that maintains continuous elastic contact between the electrode carrier element and the evaluation unit. This dynamic connection compensates for thermal expansion, mechanical stress, and assembly tolerances, ensuring reliable electrical contact over time despite external influences such as temperature changes and vibrations.
Solution Approach 2:
The spring arm is designed with predetermined elastic properties to compensate for potential contact losses before they occur. The spring preload and material selection are optimized in advance to accommodate expected thermal expansion, mechanical stress, and wear, thereby maintaining reliable electrical contact throughout the device's operational lifetime without requiring adjustment or maintenance.
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 design reduces the design and assembly effort while enabling reliable detection of object proximity and uniform illumination of symbol fields, improving the overall performance and usability of the operating device.
Implementation Method 1
wobei mindestens ein Federarm (34) zur kompensierenden Auslenkung bei Toleranzabweichungen zur Kontaktierung mit der Trägerplatte (26) vorgesehen ist
Implementation Method 2
mit Hilfe der in der Nähe der Symbolfelder (16) angeordneten Elektroden (42) eine Kapazitätsänderung der Elektroden (42) und/oder eine Störung der elektrischen Felder um die Elektroden (42) herum erkannt werden kann
Data Source
Figure 1~2
Figure 3
AI summary
The operating device (10), such a human-machine interface, in particular for a vehicle component, is provided with a front wall (12) having a front side (14) that has several fixed symbol fields (16) and having a rear side (38), a capacitive proximity sensor system that has individual electrodes (42) associated with the symbol fields (16), which electrodes are arranged on the rear side (38) of the front wall (12), and a carrier plate (26) that faces the rear side (38) of the front wall (12) and is arranged at a distance from the front wall (12). The capacitive proximity sensor system comprises an evaluating unit (50) connected to the electrodes (42) for identifying the particular symbol field (16) that an object, in particular a hand or a finger of a hand, is approaching. Electrode carrier elements (20) associated with the individual symbol fields (16) are arranged between the front wall (12) and the carrier plate (26). Each electrode carrier element (20) has an electrode end (24) facing the rear side (38) of the front wall (12), which electrode end is provided with an electrode (42), and an opposite contact end (28) that electrically contacts a contact field (48) of the carrier plate (26), which contact field is electrically connected to the evaluating unit (50). The electrode end (24) of each electrode carrier element (20) has a protruding contact edge (30) that extends at least partially around a symbol field (16) associated with the electrode carrier element (20) and lies in contact with the rear side (38) of the front wall (12). The electrode (42) is formed along the contact edge (30) of the electrode carrier element (20) without being electrically connected to the front wall (12). Each electrode carrier element (20) has an electrically conductive region (44) for electrically connecting the electrode (42) of the electrode carrier element to the contact end (28) of the electrode carrier element and thus to the contact field (48) of the carrier plate (26).